2023 Vol. 43, No. 3
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2023, 43(3): 031101.
doi: 10.11883/bzycj-2022-0408
Abstract:
Magnetically driven quasi-isentropic compression is one of the important experimental techniques to study high-pressure physics and dynamic behaviors of materials under off Hugoniot states. It is of great significance to carry out quantitative evaluation of experimental uncertainty. By combining with the process analysis of magnetically driven quasi-isentropic compression experiments and two forward data processing methods, an uncertainty quantitative evaluation method was established for such experiments based on the Monte Carlo method (MCM). The uncertainty quantification evaluations of physical quantities such as sound speed, stress, strain, and the parameters of equations of state and constitutive models were realized. Compared with the conventional method such as guide to the expression of uncertainty in measurement (GUM), the MCM uncertainty evaluation is more applicable to the cases in which the probability distribution of the input quantities is non-symmetric and the measurement model is non-linear. In fact, the uncertainty evaluation results obtained by the MCM is reasonable and not the ones under the maximum estimation condition. Employing the law of large numbers, nested cycle setting of the probability density functions (PDF) and nested loop construction of virtual samples makes the uncertainty evaluation results more accurate. By using the established MCM uncertainty evaluation method, the uncertainty evaluations of the experimental results of tantalum and copper samples under magnetically-driven quasi-isentropic compression were quantitatively analyzed firstly. The results are consistent with the data proposed in the literatures, which proves the correctness and reliability of our method. And then, the quantitative evaluation was conducted on magnetically-driven quasi-isentropic compression experiments of NiTi alloy carried out on a CQ-4 device. The results show that the experiments on the CQ-4 device are reliable and precise for high-pressure physics and material dynamics studies. Finally, the error correlation and sensitivity of magnetically-driven quasi-isentropic compression experiments were discussed in depth, and the results show that the measurements of step sample thickness and particle velocity are the main factors affecting the experimental accuracy but have different influence weights. This work has important guiding significance for studying high-pressure physics and dynamic behaviors of materials by using magnetically-driven quasi-isentropic compression experimental technology.
Magnetically driven quasi-isentropic compression is one of the important experimental techniques to study high-pressure physics and dynamic behaviors of materials under off Hugoniot states. It is of great significance to carry out quantitative evaluation of experimental uncertainty. By combining with the process analysis of magnetically driven quasi-isentropic compression experiments and two forward data processing methods, an uncertainty quantitative evaluation method was established for such experiments based on the Monte Carlo method (MCM). The uncertainty quantification evaluations of physical quantities such as sound speed, stress, strain, and the parameters of equations of state and constitutive models were realized. Compared with the conventional method such as guide to the expression of uncertainty in measurement (GUM), the MCM uncertainty evaluation is more applicable to the cases in which the probability distribution of the input quantities is non-symmetric and the measurement model is non-linear. In fact, the uncertainty evaluation results obtained by the MCM is reasonable and not the ones under the maximum estimation condition. Employing the law of large numbers, nested cycle setting of the probability density functions (PDF) and nested loop construction of virtual samples makes the uncertainty evaluation results more accurate. By using the established MCM uncertainty evaluation method, the uncertainty evaluations of the experimental results of tantalum and copper samples under magnetically-driven quasi-isentropic compression were quantitatively analyzed firstly. The results are consistent with the data proposed in the literatures, which proves the correctness and reliability of our method. And then, the quantitative evaluation was conducted on magnetically-driven quasi-isentropic compression experiments of NiTi alloy carried out on a CQ-4 device. The results show that the experiments on the CQ-4 device are reliable and precise for high-pressure physics and material dynamics studies. Finally, the error correlation and sensitivity of magnetically-driven quasi-isentropic compression experiments were discussed in depth, and the results show that the measurements of step sample thickness and particle velocity are the main factors affecting the experimental accuracy but have different influence weights. This work has important guiding significance for studying high-pressure physics and dynamic behaviors of materials by using magnetically-driven quasi-isentropic compression experimental technology.
2023, 43(3): 032101.
doi: 10.11883/bzycj-2022-0352
Abstract:
To investigate the influence of multi-factor coupling on the explosion characteristics of methane, an explosive gas test platform with a 1.2 L cylindrical explosive device was designed and established. From the perspective of the maximum explosion pressure, the effects of different equivalence ratios φ (0.6–1.4), initial temperatures T0 (25–200 ℃) and initial pressures p0 (0.1–0.5 MPa) on methane explosion characteristics were comprehensively analyzed. Based on the maximum explosion pressure data by the experiments, a nonlinear regression prediction model among the maximum explosion pressure of methane, equivalence ratio, initial temperature and initial pressure was developed by the 1stOpt software. The results show that: under the coupling effect of the initial temperature and initial pressure, the higher the initial pressure, the more the significant effect of the initial temperature on the maximum explosion pressure. However, with the increasing of the initial temperature, the effect of initial pressure on the maximum explosion pressure is weakened. Under the coupling effect of the initial pressure and equivalence ratio, and within the experimental conditions of the study, when φ<0.9 or φ>1.2, the higher the initial pressure, the more dramatically on the maximum explosion pressure changes. Under the coupling effect of initial temperature and equivalence ratio, and within the experimental conditions of the study, when φ>1.15, the higher the initial temperature, the more significantly the maximum explosion pressure changes. In addition, comparing the prediction results of the 1stOpt prediction model with the experimental results, the relative error is less than 10%. It is indicated that the prediction model can provide high accuracy and good adaptability.
To investigate the influence of multi-factor coupling on the explosion characteristics of methane, an explosive gas test platform with a 1.2 L cylindrical explosive device was designed and established. From the perspective of the maximum explosion pressure, the effects of different equivalence ratios φ (0.6–1.4), initial temperatures T0 (25–200 ℃) and initial pressures p0 (0.1–0.5 MPa) on methane explosion characteristics were comprehensively analyzed. Based on the maximum explosion pressure data by the experiments, a nonlinear regression prediction model among the maximum explosion pressure of methane, equivalence ratio, initial temperature and initial pressure was developed by the 1stOpt software. The results show that: under the coupling effect of the initial temperature and initial pressure, the higher the initial pressure, the more the significant effect of the initial temperature on the maximum explosion pressure. However, with the increasing of the initial temperature, the effect of initial pressure on the maximum explosion pressure is weakened. Under the coupling effect of the initial pressure and equivalence ratio, and within the experimental conditions of the study, when φ<0.9 or φ>1.2, the higher the initial pressure, the more dramatically on the maximum explosion pressure changes. Under the coupling effect of initial temperature and equivalence ratio, and within the experimental conditions of the study, when φ>1.15, the higher the initial temperature, the more significantly the maximum explosion pressure changes. In addition, comparing the prediction results of the 1stOpt prediction model with the experimental results, the relative error is less than 10%. It is indicated that the prediction model can provide high accuracy and good adaptability.
2023, 43(3): 032201.
doi: 10.11883/bzycj-2022-0075
Abstract:
In order to deeply understand the formation mechanism of local cavitation in the near-wall flow field caused by an underwater explosion, the optical images showing the local cavitation effect near the wall were obtained by using a self-developed rotating-mirror framing camera with high frequency and high resolution. Numerical simulations were carried out to present the flow-field pressure of shock wave propagation by giving the location of the cavitation area. The Taylor plane wave theory, an efficient method for describing the formation time of local cavitation, was applied to explain the reason that the cavitation did not form in the experimental case 1 that the explosive center was 120 mm from the wall. And the cavitation dynamics theory was used to analyze the local cavitation effect in the experimental case 2 that the explosive center was 80 mm from the wall, by calculating the motion laws of the cavities with different radii under different external environmental pressures. It is indicated that the existence of the rarefaction waves reflected by the interfaces and the expansion of the cavitation nuclei in the water result in the cavitation effects in the near-wall flow field. The external flow-field pressure hardly affects the initial stage of cavitation bubble expansion, but it exerts great influences on the movement behavior of the cavitation bubbles in the later stage. The cavitation bubbles with different sizes will take on different movement behaviors in the low-pressure environment. The cavitation bubbles with the small size less than 10 μm will expand and collapse rapidly in the low-pressure environment so that they have little effects on the flow field cavitation. While the cavitaion bubbles with the large size more than 10 μm may lose the stability, with the result that they have great influences on the flow-field cavition. The random spatial distribution of different-size cavitation nuclei in water is the main reason that the cavitation zone presents an irregular shape during the evolution progress.
In order to deeply understand the formation mechanism of local cavitation in the near-wall flow field caused by an underwater explosion, the optical images showing the local cavitation effect near the wall were obtained by using a self-developed rotating-mirror framing camera with high frequency and high resolution. Numerical simulations were carried out to present the flow-field pressure of shock wave propagation by giving the location of the cavitation area. The Taylor plane wave theory, an efficient method for describing the formation time of local cavitation, was applied to explain the reason that the cavitation did not form in the experimental case 1 that the explosive center was 120 mm from the wall. And the cavitation dynamics theory was used to analyze the local cavitation effect in the experimental case 2 that the explosive center was 80 mm from the wall, by calculating the motion laws of the cavities with different radii under different external environmental pressures. It is indicated that the existence of the rarefaction waves reflected by the interfaces and the expansion of the cavitation nuclei in the water result in the cavitation effects in the near-wall flow field. The external flow-field pressure hardly affects the initial stage of cavitation bubble expansion, but it exerts great influences on the movement behavior of the cavitation bubbles in the later stage. The cavitation bubbles with different sizes will take on different movement behaviors in the low-pressure environment. The cavitation bubbles with the small size less than 10 μm will expand and collapse rapidly in the low-pressure environment so that they have little effects on the flow field cavitation. While the cavitaion bubbles with the large size more than 10 μm may lose the stability, with the result that they have great influences on the flow-field cavition. The random spatial distribution of different-size cavitation nuclei in water is the main reason that the cavitation zone presents an irregular shape during the evolution progress.
2023, 43(3): 032202.
doi: 10.11883/bzycj-2022-0268
Abstract:
A detonation experimental system was established to explore the characteristics of underwater detonation gas jets from the detonation tubes with different types of nozzles. The effects of different types of nozzles on underwater bubble shapes and pressure characteristics during detonation were experimentally studied. The digital particle image velocimetry was used to visualize the bubble pulsation pictures captured by a high-speed camera, and the bubble velocity fields in the different nozzle cases were obtained. Two dynamic pressure sensors were installed at the end of the detonation tube to confirm whether the stable detonation wave was formed, and to observe the transmission and reflection characteristics of the detonation wave on the gas-liquid two-phase interface, respectively. An underwater explosion sensor was installed at a certain distance from the nozzle to measure the underwater pressure wave. The results show that the bubble pulsation process in the divergent nozzle case is basically the same as that in the case of the straight nozzle, but the divergent nozzle improves the gas jet velocity and increases the bubble volume of the first bubble pulsation. The combined effect of the convergent nozzle and its reflected shock wave reduces the injection speed of the detonation gas. Because of the continuity of the gas jet, the bubble pulsation process in the convergent nozzle case is obviously different. The maximum bubble volume in the convergent nozzle case is smaller, but the attenuation of the second bubble pulsation duration is smaller than that of the first pulsation duration. The divergent nozzle increases the gas velocity and kinetic energy, which enhances the bubble pulsation intensity, the bubble pulsation pressure and transmitted shock wave pressure in the divergent nozzle case are much higher than those in the straight nozzle case. The bubble pulsation pressure and the transmitted shock wave pressure in the convergent nozzle case are both low, but the continuity of the convergent nozzle gas jet retards the attenuation speed of the bubble pulsation pressure. Compared with the straight nozzle, the bubble pulsation time in the divergent nozzle case is longer, the bubble pulsation pressure and transmitted shock wave pressure are higher. The duration of the bubble pulsation in the convergent nozzle case is shorter, and the convergent nozzle can obviously inhibit the transmitted shock wave pressure and the bubble pulsation pressure.
A detonation experimental system was established to explore the characteristics of underwater detonation gas jets from the detonation tubes with different types of nozzles. The effects of different types of nozzles on underwater bubble shapes and pressure characteristics during detonation were experimentally studied. The digital particle image velocimetry was used to visualize the bubble pulsation pictures captured by a high-speed camera, and the bubble velocity fields in the different nozzle cases were obtained. Two dynamic pressure sensors were installed at the end of the detonation tube to confirm whether the stable detonation wave was formed, and to observe the transmission and reflection characteristics of the detonation wave on the gas-liquid two-phase interface, respectively. An underwater explosion sensor was installed at a certain distance from the nozzle to measure the underwater pressure wave. The results show that the bubble pulsation process in the divergent nozzle case is basically the same as that in the case of the straight nozzle, but the divergent nozzle improves the gas jet velocity and increases the bubble volume of the first bubble pulsation. The combined effect of the convergent nozzle and its reflected shock wave reduces the injection speed of the detonation gas. Because of the continuity of the gas jet, the bubble pulsation process in the convergent nozzle case is obviously different. The maximum bubble volume in the convergent nozzle case is smaller, but the attenuation of the second bubble pulsation duration is smaller than that of the first pulsation duration. The divergent nozzle increases the gas velocity and kinetic energy, which enhances the bubble pulsation intensity, the bubble pulsation pressure and transmitted shock wave pressure in the divergent nozzle case are much higher than those in the straight nozzle case. The bubble pulsation pressure and the transmitted shock wave pressure in the convergent nozzle case are both low, but the continuity of the convergent nozzle gas jet retards the attenuation speed of the bubble pulsation pressure. Compared with the straight nozzle, the bubble pulsation time in the divergent nozzle case is longer, the bubble pulsation pressure and transmitted shock wave pressure are higher. The duration of the bubble pulsation in the convergent nozzle case is shorter, and the convergent nozzle can obviously inhibit the transmitted shock wave pressure and the bubble pulsation pressure.
2023, 43(3): 033101.
doi: 10.11883/bzycj-2022-0374
Abstract:
Molybdenum (Mo) and zirconium carbide (ZrC) ceramic possess high strength and good wear resistance. Specific gradient changes of layered gradient structure can effectively take advantage of the two materials. To study the effects of gradient structure and impact direction on the dynamic responses of Mo-ZrC layered gradient cermet, the low-speed dynamic compression test of layered gradient cermet was launched by the split Hopkinson pressure bar device combined with high-speed photography technology, and three kinds of samples with different graded structures were pre-designed and sintered. Based on the digital image correlation (DIC) technology, the effects of gradient structure and impact direction on the failure modes of layered gradient cermet were discussed in detail. The propagation of the one-dimensional stress wave in the layered gradient composite was analyzed according to the equivalent properties of each layer of graded cermet calculated by the Mori-Tanaka theory. Results show as follows. (1) Under the same loading condition, the layered gradient structure has an important influence on material strength and integrity of the damaged product. Samples with a higher overall metal content exhibit better performance. In the process of impaction, the dynamic impaction responses can divide into three stages: compression, crack nucleation, and penetration. According to the results of high-speed photography, different gradient structure and direction of impact damage present different temporal and modes. (2) With the help of the calculation results based on the DIC method, the local deformation development of layered gradient cermet is tracked. When the local incremental development reaches a critical state, the local deformation development turns to the formation and accumulation of micro-cracks, which would lead to overall failure eventually. (3) Based on the one-dimensional stress wave propagation theory of layered gradient materials, the changing of impact direction influences the permeability and reflection coefficient of the stress wave, different gradient structure design shows sensitivity difference to the impact direction change, and there are extreme values.
Molybdenum (Mo) and zirconium carbide (ZrC) ceramic possess high strength and good wear resistance. Specific gradient changes of layered gradient structure can effectively take advantage of the two materials. To study the effects of gradient structure and impact direction on the dynamic responses of Mo-ZrC layered gradient cermet, the low-speed dynamic compression test of layered gradient cermet was launched by the split Hopkinson pressure bar device combined with high-speed photography technology, and three kinds of samples with different graded structures were pre-designed and sintered. Based on the digital image correlation (DIC) technology, the effects of gradient structure and impact direction on the failure modes of layered gradient cermet were discussed in detail. The propagation of the one-dimensional stress wave in the layered gradient composite was analyzed according to the equivalent properties of each layer of graded cermet calculated by the Mori-Tanaka theory. Results show as follows. (1) Under the same loading condition, the layered gradient structure has an important influence on material strength and integrity of the damaged product. Samples with a higher overall metal content exhibit better performance. In the process of impaction, the dynamic impaction responses can divide into three stages: compression, crack nucleation, and penetration. According to the results of high-speed photography, different gradient structure and direction of impact damage present different temporal and modes. (2) With the help of the calculation results based on the DIC method, the local deformation development of layered gradient cermet is tracked. When the local incremental development reaches a critical state, the local deformation development turns to the formation and accumulation of micro-cracks, which would lead to overall failure eventually. (3) Based on the one-dimensional stress wave propagation theory of layered gradient materials, the changing of impact direction influences the permeability and reflection coefficient of the stress wave, different gradient structure design shows sensitivity difference to the impact direction change, and there are extreme values.
2023, 43(3): 033201.
doi: 10.11883/bzycj-2022-0098
Abstract:
To promote the explosive safety assessment and the warhead structure design, the loading characteristics and structural response of the warhead during the drop impact process were analyzed based on numerical simulation and shock wave analysis, focusing on the deformation and damage characteristics of the explosive subassembly. And the influences of various factors, including drop posture, explosive configuration, drop height, etc., were discussed in detail. In the numerical simulations, materials were characterized by the viscoplasticity constitutive model combined with the accumulative damage model, which considers the effects of strain rate and temperature. The thermodynamic equation of state was employed to calculate the pressure in materials during the deformation process. Firstly, the effect of drop posture was investigated by comparative analysis among five typical cases, i.e., tail-downward vertical drop, nose-downward vertical drop, horizontal drop, tail-downward inclined drop, and nose-downward inclined drop. Secondly, the influence of warhead configuration was analyzed based on three configurations, i.e., one explosive segment warhead, eight explosive segment warheads, and eight explosive segments combined with a separator warhead. Finally, the effect of drop height was discussed, where the height ranges from 3 m to 40 m. Related results indicate that during the drop impact process, the deformation of the explosive subassembly is dominated by the stress wave propagation rather than the interaction between the explosive subassembly and warhead shell. Correspondingly, the severest damage zone in the explosive subassembly is located in its internal region instead of the outer region, which contacts the warhead shell. The transmission of stress waves between explosive subassembly and warhead shell and the reflection and superposition of stress waves within the structures dominate the major deformation region in the explosive subassembly and the deformation degree. Furthermore, the drop posture significantly affects the response characteristics and the deformation of the explosive subassembly. The most dangerous drop posture which leads to high safety risk is, in turn, tail-downward vertical drop, horizontal drop, nose-downward vertical drop, and inclined drop. The explosive configuration also acts an important role. The explosive segment interface can easily induce an increase in the deformation degree, but it has little influence on the acceleration and distribution of the deformation region. The separator usually leads to high acceleration, and it changes the location of the deformation region as well as the deformation degree. Comparatively, the drop height has little influence on the distribution feature of the deformation zone. It mainly affects the loading amplitude, the degree of the deformation, the size of the deformation zone, etc. The influences of these factors increase with increasing drop height. The present method, which investigates the structural response of complex warheads based on numerical simulation integrated with stress wave analysis, has built an effective bridge linking the basic theory and the engineering application.
To promote the explosive safety assessment and the warhead structure design, the loading characteristics and structural response of the warhead during the drop impact process were analyzed based on numerical simulation and shock wave analysis, focusing on the deformation and damage characteristics of the explosive subassembly. And the influences of various factors, including drop posture, explosive configuration, drop height, etc., were discussed in detail. In the numerical simulations, materials were characterized by the viscoplasticity constitutive model combined with the accumulative damage model, which considers the effects of strain rate and temperature. The thermodynamic equation of state was employed to calculate the pressure in materials during the deformation process. Firstly, the effect of drop posture was investigated by comparative analysis among five typical cases, i.e., tail-downward vertical drop, nose-downward vertical drop, horizontal drop, tail-downward inclined drop, and nose-downward inclined drop. Secondly, the influence of warhead configuration was analyzed based on three configurations, i.e., one explosive segment warhead, eight explosive segment warheads, and eight explosive segments combined with a separator warhead. Finally, the effect of drop height was discussed, where the height ranges from 3 m to 40 m. Related results indicate that during the drop impact process, the deformation of the explosive subassembly is dominated by the stress wave propagation rather than the interaction between the explosive subassembly and warhead shell. Correspondingly, the severest damage zone in the explosive subassembly is located in its internal region instead of the outer region, which contacts the warhead shell. The transmission of stress waves between explosive subassembly and warhead shell and the reflection and superposition of stress waves within the structures dominate the major deformation region in the explosive subassembly and the deformation degree. Furthermore, the drop posture significantly affects the response characteristics and the deformation of the explosive subassembly. The most dangerous drop posture which leads to high safety risk is, in turn, tail-downward vertical drop, horizontal drop, nose-downward vertical drop, and inclined drop. The explosive configuration also acts an important role. The explosive segment interface can easily induce an increase in the deformation degree, but it has little influence on the acceleration and distribution of the deformation region. The separator usually leads to high acceleration, and it changes the location of the deformation region as well as the deformation degree. Comparatively, the drop height has little influence on the distribution feature of the deformation zone. It mainly affects the loading amplitude, the degree of the deformation, the size of the deformation zone, etc. The influences of these factors increase with increasing drop height. The present method, which investigates the structural response of complex warheads based on numerical simulation integrated with stress wave analysis, has built an effective bridge linking the basic theory and the engineering application.
2023, 43(3): 033301.
doi: 10.11883/bzycj-2022-0182
Abstract:
To study the influence mechanism of shaped charge liner on the perforation and damage-induced fracturing effect of shale reservoir by shaped charge penetration, a three-dimensional perforating charge-air-shale model was established. The cone angles of the liner are 50°, 60°, 70°, and 80°. The liner thicknesses are 0.5 mm, 1.0 mm, and 1.5 mm. And the materials of the liner are copper, steel, titanium, and tungsten. The numerical calculation was carried out using the ALE-Lagrangian coupling method in the non-linear program ANSYS/LS-DYNA. The ALE method was used to describe shell, explosive, liner, and air, while the Lagrangian method was used to describe the shale reservoir. A systematic analysis was carried out on the aspects of jet velocity and shape, shale perforation effect, and fracture extension characteristics of shale. The results show that with the decrease of the cone angle of the liner, the jet velocity and penetration depth increase, and the pestle velocity and perforation diameter decrease. In a certain range, with the decreasing liner thickness, the jet velocity, penetration depth, and perforation inclination increase, and the mass of the pestle decrease. The liner material significantly influences the jet velocity, pestle structure, and shale perforation effect. Among them, the penetration depth of perforating charge with a tungsten liner is the largest, but the perforation diameter is the smallest, the penetration depth of perforating charge with a titanium liner is the smallest, but the perforation inclination is the largest, and the penetration depth of perforating charge with a copper liner is slightly larger than that with a steel liner, but the perforation diameter is slightly smaller. Because the detonation pressure has an obvious difference before and after the detonation wave transmitted to the end of the explosive, which affects the jet velocity and penetration depth, the charge with a shell has a greater jet velocity and penetration depth than the charge without a shell. By comparing the fracture extension characteristics of shale in different groups, it is found that the fracture extension of shale mainly occurs in the stage of re-reaming of a pestle on shale. It is concluded that the material and structure of the liner have a significant influence on the shaped charge jet and its penetration effect, which then affects the damage-induced fracture formation and extension in shale. The fracture extension of the shale can be promoted by reducing the initial perforation diameter of penetration, increasing the diameter of the pestle, and increasing the speed of the pestle.
To study the influence mechanism of shaped charge liner on the perforation and damage-induced fracturing effect of shale reservoir by shaped charge penetration, a three-dimensional perforating charge-air-shale model was established. The cone angles of the liner are 50°, 60°, 70°, and 80°. The liner thicknesses are 0.5 mm, 1.0 mm, and 1.5 mm. And the materials of the liner are copper, steel, titanium, and tungsten. The numerical calculation was carried out using the ALE-Lagrangian coupling method in the non-linear program ANSYS/LS-DYNA. The ALE method was used to describe shell, explosive, liner, and air, while the Lagrangian method was used to describe the shale reservoir. A systematic analysis was carried out on the aspects of jet velocity and shape, shale perforation effect, and fracture extension characteristics of shale. The results show that with the decrease of the cone angle of the liner, the jet velocity and penetration depth increase, and the pestle velocity and perforation diameter decrease. In a certain range, with the decreasing liner thickness, the jet velocity, penetration depth, and perforation inclination increase, and the mass of the pestle decrease. The liner material significantly influences the jet velocity, pestle structure, and shale perforation effect. Among them, the penetration depth of perforating charge with a tungsten liner is the largest, but the perforation diameter is the smallest, the penetration depth of perforating charge with a titanium liner is the smallest, but the perforation inclination is the largest, and the penetration depth of perforating charge with a copper liner is slightly larger than that with a steel liner, but the perforation diameter is slightly smaller. Because the detonation pressure has an obvious difference before and after the detonation wave transmitted to the end of the explosive, which affects the jet velocity and penetration depth, the charge with a shell has a greater jet velocity and penetration depth than the charge without a shell. By comparing the fracture extension characteristics of shale in different groups, it is found that the fracture extension of shale mainly occurs in the stage of re-reaming of a pestle on shale. It is concluded that the material and structure of the liner have a significant influence on the shaped charge jet and its penetration effect, which then affects the damage-induced fracture formation and extension in shale. The fracture extension of the shale can be promoted by reducing the initial perforation diameter of penetration, increasing the diameter of the pestle, and increasing the speed of the pestle.
2023, 43(3): 033302.
doi: 10.11883/bzycj-2022-0029
Abstract:
To investigate the dynamical responses and failure behaviors of prefabricated reinforced-concrete (RC) box-girder flyovers caused by collision of over-height vehicles, a recent actual engineering accident is taken as an example to carry out refined numerical analysis by the finite element method, and a double mass-parallel spring (DM-PS) simplified vehicle model is proposed to effectively simulate the eccentric collision between the over-height vehicle and bridge superstructures. The effectiveness of the proposed DM-PS model is fully assessed through comparison with two widely-employed vehicle models, i.e., a full-scale (FS) model and a simple rigid (SR) model. The comparisons display that the failure characteristics of the collision area can be obtained by using the FS model, which is basically consistent with the photos of the accident scene; the SR model overestimates the local damage of the structure and underestimates the overall structural deformation; while the DM-PS model has high accuracy for predicting the structural failure. Therefore, the proposed DM-PS model can provide a simple and effective analysis tool for the protection design of bridge structures subjected to over-height vehicle collision. On this basis, a detailed parameter analysis of the structural behaviors is carried out by the DM-PS model, and the effects of vehicle collision velocity, mass, position, and structural form are investigated in depth. It is shown that the structural sensitivity of the impact dynamic behavior to the collision velocity of the vehicle is significantly greater than that of the collision mass of the vehicle; the deformation and failure modes of mid-span collision and side-span collision are quite different, and the damage of side-span collision to one side base is more serious; the box plate and reinforced plate in the box girder can effectively improve the structural impact resistance. Numerical results and conclusions can provide a reference for the crashworthiness design of bridges. The critical information of the finite element analysis process is presented in detail.
To investigate the dynamical responses and failure behaviors of prefabricated reinforced-concrete (RC) box-girder flyovers caused by collision of over-height vehicles, a recent actual engineering accident is taken as an example to carry out refined numerical analysis by the finite element method, and a double mass-parallel spring (DM-PS) simplified vehicle model is proposed to effectively simulate the eccentric collision between the over-height vehicle and bridge superstructures. The effectiveness of the proposed DM-PS model is fully assessed through comparison with two widely-employed vehicle models, i.e., a full-scale (FS) model and a simple rigid (SR) model. The comparisons display that the failure characteristics of the collision area can be obtained by using the FS model, which is basically consistent with the photos of the accident scene; the SR model overestimates the local damage of the structure and underestimates the overall structural deformation; while the DM-PS model has high accuracy for predicting the structural failure. Therefore, the proposed DM-PS model can provide a simple and effective analysis tool for the protection design of bridge structures subjected to over-height vehicle collision. On this basis, a detailed parameter analysis of the structural behaviors is carried out by the DM-PS model, and the effects of vehicle collision velocity, mass, position, and structural form are investigated in depth. It is shown that the structural sensitivity of the impact dynamic behavior to the collision velocity of the vehicle is significantly greater than that of the collision mass of the vehicle; the deformation and failure modes of mid-span collision and side-span collision are quite different, and the damage of side-span collision to one side base is more serious; the box plate and reinforced plate in the box girder can effectively improve the structural impact resistance. Numerical results and conclusions can provide a reference for the crashworthiness design of bridges. The critical information of the finite element analysis process is presented in detail.
2023, 43(3): 033303.
doi: 10.11883/bzycj-2022-0115
Abstract:
The formation process of the Yilan crater was numerically studied based on the iSALE-2D simulation code. The Euler algorithm was used to carry out the numerical simulation, and eight groups of working conditions were simulated. According to the scaling law, it was determined that the projectile diameter range was 90 to 120 m, and the projectile velocity was 12 and 15 km/s. Simulation results under the corresponding working conditions within 150 s of impact were obtained, including the crater diameter, depth, and crater profile curve. The optimal impact conditions of the Yilan crater were studied, and the formation and distribution of the molten layer during the cratering process were statistically analyzed. Combined with the point source cratering similarity law model, the relationship of cratering radius under the strength mechanism was obtained by fitting. The research results show that, according to the comparison between the simulated data and actual exploration data, a granite asteroid with a diameter of 120 m and an impact velocity of 12 km/s vertically hits the surface, forming a crater with a shape similar to the Yilan crater. The crater has a final diameter of 1 840 m and a crater edge depth of 263 m, which is in good agreement with the exploration data of the Yilan crater. Three stages of crater formation were reproduced: contact and compression, excavation, and modification. The distribution of the impact melting layer of the target plate material during the crater formation under the simulated conditions were revealed. The material melted completely when the peak pressure exceeds 56 GPa during the impact process, and this process was completed within 20 ms. Most melts was distributed at the bottom of the crater in layers and stacks, and a small amount of melts was deposited discretely on the surface of the target plate. The mass of the completely melted material is about 24 times the projectile mass. The relative error between the simulation results and the fitted crater radius relational results under the conditions with 120 m diameter and 12 km/s impact velocity is 10.3%.
The formation process of the Yilan crater was numerically studied based on the iSALE-2D simulation code. The Euler algorithm was used to carry out the numerical simulation, and eight groups of working conditions were simulated. According to the scaling law, it was determined that the projectile diameter range was 90 to 120 m, and the projectile velocity was 12 and 15 km/s. Simulation results under the corresponding working conditions within 150 s of impact were obtained, including the crater diameter, depth, and crater profile curve. The optimal impact conditions of the Yilan crater were studied, and the formation and distribution of the molten layer during the cratering process were statistically analyzed. Combined with the point source cratering similarity law model, the relationship of cratering radius under the strength mechanism was obtained by fitting. The research results show that, according to the comparison between the simulated data and actual exploration data, a granite asteroid with a diameter of 120 m and an impact velocity of 12 km/s vertically hits the surface, forming a crater with a shape similar to the Yilan crater. The crater has a final diameter of 1 840 m and a crater edge depth of 263 m, which is in good agreement with the exploration data of the Yilan crater. Three stages of crater formation were reproduced: contact and compression, excavation, and modification. The distribution of the impact melting layer of the target plate material during the crater formation under the simulated conditions were revealed. The material melted completely when the peak pressure exceeds 56 GPa during the impact process, and this process was completed within 20 ms. Most melts was distributed at the bottom of the crater in layers and stacks, and a small amount of melts was deposited discretely on the surface of the target plate. The mass of the completely melted material is about 24 times the projectile mass. The relative error between the simulation results and the fitted crater radius relational results under the conditions with 120 m diameter and 12 km/s impact velocity is 10.3%.
2023, 43(3): 034101.
doi: 10.11883/bzycj-2022-0344
Abstract:
A medium strain rate compression experimental system based on a progressive cam was developed to realize multiple medium strain rate loading. The developed experimental system uses the servo motor to drive the energy storage flywheel to rotate at a certain speed, and when the clutch is started, the energy storage flywheel can drive the loading cam to rotate. The loading cam pushes the loading guide bar and the input bar to compress the sample. When the loading cam rotates one circle, a single medium strain-rate compression is completed. At the same time, when the first stage compression is about to end, the stepper motor rapidly pushes the energy storage flywheel close to the loading cam for the next compression, and the cycles repeat to achieve multiple medium strain rate compression. The load and deformation of the material during compression were measured by strain gauges and a velocity interferometer system for any reflector (VISAR), respectively. The strain gauges were affixed to the input bar and the support bar, respectively. The strain signals of the bars during compression were recorded by the strain gauges and the forces exerted on the sample were obtained based on these strain signals. Two fiber optic probes of the VISAR system were used to measure the velocities of the input bar and the support bar during compression. Based on the two velocity curves measured, the velocity difference curve between the two ends of the sample was obtained, and then the deformation of the sample was gained by integrating the velocity difference. The stress-strain curves were obtained from the load- and deformation-time curves. Taking the paper honeycomb sample as an example, the reliability of the developed medium strain rate experimental system was discussed based on the high-speed images. The dynamic compressive mechanical properties of the paper honeycomb samples with the thickness of 10 mm and the diameter of 14.5 mm at the strain rate of 3.5 s−1 were studied. The stress-strain curves and deformation processes of the paper honeycomb samples during single compression and double compression were obtained. The experimental system could realize multistage progressive medium strain rate loading. The peak strength and plateau stress of the paper honeycomb samples at medium strain rates well connect the dynamic compression results at high strain rates with the quasi-static compression results at low strain rates. The failure modes of the samples are mainly out-of-plane buckling and in-plane shear after quasi-elastic deformation.
A medium strain rate compression experimental system based on a progressive cam was developed to realize multiple medium strain rate loading. The developed experimental system uses the servo motor to drive the energy storage flywheel to rotate at a certain speed, and when the clutch is started, the energy storage flywheel can drive the loading cam to rotate. The loading cam pushes the loading guide bar and the input bar to compress the sample. When the loading cam rotates one circle, a single medium strain-rate compression is completed. At the same time, when the first stage compression is about to end, the stepper motor rapidly pushes the energy storage flywheel close to the loading cam for the next compression, and the cycles repeat to achieve multiple medium strain rate compression. The load and deformation of the material during compression were measured by strain gauges and a velocity interferometer system for any reflector (VISAR), respectively. The strain gauges were affixed to the input bar and the support bar, respectively. The strain signals of the bars during compression were recorded by the strain gauges and the forces exerted on the sample were obtained based on these strain signals. Two fiber optic probes of the VISAR system were used to measure the velocities of the input bar and the support bar during compression. Based on the two velocity curves measured, the velocity difference curve between the two ends of the sample was obtained, and then the deformation of the sample was gained by integrating the velocity difference. The stress-strain curves were obtained from the load- and deformation-time curves. Taking the paper honeycomb sample as an example, the reliability of the developed medium strain rate experimental system was discussed based on the high-speed images. The dynamic compressive mechanical properties of the paper honeycomb samples with the thickness of 10 mm and the diameter of 14.5 mm at the strain rate of 3.5 s−1 were studied. The stress-strain curves and deformation processes of the paper honeycomb samples during single compression and double compression were obtained. The experimental system could realize multistage progressive medium strain rate loading. The peak strength and plateau stress of the paper honeycomb samples at medium strain rates well connect the dynamic compression results at high strain rates with the quasi-static compression results at low strain rates. The failure modes of the samples are mainly out-of-plane buckling and in-plane shear after quasi-elastic deformation.
2023, 43(3): 034201.
doi: 10.11883/bzycj-2022-0390
Abstract:
Gun barrel erosion is primarily caused by the intense heat and mass transfer between the propellant gas and the tube during firing. To investigate the erosion characteristics of a 155 mm barrel in a high-temperature, high-pressure, and high-velocity gas, an unsteady CFD fluid-solid interaction heat transfer model is developed with improved accuracy of temperature calculation. The eroding process is separated into two stages relevant to its temperature dependence. Thermochemical erosion occurs when the temperature is between the austenite phase-transition temperature and the melting point of cementite. When the temperature is above the melting point, melting becomes the dominant factor influencing erosion, so this is the melting erosion stage. Therefore, a piecewise model is developed. The numerical results of the calculation are as follows. The wall temperature rises rapidly and then falls gradually. In addition, the temperature decreases with the increase of axial distance in general. At the beginning of rifling, the wall temperature is the highest, and the erosion consists of melting and thermochemical erosion. In most of the rifling areas, only thermochemical erosion occurs. The amount of erosion is reduced continuously with the increase of axial distance. The most severe erosion happens near the beginning of rifling, where 5.06 μm (288 K) of erosion is found after one shot. The method is valid through the comparison with test results. Concurrently, the effect of different operating conditions on the erosion characteristics of the tube is investigated. The erosion distribution properties are found to be similar at different ambient temperatures and firing times. The erosion is the most severe near the beginning of rifling and decreases monotonically along the axis, although the peak value and range of erosion are different. Continuous firing and the increase of the external environment temperature will aggravate erosion. As a result, erosion has a strong positive correlation with initial wall temperature, and the temperature rise will accelerate the tube’s deterioration; therefore, rapid cooling of the barrel will effectively extend the service life of the artillery.
Gun barrel erosion is primarily caused by the intense heat and mass transfer between the propellant gas and the tube during firing. To investigate the erosion characteristics of a 155 mm barrel in a high-temperature, high-pressure, and high-velocity gas, an unsteady CFD fluid-solid interaction heat transfer model is developed with improved accuracy of temperature calculation. The eroding process is separated into two stages relevant to its temperature dependence. Thermochemical erosion occurs when the temperature is between the austenite phase-transition temperature and the melting point of cementite. When the temperature is above the melting point, melting becomes the dominant factor influencing erosion, so this is the melting erosion stage. Therefore, a piecewise model is developed. The numerical results of the calculation are as follows. The wall temperature rises rapidly and then falls gradually. In addition, the temperature decreases with the increase of axial distance in general. At the beginning of rifling, the wall temperature is the highest, and the erosion consists of melting and thermochemical erosion. In most of the rifling areas, only thermochemical erosion occurs. The amount of erosion is reduced continuously with the increase of axial distance. The most severe erosion happens near the beginning of rifling, where 5.06 μm (288 K) of erosion is found after one shot. The method is valid through the comparison with test results. Concurrently, the effect of different operating conditions on the erosion characteristics of the tube is investigated. The erosion distribution properties are found to be similar at different ambient temperatures and firing times. The erosion is the most severe near the beginning of rifling and decreases monotonically along the axis, although the peak value and range of erosion are different. Continuous firing and the increase of the external environment temperature will aggravate erosion. As a result, erosion has a strong positive correlation with initial wall temperature, and the temperature rise will accelerate the tube’s deterioration; therefore, rapid cooling of the barrel will effectively extend the service life of the artillery.
2023, 43(3): 034202.
doi: 10.11883/bzycj-2022-0110
Abstract:
Under impact, aluminum foam undergoes significant plastic deformation, and the kinetic energy of the impactor is dissipated in the process, thereby protecting the structure from damage. The failure modes of aluminum foam sandwich structures under impact are complex, involving plastic deformation, panel failure, and cracking of the bonding interface. Traditional numerical simulation methods are difficult to solve these discontinuous problems. Peridynamics is a non-local numerical method that describes the mechanical behavior of materials by solving spatial integral equations. It has unique advantages in solving crack propagation, material failure, progressive damage of composite materials, and multi-scale problems. Although the basic bond-based peridynamic theory cannot describe plasticity, the ordinary state-based peridynamic method decouples distortion and dilation and can easily simulate the plastic deformation of materials. Therefore, based on ordinary state-based peridynamics, the Mises yield criterion and the linear isotropic hardening model were introduced to study the factors affecting the impact resistance of aluminum foam sandwich structures. Two-dimensional mesoscopic models of aluminum foam sandwich structure were established by the Monte-Carlo method and impact was simulated using the peridynamic method. The influence of the porosity of aluminum foam on the impact resistance and damage mode of the sandwich structure was analyzed. The results show that the good plastic deformation ability of aluminum foam sandwich structure is the main factor for its buffering and protection, and within a certain range, the higher the porosity of aluminum foam core, the better impact resistance of the sandwich structure. When the porosity of aluminum foam increases from 0.4 to 0.7, the kinetic energy absorption rate of aluminum foam to the impactor increases from 90% to 99%. The simulation results are in good agreement with the experimental results, which verifies the accuracy of the simulation results and the effectiveness of the analysis conclusions. The numerical simulation predicts the crack propagation morphology of the plexiglass backplate, and the results show that improving the porosity of aluminum foam can obtain a better protection effect.
Under impact, aluminum foam undergoes significant plastic deformation, and the kinetic energy of the impactor is dissipated in the process, thereby protecting the structure from damage. The failure modes of aluminum foam sandwich structures under impact are complex, involving plastic deformation, panel failure, and cracking of the bonding interface. Traditional numerical simulation methods are difficult to solve these discontinuous problems. Peridynamics is a non-local numerical method that describes the mechanical behavior of materials by solving spatial integral equations. It has unique advantages in solving crack propagation, material failure, progressive damage of composite materials, and multi-scale problems. Although the basic bond-based peridynamic theory cannot describe plasticity, the ordinary state-based peridynamic method decouples distortion and dilation and can easily simulate the plastic deformation of materials. Therefore, based on ordinary state-based peridynamics, the Mises yield criterion and the linear isotropic hardening model were introduced to study the factors affecting the impact resistance of aluminum foam sandwich structures. Two-dimensional mesoscopic models of aluminum foam sandwich structure were established by the Monte-Carlo method and impact was simulated using the peridynamic method. The influence of the porosity of aluminum foam on the impact resistance and damage mode of the sandwich structure was analyzed. The results show that the good plastic deformation ability of aluminum foam sandwich structure is the main factor for its buffering and protection, and within a certain range, the higher the porosity of aluminum foam core, the better impact resistance of the sandwich structure. When the porosity of aluminum foam increases from 0.4 to 0.7, the kinetic energy absorption rate of aluminum foam to the impactor increases from 90% to 99%. The simulation results are in good agreement with the experimental results, which verifies the accuracy of the simulation results and the effectiveness of the analysis conclusions. The numerical simulation predicts the crack propagation morphology of the plexiglass backplate, and the results show that improving the porosity of aluminum foam can obtain a better protection effect.
2023, 43(3): 034203.
doi: 10.11883/bzycj-2022-0017
Abstract:
To investigate the propagation process of the underwater blasting shock wave in a fish body and its effect on typical swim bladder fishes, a critical safety wave pressure model for typical fishes was established and verified through theoretical analysis and field tests. According to the transverse reflection pattern of one-dimensional elastic compression wave between different media, the relationship between the critical safety wave pressure and the body length of typical swim bladder fishes was established. The length and mechanical properties of the swim bladder and fish body were measured using a vernier caliper, a digital micrometer, and a microcomputer tensile tester. Based on the measured data, the positive correlations of the length, width, wall thickness, and radial critical tensile stress of the swim bladder with the fish body length were determined, and the parameters in the fish critical safety wave pressure model were calibrated. The wave impedance ratio of the water medium and swim bladder wall medium was 0.3–2.0. The width, wall thickness, shape, and radial critical tensile stress coefficients of the swimming bladder were 0.04–0.09, 0.002, 0.6–1.1 and 60, respectively. The underwater blasting shock wave pressure and its effect on the fishes were measured using a blast wave tester, and the damage to the fishes was divided into three types: death, survival with influence, and survival without influence. The fish critical safety wave pressure model was verified by the statistical results of fish damage. The results show that the damage states of fishes with different body lengths at different shock pressures are conformed with the maximum and minimum critical safety wave pressure that the fishes can withstand. The proposed fish critical safety wave pressure model can be used to describe the relationship between the critical safety wave pressure and body length of the swim bladder fishes under the action of the underwater blasting shock waves. The research achievement can provide a theoretical basis for ecological protection of the fishes in the waterway regulation project of the upper reaches of the Yangtze River.
To investigate the propagation process of the underwater blasting shock wave in a fish body and its effect on typical swim bladder fishes, a critical safety wave pressure model for typical fishes was established and verified through theoretical analysis and field tests. According to the transverse reflection pattern of one-dimensional elastic compression wave between different media, the relationship between the critical safety wave pressure and the body length of typical swim bladder fishes was established. The length and mechanical properties of the swim bladder and fish body were measured using a vernier caliper, a digital micrometer, and a microcomputer tensile tester. Based on the measured data, the positive correlations of the length, width, wall thickness, and radial critical tensile stress of the swim bladder with the fish body length were determined, and the parameters in the fish critical safety wave pressure model were calibrated. The wave impedance ratio of the water medium and swim bladder wall medium was 0.3–2.0. The width, wall thickness, shape, and radial critical tensile stress coefficients of the swimming bladder were 0.04–0.09, 0.002, 0.6–1.1 and 60, respectively. The underwater blasting shock wave pressure and its effect on the fishes were measured using a blast wave tester, and the damage to the fishes was divided into three types: death, survival with influence, and survival without influence. The fish critical safety wave pressure model was verified by the statistical results of fish damage. The results show that the damage states of fishes with different body lengths at different shock pressures are conformed with the maximum and minimum critical safety wave pressure that the fishes can withstand. The proposed fish critical safety wave pressure model can be used to describe the relationship between the critical safety wave pressure and body length of the swim bladder fishes under the action of the underwater blasting shock waves. The research achievement can provide a theoretical basis for ecological protection of the fishes in the waterway regulation project of the upper reaches of the Yangtze River.
2023, 43(3): 035101.
doi: 10.11883/bzycj-2022-0333
Abstract:
In order to explore the distribution of the explosion strain field and fracture field of segmented charge explosion, used digital image correlation analysis (DIC) and computerized tomography (CT) scanning experiment analyzed the distribution of the explosion strain field and fracture field of the segment charge, established three-dimensional reconstruction model of “rock-explosion crack”, described the spatial distribution of the location and shape of the explosion crack, and obtained the fractal dimension and damage degree of the explosion crack. The research results show that: the segment charge changes the full-field strain morphology of the medium caused by continuous charge. Under the condition of satisfying the damage effect of upper sublevel explosive on medium, the effect of lower sublevel explosive on medium is increased, at the same time, the time of blast stress wave is prolonged. It can be seen from the three-dimensional cracks of segmented charge and continuous charge explosion, the explosion crack mainly expands along the radial direction, the annular crack formed by axial stress and strain is not obvious, and the radial direction is the main direction of rock failure. When the charge ratio of the upper segment is 0.4, the strain peak value of the lower segment is larger, which better meets the demand of the rock mass for explosion energy in the lower segment in engineering practice. Under the same charging coefficient, the explosive cracks in the continuous charging structure do not run through the whole specimen, and the explosive cracks in the plugging section are less, under the segment charge structure, the upper sublevel of rock mass can better use the energy of explosive explosion to break rock because the position of explosive is improve. The overall damage degree of rock in segment charge is 23.5% higher than that in continuous charge, and the damage degree of rock in upper sublevel is 46.4% higher than that in continuous charge.
In order to explore the distribution of the explosion strain field and fracture field of segmented charge explosion, used digital image correlation analysis (DIC) and computerized tomography (CT) scanning experiment analyzed the distribution of the explosion strain field and fracture field of the segment charge, established three-dimensional reconstruction model of “rock-explosion crack”, described the spatial distribution of the location and shape of the explosion crack, and obtained the fractal dimension and damage degree of the explosion crack. The research results show that: the segment charge changes the full-field strain morphology of the medium caused by continuous charge. Under the condition of satisfying the damage effect of upper sublevel explosive on medium, the effect of lower sublevel explosive on medium is increased, at the same time, the time of blast stress wave is prolonged. It can be seen from the three-dimensional cracks of segmented charge and continuous charge explosion, the explosion crack mainly expands along the radial direction, the annular crack formed by axial stress and strain is not obvious, and the radial direction is the main direction of rock failure. When the charge ratio of the upper segment is 0.4, the strain peak value of the lower segment is larger, which better meets the demand of the rock mass for explosion energy in the lower segment in engineering practice. Under the same charging coefficient, the explosive cracks in the continuous charging structure do not run through the whole specimen, and the explosive cracks in the plugging section are less, under the segment charge structure, the upper sublevel of rock mass can better use the energy of explosive explosion to break rock because the position of explosive is improve. The overall damage degree of rock in segment charge is 23.5% higher than that in continuous charge, and the damage degree of rock in upper sublevel is 46.4% higher than that in continuous charge.
