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, Available online , doi: 10.11883/bzycj-2024-0089
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Plasma blasting rock breaking technology is characterized by green, high efficiency, controllability, and has a good application prospect in deep rock breaking. In order to provide a new rock-breaking method for the rock-breaking engineering under deep stress, four groups of plasma sandstone blasting tests under different peripheral pressures were carried out. The morphology, structure and distribution of three-dimensional cracks inside the rock were comparatively analyzed by CT scanning and three-dimensional reconstruction, so as to study the effectiveness of the plasma blasting technology in rock breaking under different peripheral pressures. Meanwhile numerical simulation was conducted by using LS-DYNA to establish the plasma equivalent explosive model, supplementing the verification of the role of plasma blasting in the coupled stress field, and investigating the mechanism of plasma blasting under different pressures, as well as the internal crack expansion, distribution and damage evolution laws in the rock body in the blasting process. The results show that under the same voltage, with the increase of the 3D peripheral pressure, the number and distribution range of cracks on the surface of the rock exhibit a trend of gradual reduction, while the complexity of the cracks within the sandstone and the depth of penetration are significantly reduced. Due to the dynamic stress field generated by plasma blasting and the static stress coupling field generated by the surrounding pressure, the shock wave generated by the plasma blasting in the initial stage of the explosion plays a major role for the effect of different pressures under the action of the rock crack morphology and the center of the expansion of the region does not show obvious differences. With the attenuation of the shock wave, the 3D surrounding pressure in the middle and late stages of the plasma blasting process plays a decisive role in inhibiting the cracks of the rock mass expansion and damage evolution. At the same time, with the increase of the surrounding pressure, the more significant inhibition effect on the expansion of cracks in the rock body, resulting in the body fractal dimension and damage degree of 3D cracks in the rock body, while the role of the surrounding pressure approximately follows a linearly decreasing relationship.
Plasma blasting rock breaking technology is characterized by green, high efficiency, controllability, and has a good application prospect in deep rock breaking. In order to provide a new rock-breaking method for the rock-breaking engineering under deep stress, four groups of plasma sandstone blasting tests under different peripheral pressures were carried out. The morphology, structure and distribution of three-dimensional cracks inside the rock were comparatively analyzed by CT scanning and three-dimensional reconstruction, so as to study the effectiveness of the plasma blasting technology in rock breaking under different peripheral pressures. Meanwhile numerical simulation was conducted by using LS-DYNA to establish the plasma equivalent explosive model, supplementing the verification of the role of plasma blasting in the coupled stress field, and investigating the mechanism of plasma blasting under different pressures, as well as the internal crack expansion, distribution and damage evolution laws in the rock body in the blasting process. The results show that under the same voltage, with the increase of the 3D peripheral pressure, the number and distribution range of cracks on the surface of the rock exhibit a trend of gradual reduction, while the complexity of the cracks within the sandstone and the depth of penetration are significantly reduced. Due to the dynamic stress field generated by plasma blasting and the static stress coupling field generated by the surrounding pressure, the shock wave generated by the plasma blasting in the initial stage of the explosion plays a major role for the effect of different pressures under the action of the rock crack morphology and the center of the expansion of the region does not show obvious differences. With the attenuation of the shock wave, the 3D surrounding pressure in the middle and late stages of the plasma blasting process plays a decisive role in inhibiting the cracks of the rock mass expansion and damage evolution. At the same time, with the increase of the surrounding pressure, the more significant inhibition effect on the expansion of cracks in the rock body, resulting in the body fractal dimension and damage degree of 3D cracks in the rock body, while the role of the surrounding pressure approximately follows a linearly decreasing relationship.
, Available online , doi: 10.11883/bzycj-2024-0272
Abstract:
In order to study the dynamic mechanical properties of concrete and the dynamic temperature at the crack under impact, steel-polypropylene fiber reinforced concrete (SPFRC) was taken as the research object using a self-built high-speed infrared temperature measurement system. The time resolution of the high-speed infrared temperature measurement system is in the order of microsecond. The concrete temperature curve was fitted by static calibration test as a reference. Combined with the Hopkinson pressure bar test device, the dynamic properties of SPFRC specimens with different steel fiber contents and the dynamic temperature change at the crack were studied. The results indicate a significant coupling effect between the temperature evolution and mechanical properties of the concrete specimens and substantial influences of the steel fiber content on both dynamic performance and temperature. Specifically, as the steel fiber content increases, the compressive strength of the concrete improves, reaching optimal mechanical performance at 1.5% steel fiber content. However, at 2% steel fiber content, the mechanical performance slightly decreases due to an increase in internal voids within the concrete. During impact, the dynamic temperature effect at the crack location exhibits a "stepped" pattern, with temperature change occurring in two distinct stages: an initial slow rise during early crack formation, followed by a sharp increase as friction and shear effects intensify with crack propagation. The influence of varying steel fiber content on temperature change is limited, with peak temperature and peak stress showing similar trends. The primary temperature variations are driven by crack propagation and frictional effects. After impact, the overall temperature in SPFRC specimens continues to rise within the first 300 μs. Due to the thermal lag, the temperature does not decrease immediately after unloading. The high-speed infrared temperature measurement system provides a new method for real-time monitoring of temperature changes at concrete crack locations, offering a basis for assessing temperature evolution at cracks and the evaluation of crack propagation behavior.
In order to study the dynamic mechanical properties of concrete and the dynamic temperature at the crack under impact, steel-polypropylene fiber reinforced concrete (SPFRC) was taken as the research object using a self-built high-speed infrared temperature measurement system. The time resolution of the high-speed infrared temperature measurement system is in the order of microsecond. The concrete temperature curve was fitted by static calibration test as a reference. Combined with the Hopkinson pressure bar test device, the dynamic properties of SPFRC specimens with different steel fiber contents and the dynamic temperature change at the crack were studied. The results indicate a significant coupling effect between the temperature evolution and mechanical properties of the concrete specimens and substantial influences of the steel fiber content on both dynamic performance and temperature. Specifically, as the steel fiber content increases, the compressive strength of the concrete improves, reaching optimal mechanical performance at 1.5% steel fiber content. However, at 2% steel fiber content, the mechanical performance slightly decreases due to an increase in internal voids within the concrete. During impact, the dynamic temperature effect at the crack location exhibits a "stepped" pattern, with temperature change occurring in two distinct stages: an initial slow rise during early crack formation, followed by a sharp increase as friction and shear effects intensify with crack propagation. The influence of varying steel fiber content on temperature change is limited, with peak temperature and peak stress showing similar trends. The primary temperature variations are driven by crack propagation and frictional effects. After impact, the overall temperature in SPFRC specimens continues to rise within the first 300 μs. Due to the thermal lag, the temperature does not decrease immediately after unloading. The high-speed infrared temperature measurement system provides a new method for real-time monitoring of temperature changes at concrete crack locations, offering a basis for assessing temperature evolution at cracks and the evaluation of crack propagation behavior.
, Available online , doi: 10.11883/bzycj-2024-0159
Abstract:
To exploring the dynamic response characteristics of the shed-tunnel structure under multiple rockfall impacts, an FEM-SPH coupled numerical model is established based on ANSYS/LS-DYNA and is also tested with the data before. Then, the model is combined with the full restart technique to study the effects of the shed-tunnel structure dynamic response under multiple rockfall impacts by considering four factors, e.g., rockfall impact velocity, rockfall mass, impact angle and rockfall shape. The results show that the impact force, buffer top impact displacement, roof displacement and plastic strain of the shed-tunnel are positively correlated with the rockfall mass, velocity and angle. The impact force, roof displacement and plastic strain of the shed-tunnel structure generated by the cuboid rockfall impact are all larger than those of the spherical rockfall, and the impact displacement generated by the spherical rockfall impact is larger than that of the cuboid. For the cuboid rockfall, the impact displacement, roof displacement and plastic strain are negatively correlated with the contact area. Under the multiple rockfall impacts, the peak impact force usually increases firstly and then tends to be stable.
To exploring the dynamic response characteristics of the shed-tunnel structure under multiple rockfall impacts, an FEM-SPH coupled numerical model is established based on ANSYS/LS-DYNA and is also tested with the data before. Then, the model is combined with the full restart technique to study the effects of the shed-tunnel structure dynamic response under multiple rockfall impacts by considering four factors, e.g., rockfall impact velocity, rockfall mass, impact angle and rockfall shape. The results show that the impact force, buffer top impact displacement, roof displacement and plastic strain of the shed-tunnel are positively correlated with the rockfall mass, velocity and angle. The impact force, roof displacement and plastic strain of the shed-tunnel structure generated by the cuboid rockfall impact are all larger than those of the spherical rockfall, and the impact displacement generated by the spherical rockfall impact is larger than that of the cuboid. For the cuboid rockfall, the impact displacement, roof displacement and plastic strain are negatively correlated with the contact area. Under the multiple rockfall impacts, the peak impact force usually increases firstly and then tends to be stable.
, Available online , doi: 10.11883/bzycj-2024-0093
Abstract:
Explosion experiments utilizing a 20 L spherical explosion apparatus were conducted to investigate the explosion characteristics of aluminum and aluminum-silicon alloy powders, prevalent in additive manufacturing. The tested samples included Al, Al-12Si, and Al-20Si. Various parameters were measured under different influencing factors, including the lower explosion limit, maximum explosion pressure, maximum pressure rise rate, explosion temperature, and time to reach peak temperature. Thermogravimetric analysis-differential scanning calorimetry was employed to analyze the thermal oxidation properties of the samples. The results indicated that an increase in the silicon content within the alloy corresponded with a lower explosion limit. Conversely, the maximum explosion pressure and peak temperature showed a downward trend. Meanwhile. a reduction in the maximum pressure rise rate was observed. The exothermic amount of the oxidation process reduced, and the oxidation rate slowed down. The concentrations at which the three samples reached the maximum explosion pressure and peak temperature were 300 g/m3 for Al, 750 g/m3 for Al-12Si, and 900 g/m3 for Al-20Si, respectively. When the ignition energy increased, the rate of increase in maximum explosion pressure for the aluminum-silicon alloys was lower than that for aluminum powder. The effect of environmental temperature changes on the lower explosive limit was less significant compared to that of particle size variations. As the environmental temperature increased, the explosion pressure did not show a significant change, while the pressure rise rate increased slightly. X-ray diffraction analysis of the explosion products revealed that, in addition to Al2O3 and Al, the explosion products of the aluminum-silicon alloys also contained SiO2 and Si. This indicates that the Si element in the alloy participated in the explosion reaction. It confirms that the explosion of aluminum-silicon alloy powder is caused by the heating and vaporization of the particles, leading to the formation of a combustible gas composed of gaseous aluminum and silicon, which then combusts with oxygen.
Explosion experiments utilizing a 20 L spherical explosion apparatus were conducted to investigate the explosion characteristics of aluminum and aluminum-silicon alloy powders, prevalent in additive manufacturing. The tested samples included Al, Al-12Si, and Al-20Si. Various parameters were measured under different influencing factors, including the lower explosion limit, maximum explosion pressure, maximum pressure rise rate, explosion temperature, and time to reach peak temperature. Thermogravimetric analysis-differential scanning calorimetry was employed to analyze the thermal oxidation properties of the samples. The results indicated that an increase in the silicon content within the alloy corresponded with a lower explosion limit. Conversely, the maximum explosion pressure and peak temperature showed a downward trend. Meanwhile. a reduction in the maximum pressure rise rate was observed. The exothermic amount of the oxidation process reduced, and the oxidation rate slowed down. The concentrations at which the three samples reached the maximum explosion pressure and peak temperature were 300 g/m3 for Al, 750 g/m3 for Al-12Si, and 900 g/m3 for Al-20Si, respectively. When the ignition energy increased, the rate of increase in maximum explosion pressure for the aluminum-silicon alloys was lower than that for aluminum powder. The effect of environmental temperature changes on the lower explosive limit was less significant compared to that of particle size variations. As the environmental temperature increased, the explosion pressure did not show a significant change, while the pressure rise rate increased slightly. X-ray diffraction analysis of the explosion products revealed that, in addition to Al2O3 and Al, the explosion products of the aluminum-silicon alloys also contained SiO2 and Si. This indicates that the Si element in the alloy participated in the explosion reaction. It confirms that the explosion of aluminum-silicon alloy powder is caused by the heating and vaporization of the particles, leading to the formation of a combustible gas composed of gaseous aluminum and silicon, which then combusts with oxygen.
, Available online , doi: 10.11883/bzycj-2024-0218
Abstract:
In order to predict the quasi-static pressure of internal explosion in a closed environment composed of aluminum containing active materials and explosive rings, this paper summarizes the existing quasi-static pressure calculation models for hydrogen, oxygen, and nitrogen explosives considering post ignition effects, and proposes an optimization method for the quasi-static pressure calculation mode applicable to internal explosion of aluminum containing composite charges. After obtaining the ideal maximum reaction heat using the Geiss theorem, this method uses a parameter correction related to the aluminum containing composite explosive itself. Taking Herzog as an example, a specific prediction formula is provided. Then, composite charges of active materials and explosives, as well as aluminum containing explosives, were tested for implosion. Typical overpressure curves were provided, and the method for obtaining quasi-static pressure in the tests and related sources were explained. The experimental data was compared and analyzed with the quasi-static pressure results calculated by the established optimization model, demonstrating the reliability of the modified model. At the same time, the internal explosion results of two types of explosives were compared, and the calculation model was extended to general aluminum containing explosives. The accuracy of the model was verified using quasi-static pressure data from relevant literature, and the reasons for errors and possible improvement methods were analyzed. The research results show that the established quasi-static pressure correction model for post combustion of composite explosives is in good agreement with experimental and literature data, with an average error of 9.1% and a maximum error of 15.8%; The average error of the calculation results for aluminum containing explosives is 12.1%, with a maximum error of 20.6%.
In order to predict the quasi-static pressure of internal explosion in a closed environment composed of aluminum containing active materials and explosive rings, this paper summarizes the existing quasi-static pressure calculation models for hydrogen, oxygen, and nitrogen explosives considering post ignition effects, and proposes an optimization method for the quasi-static pressure calculation mode applicable to internal explosion of aluminum containing composite charges. After obtaining the ideal maximum reaction heat using the Geiss theorem, this method uses a parameter correction related to the aluminum containing composite explosive itself. Taking Herzog as an example, a specific prediction formula is provided. Then, composite charges of active materials and explosives, as well as aluminum containing explosives, were tested for implosion. Typical overpressure curves were provided, and the method for obtaining quasi-static pressure in the tests and related sources were explained. The experimental data was compared and analyzed with the quasi-static pressure results calculated by the established optimization model, demonstrating the reliability of the modified model. At the same time, the internal explosion results of two types of explosives were compared, and the calculation model was extended to general aluminum containing explosives. The accuracy of the model was verified using quasi-static pressure data from relevant literature, and the reasons for errors and possible improvement methods were analyzed. The research results show that the established quasi-static pressure correction model for post combustion of composite explosives is in good agreement with experimental and literature data, with an average error of 9.1% and a maximum error of 15.8%; The average error of the calculation results for aluminum containing explosives is 12.1%, with a maximum error of 20.6%.
, Available online , doi: 10.11883/bzycj-2024-0214
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To understand the relationship between fragmentation and energy dissipation in copper-bearing ore rock subjected to impact loading, a split Hopkinson pressure bar (SHPB) testing apparatus was employed to study the mechanical properties and energy transfer mechanisms of copper-bearing tuff under varying impact loads. Additionally, fractal theory was used to establish the correlation between dissipated energy and rock fragmentation. Utilizing the finite discrete element method (FDEM), numerical simulations of crack propagation within the rock were conducted. The results indicate that as the incident energy increases, the distribution patterns of the transmission energy, absorbed energy and reflection energy remain consistent, which are characterized by transmission energy, absorbed energy and reflection energy decreased successively. Furthermore, significant variations in fragment size distribution are observed with changes in dissipated energy. Specifically, as dissipated energy increases from 19.52 J to 105.72 J, the average fragment size decreases from 27.98 mm to 16.94 mm, while the fractal dimension increases by 26.43%. This suggests that higher dissipated energy results in more extensive macroscopic fragmentation, an increase in the number of fragments, smaller particle sizes and enhanced uniformity. As the impact load intensifies, the time to crack initiation decreases, and the proportion of tensile cracks relative to total cracks increases. The application of the FDEM offers new insights into the fracture and failure characteristics of rocks.
To understand the relationship between fragmentation and energy dissipation in copper-bearing ore rock subjected to impact loading, a split Hopkinson pressure bar (SHPB) testing apparatus was employed to study the mechanical properties and energy transfer mechanisms of copper-bearing tuff under varying impact loads. Additionally, fractal theory was used to establish the correlation between dissipated energy and rock fragmentation. Utilizing the finite discrete element method (FDEM), numerical simulations of crack propagation within the rock were conducted. The results indicate that as the incident energy increases, the distribution patterns of the transmission energy, absorbed energy and reflection energy remain consistent, which are characterized by transmission energy, absorbed energy and reflection energy decreased successively. Furthermore, significant variations in fragment size distribution are observed with changes in dissipated energy. Specifically, as dissipated energy increases from 19.52 J to 105.72 J, the average fragment size decreases from 27.98 mm to 16.94 mm, while the fractal dimension increases by 26.43%. This suggests that higher dissipated energy results in more extensive macroscopic fragmentation, an increase in the number of fragments, smaller particle sizes and enhanced uniformity. As the impact load intensifies, the time to crack initiation decreases, and the proportion of tensile cracks relative to total cracks increases. The application of the FDEM offers new insights into the fracture and failure characteristics of rocks.
, Available online , doi: 10.11883/bzycj-2024-0250
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In the process of deep penetration of the earth penetration weapon (EPW) attacking the underground target, the non-ideal penetration attitude with an initial attack angle is inevitable, which will introduce transverse overload with a large peak value for the earth penetrator. It could damage some important components of the earth-penetrating projectile and reduce the penetration efficiency of the projectile. Therefore, it is necessary to study the methodology of reducing the transverse overload peak value of the earth-penetrating projectile. However, the previous research on the earth-penetrating projectile seldom considered the influence of transverse overload, making it difficult to effectively reduce the transverse overload. In order to overcome this problem, a numerical simulation method was used to study the special transverse overload shedding effect and its mechanism of a new type of earth-penetrating projectile with a serrated configuration penetrating concrete targets at non-zero attack angles. The influences of the initial attack angle and the coefficient of the center of mass of the projectile were studied, and the motion, contact force, contact moment, and contact area of the projectile were analyzed using a conventional smooth projectile for comparison. The results show that for small initial attack angles of 1°, 2° and 3°, the peak value of transverse overload of the serrated projectile is reduced by about 30.6%, 5.2%, and 11.3%, respectively, compared to the smooth projectile but the peak value of contact moment, pulse width, and deflection angle are increased. The research reveals the mechanical mechanism to reduce transverse overload: the serrated body of the projectile reduces the contact area between the projectile and the target, and the transverse contact force is mainly concentrated on the upper surface of the right serrated parts of the first two serrated grooves near the head of the projectile; the transverse contact force between the serrated body and the target decreases, while the transverse contact force between the non-serrated parts (mainly the head of the projectile) and the target increases. Therefore, these two parts of the projectile compete and control the reduction effects of the transverse overload of the whole projectile in the process of deep penetration with an initial attack angle. When optimizations of structural design are used to suppress the ballistic deflection of the serrated projectile, the transverse overload shedding efficiency of serrated projectiles can be effectively improved.
In the process of deep penetration of the earth penetration weapon (EPW) attacking the underground target, the non-ideal penetration attitude with an initial attack angle is inevitable, which will introduce transverse overload with a large peak value for the earth penetrator. It could damage some important components of the earth-penetrating projectile and reduce the penetration efficiency of the projectile. Therefore, it is necessary to study the methodology of reducing the transverse overload peak value of the earth-penetrating projectile. However, the previous research on the earth-penetrating projectile seldom considered the influence of transverse overload, making it difficult to effectively reduce the transverse overload. In order to overcome this problem, a numerical simulation method was used to study the special transverse overload shedding effect and its mechanism of a new type of earth-penetrating projectile with a serrated configuration penetrating concrete targets at non-zero attack angles. The influences of the initial attack angle and the coefficient of the center of mass of the projectile were studied, and the motion, contact force, contact moment, and contact area of the projectile were analyzed using a conventional smooth projectile for comparison. The results show that for small initial attack angles of 1°, 2° and 3°, the peak value of transverse overload of the serrated projectile is reduced by about 30.6%, 5.2%, and 11.3%, respectively, compared to the smooth projectile but the peak value of contact moment, pulse width, and deflection angle are increased. The research reveals the mechanical mechanism to reduce transverse overload: the serrated body of the projectile reduces the contact area between the projectile and the target, and the transverse contact force is mainly concentrated on the upper surface of the right serrated parts of the first two serrated grooves near the head of the projectile; the transverse contact force between the serrated body and the target decreases, while the transverse contact force between the non-serrated parts (mainly the head of the projectile) and the target increases. Therefore, these two parts of the projectile compete and control the reduction effects of the transverse overload of the whole projectile in the process of deep penetration with an initial attack angle. When optimizations of structural design are used to suppress the ballistic deflection of the serrated projectile, the transverse overload shedding efficiency of serrated projectiles can be effectively improved.
, Available online , doi: 10.11883/bzycj-2024-0361
Abstract:
To study the damage law of calcareous conglomerate under blasting, firstly, the damage fracture process and mechanism of calcareous conglomerate under blasting load were revealed based on the theory of damage fracture mechanics. A meso-scale model of conglomerate, including filler, conglomerate and interfacial transition zone (ITZ), was established by using LS-DYNA and Fortran programming, and the propagation law of explosive stress wave and its damage characteristics were analyzed. The damage fracture process of calcareous conglomerate under blasting can be divided into four stages, namely: compression damage in both gravel and fill; tensile damage in gravel and compression damage in fill; tensile damage in both gravel and fill; and tensile damage at the intersection of gravel and fill. Numerical results show that under blasting loads, the gravel has higher equivalent stresses, the fill has the lowest, stress concentration is evident at the ITZ, and the stress gap between the gravel and the fill decreases as the distance increases. The conglomerate sustains relatively minor damage, with a notable phenomenon of damage occurring around it. However, and the filler experiences significant damage. The expansion of blasting crack in Calcareous conglomerate forms mainly along the direction of stress wave propagation. Cracks tend to develop along the filler with lower physical and mechanical properties, as well as along the junction surfaces. The damage to the gravel is comparatively less severe. Blasting blockiness is mainly manifested as the filler wrapping gravel, and the distribution of blasting blockiness is affected by the bonding force at the intersection surface and the distribution of gravel.
To study the damage law of calcareous conglomerate under blasting, firstly, the damage fracture process and mechanism of calcareous conglomerate under blasting load were revealed based on the theory of damage fracture mechanics. A meso-scale model of conglomerate, including filler, conglomerate and interfacial transition zone (ITZ), was established by using LS-DYNA and Fortran programming, and the propagation law of explosive stress wave and its damage characteristics were analyzed. The damage fracture process of calcareous conglomerate under blasting can be divided into four stages, namely: compression damage in both gravel and fill; tensile damage in gravel and compression damage in fill; tensile damage in both gravel and fill; and tensile damage at the intersection of gravel and fill. Numerical results show that under blasting loads, the gravel has higher equivalent stresses, the fill has the lowest, stress concentration is evident at the ITZ, and the stress gap between the gravel and the fill decreases as the distance increases. The conglomerate sustains relatively minor damage, with a notable phenomenon of damage occurring around it. However, and the filler experiences significant damage. The expansion of blasting crack in Calcareous conglomerate forms mainly along the direction of stress wave propagation. Cracks tend to develop along the filler with lower physical and mechanical properties, as well as along the junction surfaces. The damage to the gravel is comparatively less severe. Blasting blockiness is mainly manifested as the filler wrapping gravel, and the distribution of blasting blockiness is affected by the bonding force at the intersection surface and the distribution of gravel.
, Available online , doi: 10.11883/bzycj-2024-0165
Abstract:
To investigate the effect of the longitudinal air gap on the detonation performance of HMX-based explosive, direct observation of steel plate deformation and damage under forward and slipping detonation of HMX based explosive was conducted based on the laser illumination combined with the ultra-high speed framing imaging technology. The multi-position optical speed measurement technology was also introduced to continuously measure the speed of steel plate, which enables a multidimensional characterization and quantitative research on steel plate damage under the influence of air gaps. It is found that when the air gap width is 0.05, 0.10 and 0.20 mm, the motion mode of the steel plate changes obviously under the forward detonation. The trend of the center point movement changes from step rising to oblique wave rising, indicating a notable elongation of the lead time of detonation wave. And the steel plate also has an obvious deformation and breakdown. Driven by slipping detonation, the motion patterns across various points of the steel plate are largely uniform, with only marginal variations in the lead time of detonation wave. No significant deformation or rupture of the steel plate is observed. It is considered that the wedge-shaped wave formed by the precursor shock wave and detonation waves is the key to the breakdown of the bottom of steel plate in the case of forward detonation. However, the momentum component of the precursor shock wave and detonation wave acting on the side of steel plate in the case of slipping detonation is small, so that no obvious damage occurs. This article also provides a lot of quantitative data on the deformation of steel plates subjected to longitudinal air gaps, which can provide high-precision experimental data for the related numerical simulations and theoretical analysis work.
To investigate the effect of the longitudinal air gap on the detonation performance of HMX-based explosive, direct observation of steel plate deformation and damage under forward and slipping detonation of HMX based explosive was conducted based on the laser illumination combined with the ultra-high speed framing imaging technology. The multi-position optical speed measurement technology was also introduced to continuously measure the speed of steel plate, which enables a multidimensional characterization and quantitative research on steel plate damage under the influence of air gaps. It is found that when the air gap width is 0.05, 0.10 and 0.20 mm, the motion mode of the steel plate changes obviously under the forward detonation. The trend of the center point movement changes from step rising to oblique wave rising, indicating a notable elongation of the lead time of detonation wave. And the steel plate also has an obvious deformation and breakdown. Driven by slipping detonation, the motion patterns across various points of the steel plate are largely uniform, with only marginal variations in the lead time of detonation wave. No significant deformation or rupture of the steel plate is observed. It is considered that the wedge-shaped wave formed by the precursor shock wave and detonation waves is the key to the breakdown of the bottom of steel plate in the case of forward detonation. However, the momentum component of the precursor shock wave and detonation wave acting on the side of steel plate in the case of slipping detonation is small, so that no obvious damage occurs. This article also provides a lot of quantitative data on the deformation of steel plates subjected to longitudinal air gaps, which can provide high-precision experimental data for the related numerical simulations and theoretical analysis work.
, Available online , doi: 10.11883/bzycj-2024-0142
Abstract:
Numerical simulation was carried out by using the Fluent simulation software and combining it with the situation of the working face3906 in a mine to investigate the propagation law of gas explosion in a U-shaped ventilation coal mining face and to explore the sensitivities of the overpressure attenuation of a gas explosion to different influencing factors. The relative errors between the numerically-simulated results and experimental ones are less than 15%, which verifies the reliability of the mathematical model developed in this paper. Then, the key parameters, namely, grid size, iteration time step, and ignition temperature are optimized to 0.2 m, 0.05 ms, and 1900 K, respectively. Numerical simulation indicates that the relationship between the peak of the explosion overpressure and the distance away from the explosion center of the coal face meets an exponential function relationship. The relationship between the arrival time of the peak explosion overpressure and the distance away from the explosion center meets a linear function. By designing an orthogonal array, 16 sets of data were obtained through simulation, and the following analyses were conducted based on this data. The extreme difference values of the three main control factors were obtained by using extreme difference analysis. The extreme difference value of the temperature is the greatest, the one of the gas concentration take the second, and the one of the gas accumulation area pressure is the least. The most significant impact of the temperature on the explosion overpressure attenuation in the numerical simulation, in which the R-value reaches 5.928. ANOVA analysis was carried out to study the significances of the main control factors affecting the explosion overpressure attenuation rate. In the three main control factors, the significance of the temperature is the most, the one of the gas accumulation zone pressure comes second, and the one of the gas concentration is the weakest. And the temperature shows a significance level of 31.835, while the other two factors are not significant.
Numerical simulation was carried out by using the Fluent simulation software and combining it with the situation of the working face
, Available online , doi: 10.11883/bzycj-2024-0192
Abstract:
The evaluation of protective performance and optimization of the design of building structures under impact loading is a key issue of concern in the fields of national defense, civil engineering, and other military and civilian use. Lattice columns are often used as the main load-bearing components in engineering structures and are inevitably impacted by other unintentional loads under engineering service environments. In this paper, 1∶2 scaled-down secondary impact tests were carried out on lattice columns along different impact directions with the same impact energy each time and compared with single-impact lattice columns under the same total energy to analyze the force and deformation characteristics of the lattice columns under the impact loads. Then, based on the experimentally verified finite element model, a continuous secondary impact simulation was carried out on the foot-foot lattice column. The dynamic response of the lattice column subjected to two consecutive impacts with the same total energy was obtained, and the effects of different energy distributions on the impact force, residual displacement, and residual kinetic energy were analyzed. The results show that under the same total energy, the displacement of lattice columns under a single impact is greater than that of a secondary impact. The optimal energy distribution obtained by numerical simulation can reduce the residual displacement of members impacted along different directions by about 12%. When the lattice column is subjected to a larger proportion of energy for the first time or a smaller proportion of impact energy for the second time, the total energy absorbed by the column is smaller. Finally, based on the results of tests and numerical simulations, the maximum impact velocity at which the damaged column can withstand a second impact is proposed. The results of the study can provide a reference for the design method of lattice steel columns under such loading conditions.
The evaluation of protective performance and optimization of the design of building structures under impact loading is a key issue of concern in the fields of national defense, civil engineering, and other military and civilian use. Lattice columns are often used as the main load-bearing components in engineering structures and are inevitably impacted by other unintentional loads under engineering service environments. In this paper, 1∶2 scaled-down secondary impact tests were carried out on lattice columns along different impact directions with the same impact energy each time and compared with single-impact lattice columns under the same total energy to analyze the force and deformation characteristics of the lattice columns under the impact loads. Then, based on the experimentally verified finite element model, a continuous secondary impact simulation was carried out on the foot-foot lattice column. The dynamic response of the lattice column subjected to two consecutive impacts with the same total energy was obtained, and the effects of different energy distributions on the impact force, residual displacement, and residual kinetic energy were analyzed. The results show that under the same total energy, the displacement of lattice columns under a single impact is greater than that of a secondary impact. The optimal energy distribution obtained by numerical simulation can reduce the residual displacement of members impacted along different directions by about 12%. When the lattice column is subjected to a larger proportion of energy for the first time or a smaller proportion of impact energy for the second time, the total energy absorbed by the column is smaller. Finally, based on the results of tests and numerical simulations, the maximum impact velocity at which the damaged column can withstand a second impact is proposed. The results of the study can provide a reference for the design method of lattice steel columns under such loading conditions.
, Available online , doi: 10.11883/bzycj-2024-0232
Abstract:
Applicable buffer-head covers and various open-cell foam buffer configurations were designed to meet the buffering and load reduction challenges during high-speed water entry vehicles. In the arbitrary Lagrangian-Euler method, the grid can move as the material flows within the spatial grid. This unique feature allows the arbitrary Lagrangian-Euler method to harness the advantages of both the Lagrangian and Euler methods. It not only overcomes numerical calculation challenges stemming from element distortion but also facilitates accurate computation of large deformations and displacements in solids and fluids. This makes it particularly well-suited for addressing high-speed water buffer load reduction problems. Based on the arbitrary Lagrangian-Eulerian method and considering the large deformation of the buffer foam and the hood, a numerical calculation model for buffering and load reduction during high-speed water entry of navigational bodies was established. Through numerical simulations, an in-depth study was conducted on the load reduction performance of buffer foams with different open-cell patterns. The results indicate that open-cell buffer foam exhibits significant advantages in dispersing the impact force and absorbing impact energy during water entry of navigational bodies, offering better buffering effects. Simultaneously, the buffer head cover experiences local progressive fragmentation upon water entry. The deformation and rupture of the outer wall surface of the buffer head cover at the connector between the buffer shell and the navigational body are caused by the stress concentration distribution generated during water impact. When the open-cell foam contacts the water surface, the front part enters the collapse stage, absorbing a large amount of energy and undergoing plastic deformation, resulting in a reduction of pores. This stage is the primary energy absorption phase for the buffer foam. In comparison, closed-cell foam exhibits poorer load reduction performance. Therefore, the adoption of open-cell foam represents a superior solution for buffering and load reduction during high-speed water entry of navigational bodies.
Applicable buffer-head covers and various open-cell foam buffer configurations were designed to meet the buffering and load reduction challenges during high-speed water entry vehicles. In the arbitrary Lagrangian-Euler method, the grid can move as the material flows within the spatial grid. This unique feature allows the arbitrary Lagrangian-Euler method to harness the advantages of both the Lagrangian and Euler methods. It not only overcomes numerical calculation challenges stemming from element distortion but also facilitates accurate computation of large deformations and displacements in solids and fluids. This makes it particularly well-suited for addressing high-speed water buffer load reduction problems. Based on the arbitrary Lagrangian-Eulerian method and considering the large deformation of the buffer foam and the hood, a numerical calculation model for buffering and load reduction during high-speed water entry of navigational bodies was established. Through numerical simulations, an in-depth study was conducted on the load reduction performance of buffer foams with different open-cell patterns. The results indicate that open-cell buffer foam exhibits significant advantages in dispersing the impact force and absorbing impact energy during water entry of navigational bodies, offering better buffering effects. Simultaneously, the buffer head cover experiences local progressive fragmentation upon water entry. The deformation and rupture of the outer wall surface of the buffer head cover at the connector between the buffer shell and the navigational body are caused by the stress concentration distribution generated during water impact. When the open-cell foam contacts the water surface, the front part enters the collapse stage, absorbing a large amount of energy and undergoing plastic deformation, resulting in a reduction of pores. This stage is the primary energy absorption phase for the buffer foam. In comparison, closed-cell foam exhibits poorer load reduction performance. Therefore, the adoption of open-cell foam represents a superior solution for buffering and load reduction during high-speed water entry of navigational bodies.
, Available online , doi: 10.11883/bzycj-2024-0132
Abstract:
The sheet explosive loading technology is a crucial method for evaluating the dynamic response of the space structure under the X-ray radiation in laboratory. To achieve the ultra-low specific impulse explosive loading required for the structural assessment of new space vehicles, a sheet explosive has been developed, primarily composed of PETN as the main explosive and polymer rubber as the binder. The mass fraction of PETN is 90%–92%, the thickness range is 0.15–0.20 mm, the density range is 1.63–1.68 g/cm3, and the explosive velocity range is 7.44–7.71 km/s. To verify the high-impact initiation sensitivity of the sheet explosive, three rounds of verification experiments were designed based on the blast marketing method. In the experiment, the sheet explosive was directly applied to the effect plate or a certain air gap reserved between the sheet explosive and the effect plate. The detonation of the explosive is confirmed by examining the explosive marks left on the effect plate post-explosion. The experimental results show that: the sheet explosive with a thickness of 0.15–0.50 mm can be reliably detonated by a mild detonating fuse with a charge line density of 0.2 g/m, and the explosive strips with a thickness of 0.20–0.50 mm can reliably transmit detonation. The specific impulse characteristic of the sheet explosive with different diameters and thicknesses was measured and studied by the impact pendulum measurement device. Combined with theoretical analysis, The specific impulse calculation model of sheet explosive was used to perform polynomial fitting on the specific impulse direct measurement data of sheet explosives with thicknesses of 0.20, 0.30, 0.40 and 0.50 mm, respectively. The specific impulse values of sheet explosives with four thicknesses were linearly fitted. The results show that the specific impulse of the sheet explosive is proportional to the thickness and the ratio coefficient is 3 418.56 Pa·s/mm. The development of ultra-thin sheet explosive with a thickness of 0.2 mm and a specific impulse of about 680 Pa·s has been successfully realized.
The sheet explosive loading technology is a crucial method for evaluating the dynamic response of the space structure under the X-ray radiation in laboratory. To achieve the ultra-low specific impulse explosive loading required for the structural assessment of new space vehicles, a sheet explosive has been developed, primarily composed of PETN as the main explosive and polymer rubber as the binder. The mass fraction of PETN is 90%–92%, the thickness range is 0.15–0.20 mm, the density range is 1.63–1.68 g/cm3, and the explosive velocity range is 7.44–7.71 km/s. To verify the high-impact initiation sensitivity of the sheet explosive, three rounds of verification experiments were designed based on the blast marketing method. In the experiment, the sheet explosive was directly applied to the effect plate or a certain air gap reserved between the sheet explosive and the effect plate. The detonation of the explosive is confirmed by examining the explosive marks left on the effect plate post-explosion. The experimental results show that: the sheet explosive with a thickness of 0.15–0.50 mm can be reliably detonated by a mild detonating fuse with a charge line density of 0.2 g/m, and the explosive strips with a thickness of 0.20–0.50 mm can reliably transmit detonation. The specific impulse characteristic of the sheet explosive with different diameters and thicknesses was measured and studied by the impact pendulum measurement device. Combined with theoretical analysis, The specific impulse calculation model of sheet explosive was used to perform polynomial fitting on the specific impulse direct measurement data of sheet explosives with thicknesses of 0.20, 0.30, 0.40 and 0.50 mm, respectively. The specific impulse values of sheet explosives with four thicknesses were linearly fitted. The results show that the specific impulse of the sheet explosive is proportional to the thickness and the ratio coefficient is 3 418.56 Pa·s/mm. The development of ultra-thin sheet explosive with a thickness of 0.2 mm and a specific impulse of about 680 Pa·s has been successfully realized.
, Available online , doi: 10.11883/bzycj-2024-0181
Abstract:
To investigate the stress wave characteristics within concrete targets under hypervelocity impact, a stress wave testing system based on PVDF piezoelectric stress gauges was established. A calibration method for PVDF piezoelectric stress gauges was proposed and conducted. The stress waveforms within concrete targets impacted by kilogram-scale cylindrical 93W tungsten alloy projectiles at hypervelocity were measured, and the generation and propagation mechanisms of stress waves were analyzed using numerical simulation methods. The following conclusions were drawn: (1) The dynamic characteristic parameters of the PVDF piezoelectric stress gauge were calibrated to yield a dynamic sensitivity coefficient of 17.5±0.5 pC/N for the PVDF piezoelectric stress gauge; (2) High signal-to-noise ratio stress waveforms within the concrete target under hypervelocity impact conditions were obtained using the PVDF piezoelectric stress gauge; (3) The stress waveforms obtained from numerical simulation were in good agreement with the experimentally measured waveforms where the maximum deviation of the stress wave peak values between simulation and experimental results is less than 20%, providing a useful tool for mechanism exploration; (4) The characteristics of stress waves within the concrete target and the mechanisms of generation and attenuation were further explored using numerical simulation methods.
To investigate the stress wave characteristics within concrete targets under hypervelocity impact, a stress wave testing system based on PVDF piezoelectric stress gauges was established. A calibration method for PVDF piezoelectric stress gauges was proposed and conducted. The stress waveforms within concrete targets impacted by kilogram-scale cylindrical 93W tungsten alloy projectiles at hypervelocity were measured, and the generation and propagation mechanisms of stress waves were analyzed using numerical simulation methods. The following conclusions were drawn: (1) The dynamic characteristic parameters of the PVDF piezoelectric stress gauge were calibrated to yield a dynamic sensitivity coefficient of 17.5±0.5 pC/N for the PVDF piezoelectric stress gauge; (2) High signal-to-noise ratio stress waveforms within the concrete target under hypervelocity impact conditions were obtained using the PVDF piezoelectric stress gauge; (3) The stress waveforms obtained from numerical simulation were in good agreement with the experimentally measured waveforms where the maximum deviation of the stress wave peak values between simulation and experimental results is less than 20%, providing a useful tool for mechanism exploration; (4) The characteristics of stress waves within the concrete target and the mechanisms of generation and attenuation were further explored using numerical simulation methods.
, Available online , doi: 10.11883/bzycj-2024-0121
Abstract:
The large-scale explosive dispersal and the unconfined detonation of particle-spray-air ternary mixtures are closely related to industrial accidents and military applications. However, most of the existing research focuses on the small-scale experiment in the laboratory. The large-scale explosive dispersal experiment is rare. According to most of the research findings, the explosive power was determined by the detonation state of aerosol. The charge and specific central explosive were the main factors affecting the shape of the aerosol. To study the damaging effect of aerosol, the large-scale dispersed experiment of 125 kg fuel was carried out. The process of aerosol development was observed by high-speed video recording. Variation characteristics of FAE cloud with different canisters and the specific central explosive were studied. The aerosol diameter and height were used to describing the aerosol shape, then they were analyzed under different initial experiment conditions. There were three types of designing canisters, including basic canister, compound canister and strengthen canister. And the main difference between those types of canisters was the radial restraint. The specific quantities of buster charge was adopted the T-shaped charge. The results show that the aerosol formation is reliable through the replication experiments. Because of its strong radial restraint, the compound canister has the advantage in the aerosol diameters. The aerosol diameters of compound canister can reach 25.5 m, compared to strong canister coverage area increased by 13%. Therefore, the compound canister with the specific quantities of buster charge of 0.8% has the best aerosol performance for 125 kg fuel. On this basis, characteristics of the aerosol were further analyzed. Thus the optimal secondary detonation delay time is 240 ms. The aerosol calculating concentration before burst is 64 g/m3 and the chemical equivalent ratio of fuel to oxygen in the air is 0.54.
The large-scale explosive dispersal and the unconfined detonation of particle-spray-air ternary mixtures are closely related to industrial accidents and military applications. However, most of the existing research focuses on the small-scale experiment in the laboratory. The large-scale explosive dispersal experiment is rare. According to most of the research findings, the explosive power was determined by the detonation state of aerosol. The charge and specific central explosive were the main factors affecting the shape of the aerosol. To study the damaging effect of aerosol, the large-scale dispersed experiment of 125 kg fuel was carried out. The process of aerosol development was observed by high-speed video recording. Variation characteristics of FAE cloud with different canisters and the specific central explosive were studied. The aerosol diameter and height were used to describing the aerosol shape, then they were analyzed under different initial experiment conditions. There were three types of designing canisters, including basic canister, compound canister and strengthen canister. And the main difference between those types of canisters was the radial restraint. The specific quantities of buster charge was adopted the T-shaped charge. The results show that the aerosol formation is reliable through the replication experiments. Because of its strong radial restraint, the compound canister has the advantage in the aerosol diameters. The aerosol diameters of compound canister can reach 25.5 m, compared to strong canister coverage area increased by 13%. Therefore, the compound canister with the specific quantities of buster charge of 0.8% has the best aerosol performance for 125 kg fuel. On this basis, characteristics of the aerosol were further analyzed. Thus the optimal secondary detonation delay time is 240 ms. The aerosol calculating concentration before burst is 64 g/m3 and the chemical equivalent ratio of fuel to oxygen in the air is 0.54.
, Available online , doi: 10.11883/bzycj-2024-0359
Abstract:
Oxy-fuel combustion is one of the effective means to reduce greenhouse gases. In order to grasp the combustion characteristics of the clean fuel acetylene in O2/CO2 atmosphere and to investigate the effect of different concentrations of CO2 on the lower flammable limit of acetylene, the lower flammable limit of acetylene was experimentally measured in a 5L cylindrical explosive reaction device. With the increase of CO2 concentration from 14% to 85%, the experimental value of the lower flammable limit of acetylene increased from 2.64% to 3.93%, which was linearly increased in a small range. Compared with hydrocarbon fuels such as ethylene, ethane, and propylene, the lower flammability limit presents alkanes > olefins > alkynes, indicating that alkynes have a larger combustion range and a higher hazard factor. Based on the calculation model of limiting laminar flame velocity method, a prediction model applicable to the lower flammability limit of acetylene was established. Through the verification of experimental data, the average absolute error of this prediction model using the USC II combustion reaction mechanism is at 0.52%, and the model is accurate and reliable. In order to explain the reason for the existence of the lower flammability limit from the perspective of the competition between the temperature rise of the heat generation from fuel consumption and the temperature drop of the heat dissipation from the expansion of the fuel body, the thermodynamic, chemical, and transport effects of CO2 on the lower flammability limit are discussed by using the model and modifying the combustion reaction mechanism of USC II to introduce the virtual substances FCO2, TCO2, and MCO2, and comparing the flammability limits of the three virtual substances as well as those of the five atmospheres of N2 and CO2. The thermodynamic, chemical and transport effects of CO2 on the lower flammability limit were discussed. The results show that the average proportion of thermodynamic effect is 64%, chemical effect is 35% and transportation effect is 1%.
Oxy-fuel combustion is one of the effective means to reduce greenhouse gases. In order to grasp the combustion characteristics of the clean fuel acetylene in O2/CO2 atmosphere and to investigate the effect of different concentrations of CO2 on the lower flammable limit of acetylene, the lower flammable limit of acetylene was experimentally measured in a 5L cylindrical explosive reaction device. With the increase of CO2 concentration from 14% to 85%, the experimental value of the lower flammable limit of acetylene increased from 2.64% to 3.93%, which was linearly increased in a small range. Compared with hydrocarbon fuels such as ethylene, ethane, and propylene, the lower flammability limit presents alkanes > olefins > alkynes, indicating that alkynes have a larger combustion range and a higher hazard factor. Based on the calculation model of limiting laminar flame velocity method, a prediction model applicable to the lower flammability limit of acetylene was established. Through the verification of experimental data, the average absolute error of this prediction model using the USC II combustion reaction mechanism is at 0.52%, and the model is accurate and reliable. In order to explain the reason for the existence of the lower flammability limit from the perspective of the competition between the temperature rise of the heat generation from fuel consumption and the temperature drop of the heat dissipation from the expansion of the fuel body, the thermodynamic, chemical, and transport effects of CO2 on the lower flammability limit are discussed by using the model and modifying the combustion reaction mechanism of USC II to introduce the virtual substances FCO2, TCO2, and MCO2, and comparing the flammability limits of the three virtual substances as well as those of the five atmospheres of N2 and CO2. The thermodynamic, chemical and transport effects of CO2 on the lower flammability limit were discussed. The results show that the average proportion of thermodynamic effect is 64%, chemical effect is 35% and transportation effect is 1%.
, Available online , doi: 10.11883/bzycj-2024-0163
Abstract:
To discuss the flying gap effect of the metal flyer on the initiating behavior for TATB-based explosives, initiation experiments for PBX-6 and PBXL-7 were performed. The target velocity and shape of the flyer to explosives were obtained using a 1 550 nm photon Doppler velocimetry. The running distance to detonation (RDTD) of explosive samples was gained by a Terahertz-wave Doppler interferometric velocimetry at the center point. The relationship between the experiment data captured above was analyzed. It reveals that the running distance to detonation of the TATB-based explosive changes non-monotonously with the increase of gap. With the gap increasing from zero to 20 mm, there are five stages. The initial stage is named S0, the flyer velocity declining stage is named S1, the free running stage of spallation is named S2, the remerging stage when the main flyer catches up and remerging with its spallation layer is named S3, and the stage when the main flyer and spallation are united as one is named S4. The RDTD for the TATB-based explosive is the smallest when the flyer velocity comes to stage S4, the RDTD at stage S0 is the next, and the RDTD at the velocity declining stage S1 and remerging stage S3 are the worst together. These experiment results suggest that the initiating performance of TATB-based explosives impacted by the flyer is not always better than the gap layer results. The initiation mechanism of explosives by flyer under different gaps is probably related to the target velocity together with the structure of the flyer. The simplex target velocity rising of flyer can’t always make the running distance to detonation of TATB-based explosives shorter. The initiation mechanism of TATB-based explosives impacted by flyer is more complex than the gap layer, requiring much experiment data and numerical simulation for further discussion.
To discuss the flying gap effect of the metal flyer on the initiating behavior for TATB-based explosives, initiation experiments for PBX-6 and PBXL-7 were performed. The target velocity and shape of the flyer to explosives were obtained using a 1 550 nm photon Doppler velocimetry. The running distance to detonation (RDTD) of explosive samples was gained by a Terahertz-wave Doppler interferometric velocimetry at the center point. The relationship between the experiment data captured above was analyzed. It reveals that the running distance to detonation of the TATB-based explosive changes non-monotonously with the increase of gap. With the gap increasing from zero to 20 mm, there are five stages. The initial stage is named S0, the flyer velocity declining stage is named S1, the free running stage of spallation is named S2, the remerging stage when the main flyer catches up and remerging with its spallation layer is named S3, and the stage when the main flyer and spallation are united as one is named S4. The RDTD for the TATB-based explosive is the smallest when the flyer velocity comes to stage S4, the RDTD at stage S0 is the next, and the RDTD at the velocity declining stage S1 and remerging stage S3 are the worst together. These experiment results suggest that the initiating performance of TATB-based explosives impacted by the flyer is not always better than the gap layer results. The initiation mechanism of explosives by flyer under different gaps is probably related to the target velocity together with the structure of the flyer. The simplex target velocity rising of flyer can’t always make the running distance to detonation of TATB-based explosives shorter. The initiation mechanism of TATB-based explosives impacted by flyer is more complex than the gap layer, requiring much experiment data and numerical simulation for further discussion.
, Available online , doi: 10.11883/bzycj-2024-0112
Abstract:
Research on blasting craters is one of the most fundamental studies in blasting engineering. To elucidate the formation process and mechanisms of blasting craters and to investigate the roles of blasting stress waves and explosion gases in rock fragmentation during this process, a blasting load model was developed. This model is based on a double-exponential explosive load function and the equation of state for explosion gas pressure, incorporating the dynamic-static sequential effects of blasting. By combining the distinct loading characteristics of blasting stress waves and explosion gases, a discrete element numerical model of the blasting crater was established to simulate the development of fractures, rock fragmentation, and ejection of blasted rock. Simulations were performed both with and without the inclusion of explosion gas loading to explore the respective contributions of blasting stress waves and explosion gases to crater formation. The results show that the blasting crater dimensions simulated with the dynamic-static sequential loading model align closely with field test results, accurately capturing the formation and evolution of fractures in the blasting zone and the ejection behavior of fragmented rock. The high loading rate of blasting stress waves is the primary cause of ring-shaped microfractures in the near-field region of the explosion source, which can also induce reflective tensile damage, forming “slice drop” failure at free surfaces. Explosion gases, on the other hand, are the main drivers of radially extensive fractures in the far-field region of the explosion source and propel fragmented rock outward at a high velocity. Explosion gases exhibit not only quasi-static effects but also dynamic effects, extending the duration of blasting vibrations and amplifying the peak vibration velocity. The development of fractures during crater formation can be broadly categorized into three stages: stress wave-induced fracturing, explosion gas-induced fracturing, and deformation energy release-induced fracturing.
Research on blasting craters is one of the most fundamental studies in blasting engineering. To elucidate the formation process and mechanisms of blasting craters and to investigate the roles of blasting stress waves and explosion gases in rock fragmentation during this process, a blasting load model was developed. This model is based on a double-exponential explosive load function and the equation of state for explosion gas pressure, incorporating the dynamic-static sequential effects of blasting. By combining the distinct loading characteristics of blasting stress waves and explosion gases, a discrete element numerical model of the blasting crater was established to simulate the development of fractures, rock fragmentation, and ejection of blasted rock. Simulations were performed both with and without the inclusion of explosion gas loading to explore the respective contributions of blasting stress waves and explosion gases to crater formation. The results show that the blasting crater dimensions simulated with the dynamic-static sequential loading model align closely with field test results, accurately capturing the formation and evolution of fractures in the blasting zone and the ejection behavior of fragmented rock. The high loading rate of blasting stress waves is the primary cause of ring-shaped microfractures in the near-field region of the explosion source, which can also induce reflective tensile damage, forming “slice drop” failure at free surfaces. Explosion gases, on the other hand, are the main drivers of radially extensive fractures in the far-field region of the explosion source and propel fragmented rock outward at a high velocity. Explosion gases exhibit not only quasi-static effects but also dynamic effects, extending the duration of blasting vibrations and amplifying the peak vibration velocity. The development of fractures during crater formation can be broadly categorized into three stages: stress wave-induced fracturing, explosion gas-induced fracturing, and deformation energy release-induced fracturing.
, Available online , doi: 10.11883/bzycj-2024-0117
Abstract:
In this paper, the microspheres in flying-ash are used as sensitizer and inert additive to prepare the low detonation velocity emulsion explosives. The detonation velocity and the parameters of explosive shock wave in the air of emulsion explosives were measured by the probe method, the lead column compression method and the air explosion method, respectively. The safety of emulsion explosives was tested by the storage life experiment and thermal analysis experiment. The experimental results show that the detonation velocity, the brisance, the peak pressure, the positive impulse and the positive pressure action time of shock wave of emulsion explosives increased first and then decreased with the increase of the content of flying-ash microspheres. When the content of flying-ash microspheres was 15%, the detonation performance of emulsion explosive was the best, and when the content of flying-ash microspheres was 45% , the detonation velocity of the explosive decreased obviously. Meanwhile, the detonation velocity ranged from 2191 to 2312 m/s, which can satisfy the condition of using explosive for explosive welding. In addition, it is found that the detonation performance of emulsion explosives with D50=79 μm flying-ash microspheres was higher than those of flying-ash microspheres with D50=116 and 47 μm. The storage life and thermal analysis results indicate that the storage life of low detonation velocity emulsion explosives with flying-ash microspheres is significantly better than that of traditional low detonation velocity emulsion explosive with clay particles, the activation energy of thermal decomposition of the emulsion explosive with 15% flying-ash microspheres was only 0.3% higher than that of emulsion matrix. The results also show that the addition of flying-ash microspheres has no obvious effect on the thermal stability of the emulsion matrix. The research results have important reference value for green resource disposal of coal-based solid waste and formulation design of the low detonation velocity emulsion explosive.
In this paper, the microspheres in flying-ash are used as sensitizer and inert additive to prepare the low detonation velocity emulsion explosives. The detonation velocity and the parameters of explosive shock wave in the air of emulsion explosives were measured by the probe method, the lead column compression method and the air explosion method, respectively. The safety of emulsion explosives was tested by the storage life experiment and thermal analysis experiment. The experimental results show that the detonation velocity, the brisance, the peak pressure, the positive impulse and the positive pressure action time of shock wave of emulsion explosives increased first and then decreased with the increase of the content of flying-ash microspheres. When the content of flying-ash microspheres was 15%, the detonation performance of emulsion explosive was the best, and when the content of flying-ash microspheres was 45% , the detonation velocity of the explosive decreased obviously. Meanwhile, the detonation velocity ranged from 2191 to 2312 m/s, which can satisfy the condition of using explosive for explosive welding. In addition, it is found that the detonation performance of emulsion explosives with D50=79 μm flying-ash microspheres was higher than those of flying-ash microspheres with D50=116 and 47 μm. The storage life and thermal analysis results indicate that the storage life of low detonation velocity emulsion explosives with flying-ash microspheres is significantly better than that of traditional low detonation velocity emulsion explosive with clay particles, the activation energy of thermal decomposition of the emulsion explosive with 15% flying-ash microspheres was only 0.3% higher than that of emulsion matrix. The results also show that the addition of flying-ash microspheres has no obvious effect on the thermal stability of the emulsion matrix. The research results have important reference value for green resource disposal of coal-based solid waste and formulation design of the low detonation velocity emulsion explosive.
, Available online , doi: 10.11883/bzycj-2024-0393
Abstract:
Traumatic brain injury (TBI) is the neurological disorder with the highest incidence and prevalence, and poses a huge public health burden for the whole society. An in-depth study of the biomechanics of TBI can help to improve the effectiveness of head protection, develop rapid assessment techniques and take timely interventions, thus reducing the risk of injury deterioration. As a numerical analysis tool, the finite element head model (FEHM) is able to simulate the dynamic response of the head during impact, including the spatial and temporal distribution of stress-strain in brain tissues, and the change of intracranial pressure, which provides an important basis for understanding the mechanical mechanism of traumatic brain injury (TBI). This paper summarizes in detail the current status and development of mainstream finite element models of the human head at home and abroad, traces the development of the models, summarises the characteristics of the models and introduces the research progress of TBI mechanisms based on finite element models. The summary and sorting out of related research will be helpful for the development of new FEHMs and provide theoretical guidance and technical support for the risk assessment of traumatic brain injury and the design of protective equipment.
Traumatic brain injury (TBI) is the neurological disorder with the highest incidence and prevalence, and poses a huge public health burden for the whole society. An in-depth study of the biomechanics of TBI can help to improve the effectiveness of head protection, develop rapid assessment techniques and take timely interventions, thus reducing the risk of injury deterioration. As a numerical analysis tool, the finite element head model (FEHM) is able to simulate the dynamic response of the head during impact, including the spatial and temporal distribution of stress-strain in brain tissues, and the change of intracranial pressure, which provides an important basis for understanding the mechanical mechanism of traumatic brain injury (TBI). This paper summarizes in detail the current status and development of mainstream finite element models of the human head at home and abroad, traces the development of the models, summarises the characteristics of the models and introduces the research progress of TBI mechanisms based on finite element models. The summary and sorting out of related research will be helpful for the development of new FEHMs and provide theoretical guidance and technical support for the risk assessment of traumatic brain injury and the design of protective equipment.
, Available online , doi: 10.11883/bzycj-2024-0191
Abstract:
For the estimation of blast loading in complex structures, traditional numerical simulation methods were computationally intensive whereas rapid estimation methods based on neural networks can only provide estimates at local points without providing confidence intervals for the predicted results. To achieve fast and reliable estimation of the blast loading in complex structures, Bayesian theory was combined with deep learning to develop a Bayesian deep learning approach for rapid estimation of blast loading in complex structures. The approach initially utilized open-source numerical simulation software to generate a dataset of blast loading in complex structures, encompassing a wide range of parameters such as explosion equivalents, locations, and velocities. During this process, mesh sizes that balanced computational accuracy and speed were determined through mesh sensitivity analysis and the verification of the numerical simulation accuracy. Then, the deep learning model was extended into a Bayesian deep learning model based on Bayesian theory. By introducing probability distributions over the weights of the neural network, the model parameters were treated as random variables. Variational Bayesian inference was then employed to efficiently train the model, ensuring the accuracy of rapid blast loading estimation while also equipping the model with the ability to quantify uncertainty. Finally, metrics such as mean absolute percentage error (MAPE), normalized mean prediction interval width (NMPIW) and prediction interval coverage probability (PICP) were adopted to quantitatively assess the model's estimated accuracy and the precision of the uncertainty quantification. Additionally, an error decomposition of the estimation results was conducted to analyze model’s performance based on target parameters and scaled distance. The results indicate that the proposed method achieved an estimation error of 12.2% on the test set, with a confidence interval covering over 81.6% of true values, and less than 20 milliseconds of the estimation time for a single sample point. This method provides a novel approach for fast and accurate estimation of blast loading in complex structures with sufficient confidence for the estimation results.
For the estimation of blast loading in complex structures, traditional numerical simulation methods were computationally intensive whereas rapid estimation methods based on neural networks can only provide estimates at local points without providing confidence intervals for the predicted results. To achieve fast and reliable estimation of the blast loading in complex structures, Bayesian theory was combined with deep learning to develop a Bayesian deep learning approach for rapid estimation of blast loading in complex structures. The approach initially utilized open-source numerical simulation software to generate a dataset of blast loading in complex structures, encompassing a wide range of parameters such as explosion equivalents, locations, and velocities. During this process, mesh sizes that balanced computational accuracy and speed were determined through mesh sensitivity analysis and the verification of the numerical simulation accuracy. Then, the deep learning model was extended into a Bayesian deep learning model based on Bayesian theory. By introducing probability distributions over the weights of the neural network, the model parameters were treated as random variables. Variational Bayesian inference was then employed to efficiently train the model, ensuring the accuracy of rapid blast loading estimation while also equipping the model with the ability to quantify uncertainty. Finally, metrics such as mean absolute percentage error (MAPE), normalized mean prediction interval width (NMPIW) and prediction interval coverage probability (PICP) were adopted to quantitatively assess the model's estimated accuracy and the precision of the uncertainty quantification. Additionally, an error decomposition of the estimation results was conducted to analyze model’s performance based on target parameters and scaled distance. The results indicate that the proposed method achieved an estimation error of 12.2% on the test set, with a confidence interval covering over 81.6% of true values, and less than 20 milliseconds of the estimation time for a single sample point. This method provides a novel approach for fast and accurate estimation of blast loading in complex structures with sufficient confidence for the estimation results.
, Available online , doi: 10.11883/bzycj-2024-0248
Abstract:
The penetration depth of the earth-penetrating projectile is a basic problem in the design of protection engineering. Scaled testing is an important method to study the penetration law. The size effect between the model test results and the prototype is a problem that must be solved to establish the calculation method of penetration using scaled tests. In this study, the stress and strain state evolution of the rock-like target medium subjected to the penetration of earth-penetrating projectiles and the penetration resistance function of the projectiles were derived using cavity expansion theory. The formula for the caliber coefficient characterizing the size effect was obtained, and a simplified analysis of the nose shape coefficient and caliber coefficient was conducted using curve fitting and Taylor expansion within the penetration velocity range of the conventional earth-penetrating weapons. A practical calculation formula for the penetration depth of conventional earth-penetrating weapons into rock-like media was proposed, whose coefficients can be directly determined by parameters of target and projectiles. The results show that the main influencing factor of the projectile’s penetration resistance is the impedance of the target. The source of the size effect is originated from the fact that the ranges of the target damage zones do not satisfy the geometric similarity law. The nose shape coefficient can be simplified into a linear function of the projectile’s aspect ratio, and the nose shape coefficient of a flat-nosed projectile is 0.57. The caliber coefficient of the projectile is determined by the ratio of the cavity radius of the penetration to the radius of the fracture zone and can be taken as 1.2−1.4 for conventional earth-penetrating weapons. The theoretical calculation formula of penetration depth is in good agreement with experimental results, and thus, has high reliability.
The penetration depth of the earth-penetrating projectile is a basic problem in the design of protection engineering. Scaled testing is an important method to study the penetration law. The size effect between the model test results and the prototype is a problem that must be solved to establish the calculation method of penetration using scaled tests. In this study, the stress and strain state evolution of the rock-like target medium subjected to the penetration of earth-penetrating projectiles and the penetration resistance function of the projectiles were derived using cavity expansion theory. The formula for the caliber coefficient characterizing the size effect was obtained, and a simplified analysis of the nose shape coefficient and caliber coefficient was conducted using curve fitting and Taylor expansion within the penetration velocity range of the conventional earth-penetrating weapons. A practical calculation formula for the penetration depth of conventional earth-penetrating weapons into rock-like media was proposed, whose coefficients can be directly determined by parameters of target and projectiles. The results show that the main influencing factor of the projectile’s penetration resistance is the impedance of the target. The source of the size effect is originated from the fact that the ranges of the target damage zones do not satisfy the geometric similarity law. The nose shape coefficient can be simplified into a linear function of the projectile’s aspect ratio, and the nose shape coefficient of a flat-nosed projectile is 0.57. The caliber coefficient of the projectile is determined by the ratio of the cavity radius of the penetration to the radius of the fracture zone and can be taken as 1.2−1.4 for conventional earth-penetrating weapons. The theoretical calculation formula of penetration depth is in good agreement with experimental results, and thus, has high reliability.
, Available online , doi: 10.11883/bzycj-2024-0203
Abstract:
The equation of state for the detonation products of explosives is one of the foundations in explosion physics. JWL equation of state has been widely applied to study the properties of various explosives. In order to obtain the equation of state of the detonation products, an underwater explosion method was used to study JWL equation of state for the detonation of RDX. It considered the explosion bubble expansion process based on the conservation of energy including Es0 (initial shock wave energy), Ept (potential energy of water), Ec (kinetic energy of water) and Er (energy loss by bubble expansion), which are related to the underwater explosion bubble radius (R-t) and shock wave front (Rs-t) measured in the underwater explosion experiments as functions of time. Based on the experimental results and using the same method to process the experimental data in cylinder experiment, the time functions of explosion bubble expansion radius and variation of shock wave front position were fitted and the parameters of the JWL equation of state for RDX detonation products were obtained. In order to analyze the accuracy of the parameters of the JWL equation of state obtained by the underwater explosion method, the time history of the underwater explosions bubble pulsating pressure wave was calculated using the bubble dynamics equation. It shows that the calculation results agree well with the bubble expansion radius and bubble pulsation period determined using the underwater explosion experiments in a pool. The calculated bubble radius obtained by the proposed measurement method has a smaller deviation from that obtained by the cylinder experimental value, especially in the low-pressure stage compare with the JWL state parameters obtained from cylinder method. This method provides a testing approach for the equation of state of detonation products with low cost, reduced size limitations and a wide pressure range.
The equation of state for the detonation products of explosives is one of the foundations in explosion physics. JWL equation of state has been widely applied to study the properties of various explosives. In order to obtain the equation of state of the detonation products, an underwater explosion method was used to study JWL equation of state for the detonation of RDX. It considered the explosion bubble expansion process based on the conservation of energy including Es0 (initial shock wave energy), Ept (potential energy of water), Ec (kinetic energy of water) and Er (energy loss by bubble expansion), which are related to the underwater explosion bubble radius (R-t) and shock wave front (Rs-t) measured in the underwater explosion experiments as functions of time. Based on the experimental results and using the same method to process the experimental data in cylinder experiment, the time functions of explosion bubble expansion radius and variation of shock wave front position were fitted and the parameters of the JWL equation of state for RDX detonation products were obtained. In order to analyze the accuracy of the parameters of the JWL equation of state obtained by the underwater explosion method, the time history of the underwater explosions bubble pulsating pressure wave was calculated using the bubble dynamics equation. It shows that the calculation results agree well with the bubble expansion radius and bubble pulsation period determined using the underwater explosion experiments in a pool. The calculated bubble radius obtained by the proposed measurement method has a smaller deviation from that obtained by the cylinder experimental value, especially in the low-pressure stage compare with the JWL state parameters obtained from cylinder method. This method provides a testing approach for the equation of state of detonation products with low cost, reduced size limitations and a wide pressure range.
, Available online , doi: 10.11883/bzycj-2024-0239
Abstract:
In order to explore the underwater anti-explosion protection effect of steel fiber reinforced cellular concrete materials, the damage process of reinforced concrete slabs under underwater contact explosion was reproduced by the coupling method of smoothed particle hydrodynamics and finite element method (SPH-FEM). The validity of the simulation method was verified by comparing with the experimental results. On this basis, a three-dimensional refined simulation model of water-explosive-protective layer-reinforced concrete slab was established by the SPH-FEM coupling method. The damage evolution process, failure mode and failure mechanism of protective layer of steel fiber reinforced cellular concrete (SAP10S5, SAP10S10, SAP10S15 and SAP10S20) with different fiber ratios and explosive mass were studied, and the prediction curve of damage level of reinforced concrete slabs was constructed. The results show that the numerical simulation results are in good agreement with the experimental results, which verifies the effectiveness of the simulation method. Under the underwater contact explosion, the addition of protective layer of steel fiber reinforced cellular concrete can effectively reduce the damage degree of protected reinforced concrete (RC) slab, and its influence on the damage degree of RC slab decreases first and then increases with the increase of steel fiber volume fraction in the protective layer. Among them, the anti-explosion protection effect of protective layer of SAP10S15 ratio is the best. When the amount of explosive increases within a certain range, the protective layer of SAP10S15 ratio can still maintain a high proportion of energy consumption and effectively reduce the damage degree of the RC plate. When the amount of explosive is 0.25 kg, the damage index of RC slabs strengthened with protective layer of SAP10S15 has the most obvious attenuation compared with the unprotected scheme, which is 42.5%, and the damage level is reduced from serious damage to moderate damage. The prediction curve of constructed damage level can directly evaluate the influence of steel fiber volume fraction/explosive amount on the damage degree of RC panel. The above research results can provide reference for the anti-explosion protection design of wading concrete structures.
In order to explore the underwater anti-explosion protection effect of steel fiber reinforced cellular concrete materials, the damage process of reinforced concrete slabs under underwater contact explosion was reproduced by the coupling method of smoothed particle hydrodynamics and finite element method (SPH-FEM). The validity of the simulation method was verified by comparing with the experimental results. On this basis, a three-dimensional refined simulation model of water-explosive-protective layer-reinforced concrete slab was established by the SPH-FEM coupling method. The damage evolution process, failure mode and failure mechanism of protective layer of steel fiber reinforced cellular concrete (SAP10S5, SAP10S10, SAP10S15 and SAP10S20) with different fiber ratios and explosive mass were studied, and the prediction curve of damage level of reinforced concrete slabs was constructed. The results show that the numerical simulation results are in good agreement with the experimental results, which verifies the effectiveness of the simulation method. Under the underwater contact explosion, the addition of protective layer of steel fiber reinforced cellular concrete can effectively reduce the damage degree of protected reinforced concrete (RC) slab, and its influence on the damage degree of RC slab decreases first and then increases with the increase of steel fiber volume fraction in the protective layer. Among them, the anti-explosion protection effect of protective layer of SAP10S15 ratio is the best. When the amount of explosive increases within a certain range, the protective layer of SAP10S15 ratio can still maintain a high proportion of energy consumption and effectively reduce the damage degree of the RC plate. When the amount of explosive is 0.25 kg, the damage index of RC slabs strengthened with protective layer of SAP10S15 has the most obvious attenuation compared with the unprotected scheme, which is 42.5%, and the damage level is reduced from serious damage to moderate damage. The prediction curve of constructed damage level can directly evaluate the influence of steel fiber volume fraction/explosive amount on the damage degree of RC panel. The above research results can provide reference for the anti-explosion protection design of wading concrete structures.
, Available online , doi: 10.11883/bzycj-2024-0279
Abstract:
Prefabricated concrete bursting layer has a very important application prospect in the field of protective engineering attributed to its technical advantages including high construction efficiency and construction quality. However, compared with the monolithic cast-in-situ concrete bursting layer, the impact resistance of the prefabricated concrete bursting layer may be significantly reduced because of the interfaces between the prefabricated blocks and the cast-in-situ part. Therefore, it is important for engineers to reasonably design the prefabricated concrete bursting layer to make its penetration resistance comparable to the monolithic one. To this end, a kind of prefabricated bursting layer connected by wet joints and rebars was proposed in our previous study. In order to apply the prefabricated bursting layer in protective engineering, a series of numerical models were developed to further study its penetration resistance. Firstly, based on the Kong-Fang model and smoothed particle Galerkin (SPG) method, the numerical models were developed and validated against the experimental data of projectile penetrating monolithic and prefabricated targets. Then, the validated numerical models were further used to investigate the influences of prefabricated block size, wet joint width and anchorage length, spacing and diameter of rebars on the penetration resistance of prefabricated targets. Numerical results indicate that increasing the width of wet joints, reducing the spacing between rebars, and extending the anchorage length of rebars can significantly enhance the penetration resistance of prefabricated targets. After clarifying the influences of these parameters, an engineering design method for a prefabricated concrete bursting layer was proposed. Finally, based on this method, two prefabricated high performance concrete targets subjected to two typical types of warhead penetration were designed. Numerical results show that the penetration resistances of two prefabricated targets were comparable to monolithic targets. The proposed engineering design method can provide a reference for engineering applications of prefabricated concrete bursting layers connected by the wet joints and rebars.
Prefabricated concrete bursting layer has a very important application prospect in the field of protective engineering attributed to its technical advantages including high construction efficiency and construction quality. However, compared with the monolithic cast-in-situ concrete bursting layer, the impact resistance of the prefabricated concrete bursting layer may be significantly reduced because of the interfaces between the prefabricated blocks and the cast-in-situ part. Therefore, it is important for engineers to reasonably design the prefabricated concrete bursting layer to make its penetration resistance comparable to the monolithic one. To this end, a kind of prefabricated bursting layer connected by wet joints and rebars was proposed in our previous study. In order to apply the prefabricated bursting layer in protective engineering, a series of numerical models were developed to further study its penetration resistance. Firstly, based on the Kong-Fang model and smoothed particle Galerkin (SPG) method, the numerical models were developed and validated against the experimental data of projectile penetrating monolithic and prefabricated targets. Then, the validated numerical models were further used to investigate the influences of prefabricated block size, wet joint width and anchorage length, spacing and diameter of rebars on the penetration resistance of prefabricated targets. Numerical results indicate that increasing the width of wet joints, reducing the spacing between rebars, and extending the anchorage length of rebars can significantly enhance the penetration resistance of prefabricated targets. After clarifying the influences of these parameters, an engineering design method for a prefabricated concrete bursting layer was proposed. Finally, based on this method, two prefabricated high performance concrete targets subjected to two typical types of warhead penetration were designed. Numerical results show that the penetration resistances of two prefabricated targets were comparable to monolithic targets. The proposed engineering design method can provide a reference for engineering applications of prefabricated concrete bursting layers connected by the wet joints and rebars.
, Available online , doi: 10.11883/bzycj-2024-0207
Abstract:
To investigate the dynamic mechanical characterization of non-pure and non-intact ice materials under impact loads, a modified split Hopkinson pressure bar (SHPB) was used. Rapid loading, rod end cooling and waveform shaping techniques were used to ensure the stability of the ice material and achieve dynamic stress balance during loading. The impact mechanical properties of complete ice (pure water, containing 2.5%, 3.5%, 4.5% salt, containing 2.0%, 4.5%, 8.5% coconut) and spliced ice (splicing interface inclination 30°, 60°) at freezing temperature of −10 ℃ were studied. The strain rate ranges from 150~250 s−1. The failure process was recorded by using the high-speed camera triggered simultaneously with the pressure rod. The correlation between the stress and strain of the sample, along with the failure process, was determined by analyzing the time history curve of sample. The failure mode of the spliced ice sample was analyzed by combining the Mohr-Coulomb strength criterion. The results show that the pure water ice exhibits the highest compressive strength, followed by the ice with coconut shreds, and both of them show a positive strain rate effect. However, the compressive strength of the ice with salt addition decreases significantly due to its loose structure and the strain rate effect is not obvious. The dynamic compressive strength of ice samples added with coconut fiber increases firstly and then decreases with the increase of coconut fiber content. Ice samples with high coconut fiber content are prone to "double peak" phenomenon due to the binding effect of coconut fiber on broken ice with small particle size. The splicing plane affects the crack growth, resulting in lower compressive strength than the intact ice sample, and affects the failure mode as well. The ice with small interface inclination is mainly damaged by interface slip, while the ice with large interface inclination is mainly damaged by whole ice, which is similar to the intact ice. The research results provide theoretical basis and method reference for the dynamic mechanical properties of non-pure and non-intact ice materials under impact loads.
To investigate the dynamic mechanical characterization of non-pure and non-intact ice materials under impact loads, a modified split Hopkinson pressure bar (SHPB) was used. Rapid loading, rod end cooling and waveform shaping techniques were used to ensure the stability of the ice material and achieve dynamic stress balance during loading. The impact mechanical properties of complete ice (pure water, containing 2.5%, 3.5%, 4.5% salt, containing 2.0%, 4.5%, 8.5% coconut) and spliced ice (splicing interface inclination 30°, 60°) at freezing temperature of −10 ℃ were studied. The strain rate ranges from 150~250 s−1. The failure process was recorded by using the high-speed camera triggered simultaneously with the pressure rod. The correlation between the stress and strain of the sample, along with the failure process, was determined by analyzing the time history curve of sample. The failure mode of the spliced ice sample was analyzed by combining the Mohr-Coulomb strength criterion. The results show that the pure water ice exhibits the highest compressive strength, followed by the ice with coconut shreds, and both of them show a positive strain rate effect. However, the compressive strength of the ice with salt addition decreases significantly due to its loose structure and the strain rate effect is not obvious. The dynamic compressive strength of ice samples added with coconut fiber increases firstly and then decreases with the increase of coconut fiber content. Ice samples with high coconut fiber content are prone to "double peak" phenomenon due to the binding effect of coconut fiber on broken ice with small particle size. The splicing plane affects the crack growth, resulting in lower compressive strength than the intact ice sample, and affects the failure mode as well. The ice with small interface inclination is mainly damaged by interface slip, while the ice with large interface inclination is mainly damaged by whole ice, which is similar to the intact ice. The research results provide theoretical basis and method reference for the dynamic mechanical properties of non-pure and non-intact ice materials under impact loads.
, Available online , doi: 10.11883/bzycj-2024-0099
Abstract:
Artificial intelligence/machine learning methods can discover hidden physical patterns in data. By constructing an end-to-end surrogate model between state parameters and dynamic results, many complex engineering problems such as strong coupling, nonlinearity, and multiphysics can be efficiently solved. In the field of highly nonlinear explosion and shock dynamics, a classic detonation driving problem was chosen as the research object. Using numerical simulation results as training data for machine learning surrogate models, and combining forward simulation and reverse design organically. Based on deep neural network technology, an end-to-end surrogate model was constructed between feature position velocity profiles, material dynamic deformation, and engineering factors. And the calculation accuracy of the surrogate model was provided, verifying the ability to invert engineering factors from velocity profiles. The research results indicate that the end-to-end surrogate model has high predictive ability, with relative errors of less than 1% in both velocity profile prediction and engineering factor estimation. It can be applied to the rapid design, high-precision prediction, and agile iteration of highly nonlinear explosion and impact dynamics problems.
Artificial intelligence/machine learning methods can discover hidden physical patterns in data. By constructing an end-to-end surrogate model between state parameters and dynamic results, many complex engineering problems such as strong coupling, nonlinearity, and multiphysics can be efficiently solved. In the field of highly nonlinear explosion and shock dynamics, a classic detonation driving problem was chosen as the research object. Using numerical simulation results as training data for machine learning surrogate models, and combining forward simulation and reverse design organically. Based on deep neural network technology, an end-to-end surrogate model was constructed between feature position velocity profiles, material dynamic deformation, and engineering factors. And the calculation accuracy of the surrogate model was provided, verifying the ability to invert engineering factors from velocity profiles. The research results indicate that the end-to-end surrogate model has high predictive ability, with relative errors of less than 1% in both velocity profile prediction and engineering factor estimation. It can be applied to the rapid design, high-precision prediction, and agile iteration of highly nonlinear explosion and impact dynamics problems.
, Available online , doi: 10.11883/bzycj-2024-0118
Abstract:
With the wide application of new types of ammunition and large-caliber heavy artillery, the non-contact killing mode caused by explosive shock is rapidly replacing the original direct contact killing caused by bullets, fragments, etc., and its killing power, precision, etc., on the combat personnel and equipment is more threatening. This paper will start from the introduction of the typical test environment and methods of explosive shock wave, through an overview of the explosive impact monitoring and sensing technology and explosive impact flow field reconstruction technology analysis to summarize the development trend, and finally the application of portable explosive shock wave sensing system in the foreign military was briefly introduced for the research and development of China's related products to provide reference experience. At present, the most commonly used sensors in explosion impact tests are overpressure sensors and acceleration sensors. Among them, overpressure sensors can be divided into piezoresistive sensor, piezoelectric sensor and fiber-optic sensor; acceleration sensors cloud be divided into piezoresistive acceleration sensors, piezoelectric acceleration sensors, capacitive acceleration sensors, resonance acceleration sensors, electron tunneling acceleration sensors, thermal convection acceleration sensors and optical acceleration sensors (space light acceleration sensors, fiber-optic acceleration sensors). accelerometers, fiber optic accelerometers). The demanding testing environment requires all sensors to have high frequency response , good detection linear characteristics, high signal-to-noise ratio, high sensitivity, good anti-interference performance, and excellent characteristics such as small size and light weight. Shock wave over-pressure sensor toward miniaturization, standardization, integration and intelligent research direction, while vigorously developing new sensing technology research. Based on CFD data and experimental data, artificial intelligence technology is introduced into the explosion wave signal processing and flow field reconstruction; portable explosion impact detection and evaluation system with independent intellectual property rights in China is developed to provide rapid classification and rapid diagnosis and treatment basis for the protection and rescue of special industry practitioners in extreme environments.
With the wide application of new types of ammunition and large-caliber heavy artillery, the non-contact killing mode caused by explosive shock is rapidly replacing the original direct contact killing caused by bullets, fragments, etc., and its killing power, precision, etc., on the combat personnel and equipment is more threatening. This paper will start from the introduction of the typical test environment and methods of explosive shock wave, through an overview of the explosive impact monitoring and sensing technology and explosive impact flow field reconstruction technology analysis to summarize the development trend, and finally the application of portable explosive shock wave sensing system in the foreign military was briefly introduced for the research and development of China's related products to provide reference experience. At present, the most commonly used sensors in explosion impact tests are overpressure sensors and acceleration sensors. Among them, overpressure sensors can be divided into piezoresistive sensor, piezoelectric sensor and fiber-optic sensor; acceleration sensors cloud be divided into piezoresistive acceleration sensors, piezoelectric acceleration sensors, capacitive acceleration sensors, resonance acceleration sensors, electron tunneling acceleration sensors, thermal convection acceleration sensors and optical acceleration sensors (space light acceleration sensors, fiber-optic acceleration sensors). accelerometers, fiber optic accelerometers). The demanding testing environment requires all sensors to have high frequency response , good detection linear characteristics, high signal-to-noise ratio, high sensitivity, good anti-interference performance, and excellent characteristics such as small size and light weight. Shock wave over-pressure sensor toward miniaturization, standardization, integration and intelligent research direction, while vigorously developing new sensing technology research. Based on CFD data and experimental data, artificial intelligence technology is introduced into the explosion wave signal processing and flow field reconstruction; portable explosion impact detection and evaluation system with independent intellectual property rights in China is developed to provide rapid classification and rapid diagnosis and treatment basis for the protection and rescue of special industry practitioners in extreme environments.
, Available online , doi: 10.11883/bzycj-2024-0254
Abstract:
To address the issues of over-excavation at the tunnel arch foot due to the difficulty of forming the perimeter hole blasting and under-excavation at the tunnel face bottom, the damage characteristics of surrounding rock caused by perimeter hole blasting at the arch foot of a horseshoe-shaped tunnel were studied through a combination of theoretical calculations and numerical simulations. On the theoretical level, an in-depth analysis of the stress distribution and crack radius in the arch foot area was conducted based on the principles of blasting mechanics, and the theoretical charge length for the perimeter holes at the arch foot was derived. Building on this, a 3D numerical model of the perimeter holes at the arch foot was established through numerical simulation. During the modeling process, the damage evolution in the surrounding rock during blasting was simulated by introducing an appropriate damage model, and post-blast damage cloud maps were generated. By comparing the damage cloud maps under different conditions, the relationship between blasting effectiveness and parameters such as free surface shape, charge amount, and void deflection angle was analyzed, further revealing the mechanisms by which these parameters influence the blasting formation results, which were validated through field experiments. The research results indicate that the shape of the free surface significantly impacts the extent of surrounding rock damage and the energy utilization efficiency of explosives. A concave free surface results in a smaller damage range compared to a flat free surface, with greater rock confinement, making it difficult for the explosives to effectively fracture the surrounding rock, leading to an energy utilization rate of only 78%. The blasting effectiveness shows a trend of first increasing and then decreasing with the increase in charge amount, with the optimal blasting effectiveness achieved when the linear charge density of the perimeter holes at the arch foot is 0.624. Additionally, by setting voids and adjusting the void deflection angle, the blasting effectiveness of the perimeter holes at the arch foot can be improved. With the optimized blasting parameters, the maximum linear over-excavation at the arch foot was reduced by 53.1%, resulting in a smooth tunnel contour. The research outcomes are engineeringly feasible and provide valuable insights for similar projects.
To address the issues of over-excavation at the tunnel arch foot due to the difficulty of forming the perimeter hole blasting and under-excavation at the tunnel face bottom, the damage characteristics of surrounding rock caused by perimeter hole blasting at the arch foot of a horseshoe-shaped tunnel were studied through a combination of theoretical calculations and numerical simulations. On the theoretical level, an in-depth analysis of the stress distribution and crack radius in the arch foot area was conducted based on the principles of blasting mechanics, and the theoretical charge length for the perimeter holes at the arch foot was derived. Building on this, a 3D numerical model of the perimeter holes at the arch foot was established through numerical simulation. During the modeling process, the damage evolution in the surrounding rock during blasting was simulated by introducing an appropriate damage model, and post-blast damage cloud maps were generated. By comparing the damage cloud maps under different conditions, the relationship between blasting effectiveness and parameters such as free surface shape, charge amount, and void deflection angle was analyzed, further revealing the mechanisms by which these parameters influence the blasting formation results, which were validated through field experiments. The research results indicate that the shape of the free surface significantly impacts the extent of surrounding rock damage and the energy utilization efficiency of explosives. A concave free surface results in a smaller damage range compared to a flat free surface, with greater rock confinement, making it difficult for the explosives to effectively fracture the surrounding rock, leading to an energy utilization rate of only 78%. The blasting effectiveness shows a trend of first increasing and then decreasing with the increase in charge amount, with the optimal blasting effectiveness achieved when the linear charge density of the perimeter holes at the arch foot is 0.624. Additionally, by setting voids and adjusting the void deflection angle, the blasting effectiveness of the perimeter holes at the arch foot can be improved. With the optimized blasting parameters, the maximum linear over-excavation at the arch foot was reduced by 53.1%, resulting in a smooth tunnel contour. The research outcomes are engineeringly feasible and provide valuable insights for similar projects.
, Available online , doi: 10.11883/bzycj-2024-0109
Abstract:
For the launch safety problem of the typical CL-20-based high detonation velocity pressed explosive (C-1, 94.5% CL-20+5.5% additive), the impact response characteristics of the explosive were studied by a large-scale hammer test with 400 kg, which has an impact loading curve similar to the loading characteristics of artillery chamber pressure. Meanwhile, the improved stress rate characterization method, the lower limit method, and the drop height method were used to characterize the drop hammer impact response characteristics of the explosive, and compared with the same kind of pressed explosives JO-8 and JH-2. The improved stress rate characterization method is obtained by improving the data processing process based on existing criteria and weakening the sensitivity of the original criterion formula to oscillatory waveforms. The measured stress curves and characterization parameters of the bottom of the three pressed explosives under different drop heights are obtained by tests, and the impact sensitivity differences of the explosives and influence factors of the impact sensitivity of C-1 are discussed. The results show that the improved stress rate characterization method has certain effectiveness and universality for characterizing the impact sensitivity of explosives. Meanwhile, the improved stress rate characterization method is consistent with other methods in reflecting the law. The drop height of C-1 (H50) is 1.0 m, which is 62.5% and 50.0% of JO-8 and JH-2, respectively; the peak stress of the backseat corresponding to non-detonation (σ0) is 748.90 MPa, which is 85.42% and 64.33% of JO-8 and JH-2, respectively; the safety stress rate parameter (C0) is 344 GPa2/s, which is 45.87% and 39.14% of JO-8 and JH-2, respectively. The molecular structure of CL-20, the mechanical properties, and the thermal-chemical characteristics of the C-1 explosive cylinder are the main factors that make its impact sensitivity higher than JO-8 and JH-2. The research results can provide a reference for the application and design calculation of CL-20-based high detonation velocity pressed explosives in a high overload environment.
For the launch safety problem of the typical CL-20-based high detonation velocity pressed explosive (C-1, 94.5% CL-20+5.5% additive), the impact response characteristics of the explosive were studied by a large-scale hammer test with 400 kg, which has an impact loading curve similar to the loading characteristics of artillery chamber pressure. Meanwhile, the improved stress rate characterization method, the lower limit method, and the drop height method were used to characterize the drop hammer impact response characteristics of the explosive, and compared with the same kind of pressed explosives JO-8 and JH-2. The improved stress rate characterization method is obtained by improving the data processing process based on existing criteria and weakening the sensitivity of the original criterion formula to oscillatory waveforms. The measured stress curves and characterization parameters of the bottom of the three pressed explosives under different drop heights are obtained by tests, and the impact sensitivity differences of the explosives and influence factors of the impact sensitivity of C-1 are discussed. The results show that the improved stress rate characterization method has certain effectiveness and universality for characterizing the impact sensitivity of explosives. Meanwhile, the improved stress rate characterization method is consistent with other methods in reflecting the law. The drop height of C-1 (H50) is 1.0 m, which is 62.5% and 50.0% of JO-8 and JH-2, respectively; the peak stress of the backseat corresponding to non-detonation (σ0) is 748.90 MPa, which is 85.42% and 64.33% of JO-8 and JH-2, respectively; the safety stress rate parameter (C0) is 344 GPa2/s, which is 45.87% and 39.14% of JO-8 and JH-2, respectively. The molecular structure of CL-20, the mechanical properties, and the thermal-chemical characteristics of the C-1 explosive cylinder are the main factors that make its impact sensitivity higher than JO-8 and JH-2. The research results can provide a reference for the application and design calculation of CL-20-based high detonation velocity pressed explosives in a high overload environment.
, Available online , doi: 10.11883/bzycj-2024-0244
Abstract:
Accurately evaluating the continuous effect of penetration and moving charge explosion of earth penetrating weapons is the premise of reliable design of shield on the protective structure. Firstly, a three-stage integrated projectile penetration and moving charge explosion finite element analysis method was proposed based on the technologies of volume filling of explosive and the two-step coupling in penetration and explosion processes. By conducting the numerical simulations of the existing tests of moving charge explosion, penetration and static charge explosion of normal strength concrete (NSC) and ultra-high performance concrete (UHPC) targets, the accuracy of the proposed method in describing the propagation of explosive waves, peak stress, cracking behavior and damage evolution of target under the penetration and explosion was fully verified. Besides, for the scenario of an NSC target against a 105 mm-caliber scaled projectile, the differences of target damage predicted by the proposed finite element analysis method and traditional penetration and static charge explosion method were compared. Meanwhile, the superimposed effect of the penetration and explosion stress field and the influence of shell constraint and fracture fragment were analyzed. Based on the damage characteristics of targets at different detonation time instants of explosive, the most unfavorable detonation time instant of the warhead was determined. Finally, numerical simulations were conducted for the scenarios of three prototype warheads: SDB, WDU-43/B and BLU-109/B. The destructive depths of NSC and UHPC shields subjected to the penetration and moving charge explosion loadings are 1.33, 2.70, 2.35 m and 0.79, 1.76, 1.70 m, respectively. The corresponding scabbing and perforation limits of shields were further given. The results show that the destructive depths, scabbing limits and perforation limits calculated by the finite element analysis method with considering integrated penetration and moving charge explosion are about 5%–30% higher than those calculated by the traditional penetration and static charge explosion method.
Accurately evaluating the continuous effect of penetration and moving charge explosion of earth penetrating weapons is the premise of reliable design of shield on the protective structure. Firstly, a three-stage integrated projectile penetration and moving charge explosion finite element analysis method was proposed based on the technologies of volume filling of explosive and the two-step coupling in penetration and explosion processes. By conducting the numerical simulations of the existing tests of moving charge explosion, penetration and static charge explosion of normal strength concrete (NSC) and ultra-high performance concrete (UHPC) targets, the accuracy of the proposed method in describing the propagation of explosive waves, peak stress, cracking behavior and damage evolution of target under the penetration and explosion was fully verified. Besides, for the scenario of an NSC target against a 105 mm-caliber scaled projectile, the differences of target damage predicted by the proposed finite element analysis method and traditional penetration and static charge explosion method were compared. Meanwhile, the superimposed effect of the penetration and explosion stress field and the influence of shell constraint and fracture fragment were analyzed. Based on the damage characteristics of targets at different detonation time instants of explosive, the most unfavorable detonation time instant of the warhead was determined. Finally, numerical simulations were conducted for the scenarios of three prototype warheads: SDB, WDU-43/B and BLU-109/B. The destructive depths of NSC and UHPC shields subjected to the penetration and moving charge explosion loadings are 1.33, 2.70, 2.35 m and 0.79, 1.76, 1.70 m, respectively. The corresponding scabbing and perforation limits of shields were further given. The results show that the destructive depths, scabbing limits and perforation limits calculated by the finite element analysis method with considering integrated penetration and moving charge explosion are about 5%–30% higher than those calculated by the traditional penetration and static charge explosion method.
, Available online , doi: 10.11883/bzycj-2024-0136
Abstract:
Aiming at the resistance evaluation and engineering design of the rock-rubble concrete shield under the combination of penetration and explosion of earth penetrating weapons, firstly, a finite element modeling method for rock-rubble concrete shields was proposed. By conducting numerical simulations of quasi-static and penetration tests on ultra-high performance concrete (UHPC) targets containing different coarse aggregate types (corundum and basalt), particle sizes (5–15 mm, 5–20 mm, 35–45 mm, and 65–75 mm), and volume fractions (15% and 30%), the reliability of the finite element analysis approach was thoroughly verified. Then, using the semi-infinite rock-rubble concrete shield penetrated by the SDB as a case study, the quantitative influence of type (corundum, basalt, and granite) and dimensionless particle size of rock-rubble (ranging from 0.3 to 2.2 times the projectile diameter) on the penetration depth was analyzed, and optimal design recommendations were determined. Furthermore, the penetration analyses of three typical prototype warheads, i.e., SDB, WDU-43/B, and BLU-109/B, were carried out, and the corresponding penetration resistances of normal strength concrete (NSC), ultra-high performance concrete, and corundum rubble concrete (CRC) shields against the above three warheads were quantitatively compared. Finally, the engineering design method for the CRC shield under the combined effects of penetration and explosion of prototype warheads was proposed. The results indicate that the CRC shield containing the particle size of 1.3 to 1.7 times the projectile diameter exhibits the most excellent penetration resistance. Under the penetration of three types of warheads, the penetration depths in CRC shield were 0.29, 0.78, and 0.68 m, respectively, which are reduced by 61.8%–69.1% and 43.3%–58.0% compared to those in NSC and UHPC shields. Under the combined effects of penetration and explosion, the perforation limits of the CRC shield are 0.55, 1.41, and 1.48 m, while the scabbing limits are 1.11, 2.26, and 3.17 m. Compared with NSC and UHPC shields, the perforation limits are reduced by 58.5%–61.2% and 43.2%–58.1%, respectively, and the scabbing limits are reduced by 61.8%–69.2% and 34.7%–40.5%, respectively.
Aiming at the resistance evaluation and engineering design of the rock-rubble concrete shield under the combination of penetration and explosion of earth penetrating weapons, firstly, a finite element modeling method for rock-rubble concrete shields was proposed. By conducting numerical simulations of quasi-static and penetration tests on ultra-high performance concrete (UHPC) targets containing different coarse aggregate types (corundum and basalt), particle sizes (5–15 mm, 5–20 mm, 35–45 mm, and 65–75 mm), and volume fractions (15% and 30%), the reliability of the finite element analysis approach was thoroughly verified. Then, using the semi-infinite rock-rubble concrete shield penetrated by the SDB as a case study, the quantitative influence of type (corundum, basalt, and granite) and dimensionless particle size of rock-rubble (ranging from 0.3 to 2.2 times the projectile diameter) on the penetration depth was analyzed, and optimal design recommendations were determined. Furthermore, the penetration analyses of three typical prototype warheads, i.e., SDB, WDU-43/B, and BLU-109/B, were carried out, and the corresponding penetration resistances of normal strength concrete (NSC), ultra-high performance concrete, and corundum rubble concrete (CRC) shields against the above three warheads were quantitatively compared. Finally, the engineering design method for the CRC shield under the combined effects of penetration and explosion of prototype warheads was proposed. The results indicate that the CRC shield containing the particle size of 1.3 to 1.7 times the projectile diameter exhibits the most excellent penetration resistance. Under the penetration of three types of warheads, the penetration depths in CRC shield were 0.29, 0.78, and 0.68 m, respectively, which are reduced by 61.8%–69.1% and 43.3%–58.0% compared to those in NSC and UHPC shields. Under the combined effects of penetration and explosion, the perforation limits of the CRC shield are 0.55, 1.41, and 1.48 m, while the scabbing limits are 1.11, 2.26, and 3.17 m. Compared with NSC and UHPC shields, the perforation limits are reduced by 58.5%–61.2% and 43.2%–58.1%, respectively, and the scabbing limits are reduced by 61.8%–69.2% and 34.7%–40.5%, respectively.
, Available online , doi: 10.11883/bzycj-2024-0229
Abstract:
To investigate the influence of the density of crushed ice region on the cavity evolution of a structure, an oblique water-entry experiment of the structure was conducted by high-speed photography technology under different crushed ice cover densities. Moreover, by comparing the water-entry process of the oblique structure in varying densities of crushed ice cover, the influence of crushed ice cover density on cavity evolution during the oblique water-entry process of the structure was obtained. Results indicate that during the cavity expansion, the presence of crushed ice reduces the cavity diameter by impeding the outward expansion of the fluid near the free surface, compared with the ice-free environment. When the cavity closes, crushed ice also impedes the inward contraction of the free surface fluid and prolongs the cavity expansion time. The augmentation in the total volume of air within the cavity results in a decrement of the pressure differential between the inside and outside of the cavity, ultimately leading to a retardation in the cavity closure time. In conditions of lower crushed ice densities, jets point to the interior of the cavity when the cavity collapses. As the coverage density of crushed ice gradually increases, the impedance exerted by the crushed ice on the inward contraction of fluid at the free surface progressively intensifies. This enhanced obstruction from the crushed ice further prolongs the cavity closure time and concurrently augments its length and maximum diameter. Besides, under conditions of higher crushed ice cover densities, the cavity wall is wrinkled by the irregular impact of the fluid. As the submerged depth of the structure increases, the cavity undergoes a deep necking under the influence of ambient pressure. As the coverage density of crushed ice gradually increases, the velocity of the underwater motion of the structure shows a trend of faster decay compared with those in ice-free environments.
To investigate the influence of the density of crushed ice region on the cavity evolution of a structure, an oblique water-entry experiment of the structure was conducted by high-speed photography technology under different crushed ice cover densities. Moreover, by comparing the water-entry process of the oblique structure in varying densities of crushed ice cover, the influence of crushed ice cover density on cavity evolution during the oblique water-entry process of the structure was obtained. Results indicate that during the cavity expansion, the presence of crushed ice reduces the cavity diameter by impeding the outward expansion of the fluid near the free surface, compared with the ice-free environment. When the cavity closes, crushed ice also impedes the inward contraction of the free surface fluid and prolongs the cavity expansion time. The augmentation in the total volume of air within the cavity results in a decrement of the pressure differential between the inside and outside of the cavity, ultimately leading to a retardation in the cavity closure time. In conditions of lower crushed ice densities, jets point to the interior of the cavity when the cavity collapses. As the coverage density of crushed ice gradually increases, the impedance exerted by the crushed ice on the inward contraction of fluid at the free surface progressively intensifies. This enhanced obstruction from the crushed ice further prolongs the cavity closure time and concurrently augments its length and maximum diameter. Besides, under conditions of higher crushed ice cover densities, the cavity wall is wrinkled by the irregular impact of the fluid. As the submerged depth of the structure increases, the cavity undergoes a deep necking under the influence of ambient pressure. As the coverage density of crushed ice gradually increases, the velocity of the underwater motion of the structure shows a trend of faster decay compared with those in ice-free environments.
