2022 Vol. 42, No. 11
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2022, 42(11): 111101.
doi: 10.11883/bzycj-2022-0280
Abstract:
The multilayer protective structure has been widely used in fortifications located above-ground, shallow burial, and tunnel entrances. And this type of structure usually consists of four parts: camouflage layer, shelter layer, sacrifice layer and protection structure. Among them, the sacrifice layer is the main functional unit to reduce the damage effect of strong explosion after penetration. Its action mechanism mainly includes: reducing the proportion of energy propagating to the substructure and extending the propagation path of stress wave by means of the wave impedance mismatch effect; using the layered interface to generate surface waves to reduce the load concentration; absorbing and dissipating shock wave energy through irreversible plastic failure of the matrix material; increasing the structural damping to reduce the vibration effect of the protection structure. Thus, it is of great practical significance to carry out relevant research to improve the overall level of engineering protection. Taking the materials and structure of sacrifice layer as clues, the current status of research on sacrifice layer in multilayer protective structure at home and abroad is systematically sorted out. On this basis, the influence of structural parameters such as the density, wave impedance, thickness, unit shapes and sizes, moisture content and other physical parameters of the sacrifice layer on the protective performance is analyzed. Moreover, several issues that need to be considered in the selection and design of the sacrifice layer are proposed. The perfect sacrifice layer should be economical, reliable, and have a low wave impedance, sufficient static compressive strength and a certain yield strength, which be able to undergo a large plastic deformation under the condition that the yield stress remains essentially constant. Finally, the problems existing in the current research on the sacrifice layer are discussed and prospected, in order to provide a reference for the research and development of the sacrifice layer in the future.
The multilayer protective structure has been widely used in fortifications located above-ground, shallow burial, and tunnel entrances. And this type of structure usually consists of four parts: camouflage layer, shelter layer, sacrifice layer and protection structure. Among them, the sacrifice layer is the main functional unit to reduce the damage effect of strong explosion after penetration. Its action mechanism mainly includes: reducing the proportion of energy propagating to the substructure and extending the propagation path of stress wave by means of the wave impedance mismatch effect; using the layered interface to generate surface waves to reduce the load concentration; absorbing and dissipating shock wave energy through irreversible plastic failure of the matrix material; increasing the structural damping to reduce the vibration effect of the protection structure. Thus, it is of great practical significance to carry out relevant research to improve the overall level of engineering protection. Taking the materials and structure of sacrifice layer as clues, the current status of research on sacrifice layer in multilayer protective structure at home and abroad is systematically sorted out. On this basis, the influence of structural parameters such as the density, wave impedance, thickness, unit shapes and sizes, moisture content and other physical parameters of the sacrifice layer on the protective performance is analyzed. Moreover, several issues that need to be considered in the selection and design of the sacrifice layer are proposed. The perfect sacrifice layer should be economical, reliable, and have a low wave impedance, sufficient static compressive strength and a certain yield strength, which be able to undergo a large plastic deformation under the condition that the yield stress remains essentially constant. Finally, the problems existing in the current research on the sacrifice layer are discussed and prospected, in order to provide a reference for the research and development of the sacrifice layer in the future.
2022, 42(11): 112101.
doi: 10.11883/bzycj-2021-0523
Abstract:
The correlation characteristics of transmitted and reflected waves in the process of impact of the gas-solid interface by the gaseous detonation wave are of great engineering significance. A one-dimensional theoretical model was established to analyze the process of the detonation wave impacting the gas-solid interface. The changes in the pressure and interface velocity on both sides of the interface with different initial pressures after the detonation wave reaching the gas-solid interface were analyzed. The process of the gas-solid interface impacted by the gas-phase detonation wave was numerically simulated. The space-time conservation element and solution element (CE/SE) method and the elementary reaction mechanism were used to simulate the gaseous detonation, and the immersed boundary method (IBM) was used to simulate the fluid-structure interaction. The pressure distribution, rules of velocity change of partial reflection wave of gas, and the waveform and velocity characteristics of stress wave transmitted into solid were analyzed. An experimental device of the impact of the piston by gaseous detonation was built and used for further verification. The results show that after the gaseous detonation wave reaches the gas-solid interface, the elastic wave in the exponential form is transmitted in the solid, and a shock wave is reflected in the gas zone at the interface. The rarefaction wave after the detonation wave intersects with the reflected shock wave, which weakens the reflected shock wave. In this process, the pressure after the reflected shock wave decreases, and the wave velocity becomes faster. The pressure in the intersection area of the original and reflected rarefaction waves remains uniform. Finally, the reflected shock wave becomes stable, and the gas-solid interface forms a constant state. Under different initial pressures of the same mixture, the ratio of maximum pressure to detonation pressure in the process of the impact of the detonation wave remains stable. The theoretical model is consistent with the calculated values and experimental data of related physical quantities at the feature points.
The correlation characteristics of transmitted and reflected waves in the process of impact of the gas-solid interface by the gaseous detonation wave are of great engineering significance. A one-dimensional theoretical model was established to analyze the process of the detonation wave impacting the gas-solid interface. The changes in the pressure and interface velocity on both sides of the interface with different initial pressures after the detonation wave reaching the gas-solid interface were analyzed. The process of the gas-solid interface impacted by the gas-phase detonation wave was numerically simulated. The space-time conservation element and solution element (CE/SE) method and the elementary reaction mechanism were used to simulate the gaseous detonation, and the immersed boundary method (IBM) was used to simulate the fluid-structure interaction. The pressure distribution, rules of velocity change of partial reflection wave of gas, and the waveform and velocity characteristics of stress wave transmitted into solid were analyzed. An experimental device of the impact of the piston by gaseous detonation was built and used for further verification. The results show that after the gaseous detonation wave reaches the gas-solid interface, the elastic wave in the exponential form is transmitted in the solid, and a shock wave is reflected in the gas zone at the interface. The rarefaction wave after the detonation wave intersects with the reflected shock wave, which weakens the reflected shock wave. In this process, the pressure after the reflected shock wave decreases, and the wave velocity becomes faster. The pressure in the intersection area of the original and reflected rarefaction waves remains uniform. Finally, the reflected shock wave becomes stable, and the gas-solid interface forms a constant state. Under different initial pressures of the same mixture, the ratio of maximum pressure to detonation pressure in the process of the impact of the detonation wave remains stable. The theoretical model is consistent with the calculated values and experimental data of related physical quantities at the feature points.
2022, 42(11): 112201.
doi: 10.11883/bzycj-2022-0062
Abstract:
Mild detonating fuse (MDF) explosive separation device is a widely used explosive separation device because of its relatively easy processing, simple structure, low cost and high reliability. In order to further study the action process and mechanism of flexible detonating cord in explosive separation device, an improved coupling algorithm of smooth particle hydrodynamics (SPH) and finite element method (FEM) is proposed in this paper. The new method is not limited to the contact algorithm between SPH method for MDF simulation and FEM method for separation device simulation; the element after complete damage failure is dynamically transformed into SPH particle by the transformation algorithm to continue its participation in the calculation, and the contact algorithm is used to calculate the relationship between the transformed particle and the untransformed finite element. By using this method, the separation process of two kinds of explosive separation structures with ring and plate shape is numerically simulated, and the accuracy and validity of the new method are verified. Then, the deformation and fracture of the separation plate and the spatter process of damage fragments are analyzed, while the stress distribution of the surface of the separation device at different time, the change trend of damage factor and the change trend of von Mises stress are obtained. Moreover, the yield damage velocity of the element and the spatter displacement velocity of fragments under various pecific internal energy of explosives are discussed. The results show that the stress at the weakening groove on the surface of the separation device is the largest, and the elements near the surface yield first; the von Mises stress shows an oscillating upward trend with time; with the increase of the initial specific internal energy of explosive, the yield damage speed of the element and the splash displacement speed of the fragments increase significantly.
Mild detonating fuse (MDF) explosive separation device is a widely used explosive separation device because of its relatively easy processing, simple structure, low cost and high reliability. In order to further study the action process and mechanism of flexible detonating cord in explosive separation device, an improved coupling algorithm of smooth particle hydrodynamics (SPH) and finite element method (FEM) is proposed in this paper. The new method is not limited to the contact algorithm between SPH method for MDF simulation and FEM method for separation device simulation; the element after complete damage failure is dynamically transformed into SPH particle by the transformation algorithm to continue its participation in the calculation, and the contact algorithm is used to calculate the relationship between the transformed particle and the untransformed finite element. By using this method, the separation process of two kinds of explosive separation structures with ring and plate shape is numerically simulated, and the accuracy and validity of the new method are verified. Then, the deformation and fracture of the separation plate and the spatter process of damage fragments are analyzed, while the stress distribution of the surface of the separation device at different time, the change trend of damage factor and the change trend of von Mises stress are obtained. Moreover, the yield damage velocity of the element and the spatter displacement velocity of fragments under various pecific internal energy of explosives are discussed. The results show that the stress at the weakening groove on the surface of the separation device is the largest, and the elements near the surface yield first; the von Mises stress shows an oscillating upward trend with time; with the increase of the initial specific internal energy of explosive, the yield damage speed of the element and the splash displacement speed of the fragments increase significantly.
2022, 42(11): 113101.
doi: 10.11883/bzycj-2022-0146
Abstract:
In order to design a lightweight thin-walled structure with high specific energy absorption and high stiffness, a new type of circular cross-section thin-walled tube with negative Gaussian curvature (negative Gaussian curvature surface circular tube, NGC-C) is proposed and studied in this paper. The finite element analysis method verified by previous experimental data is used to simulate the axial dynamic impact, and various performance indexes such as specific energy absorption and effective crushing length are extracted. The comprehensive performance of the thin wall energy absorption structure with zero Gaussian curvature and positive Gaussian curvature is compared with the complex proportional assessment method (complex proportion assessment, COPRAS). The Latin hypercube sampling method is used to extract 20 sample points from the design space and obtain the corresponding performance response values of each sample point, and the polynomial fitting method is used to establish the proxy model. Based on the agent model, the multi-objective optimization design is carried out by using the improved non dominated sorting genetic algorithm (non-dominated sorting genetic algorithm, NSGA-Ⅱ). The results show that the comprehensive performance of the thin-walled circular tube with negative Gaussian curvature is better than that of all kinds of non-negative Gaussian curvature thin-walled energy absorbing structures, especially in that it has the minimum effective crushing length. The goodness of fit of the established proxy models is higher than 98%, which can better reflect the relationship between structural design variables and performance response. After optimization, the specific energy absorption of thin-walled circular tubes with negative Gaussian curvature is increased by 16.47 %, the effective crushing length is reduced by 12.4 %, and the mass is reduced by 20.18 %. To sum up: introducing the negative Gaussian curvature surface shape into the thin-walled tube configuration can reduce the structural quality and improve the crashworthiness of the thin-walled tube, provide a new idea for the design of the thin-walled energy absorbing structure, and can be applied to the energy absorbing scenarios such as the automobile energy absorbing box.
In order to design a lightweight thin-walled structure with high specific energy absorption and high stiffness, a new type of circular cross-section thin-walled tube with negative Gaussian curvature (negative Gaussian curvature surface circular tube, NGC-C) is proposed and studied in this paper. The finite element analysis method verified by previous experimental data is used to simulate the axial dynamic impact, and various performance indexes such as specific energy absorption and effective crushing length are extracted. The comprehensive performance of the thin wall energy absorption structure with zero Gaussian curvature and positive Gaussian curvature is compared with the complex proportional assessment method (complex proportion assessment, COPRAS). The Latin hypercube sampling method is used to extract 20 sample points from the design space and obtain the corresponding performance response values of each sample point, and the polynomial fitting method is used to establish the proxy model. Based on the agent model, the multi-objective optimization design is carried out by using the improved non dominated sorting genetic algorithm (non-dominated sorting genetic algorithm, NSGA-Ⅱ). The results show that the comprehensive performance of the thin-walled circular tube with negative Gaussian curvature is better than that of all kinds of non-negative Gaussian curvature thin-walled energy absorbing structures, especially in that it has the minimum effective crushing length. The goodness of fit of the established proxy models is higher than 98%, which can better reflect the relationship between structural design variables and performance response. After optimization, the specific energy absorption of thin-walled circular tubes with negative Gaussian curvature is increased by 16.47 %, the effective crushing length is reduced by 12.4 %, and the mass is reduced by 20.18 %. To sum up: introducing the negative Gaussian curvature surface shape into the thin-walled tube configuration can reduce the structural quality and improve the crashworthiness of the thin-walled tube, provide a new idea for the design of the thin-walled energy absorbing structure, and can be applied to the energy absorbing scenarios such as the automobile energy absorbing box.
2022, 42(11): 113201.
doi: 10.11883/bzycj-2021-0411
Abstract:
To study the protective effect of a typical combat helmet against traumatic brain injury induced by blast wave, an anti-explosion test was first carried out, in which 50 g TNT was used to produce blast wave acting on a head model with or without helmet protection located at 1m away from explosion position. Pressure sensors were installed on the forehead, cranial, parietal and postcranial of the head model, while the front end of each sensor was in touch with the surface of the head model. Secondly, based on the 3rd Military Medical University’s visualization body slice data set (CVH), a finite element model with the typical head structure was established. The head of the finite element model contained skin, skull, cranial, cerebrospinal fluid, brain tissue, dura mater and pia mater. All the membrane structures are meshed into quadrilateral shell elements, while the remaining parts are all meshed into cubic solid elements. The finite element model of the head is then loaded by the blast wave, and the experimental conditions are simulated by the display dynamic analysis software of LS-DYNA. The validity of the simulation model is verified by the test results. Next, the pressure variation of the blast wave flow field under different working conditions is analyzed by numerical simulation, meanwhile the effect of foam liner on helmet protection capability is studied. The results show that the typical combat helmet can attenuate the frontal air overpressure to 54.5% of that without helmet protection, but it would enhance the air overpressure on the posterior cranial to 2.19 times that without protection, which harms the protection of posterior cranial. The foam padding in helmet suspension can reduce the negative effect of the helmet on cranial posterior protection and improve the protective ability of the helmet against the blast wave. The results also show that the auricle structure amplifies the overpressure of the blast wave to 1.7 times the free field in the same position under the frontal blast wave, which is an important target organ of blast wave action.
To study the protective effect of a typical combat helmet against traumatic brain injury induced by blast wave, an anti-explosion test was first carried out, in which 50 g TNT was used to produce blast wave acting on a head model with or without helmet protection located at 1m away from explosion position. Pressure sensors were installed on the forehead, cranial, parietal and postcranial of the head model, while the front end of each sensor was in touch with the surface of the head model. Secondly, based on the 3rd Military Medical University’s visualization body slice data set (CVH), a finite element model with the typical head structure was established. The head of the finite element model contained skin, skull, cranial, cerebrospinal fluid, brain tissue, dura mater and pia mater. All the membrane structures are meshed into quadrilateral shell elements, while the remaining parts are all meshed into cubic solid elements. The finite element model of the head is then loaded by the blast wave, and the experimental conditions are simulated by the display dynamic analysis software of LS-DYNA. The validity of the simulation model is verified by the test results. Next, the pressure variation of the blast wave flow field under different working conditions is analyzed by numerical simulation, meanwhile the effect of foam liner on helmet protection capability is studied. The results show that the typical combat helmet can attenuate the frontal air overpressure to 54.5% of that without helmet protection, but it would enhance the air overpressure on the posterior cranial to 2.19 times that without protection, which harms the protection of posterior cranial. The foam padding in helmet suspension can reduce the negative effect of the helmet on cranial posterior protection and improve the protective ability of the helmet against the blast wave. The results also show that the auricle structure amplifies the overpressure of the blast wave to 1.7 times the free field in the same position under the frontal blast wave, which is an important target organ of blast wave action.
2022, 42(11): 113301.
doi: 10.11883/bzycj-2022-0131
Abstract:
Investigating the mechanical property of concrete structures subjected to impact loading has great significance on the design and evaluation of weapons and protective structures, while appropriate material models can more accurately predict the mechanical behavior and damage mode of concrete structures. In this paper, an improved damage-plasticity material model for concrete was proposed to describe its mechanical response subjected to impact loading. The equation of state, including elastic stage, transition stage and compacted stage, is employed to describe the pressure vs. volume strain relationship. The strain rate effect is considered by combining the radial enhancement method and the semi-empirical equation of dynamic increase factor. A unified hardening/softening function related to the shear damage caused by microcracking and the compacted damage caused by pore collapse are introduced to describe the nonlinear ascend and descend of compressive strain-stress curves in plastic stage, while an exponential function related to the tensile damage is employed to reflect the strain softening behavior under tension. Based on the current extent of damage, the failure strength surface of this improved material model is determined through linearly interpolation between the maximum and yield strength surfaces or the maximum and residual strength surfaces, and the influence of third deviatoric stress invariant on the failure strength surface is considered for describing the reduction of shear strength during the transition from high pressure to low pressure. The fractionally associated flow rule is employed to consider the volumetric dilatancy of concrete materials under confining pressure. Then, the availability and accuracy of this improved material model are verified by the numerical simulations of single element under different loading conditions, and its performance improvement is discussed by comparing with the HJC model, RHT model, Kong-Fang model and empirical equation. Finally, the numerical simulations of projectile perforating reinforced concrete slab are conducted to further validate the feasibility and accuracy of this improved material model under impact loading, from which numerical results indicate that the damage mode and residual velocity predicted by this improved material model are closer to experimental results than HJC model.
Investigating the mechanical property of concrete structures subjected to impact loading has great significance on the design and evaluation of weapons and protective structures, while appropriate material models can more accurately predict the mechanical behavior and damage mode of concrete structures. In this paper, an improved damage-plasticity material model for concrete was proposed to describe its mechanical response subjected to impact loading. The equation of state, including elastic stage, transition stage and compacted stage, is employed to describe the pressure vs. volume strain relationship. The strain rate effect is considered by combining the radial enhancement method and the semi-empirical equation of dynamic increase factor. A unified hardening/softening function related to the shear damage caused by microcracking and the compacted damage caused by pore collapse are introduced to describe the nonlinear ascend and descend of compressive strain-stress curves in plastic stage, while an exponential function related to the tensile damage is employed to reflect the strain softening behavior under tension. Based on the current extent of damage, the failure strength surface of this improved material model is determined through linearly interpolation between the maximum and yield strength surfaces or the maximum and residual strength surfaces, and the influence of third deviatoric stress invariant on the failure strength surface is considered for describing the reduction of shear strength during the transition from high pressure to low pressure. The fractionally associated flow rule is employed to consider the volumetric dilatancy of concrete materials under confining pressure. Then, the availability and accuracy of this improved material model are verified by the numerical simulations of single element under different loading conditions, and its performance improvement is discussed by comparing with the HJC model, RHT model, Kong-Fang model and empirical equation. Finally, the numerical simulations of projectile perforating reinforced concrete slab are conducted to further validate the feasibility and accuracy of this improved material model under impact loading, from which numerical results indicate that the damage mode and residual velocity predicted by this improved material model are closer to experimental results than HJC model.
2022, 42(11): 113302.
doi: 10.11883/bzycj-2021-0435
Abstract:
Experiments of a 30 mm ogive-nose projectile penetration into two layers of concrete targets are carried out to study the characteristics of projectile oblique penetrating a finite thickness concrete target. A high-speed camera was used to record the projectile deflection, velocity, and trajectory in the process of penetration. Vernier caliper and ruler were used to measure the size of the front and rear craters. The parameters of the perforation damage of the concrete slab and the ballistic parameters and trajectories were obtained. The influence law of attack angle and incident angle on the characteristics of perforation damage of concrete slab, attitude deflection during the perforation process, deflection angle after penetration, and ballistic trajectory are analyzed and studied. The experimental results show that there is a phenomenon of secondary deflection in the penetration process. With the increase of incident angle, the phenomenon of secondary deflection is more obvious. The initial attack angle inhibits the occurrence of the phenomenon of secondary deflection. With the increase of the attack angle, the inhibition effect is more significant. With the increase of the incident angle, the deflection angle after penetration increases gradually. Compared with the incident angle, the initial attack angle has a greater influence on the deflection angle behind the concrete target. The initial attack angle promotes the increase of the deflection angle after penetration when the initial attack angle is the same as the incident angle. When the initial attack angle is opposite to the incident, a small initial attack angle can inhibit the increase of the deflection angle after penetration, but a large one becomes the main factor affecting the deflection angle after penetration. The larger the initial attack angle, the larger the deflection angle after penetration.
Experiments of a 30 mm ogive-nose projectile penetration into two layers of concrete targets are carried out to study the characteristics of projectile oblique penetrating a finite thickness concrete target. A high-speed camera was used to record the projectile deflection, velocity, and trajectory in the process of penetration. Vernier caliper and ruler were used to measure the size of the front and rear craters. The parameters of the perforation damage of the concrete slab and the ballistic parameters and trajectories were obtained. The influence law of attack angle and incident angle on the characteristics of perforation damage of concrete slab, attitude deflection during the perforation process, deflection angle after penetration, and ballistic trajectory are analyzed and studied. The experimental results show that there is a phenomenon of secondary deflection in the penetration process. With the increase of incident angle, the phenomenon of secondary deflection is more obvious. The initial attack angle inhibits the occurrence of the phenomenon of secondary deflection. With the increase of the attack angle, the inhibition effect is more significant. With the increase of the incident angle, the deflection angle after penetration increases gradually. Compared with the incident angle, the initial attack angle has a greater influence on the deflection angle behind the concrete target. The initial attack angle promotes the increase of the deflection angle after penetration when the initial attack angle is the same as the incident angle. When the initial attack angle is opposite to the incident, a small initial attack angle can inhibit the increase of the deflection angle after penetration, but a large one becomes the main factor affecting the deflection angle after penetration. The larger the initial attack angle, the larger the deflection angle after penetration.
2022, 42(11): 114101.
doi: 10.11883/bzycj-2021-0477
Abstract:
To study the distribution law of transient explosion temperature field, a high-speed two-dimensional temperature measuring system according to the colorimetric temperature measurement principle was constructed using a high-speed camera, the gray-body radiation principle, Bayer array of the image sensor, and a self-compiled python code. The relationship between the gray value of high-speed camera image and explosion temperature was deduced. And the Bayer filter of the image sensor was used to obtain the intensity information of red, green, and blue light on each pixel, which was calculated through Python code with the edge adaptive interpolation algorithm. A tungsten filament lamp was selected as the temperature source for calibration. The explosion temperature fields of emulsion explosives with different TiH2 powder contents, TiH2 dust, and C2H2 gas were measured by the system. The experimental results show that the addition of TiH2 powders could significantly increase the explosion temperature and fireball duration of emulsion explosives. When the mass content of TiH2 powders in emulsion explosive is 6%, the maximum average temperature of the explosion is 3048 K, a 41.5% increase than that of pure emulsion explosive. In addition, the average flame temperature of the TiH2 dust cloud increases first, then stabilizes, and finally decreases. The mean flame temperature of the 500 g/m3 dust is higher than that of 833 g/m3 dust, with the corresponding maximum mean temperatures of 2231 and 2192 K, respectively. The early flame temperature distribution of the premixed 10% C2H2/90% air was uniform, with the internal temperature slightly lower than the edge temperature. As the flame expands, the flame edge temperature gradually increases, while the average flame temperature begins to decrease, and the maximum average temperature is 2523 K. Compared with the traditional explosion temperature measurement method, the colorimetric pyrometer method can accurately measure the transient explosion temperature in a certain region and obtain the temperature distribution cloud map, which provided a new technical means for studying transient detonation temperature and its influencing factors.
To study the distribution law of transient explosion temperature field, a high-speed two-dimensional temperature measuring system according to the colorimetric temperature measurement principle was constructed using a high-speed camera, the gray-body radiation principle, Bayer array of the image sensor, and a self-compiled python code. The relationship between the gray value of high-speed camera image and explosion temperature was deduced. And the Bayer filter of the image sensor was used to obtain the intensity information of red, green, and blue light on each pixel, which was calculated through Python code with the edge adaptive interpolation algorithm. A tungsten filament lamp was selected as the temperature source for calibration. The explosion temperature fields of emulsion explosives with different TiH2 powder contents, TiH2 dust, and C2H2 gas were measured by the system. The experimental results show that the addition of TiH2 powders could significantly increase the explosion temperature and fireball duration of emulsion explosives. When the mass content of TiH2 powders in emulsion explosive is 6%, the maximum average temperature of the explosion is 3048 K, a 41.5% increase than that of pure emulsion explosive. In addition, the average flame temperature of the TiH2 dust cloud increases first, then stabilizes, and finally decreases. The mean flame temperature of the 500 g/m3 dust is higher than that of 833 g/m3 dust, with the corresponding maximum mean temperatures of 2231 and 2192 K, respectively. The early flame temperature distribution of the premixed 10% C2H2/90% air was uniform, with the internal temperature slightly lower than the edge temperature. As the flame expands, the flame edge temperature gradually increases, while the average flame temperature begins to decrease, and the maximum average temperature is 2523 K. Compared with the traditional explosion temperature measurement method, the colorimetric pyrometer method can accurately measure the transient explosion temperature in a certain region and obtain the temperature distribution cloud map, which provided a new technical means for studying transient detonation temperature and its influencing factors.
2022, 42(11): 114201.
doi: 10.11883/bzycj-2021-0499
Abstract:
The determination of the blast loading on building structures is a prerequisite for the analyses of dynamic response and damage mode, as well as the blast-resistant design and the structural reinforcement. In determining the blast loadings on building structures with the upgraded computing hardware and software, the low-cost and high-safety numerical simulation methods have increasingly attracted the attention of researchers. In order to improve the computing efficiency and accuracy, and to balance the capacities of both the hardware and the software, by adopting the simplified calculation method, i.e., using symmetry (1D-2D-3D extension) and remapping method, the optimized sets of mesh sizes for the numerical simulation of blast wave propagating for a long distance in large complex block are proposed. Firstly, aiming at the typical near-ground explosion scenarios, e.g., car bombs and ammunition depots, the sensitivity analyses of single-size mesh based on incident wave of air and ground explosions at the scaled distances of 0.2−5.0 m/kg1/3 and 0.2−39.0 m/kg1/3 are carried out, respectively. Secondly, considering the limitations of the software and hardware, a set of gradient mesh sizes against the scaled distances is recommended. Furthermore, based on the remapping technique and the suggested gradient mesh sizes, the incident overpressure and impulse of ground explosion are numerically calculated, and an improved method for correcting the peak overpressure with the scaled distances larger than 10.0 m/kg1/3 is proposed, which is then verified by UFC 3-340-02. Finally, the computing accuracy and efficiency of the proposed optimized mesh sizes are verified by comparing the simulated and experimental overpressures and impulses (71 gauges) in the field explosion test on a full-scaled building. Besides, the applicability of the proposed gradient mesh size in simple reflection field is verified, which provides a reference for the subsequent proportional amplification application of gradient mesh size and the simulation application of blast loadings in more complex reflection environment.
The determination of the blast loading on building structures is a prerequisite for the analyses of dynamic response and damage mode, as well as the blast-resistant design and the structural reinforcement. In determining the blast loadings on building structures with the upgraded computing hardware and software, the low-cost and high-safety numerical simulation methods have increasingly attracted the attention of researchers. In order to improve the computing efficiency and accuracy, and to balance the capacities of both the hardware and the software, by adopting the simplified calculation method, i.e., using symmetry (1D-2D-3D extension) and remapping method, the optimized sets of mesh sizes for the numerical simulation of blast wave propagating for a long distance in large complex block are proposed. Firstly, aiming at the typical near-ground explosion scenarios, e.g., car bombs and ammunition depots, the sensitivity analyses of single-size mesh based on incident wave of air and ground explosions at the scaled distances of 0.2−5.0 m/kg1/3 and 0.2−39.0 m/kg1/3 are carried out, respectively. Secondly, considering the limitations of the software and hardware, a set of gradient mesh sizes against the scaled distances is recommended. Furthermore, based on the remapping technique and the suggested gradient mesh sizes, the incident overpressure and impulse of ground explosion are numerically calculated, and an improved method for correcting the peak overpressure with the scaled distances larger than 10.0 m/kg1/3 is proposed, which is then verified by UFC 3-340-02. Finally, the computing accuracy and efficiency of the proposed optimized mesh sizes are verified by comparing the simulated and experimental overpressures and impulses (71 gauges) in the field explosion test on a full-scaled building. Besides, the applicability of the proposed gradient mesh size in simple reflection field is verified, which provides a reference for the subsequent proportional amplification application of gradient mesh size and the simulation application of blast loadings in more complex reflection environment.
2022, 42(11): 115201.
doi: 10.11883/bzycj-2021-0471
Abstract:
In order to explore the influence of double empty hole spacing on the tunnel excavation blasting effect, the range of empty hole spacing is calculated according to the compensation space theory and the theoretical formula of hole deviation. A finite element numerical model of a roadway of Dahongshan Copper Mine is established based on the HJC constitutive model of concrete and multi-material ALE algorithm of LS-DYNA. By adding the *MAT_ADD_EROSION keyword, the damaged rock elements are observed, and the cross-section area of the cavity for cut blasting with large-diameter double empty holes of different spacing is calculated. The results show that when the hole spacing dv is 15, 25, 35, 45 and 55 cm, the cavity section area is 0.1641, 0.2116, 0.2436, 0.1740 and 0.0951 m2, respectively. When the hole spacing increased by 10 cm each from 15 cm to 55 cm, the cavity section area increased by 18.94% and 15.1% and decreased by 17.8% and 45.3%, respectively. Thus, with the increase of empty hole spacing, the section area increases first and then decreases. When dv = 35 cm, it reaches its maximum. This case was tested in the field. The width, height, and area of the cavity section measured by the No. 2 field test are 4.0%, 3.4%, and 4.98%, respectively, smaller than the simulation results. The error between multiple tests and simulation results is within 5%, indicating that the test results are in good agreement with the simulation results, which can provide data reference for the construction of a numerical method for predicting the cavity volume of underground tunnel cutting blasting.
In order to explore the influence of double empty hole spacing on the tunnel excavation blasting effect, the range of empty hole spacing is calculated according to the compensation space theory and the theoretical formula of hole deviation. A finite element numerical model of a roadway of Dahongshan Copper Mine is established based on the HJC constitutive model of concrete and multi-material ALE algorithm of LS-DYNA. By adding the *MAT_ADD_EROSION keyword, the damaged rock elements are observed, and the cross-section area of the cavity for cut blasting with large-diameter double empty holes of different spacing is calculated. The results show that when the hole spacing dv is 15, 25, 35, 45 and 55 cm, the cavity section area is 0.1641, 0.2116, 0.2436, 0.1740 and 0.0951 m2, respectively. When the hole spacing increased by 10 cm each from 15 cm to 55 cm, the cavity section area increased by 18.94% and 15.1% and decreased by 17.8% and 45.3%, respectively. Thus, with the increase of empty hole spacing, the section area increases first and then decreases. When dv = 35 cm, it reaches its maximum. This case was tested in the field. The width, height, and area of the cavity section measured by the No. 2 field test are 4.0%, 3.4%, and 4.98%, respectively, smaller than the simulation results. The error between multiple tests and simulation results is within 5%, indicating that the test results are in good agreement with the simulation results, which can provide data reference for the construction of a numerical method for predicting the cavity volume of underground tunnel cutting blasting.
2022, 42(11): 115202.
doi: 10.11883/bzycj-2021-0276
Abstract:
The bench blasting technology is widely applied in mining, transportation and civil construction excavations, in which numerical simulation plays an increasingly important role in the selection and optimization of parameters. In order to solve the problems of dense mesh and large amount of calculation in solid hole modelling, a one-dimensional axisymmetric explosive model is proposed. In this model, the rock mass to be exploded is divided into larger solid mesh elements, and the blast hole is simplified into a bar and inserted into the designated position of the rock mass to be exploded. The bar is divided into several elements, and the classic Landau model is introduced into the bar elements. The gas expansion pressure is calculated according to the volume of the bar element. By determining the topological relationships between bar nodes and solid elements, if the bar node is located in the interior (3D) or surface (2D) of a solid element, the solid element is used as the force transfer object of the bar node, and the explosive gas pressure on the bar node is applied to the solid element. At the same time, the constitutive model is applied for solid elements according to the specific material, so as to calculate the body strain of the solid element. The bar element only expands radially is assumed, so the cross-sectional change at the bar node can be calculated according to the strain of the solid element body, which is used to calculate the explosive gas pressure at the next moment. Through numerical comparison with the entity bore hole model, when the pressure attenuation index is 1.25, the radial peak particle velocity attenuation law and vibration velocity time history curve obtained by the one-dimensional axisymmetric explosion source model are basically consistent with the entity blast-hole model, which proves the accuracy of the model in blasting simulation. Aiming at the study of dynamic blasting damage characteristics of concrete blocks, the correctness of the model is further verified by comparing with the literature. Based on the blasting technology in Angang open-pit mine, a generalized three-dimensional bench blasting model with 5 rows and 50 bore holes was set up to simulate the damage and failure status in the blasting area. The numerical calculation results show that the tensile failure is the dominant in the blasting area, and the peak particle velocity and its variation with distance at monitor points except the first point near the blasting source is well fitted with the test data, which proves the feasibility of the proposed model in the far-field simulation of three-dimensional bench blasting.
The bench blasting technology is widely applied in mining, transportation and civil construction excavations, in which numerical simulation plays an increasingly important role in the selection and optimization of parameters. In order to solve the problems of dense mesh and large amount of calculation in solid hole modelling, a one-dimensional axisymmetric explosive model is proposed. In this model, the rock mass to be exploded is divided into larger solid mesh elements, and the blast hole is simplified into a bar and inserted into the designated position of the rock mass to be exploded. The bar is divided into several elements, and the classic Landau model is introduced into the bar elements. The gas expansion pressure is calculated according to the volume of the bar element. By determining the topological relationships between bar nodes and solid elements, if the bar node is located in the interior (3D) or surface (2D) of a solid element, the solid element is used as the force transfer object of the bar node, and the explosive gas pressure on the bar node is applied to the solid element. At the same time, the constitutive model is applied for solid elements according to the specific material, so as to calculate the body strain of the solid element. The bar element only expands radially is assumed, so the cross-sectional change at the bar node can be calculated according to the strain of the solid element body, which is used to calculate the explosive gas pressure at the next moment. Through numerical comparison with the entity bore hole model, when the pressure attenuation index is 1.25, the radial peak particle velocity attenuation law and vibration velocity time history curve obtained by the one-dimensional axisymmetric explosion source model are basically consistent with the entity blast-hole model, which proves the accuracy of the model in blasting simulation. Aiming at the study of dynamic blasting damage characteristics of concrete blocks, the correctness of the model is further verified by comparing with the literature. Based on the blasting technology in Angang open-pit mine, a generalized three-dimensional bench blasting model with 5 rows and 50 bore holes was set up to simulate the damage and failure status in the blasting area. The numerical calculation results show that the tensile failure is the dominant in the blasting area, and the peak particle velocity and its variation with distance at monitor points except the first point near the blasting source is well fitted with the test data, which proves the feasibility of the proposed model in the far-field simulation of three-dimensional bench blasting.
2022, 42(11): 115301.
doi: 10.11883/bzycj-2021-0431
Abstract:
Graphene has high specific strength and stiffness, high current-carrier mobility, low resistivity, and even exceptive electromagnetic properties, which is expected as a next-generation micro-nano photoelectric material. However, most research and applications of graphene materials and photoelectric devices are still only in the laboratory stage. On the one hand, limited to current technologies, industrial mass-scale production of high-quality monolayer graphene films is impossible. On the other hand, the micro-scale patterned machining process may bring structural and performance damage to the material, making the stability and reliability of devices difficult to guarantee. In recent years, with the innovation and progress of laser processing technology, the micro-nano-scale patterned processing of graphene oxide (GO) thin films by laser has become a key technology for solving the development of integrated circuits and information communication equipment to precision and miniaturization. The existing achievements mainly focus on the process and method of laser processing graphene materials with different structures, the physical mechanism of interaction between ultrafast laser and monolayer graphene film, etc. The deformation and damage mechanism of graphene films at ultra-high strain rates are still unclear. In particular, the industrial application of micron-scale multilayer reduced graphene oxide (RGO) films has been much widely explored. However, few studies have been conducted on their mechano-thermal and complex physical processes associated with laser shock and the resulting interlayer damage due to the weak interlayer bonding force. To study the effect of ultrahigh strain rate load on the structure and properties of GO films, GO films were prepared by pumping a certain concentration of GO solution onto the membrane. The reduced GO films were obtained by laser ablation with different laser powers. The mechanism of the film’s structural change was revealed by the characterization of its surface morphology and chemical composition. Reasonable laser machining parameters were explored by measuring the hardness, elastic modulus, and conductivity of film before and after impact. The results show that the film can be reduced without ablative fracture under CO2 laser shock at 1.14 W power. Its electrical conductivity can reach 1.727×103 S/m, the elastic modulus is 49.97 GPa, and hardness is 5.71 GPa.
Graphene has high specific strength and stiffness, high current-carrier mobility, low resistivity, and even exceptive electromagnetic properties, which is expected as a next-generation micro-nano photoelectric material. However, most research and applications of graphene materials and photoelectric devices are still only in the laboratory stage. On the one hand, limited to current technologies, industrial mass-scale production of high-quality monolayer graphene films is impossible. On the other hand, the micro-scale patterned machining process may bring structural and performance damage to the material, making the stability and reliability of devices difficult to guarantee. In recent years, with the innovation and progress of laser processing technology, the micro-nano-scale patterned processing of graphene oxide (GO) thin films by laser has become a key technology for solving the development of integrated circuits and information communication equipment to precision and miniaturization. The existing achievements mainly focus on the process and method of laser processing graphene materials with different structures, the physical mechanism of interaction between ultrafast laser and monolayer graphene film, etc. The deformation and damage mechanism of graphene films at ultra-high strain rates are still unclear. In particular, the industrial application of micron-scale multilayer reduced graphene oxide (RGO) films has been much widely explored. However, few studies have been conducted on their mechano-thermal and complex physical processes associated with laser shock and the resulting interlayer damage due to the weak interlayer bonding force. To study the effect of ultrahigh strain rate load on the structure and properties of GO films, GO films were prepared by pumping a certain concentration of GO solution onto the membrane. The reduced GO films were obtained by laser ablation with different laser powers. The mechanism of the film’s structural change was revealed by the characterization of its surface morphology and chemical composition. Reasonable laser machining parameters were explored by measuring the hardness, elastic modulus, and conductivity of film before and after impact. The results show that the film can be reduced without ablative fracture under CO2 laser shock at 1.14 W power. Its electrical conductivity can reach 1.727×103 S/m, the elastic modulus is 49.97 GPa, and hardness is 5.71 GPa.
2022, 42(11): 115401.
doi: 10.11883/bzycj-2021-0418
Abstract:
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2022, 42(11): 115402.
doi: 10.11883/bzycj-2022-0300
Abstract:
In order to reveal the coupling law of the influencing factors in gas/coal dust composite explosion, experiments were conducted in a 20 L spherical explosion device. Multi-factor and single-factor experimental analyses were conducted on four influencing factors according to explosion parameters, including coal concentration, methane volume fraction, coal particle size, and coal type. By conducting orthogonal experiments on the influencing factors, and using the explosion parameters as indicators to carry out range analysis and variance analysis, the influence of each factor on the explosion had been quantified. The experimental results show that the degree of influence of the four factor on pmax are (from strong to weak): methane volume fraction, coal dust mass concentration, coal dust type, and coal dust particle size; the effects on (dp/dt)max are (from strong to weak): methane volume fraction, coal dust mass concentration, coal dust particle size, and coal dust type. For methane concentrations of 9% and 11%, the value of pmax of the composite system decreases with increasing mass of coal dust. When the mass concentration of coal dust increases to 100 g/m3 and 200 g/m3, coupled with 6% volume fraction of methane, it will produce a stronger “incentive” effect, and when the concentration of coal dust is larger, the low volatility will reduce the optimal gas concentration. The existence of a certain critical value of methane concentration will change the influence mode of volatile factors. Below this value, the value of (dp/dt)max of the high volatile coal dust system is higher, and its arrival time is shorter, while above this value, the low volatile fraction system has a higher explosion intensity. Particle size implicates the influence of volatile fraction, the larger the particle diameter, the more obvious the difference produced by the volatile fraction factor. At 11% methane concentration, coal dust with high volatile fraction is more susceptible to the effect of particle size, and the smaller diameter coal dust system has smaller Kst value; at methane concentration close to equivalent, low volatile fraction coal dust is more significantly affected by the particle size factor.
In order to reveal the coupling law of the influencing factors in gas/coal dust composite explosion, experiments were conducted in a 20 L spherical explosion device. Multi-factor and single-factor experimental analyses were conducted on four influencing factors according to explosion parameters, including coal concentration, methane volume fraction, coal particle size, and coal type. By conducting orthogonal experiments on the influencing factors, and using the explosion parameters as indicators to carry out range analysis and variance analysis, the influence of each factor on the explosion had been quantified. The experimental results show that the degree of influence of the four factor on pmax are (from strong to weak): methane volume fraction, coal dust mass concentration, coal dust type, and coal dust particle size; the effects on (dp/dt)max are (from strong to weak): methane volume fraction, coal dust mass concentration, coal dust particle size, and coal dust type. For methane concentrations of 9% and 11%, the value of pmax of the composite system decreases with increasing mass of coal dust. When the mass concentration of coal dust increases to 100 g/m3 and 200 g/m3, coupled with 6% volume fraction of methane, it will produce a stronger “incentive” effect, and when the concentration of coal dust is larger, the low volatility will reduce the optimal gas concentration. The existence of a certain critical value of methane concentration will change the influence mode of volatile factors. Below this value, the value of (dp/dt)max of the high volatile coal dust system is higher, and its arrival time is shorter, while above this value, the low volatile fraction system has a higher explosion intensity. Particle size implicates the influence of volatile fraction, the larger the particle diameter, the more obvious the difference produced by the volatile fraction factor. At 11% methane concentration, coal dust with high volatile fraction is more susceptible to the effect of particle size, and the smaller diameter coal dust system has smaller Kst value; at methane concentration close to equivalent, low volatile fraction coal dust is more significantly affected by the particle size factor.
