2020 Vol. 40, No. 2
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2020, 40(2): 022201.
doi: 10.11883/bzycj-2019-0063
Abstract:
Two kinds of soft oxygen-free copper tubes with average grain size of 100−300 micron and 20−30 micron were used to fabricate standard copper tubes for\begin{document}$\varnothing $\end{document} ![]()
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Two kinds of soft oxygen-free copper tubes with average grain size of 100−300 micron and 20−30 micron were used to fabricate standard copper tubes for
2020, 40(2): 022202.
doi: 10.11883/bzycj-2018-0443
Abstract:
A series of experiments were designed and implemented to explore dynamic responses of steel pipes to blast waves The time histories of dynamic strains, vibration velocities and accelerations of the steel pipes were obtained, and the vibration velocity-time curves were gained. It is known by analyzing the experimental data that in the near and middle fields of the blast wave, the peak dynamic strains are negatively correlated with the relative stiffness coefficient of the pipe and the soil, and they follow the attenuation law of the power function with scaled distance; that the attenuation indexes are different for the blast wave propagating in the different sections of the field. The peak particle vibration velocities of the ground and the pipes have good linear correlations with the peak strains of the measuring points at the pipes. On the basis of the spectrum analysis by the fast Fourier transform on each test quantity, it is found that the spectrum energy of each test quantity is mainly concentrated in the low-frequency band, the centroid frequency is in 10−60 Hz, but there are obvious differences compared to the spectra of natural seismic waves. The centroid frequency of the dynamic strain spectrum is decayed in the exponent form of a power function with the increase of the explosive charge. By taking logarithm, there is a linear attenuation relationship between the scaled distance and the centroid frequencies of velocity spectra that the blasting cavity factor is considered. The test data can be directly applied to the seismic calculation under similar conditions, and some conclusions can be used as the theoretical basis for further study of the impact damage mechanism of buried pipelines.
A series of experiments were designed and implemented to explore dynamic responses of steel pipes to blast waves The time histories of dynamic strains, vibration velocities and accelerations of the steel pipes were obtained, and the vibration velocity-time curves were gained. It is known by analyzing the experimental data that in the near and middle fields of the blast wave, the peak dynamic strains are negatively correlated with the relative stiffness coefficient of the pipe and the soil, and they follow the attenuation law of the power function with scaled distance; that the attenuation indexes are different for the blast wave propagating in the different sections of the field. The peak particle vibration velocities of the ground and the pipes have good linear correlations with the peak strains of the measuring points at the pipes. On the basis of the spectrum analysis by the fast Fourier transform on each test quantity, it is found that the spectrum energy of each test quantity is mainly concentrated in the low-frequency band, the centroid frequency is in 10−60 Hz, but there are obvious differences compared to the spectra of natural seismic waves. The centroid frequency of the dynamic strain spectrum is decayed in the exponent form of a power function with the increase of the explosive charge. By taking logarithm, there is a linear attenuation relationship between the scaled distance and the centroid frequencies of velocity spectra that the blasting cavity factor is considered. The test data can be directly applied to the seismic calculation under similar conditions, and some conclusions can be used as the theoretical basis for further study of the impact damage mechanism of buried pipelines.
2020, 40(2): 023101.
doi: 10.11883/bzycj-2019-0001
Abstract:
A series of experiments were carried out on a 156-mm-caliber oval projectile penetrating into an reinforced concrete target. With the pre-arranged pressure sensors, the pressures at different positions in the concrete targets were obtained during the penetration. Combined with numerical simulation, the damaged regions in the concrete targets and the stress states of the steel bars at different positions were analyzed. The results show that the pressures in the concrete nearby penetration trajectories are highest and the corresponding peak pulses are obvious. With the increases of the distances from the penetration trajectories, the peak pulses decrease and the pulse widths increase, the shape of the stress pulses changes from peak to relatively flat waveforms. The stress of the steel bar in the crushed region reaches its yield strength, the steel in the cracked region is in an elastic state, and the stress of the steel bar in the elastic region and the undisturbed region can be neglected.
A series of experiments were carried out on a 156-mm-caliber oval projectile penetrating into an reinforced concrete target. With the pre-arranged pressure sensors, the pressures at different positions in the concrete targets were obtained during the penetration. Combined with numerical simulation, the damaged regions in the concrete targets and the stress states of the steel bars at different positions were analyzed. The results show that the pressures in the concrete nearby penetration trajectories are highest and the corresponding peak pulses are obvious. With the increases of the distances from the penetration trajectories, the peak pulses decrease and the pulse widths increase, the shape of the stress pulses changes from peak to relatively flat waveforms. The stress of the steel bar in the crushed region reaches its yield strength, the steel in the cracked region is in an elastic state, and the stress of the steel bar in the elastic region and the undisturbed region can be neglected.
2020, 40(2): 023102.
doi: 10.11883/bzycj-2019-0066
Abstract:
The dynamic compression tests of calcareous sands with different moisture contents under quasi-one-dimensional strain conditions were carried out using a calibrated SHPB system in the average strain rate ranging from 209 s−1 to 1137 s−1. The test results show that the calibration of the sensitivity coefficient of the semiconductor strain gauge and the dispersion of the pressure bar have a significant influence on the accuracy of the test results. When the strain of the calcareous sand is below 0.025, the tangential modulus of moist calcareous sand is higher than that of dry sand, but the opposite is true when the strain is above 0.025. The tangential modulus of moist samples decreases first and then increases with the increase of the water content. By analyzing the variation of axial stress-strain curve and lateral pressure coefficient of unsaturated calcareous sand after lock-in phenomenon, a model of the phenomenon of unsaturated calcareous sand is proposed.
The dynamic compression tests of calcareous sands with different moisture contents under quasi-one-dimensional strain conditions were carried out using a calibrated SHPB system in the average strain rate ranging from 209 s−1 to 1137 s−1. The test results show that the calibration of the sensitivity coefficient of the semiconductor strain gauge and the dispersion of the pressure bar have a significant influence on the accuracy of the test results. When the strain of the calcareous sand is below 0.025, the tangential modulus of moist calcareous sand is higher than that of dry sand, but the opposite is true when the strain is above 0.025. The tangential modulus of moist samples decreases first and then increases with the increase of the water content. By analyzing the variation of axial stress-strain curve and lateral pressure coefficient of unsaturated calcareous sand after lock-in phenomenon, a model of the phenomenon of unsaturated calcareous sand is proposed.
2020, 40(2): 023103.
doi: 10.11883/bzycj-2019-0050
Abstract:
In order to investigate the mechanical response and damage mechanisms of Al2O3 ceramics, quasi-static and dynamic compression experiments are carried out on Al2O3 samples with a material test system and split Hopkinson pressure bar, respectively. In-situ optical imaging is adopted to capture the failure process of samples; synchrotron radiation CT and scanning electron microscopy (SEM) are, respectively, used to characterize the size and shape of recovered fragments and the micro fracture modes. Bulk strength data show that the compressive strength of Al2O3 ceramics conforms to a Weibull distribution and increases in a power law with the strain rate. In-situ optical imaging and SEM recovery analysis reveal that there exist obvious differences in crack nucleation and propagation between quasi-static and dynamic loading. Intergranular fracture around initial flaws is more likely to occur under quasi-static loading, macroscopically leading to fewer splitting cracks which tend to propagate along the loading direction and penetrate the sample; while transgranular fracture dominates micro cracking under dynamic loading, and the splitting cracks increases in number and interact with each other to form a large number of bifurcated, secondary cracks during the propagation process, which increases the crack density of sample. This is consistent with the three-dimensional CT characterizations. The mean of sphericity, convexity, elongation index and flatness index of fragments increase linearly with the logarithm of strain rate. The change in failure mode ultimately leads to the significantly enhanced strain rate sensitivity of ceramic materials at high strain rates.
In order to investigate the mechanical response and damage mechanisms of Al2O3 ceramics, quasi-static and dynamic compression experiments are carried out on Al2O3 samples with a material test system and split Hopkinson pressure bar, respectively. In-situ optical imaging is adopted to capture the failure process of samples; synchrotron radiation CT and scanning electron microscopy (SEM) are, respectively, used to characterize the size and shape of recovered fragments and the micro fracture modes. Bulk strength data show that the compressive strength of Al2O3 ceramics conforms to a Weibull distribution and increases in a power law with the strain rate. In-situ optical imaging and SEM recovery analysis reveal that there exist obvious differences in crack nucleation and propagation between quasi-static and dynamic loading. Intergranular fracture around initial flaws is more likely to occur under quasi-static loading, macroscopically leading to fewer splitting cracks which tend to propagate along the loading direction and penetrate the sample; while transgranular fracture dominates micro cracking under dynamic loading, and the splitting cracks increases in number and interact with each other to form a large number of bifurcated, secondary cracks during the propagation process, which increases the crack density of sample. This is consistent with the three-dimensional CT characterizations. The mean of sphericity, convexity, elongation index and flatness index of fragments increase linearly with the logarithm of strain rate. The change in failure mode ultimately leads to the significantly enhanced strain rate sensitivity of ceramic materials at high strain rates.
2020, 40(2): 023301.
doi: 10.11883/bzycj-2019-0065
Abstract:
To study the penetration and energy release effect of W/ZrNiAlCu metastable reactive alloy composite fragment against RHA target, the penetration tests using high-speed camera and ballistic gun system were conducted. And the energy equation and Arami-Erofeev equation was produced to theoretical analyze the results of penetration tests. The results show that the combustion reaction of fragment is induced by penetration process, which initiates distinct flame in the front of the target and behind the target. The brightness and scope of flame are enhanced with the increase of impact velocity. The relationship between impact velocity and plug velocity conforms to the penetration equation deduced by energy method. The theoretical ballistic limit velocity is 987.1 m/s. The efficiency of reaction is enhanced with the increase of impact pressure within the experimental velocities, which consistent with the experiment.
To study the penetration and energy release effect of W/ZrNiAlCu metastable reactive alloy composite fragment against RHA target, the penetration tests using high-speed camera and ballistic gun system were conducted. And the energy equation and Arami-Erofeev equation was produced to theoretical analyze the results of penetration tests. The results show that the combustion reaction of fragment is induced by penetration process, which initiates distinct flame in the front of the target and behind the target. The brightness and scope of flame are enhanced with the increase of impact velocity. The relationship between impact velocity and plug velocity conforms to the penetration equation deduced by energy method. The theoretical ballistic limit velocity is 987.1 m/s. The efficiency of reaction is enhanced with the increase of impact pressure within the experimental velocities, which consistent with the experiment.
2020, 40(2): 023302.
doi: 10.11883/bzycj-2019-0019
Abstract:
Based on the method of near-field dynamics, the effects of fragment velocity, ply mode of laminated plate, rib size of stiffened plate and impact position of fragment relative to rib on the damage mode and residual velocity of fragment are analyzed. The results show that: under the impact of high-speed fragments, the laminate will be penetrated and penetrated. The damage mode of the laminate is mainly matrix damage. With the increase of the impact speed of fragments, the damage area of the upper and lower surfaces of the laminate presents a trend of increasing first and then decreasing. Under the impact of high-speed fragments, the damage expansion direction of the laminate is related to the direction of fiber laying. For the laminates with the same fiber ply direction, the damage propagation direction of the upper and lower surfaces is generally the same as that of the fiber; the stiffened plate can obtain better fragment impact resistance than the laminated plate by increasing a small amount of mass, and the size of the stiffened plate and the impact position of the fragments relative to the stiffeners have a significant impact on the damage of the stiffened plate.
Based on the method of near-field dynamics, the effects of fragment velocity, ply mode of laminated plate, rib size of stiffened plate and impact position of fragment relative to rib on the damage mode and residual velocity of fragment are analyzed. The results show that: under the impact of high-speed fragments, the laminate will be penetrated and penetrated. The damage mode of the laminate is mainly matrix damage. With the increase of the impact speed of fragments, the damage area of the upper and lower surfaces of the laminate presents a trend of increasing first and then decreasing. Under the impact of high-speed fragments, the damage expansion direction of the laminate is related to the direction of fiber laying. For the laminates with the same fiber ply direction, the damage propagation direction of the upper and lower surfaces is generally the same as that of the fiber; the stiffened plate can obtain better fragment impact resistance than the laminated plate by increasing a small amount of mass, and the size of the stiffened plate and the impact position of the fragments relative to the stiffeners have a significant impact on the damage of the stiffened plate.
2020, 40(2): 024101.
doi: 10.11883/bzycj-2018-0516
Abstract:
In this paper, an internal central single-cracked disk (ICSCD) specimen was proposed for the study of dynamic fracture initiation toughness of sandstone under blasting loading. We conducted blasting tests on an ICSCD specimen fabricated from a blue sandstone disc (400 mm in diameter) with a crack (60 mm in length), obtained a blasting strain-time curve from the radial strain gauges fixed around the blast hole, determined the fracture initiation time with the circumferential strain gauges placed around the crack tip, and then derived the stress history on the blast hole of the sandstone specimen from the measured strain curve through the Laplace transform. Furthermore, we obtained the numerical solutions using numerical inversion, establishing a numerical model using the finite element software ANSYS, and derived Type I dynamic stress intensity factor curves of the sandstone under blasting loading by the mutual interaction, with the results achieved: (1) the ICSCD specimen can be used to measure the dynamic initiation fracture toughness of rocks; (2) the stress on the blast hole wall can be obtained by the Laplace numerical inversion method; (3) the dynamic initiation fracture toughness of the ICSCD sandstone specimen can be calculated by the experimental-numerical method with an error below 7%.
In this paper, an internal central single-cracked disk (ICSCD) specimen was proposed for the study of dynamic fracture initiation toughness of sandstone under blasting loading. We conducted blasting tests on an ICSCD specimen fabricated from a blue sandstone disc (400 mm in diameter) with a crack (60 mm in length), obtained a blasting strain-time curve from the radial strain gauges fixed around the blast hole, determined the fracture initiation time with the circumferential strain gauges placed around the crack tip, and then derived the stress history on the blast hole of the sandstone specimen from the measured strain curve through the Laplace transform. Furthermore, we obtained the numerical solutions using numerical inversion, establishing a numerical model using the finite element software ANSYS, and derived Type I dynamic stress intensity factor curves of the sandstone under blasting loading by the mutual interaction, with the results achieved: (1) the ICSCD specimen can be used to measure the dynamic initiation fracture toughness of rocks; (2) the stress on the blast hole wall can be obtained by the Laplace numerical inversion method; (3) the dynamic initiation fracture toughness of the ICSCD sandstone specimen can be calculated by the experimental-numerical method with an error below 7%.
A GPU parallel staircase finite difference mesh generation algorithm based on the ray casting method
2020, 40(2): 024201.
doi: 10.11883/bzycj-2019-0344
Abstract:
Three-dimensional large-scale finite difference mesh generation technology is the basis of three-dimensional finite difference computation, and the efficiency of mesh generation is a research hotspot of three-dimensional finite difference mesh generation. The traditional staircase finite difference mesh generation algorithm mainly includes ray casting algorithm and slicing algorithm. Based on the traditional serial ray casting algorithm, a parallel staircase finite difference mesh generation algorithm based on GPU (graphic processing unit) is proposed in this paper. Parallel algorithm uses batch-based data transmission strategy, which makes the scale of mesh generation independent of GPU memory size, and balances the relationship between data transmission efficiency and mesh generation scale. In order to reduce the time consumption of data transmission between the host memory and the device memory, the parallel algorithm proposed in this paper can generate ray starting coordinates independently within GPU threads, which further improves the execution efficiency and parallelization degree of the parallel algorithm. The comparison of numerical experiments shows that the efficiency of parallel algorithm is much higher than that of traditional ray casting algorithm. Finally, an example of finite difference calculation shows that the parallel algorithm can meet the requirement of large-scale numerical simulation of complex models.
Three-dimensional large-scale finite difference mesh generation technology is the basis of three-dimensional finite difference computation, and the efficiency of mesh generation is a research hotspot of three-dimensional finite difference mesh generation. The traditional staircase finite difference mesh generation algorithm mainly includes ray casting algorithm and slicing algorithm. Based on the traditional serial ray casting algorithm, a parallel staircase finite difference mesh generation algorithm based on GPU (graphic processing unit) is proposed in this paper. Parallel algorithm uses batch-based data transmission strategy, which makes the scale of mesh generation independent of GPU memory size, and balances the relationship between data transmission efficiency and mesh generation scale. In order to reduce the time consumption of data transmission between the host memory and the device memory, the parallel algorithm proposed in this paper can generate ray starting coordinates independently within GPU threads, which further improves the execution efficiency and parallelization degree of the parallel algorithm. The comparison of numerical experiments shows that the efficiency of parallel algorithm is much higher than that of traditional ray casting algorithm. Finally, an example of finite difference calculation shows that the parallel algorithm can meet the requirement of large-scale numerical simulation of complex models.
2020, 40(2): 024202.
doi: 10.11883/bzycj-2019-0057
Abstract:
Shock consolidation of powders is an effective method for fabrication of the high quality tungsten, and molecular dynamics simulation has unique advantages in modelling the rapid process at atomic-scale. In this work, the shock consolidation of nano tungsten powders at room temperature was studied by molecular dynamics using the embedded atomic potential of tungsten. The morphology of the compressed particles, distribution of particle velocity, p-Up, T-Up, T-p curves and radial distribution function were investigated to analyze the effects of particle velocity and jets on the shock consolidation. The mechanism of consolidation was also proposed at micro-scale. The results showed that the nanoparticles could not be compacted to full density at a relatively low impact velocity (＜500 m/s), while a good densification could be achieved at high impact velocity (＞1 000 m/s); the high pressure due to the extrusion between particles leads to flow and deformation on the surface of the particle. The voids among the particles were filled by the flowing atoms, leading to densification. Particles were melted during the impacts by adjacent particle and jet, which promotes the sintering between particles.
Shock consolidation of powders is an effective method for fabrication of the high quality tungsten, and molecular dynamics simulation has unique advantages in modelling the rapid process at atomic-scale. In this work, the shock consolidation of nano tungsten powders at room temperature was studied by molecular dynamics using the embedded atomic potential of tungsten. The morphology of the compressed particles, distribution of particle velocity, p-Up, T-Up, T-p curves and radial distribution function were investigated to analyze the effects of particle velocity and jets on the shock consolidation. The mechanism of consolidation was also proposed at micro-scale. The results showed that the nanoparticles could not be compacted to full density at a relatively low impact velocity (＜500 m/s), while a good densification could be achieved at high impact velocity (＞1 000 m/s); the high pressure due to the extrusion between particles leads to flow and deformation on the surface of the particle. The voids among the particles were filled by the flowing atoms, leading to densification. Particles were melted during the impacts by adjacent particle and jet, which promotes the sintering between particles.
2020, 40(2): 024203.
doi: 10.11883/bzycj-2019-0055
Abstract:
With the increasing requirements for the protection of military vehicles, the design of impact protection components is facing more and more challenges. In order to provide an efficient and scientific research method, this paper adopts a V-shaped structure, and uses radial basis function neural network approximation model and multi-objective genetic algorithm to optimize the design of a certain type of vehicle protection components. Taking the deformation amount of the protection component and the total mass as the design goal, the sensitivity analysis is used to select the design factor that has a great influence on the protection performance of the protection component. The approximate model of the experimental design sample is constructed by radial basis function neural network, and then multi-objective genetic algorithm is used to numerically optimize the optimal component of the protection component. Finally, through simulation and experimental verification, it is proved that the optimization scheme meets the design requirements. Provide a design idea for the future development of protective components.
With the increasing requirements for the protection of military vehicles, the design of impact protection components is facing more and more challenges. In order to provide an efficient and scientific research method, this paper adopts a V-shaped structure, and uses radial basis function neural network approximation model and multi-objective genetic algorithm to optimize the design of a certain type of vehicle protection components. Taking the deformation amount of the protection component and the total mass as the design goal, the sensitivity analysis is used to select the design factor that has a great influence on the protection performance of the protection component. The approximate model of the experimental design sample is constructed by radial basis function neural network, and then multi-objective genetic algorithm is used to numerically optimize the optimal component of the protection component. Finally, through simulation and experimental verification, it is proved that the optimization scheme meets the design requirements. Provide a design idea for the future development of protective components.
2020, 40(2): 025101.
doi: 10.11883/bzycj-2019-0045
Abstract:
The blasting air shock wave produced by tunnel excavation results in considerable casualties and damage to equipments and environments. Compared with those of the explosion of bare charges, the influencing factors of the blast wave induced by tunnel drilling are more complicated, so it is of considerable significance to study its attenuation law for taking appropriate protective measures. In this paper, a field test of blasting shock wave was carried out during the drilling and blasting of a large cross-section tunnel with a speed of 350 km/h, and the propagation law and influence factors of blasting shock wave under different conditions were analyzed. The results display that there are multiple overpressure peaks with different amplitudes in the shock wave overpressure-time curve, showing the short time intervals with significant millisecond delay characteristics between wave peaks. When the shock wave propagates to the far field, it does not form a stable plane wave, and it is different from the propagation law of shock wave of the single charge explosion. The shock wave overpressure signal is superimposed by multiple sub-signals, showing typical time domain properties, and the number of sub-signals is the same as that of the millisecond delay detonator segments. Under the same blasting conditions, the conversion factor of emulsion explosive energy into shock wave in a large-section tunnel is smaller than that in a small-section tunnel. Compared with the total charge and the maximum charge, the linear correlation between the peak values of shock wave overpressure calculated by the cut-hole charge and the measured peak values is the strongest. Then the maximum peak value of the blasting shock wave overpressure should be determined according to TNT equivalent of the cut-hole charge. Obstacles such as the large equipment in the tunnel will change the propagation law of the shock wave, showing a significant superimposed amplification effect.
The blasting air shock wave produced by tunnel excavation results in considerable casualties and damage to equipments and environments. Compared with those of the explosion of bare charges, the influencing factors of the blast wave induced by tunnel drilling are more complicated, so it is of considerable significance to study its attenuation law for taking appropriate protective measures. In this paper, a field test of blasting shock wave was carried out during the drilling and blasting of a large cross-section tunnel with a speed of 350 km/h, and the propagation law and influence factors of blasting shock wave under different conditions were analyzed. The results display that there are multiple overpressure peaks with different amplitudes in the shock wave overpressure-time curve, showing the short time intervals with significant millisecond delay characteristics between wave peaks. When the shock wave propagates to the far field, it does not form a stable plane wave, and it is different from the propagation law of shock wave of the single charge explosion. The shock wave overpressure signal is superimposed by multiple sub-signals, showing typical time domain properties, and the number of sub-signals is the same as that of the millisecond delay detonator segments. Under the same blasting conditions, the conversion factor of emulsion explosive energy into shock wave in a large-section tunnel is smaller than that in a small-section tunnel. Compared with the total charge and the maximum charge, the linear correlation between the peak values of shock wave overpressure calculated by the cut-hole charge and the measured peak values is the strongest. Then the maximum peak value of the blasting shock wave overpressure should be determined according to TNT equivalent of the cut-hole charge. Obstacles such as the large equipment in the tunnel will change the propagation law of the shock wave, showing a significant superimposed amplification effect.
