2014 Vol. 34, No. 3
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2014, 34(3): 257-263.
doi: 10.11883/1001-1455(2014)03-0257-07
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Abstract:
A calculation procedure of equivalent electrical circuit was programmed.Combining circuit calculation program with LS－DYNA980 MHD, a method for magnetically driven flyer simulation coupled with electrical circuit was proposed to simulate a real experimental process.The calculation result coupled with electrical circuit can be obtained.Then the CQ－4 experiment was simulated by using this method, the results of simulation agree well with the experimental results.Optimization of strip line length h＝25 mm is achieved by comparing flatness and velocity of flyer plates under different strip line length h＝20, 25, 30 mm conditions when the charge voltage is 73 k V.
A calculation procedure of equivalent electrical circuit was programmed.Combining circuit calculation program with LS－DYNA980 MHD, a method for magnetically driven flyer simulation coupled with electrical circuit was proposed to simulate a real experimental process.The calculation result coupled with electrical circuit can be obtained.Then the CQ－4 experiment was simulated by using this method, the results of simulation agree well with the experimental results.Optimization of strip line length h＝25 mm is achieved by comparing flatness and velocity of flyer plates under different strip line length h＝20, 25, 30 mm conditions when the charge voltage is 73 k V.
2014, 34(3): 264-271.
doi: 10.11883/1001-1455(2014)03-0264-08
Abstract:
The CSTBD (cracked straight-through Brazilian disc) specimens of sandstone were diametrically impacted by the split Hopkinson pressure bar of large diameter in the mode-Ⅰ (opening mode) rock dynamic fracture test.The experimental-numerical method was employed to obtain the dynamic initiation toughness under different dynamic loading rates; and based on some theoretical analysis and reasonable simplification, the experimental-numerical method and universal function were employed to obtain the dynamic propagation toughness with different crack velocities.In order to verify the validity of the universal function and the experimental-numerical method, comparisons with well-established references of concern were made, and our results present the same law of phenomena as those derived from other researchers.Increases in the dynamic initiation toughness and the dynamic propagation toughness were observed with increasing dynamic loading rate and crack tip speed, respectively.
The CSTBD (cracked straight-through Brazilian disc) specimens of sandstone were diametrically impacted by the split Hopkinson pressure bar of large diameter in the mode-Ⅰ (opening mode) rock dynamic fracture test.The experimental-numerical method was employed to obtain the dynamic initiation toughness under different dynamic loading rates; and based on some theoretical analysis and reasonable simplification, the experimental-numerical method and universal function were employed to obtain the dynamic propagation toughness with different crack velocities.In order to verify the validity of the universal function and the experimental-numerical method, comparisons with well-established references of concern were made, and our results present the same law of phenomena as those derived from other researchers.Increases in the dynamic initiation toughness and the dynamic propagation toughness were observed with increasing dynamic loading rate and crack tip speed, respectively.
2014, 34(3): 272-277.
doi: 10.11883/1001-1455(2014)03-0272-06
Abstract:
Based on load technique of gas gun and inertia projecting method, a device is developed to eject water column with desired speed and regular shape for hydraulic impact tests.Referring to piston push technology, this device used a projecting cylinder filled with water to replace piston.Under huge push of gas gun, the cylinder is accelerated and will impact buffer when arriving to desired speed, then water column in the cylinder will be ejected under inertial function because the cylinder suddenlly halts.The cylinder is made of alloy steel of high strength, and can be used again after impacting buffer made of rubber material.Using this device, water column with regular shape(Ø200 mm×1 m)is ejected, and satisfyed requirement of hydraulic impact tests.Ejecting speed is gained by photoelectric measurement method, corresponding to results of theoretic calculation.
Based on load technique of gas gun and inertia projecting method, a device is developed to eject water column with desired speed and regular shape for hydraulic impact tests.Referring to piston push technology, this device used a projecting cylinder filled with water to replace piston.Under huge push of gas gun, the cylinder is accelerated and will impact buffer when arriving to desired speed, then water column in the cylinder will be ejected under inertial function because the cylinder suddenlly halts.The cylinder is made of alloy steel of high strength, and can be used again after impacting buffer made of rubber material.Using this device, water column with regular shape(Ø200 mm×1 m)is ejected, and satisfyed requirement of hydraulic impact tests.Ejecting speed is gained by photoelectric measurement method, corresponding to results of theoretic calculation.
2014, 34(3): 278-284.
doi: 10.11883/1001-1455(2014)03-0278-07
Abstract:
A two-dimensional finite element model was created from a tomographic image of the aluminum foams, which represents the cell shape and geometric distribution of real foams.To determine the mechanical properties of cell wall material, the uniaxial stress versus strain curve, predicted numerically for aluminum foam, was fitted to that measured experimentally.We mainly discuss the shock wave propagation, the inertial effect and the strength of the stress on the stationary end of metallic cellular materials under high speed compression.As for aluminum foams with relative density 0.3, the elastic wave speed is calculated to be 5 km/s, whilst the plastic wave speed increases from 83 to 294 m/s, with the compression velocity increasing from 50 to 200 m/s.Within the compression velocity range of 50-100 m/s, the deformation modes change from random mode to progressive mode.However, no distinct critical velocity are observed.The dynamic locking strain increases with the increasing compression velocity.Second compression process occurs in metallic cellular materials when the plastic wave reflects on the stationary end.Accordingly, the second stress plateau appears on the stationary end, which increases with the increasing compression velocity due to inertia effect.
A two-dimensional finite element model was created from a tomographic image of the aluminum foams, which represents the cell shape and geometric distribution of real foams.To determine the mechanical properties of cell wall material, the uniaxial stress versus strain curve, predicted numerically for aluminum foam, was fitted to that measured experimentally.We mainly discuss the shock wave propagation, the inertial effect and the strength of the stress on the stationary end of metallic cellular materials under high speed compression.As for aluminum foams with relative density 0.3, the elastic wave speed is calculated to be 5 km/s, whilst the plastic wave speed increases from 83 to 294 m/s, with the compression velocity increasing from 50 to 200 m/s.Within the compression velocity range of 50-100 m/s, the deformation modes change from random mode to progressive mode.However, no distinct critical velocity are observed.The dynamic locking strain increases with the increasing compression velocity.Second compression process occurs in metallic cellular materials when the plastic wave reflects on the stationary end.Accordingly, the second stress plateau appears on the stationary end, which increases with the increasing compression velocity due to inertia effect.
2014, 34(3): 285-291.
doi: 10.11883/1001-1455(2014)03-0285-07
Abstract:
The strain-rate effects of ring structure are discussed by the numerical simulation method.The calculated results show that the buckling instability exists in both the ring structure and the folded plate structure.For the ring structure, there is a strain-rate effect at the post-buckling stage, but the degree of the strain-rate effect is not more obvious than that for the folded plate structure.In addition, the collapse instability is more obvious, and the strain-rate effect is more sensitive for a thinner thickness ring structure during the compression process.For the thicker thickness, it is difficult to buckling and the strain-rate effect is insensitive during the compression process.The model of circular honeycomb structure is created to indicate that the bucking also exists and is sensitive to the strain rate.
The strain-rate effects of ring structure are discussed by the numerical simulation method.The calculated results show that the buckling instability exists in both the ring structure and the folded plate structure.For the ring structure, there is a strain-rate effect at the post-buckling stage, but the degree of the strain-rate effect is not more obvious than that for the folded plate structure.In addition, the collapse instability is more obvious, and the strain-rate effect is more sensitive for a thinner thickness ring structure during the compression process.For the thicker thickness, it is difficult to buckling and the strain-rate effect is insensitive during the compression process.The model of circular honeycomb structure is created to indicate that the bucking also exists and is sensitive to the strain rate.
2014, 34(3): 292-299.
doi: 10.11883/1001-1455(2014)03-0292-08
Abstract:
To solve the no convergence problem due to grid distortion when simulating hypervelocity impact problems using continuum-based discrete element method (CDEM), a 2D particle contact-based meshfree method (PCMM) is presented.In PCMM, triangle elements are created based on complex and abundant contact information between particles.According to the evolution and renewal of contact pairs, old elements (satisfying the deletion condition) will be deleted and new elements (satisfying the creation condition) will be created.By introducing fluid-elastic-plastic model for elements, the hypervelocity impact problems could be simulated well.Three conditions to create triangle element are given: the three particles which the element consisted of should contact with each other; each internal angle of the triangle element should locate between 30 and 150 degree; each edge length of the element should be larger than 0.5 times of average radius.The results of numerical cases (elastic bar impacting rigid wall, Taylor bar, debris clouds, and bullet penetration) show the accuracy and rationality of PCMM.
To solve the no convergence problem due to grid distortion when simulating hypervelocity impact problems using continuum-based discrete element method (CDEM), a 2D particle contact-based meshfree method (PCMM) is presented.In PCMM, triangle elements are created based on complex and abundant contact information between particles.According to the evolution and renewal of contact pairs, old elements (satisfying the deletion condition) will be deleted and new elements (satisfying the creation condition) will be created.By introducing fluid-elastic-plastic model for elements, the hypervelocity impact problems could be simulated well.Three conditions to create triangle element are given: the three particles which the element consisted of should contact with each other; each internal angle of the triangle element should locate between 30 and 150 degree; each edge length of the element should be larger than 0.5 times of average radius.The results of numerical cases (elastic bar impacting rigid wall, Taylor bar, debris clouds, and bullet penetration) show the accuracy and rationality of PCMM.
2014, 34(3): 300-306.
doi: 10.11883/1001-1455(2014)03-0300-07
Abstract:
In order to study the confinement effect of inert materials on insensitive high explosives, the improved shock polar curve and phenomenological reaction model were employed.The confinement types were categorized by the improved shock polar theory, which was built on the leading shock wave based on the detonation ZND model, and adopted JWL equation of state in unreacted explosives and p(ρ, T)equation of state in inert material.If the sonic velocity of the confinement material is less than the CJ velocity of an explosive, the shock polar theory can be utilized.In general, there are several types of interactions that give a"match"of the pressure and streamline-deflection across the interface between IHE and confinement material.A two-dimensional Lagrangian hydrodynamic method with three-term Lee-Tarver rate law is used to numerically simulate all types of confinement interactions.The important characters of confinement material include:compressibility, thickness, the representative assembled layers, such as bakelite-iron and iron-beryllium (iron close to the explosive).
In order to study the confinement effect of inert materials on insensitive high explosives, the improved shock polar curve and phenomenological reaction model were employed.The confinement types were categorized by the improved shock polar theory, which was built on the leading shock wave based on the detonation ZND model, and adopted JWL equation of state in unreacted explosives and p(ρ, T)equation of state in inert material.If the sonic velocity of the confinement material is less than the CJ velocity of an explosive, the shock polar theory can be utilized.In general, there are several types of interactions that give a"match"of the pressure and streamline-deflection across the interface between IHE and confinement material.A two-dimensional Lagrangian hydrodynamic method with three-term Lee-Tarver rate law is used to numerically simulate all types of confinement interactions.The important characters of confinement material include:compressibility, thickness, the representative assembled layers, such as bakelite-iron and iron-beryllium (iron close to the explosive).
2014, 34(3): 307-314.
doi: 10.11883/1001-1455(2014)03-0307-08
Abstract:
Combined with the crack tip stress intensity factor criterion of linear elastic fracture mechanics, the model of initiation and extension of gas-driven fractures by compound perforation is established.A function with multiple variables describing gas pressure distribution in crack is proposed herein to realize the numerical resolution of the model using the iteration method, and the dynamic change law of gas pressure distribution in fracture with time is obtained.In addition, the effect of different characteristic parameters on the process of fracture initiation and extension as well as fracture arrest is analyzed.The example calculation shows: (1)with the progress of fracture extension, the leading edge of the flow and the fracture tip will experience the process from coincidence to noncoincidence and then to coincidence; (2)the fracture initiation and extension are more difficult as in-situ stress is greater, which makes the effective time of gas-driven and the fracture shorter; (3)the fracture initiation and extension are easier and the utilization of gas energy is higher as the initial crack is longer, resulting in the longer crack; (4)the change of fracture toughness has no obvious influence on the crack initiation and extension as well as the fracture arrest; (5)both the effective time of gas-driven and the fracture are longer as the rate of pressure rise is smaller, but its change has nearly no impact on the pressure of the fracture initiation and arrest.
Combined with the crack tip stress intensity factor criterion of linear elastic fracture mechanics, the model of initiation and extension of gas-driven fractures by compound perforation is established.A function with multiple variables describing gas pressure distribution in crack is proposed herein to realize the numerical resolution of the model using the iteration method, and the dynamic change law of gas pressure distribution in fracture with time is obtained.In addition, the effect of different characteristic parameters on the process of fracture initiation and extension as well as fracture arrest is analyzed.The example calculation shows: (1)with the progress of fracture extension, the leading edge of the flow and the fracture tip will experience the process from coincidence to noncoincidence and then to coincidence; (2)the fracture initiation and extension are more difficult as in-situ stress is greater, which makes the effective time of gas-driven and the fracture shorter; (3)the fracture initiation and extension are easier and the utilization of gas energy is higher as the initial crack is longer, resulting in the longer crack; (4)the change of fracture toughness has no obvious influence on the crack initiation and extension as well as the fracture arrest; (5)both the effective time of gas-driven and the fracture are longer as the rate of pressure rise is smaller, but its change has nearly no impact on the pressure of the fracture initiation and arrest.
2014, 34(3): 315-321.
doi: 10.11883/1001-1455(2014)03-0315-07
Abstract:
A multi-stage computational inverse technique is presented to determine the dynamic constitutive parameters of concrete based on the split Hopkinson pressure bar tests at different strain rate loadings.In this method, sensitivity analysis for parameters is carried out based on different experimental models and classification for the parameters is performed according to sensitivity, then the parameters are determined step by step through the inverse method.During parameters identification by multi-stage inverse method, last identified results are applied to current parameters identification.The results indicate that this method obtains the parameters rapidly, which are determined difficultly and expensively by traditional method, combining with different experiments.It is a potentially effective and useful tool to identify material constitutive parameters.
A multi-stage computational inverse technique is presented to determine the dynamic constitutive parameters of concrete based on the split Hopkinson pressure bar tests at different strain rate loadings.In this method, sensitivity analysis for parameters is carried out based on different experimental models and classification for the parameters is performed according to sensitivity, then the parameters are determined step by step through the inverse method.During parameters identification by multi-stage inverse method, last identified results are applied to current parameters identification.The results indicate that this method obtains the parameters rapidly, which are determined difficultly and expensively by traditional method, combining with different experiments.It is a potentially effective and useful tool to identify material constitutive parameters.
2014, 34(3): 322-327.
doi: 10.11883/1001-1455(2014)03-0322-06
Abstract:
Cylinder shells of 45 steel were freezing recovery experimented using a modified SHPB device to observe the whole fracture process, including crack initiation, crack propagation conditions and final fracture modes.By microanalysing the internal structures of the recovery samples, the whole fracture process was observed, and some conclusions were obtained:the tensile and shear fracture mechanism played a dominant role in the dynamic fracture process of cylinder shells, cracks initiated from the outer wall, then propagated into inner wall, the fracture mode changed from tensile-shear mixing to pure shear with increasing load strain rate.There were some differences between these experimental results and the results loaded by detonation, which need us to further study, that the fracture modes would change from tensile to pure shear in these experimental results, rather than adiabatic shear in detonations with increasing strain rate
Cylinder shells of 45 steel were freezing recovery experimented using a modified SHPB device to observe the whole fracture process, including crack initiation, crack propagation conditions and final fracture modes.By microanalysing the internal structures of the recovery samples, the whole fracture process was observed, and some conclusions were obtained:the tensile and shear fracture mechanism played a dominant role in the dynamic fracture process of cylinder shells, cracks initiated from the outer wall, then propagated into inner wall, the fracture mode changed from tensile-shear mixing to pure shear with increasing load strain rate.There were some differences between these experimental results and the results loaded by detonation, which need us to further study, that the fracture modes would change from tensile to pure shear in these experimental results, rather than adiabatic shear in detonations with increasing strain rate
2014, 34(3): 328-333.
doi: 10.11883/1001-1455(2014)03-0328-06
Abstract:
The relationship between elastic bar diameter of split Hopkinson pressure bar(SHPB) systems and the minimum strain rate causing rock failure under once impact with half-sine stress wave loads, is analyzed based on the Steverding-Lehnigk fracture criterion of brittle materials.The tests were carried out at different strain rates from high to low on the SHPB systems with different elastic bar diameters of 22, 36, 50 and 75 mm.Granite was used in these tests, and its size varies with the elastic bar diameter.The variation law of the lowest strain rate with the elastic bar diameter was discussed.The theoretical and experimental results show that the lowest strain rate of rock decreases with the increase of the elastic bar diameter in power relation.However, the bar diameter has already exceeded 100 mm when the strain rate decreases to the order of 10 0 s-1, and the effect of decreasing strain rate by increasing bar diameter turns to be less evident.
The relationship between elastic bar diameter of split Hopkinson pressure bar(SHPB) systems and the minimum strain rate causing rock failure under once impact with half-sine stress wave loads, is analyzed based on the Steverding-Lehnigk fracture criterion of brittle materials.The tests were carried out at different strain rates from high to low on the SHPB systems with different elastic bar diameters of 22, 36, 50 and 75 mm.Granite was used in these tests, and its size varies with the elastic bar diameter.The variation law of the lowest strain rate with the elastic bar diameter was discussed.The theoretical and experimental results show that the lowest strain rate of rock decreases with the increase of the elastic bar diameter in power relation.However, the bar diameter has already exceeded 100 mm when the strain rate decreases to the order of 10 0 s-1, and the effect of decreasing strain rate by increasing bar diameter turns to be less evident.
2014, 34(3): 334-339.
doi: 10.11883/1001-1455(2014)03-0334-06
Abstract:
A non-explosive underwater shock loading device exhibits many advantages as a new labscale research method of underwater explosion, including high reliability, low cost.This method has an important role on further research on underwater explosion.To generate impulsive loading similar to blast, the exponentially decaying underwater pressure was produced by a flyer plate struck a piston at one end of the water tank.The shock wave strength and decay constant in a certain working condition were determined.The reliability of the non-explosive underwater explosion shock loading device was investigated by experiment and numerical simulation.The results indicate that the device can effectively simulate underwater explosive shock wave.
A non-explosive underwater shock loading device exhibits many advantages as a new labscale research method of underwater explosion, including high reliability, low cost.This method has an important role on further research on underwater explosion.To generate impulsive loading similar to blast, the exponentially decaying underwater pressure was produced by a flyer plate struck a piston at one end of the water tank.The shock wave strength and decay constant in a certain working condition were determined.The reliability of the non-explosive underwater explosion shock loading device was investigated by experiment and numerical simulation.The results indicate that the device can effectively simulate underwater explosive shock wave.
2014, 34(3): 340-346.
doi: 10.11883/1001-1455(2014)03-0340-07
Abstract:
NaOH and sodium silicate-activated slag and fly ash based geopolymer concrete(NSSFGC) and NaOH and Na2CO3-activated slag and fly ash based geopolymer concrete(NNSFGC) with strength grades of C30 were prepared, the strain rate effects under impact loading were studied contrastly by using a 100-mm-diameter SHPB apparatus improved with the pulse shaper technique.The results indicate that, the peak stress of NSSFGC and NNSFGC increases with the increase of strain rate, which indicates that GC is a kind of strain rate sensitive material; strain rate sensitivity thresholds of NSSFGC and NNSFGC under dynamic compressive condition are 51.82 and 28.89 s-1; the strain rate sensitivity is much stronger than ordinary concrete; the alkali-activator prepared with NaOH and Na2CO3 can be beneficial to give full play to overall strength property of GC.Thus it can be seen, that the strain rate sensitivity of NNSFGC is stronger than NSSFGC.
NaOH and sodium silicate-activated slag and fly ash based geopolymer concrete(NSSFGC) and NaOH and Na2CO3-activated slag and fly ash based geopolymer concrete(NNSFGC) with strength grades of C30 were prepared, the strain rate effects under impact loading were studied contrastly by using a 100-mm-diameter SHPB apparatus improved with the pulse shaper technique.The results indicate that, the peak stress of NSSFGC and NNSFGC increases with the increase of strain rate, which indicates that GC is a kind of strain rate sensitive material; strain rate sensitivity thresholds of NSSFGC and NNSFGC under dynamic compressive condition are 51.82 and 28.89 s-1; the strain rate sensitivity is much stronger than ordinary concrete; the alkali-activator prepared with NaOH and Na2CO3 can be beneficial to give full play to overall strength property of GC.Thus it can be seen, that the strain rate sensitivity of NNSFGC is stronger than NSSFGC.
2014, 34(3): 347-353.
doi: 10.11883/1001-1455(2014)03-0347-07
Abstract:
Aimed at acceleration information acquisition and original signal failure problem of projectile penetrating into concrete, a projectile-borne storage testing system was used to conduct test, and the numerical simulation of high-velocity impact was carried out based on LS-DYNA, and the processed data curve corresponds to the measured penetration depth.The numerical simulation results and testing results are in good agreement, which indicates the correctness of this numerical simulation model establishment and parameter selection.The influence analysis of original acceleration signal is conducted on stress wave, fundamental motion of testing device, installed structural stiffness, installation way of accelerometer and some other influencing factors by way of combining test analysis with theoretical derivation, and the results of analysis have certain reference value for high-g-value shock test problem.
Aimed at acceleration information acquisition and original signal failure problem of projectile penetrating into concrete, a projectile-borne storage testing system was used to conduct test, and the numerical simulation of high-velocity impact was carried out based on LS-DYNA, and the processed data curve corresponds to the measured penetration depth.The numerical simulation results and testing results are in good agreement, which indicates the correctness of this numerical simulation model establishment and parameter selection.The influence analysis of original acceleration signal is conducted on stress wave, fundamental motion of testing device, installed structural stiffness, installation way of accelerometer and some other influencing factors by way of combining test analysis with theoretical derivation, and the results of analysis have certain reference value for high-g-value shock test problem.
2014, 34(3): 354-360.
doi: 10.11883/1001-1455(2014)03-0354-07
Abstract:
Wall pressure as a load parameter should be confirmed exactly, and then offered for investigating dynamic response of structure such as a plate subjected to underwater explosion.On the basis of plane shock wave hypothesis, a theoretical formula was deduced and proposed to calculate the wall pressure values of an infinite plate subjected to underwater explosion shockwaves at any angle of incidence.By using the wall pressure data derived from underwater explosion experiments, the theoretical formula of wall pressure was revised to be suitable for plates with finite dimensions.With the revised formula, the characteristics of the wall pressure on the plate were analyzed by considering various incidence angles, and the effects of the negative wall pressure values on local cavitation on the plate were discussed primarily.The results show that the wall pressure values derived from the revised formula agree well with those from the experiments.As the incidence angle increases, the wall pressure decays more rapidly, and the absolute value of the minimum wall pressure decreases.With the more explosive or the thicker plate, the absolute value of the minimum wall pressure is larger, and local cavitation takes place more likely.Local cavitation can only come into being in certain conditions, and the cavitation range will be affected by the factors such as cavitation pressure criterion, shock intensity, and so on.
Wall pressure as a load parameter should be confirmed exactly, and then offered for investigating dynamic response of structure such as a plate subjected to underwater explosion.On the basis of plane shock wave hypothesis, a theoretical formula was deduced and proposed to calculate the wall pressure values of an infinite plate subjected to underwater explosion shockwaves at any angle of incidence.By using the wall pressure data derived from underwater explosion experiments, the theoretical formula of wall pressure was revised to be suitable for plates with finite dimensions.With the revised formula, the characteristics of the wall pressure on the plate were analyzed by considering various incidence angles, and the effects of the negative wall pressure values on local cavitation on the plate were discussed primarily.The results show that the wall pressure values derived from the revised formula agree well with those from the experiments.As the incidence angle increases, the wall pressure decays more rapidly, and the absolute value of the minimum wall pressure decreases.With the more explosive or the thicker plate, the absolute value of the minimum wall pressure is larger, and local cavitation takes place more likely.Local cavitation can only come into being in certain conditions, and the cavitation range will be affected by the factors such as cavitation pressure criterion, shock intensity, and so on.
2014, 34(3): 361-366.
doi: 10.11883/1001-1455(2014)03-0361-06
Abstract:
This numerical simulation study was undertaken to investigate the penetration and explosion efficiency of a sequence of precision-guided earth penetrating weapon(EPW)into hard rock target.The main objective of the study was to ascertain the damage depth of using much more EPW, the relative depth would decreases with bomb number decreasing, the ultimate depth was limited.The simulations were performed using EP3D-a 3D explosion and penetration efficiency hydrocode.To describe the engineering rock body on the test site, it was divided into two parts, which were structure body and structure interface.A new rock constitutive model was built up for homogeneous structure body, and moreover, a space block model was brought out, which takes into account the non-homogeneousness of nature rock based on structure interface.Through this model, lots of numerical simulation works were done on repeat attack effect, and the numerical results agreed well with those of experiments, all of them made it clear that the ultimate damage depth of repeated attack was a limited value because of residual fragment, impact deviance and non-homogeneousness of nature rock.
This numerical simulation study was undertaken to investigate the penetration and explosion efficiency of a sequence of precision-guided earth penetrating weapon(EPW)into hard rock target.The main objective of the study was to ascertain the damage depth of using much more EPW, the relative depth would decreases with bomb number decreasing, the ultimate depth was limited.The simulations were performed using EP3D-a 3D explosion and penetration efficiency hydrocode.To describe the engineering rock body on the test site, it was divided into two parts, which were structure body and structure interface.A new rock constitutive model was built up for homogeneous structure body, and moreover, a space block model was brought out, which takes into account the non-homogeneousness of nature rock based on structure interface.Through this model, lots of numerical simulation works were done on repeat attack effect, and the numerical results agreed well with those of experiments, all of them made it clear that the ultimate damage depth of repeated attack was a limited value because of residual fragment, impact deviance and non-homogeneousness of nature rock.
2014, 34(3): 367-372.
doi: 10.11883/1001-1455(2014)03-0367-06
Abstract:
The conception of scaled distance was applied to tunnel blasting vibration zoning and the zoning was judged by the slope of velocity attenuation curve.Based on the results, the BP wavelet neural network method for tunnel blasting vibration velocity near tunnel blasting source was proposed, then the method was used in the Qipanshan tunnels to verify the reliability of the model.Combined with the engineering practice of Dapingshan tunnels, new tunnel next to existing tunnel blasting seismic wave attenuation law was analyzed and blasting vibration velocity near tunnel blasting source was predicted.The results show that:(1)The tunnel blasting vibration zoning can be judged by scaled distance as follow:scaled distance < 5.0 for the area near tunnel blasting source; 5.0≤scaled distance≤9.0 for the area between the area near tunnel blasting source and the area remote blasting source; scaled distance > 9.0 for the area remote blasting source without the measured data.(2)BP wavelet neural network can be used to predict the velocity near blasting source in the separated tunnel.Similarly, it can also be used to predict the velocity of new tunnel next to existing tunnel.The conclusions offer references for tunnel blasting construction under complex conditions.
The conception of scaled distance was applied to tunnel blasting vibration zoning and the zoning was judged by the slope of velocity attenuation curve.Based on the results, the BP wavelet neural network method for tunnel blasting vibration velocity near tunnel blasting source was proposed, then the method was used in the Qipanshan tunnels to verify the reliability of the model.Combined with the engineering practice of Dapingshan tunnels, new tunnel next to existing tunnel blasting seismic wave attenuation law was analyzed and blasting vibration velocity near tunnel blasting source was predicted.The results show that:(1)The tunnel blasting vibration zoning can be judged by scaled distance as follow:scaled distance < 5.0 for the area near tunnel blasting source; 5.0≤scaled distance≤9.0 for the area between the area near tunnel blasting source and the area remote blasting source; scaled distance > 9.0 for the area remote blasting source without the measured data.(2)BP wavelet neural network can be used to predict the velocity near blasting source in the separated tunnel.Similarly, it can also be used to predict the velocity of new tunnel next to existing tunnel.The conclusions offer references for tunnel blasting construction under complex conditions.
2014, 34(3): 373-378.
doi: 10.11883/1001-1455(2014)03-0373-06
Abstract:
A new kind of composite energy absorption material was made by filling the holes of open-cell aluminum foam with polyurethane.Split Hopkinson pressure bar impact experiments were performed to evaluate the dynamic mechanical property of the polyurethane foam aluminum complex material.Based on the test results, we analyzed the mechanical behaviors of the material through influencing factors including relative density, strain, strain rate and content of polyurethane.Then the dynamic constitutive model was established.It was shown that: the dynamic modulus of elasticity of the composite material is independent of the relative density; the yield strength and the flow stress of the composite material varies directly with the strain rate and the relative density; the yield strength of the composite material varies directly with the mass of the polyurethane foam.It was proved that in definite ranges of relative density and strain rate, the curves of constitutive model fit well with the curves of experimental data.So the dynamic constitutive model has some reference value to engineering applications.
A new kind of composite energy absorption material was made by filling the holes of open-cell aluminum foam with polyurethane.Split Hopkinson pressure bar impact experiments were performed to evaluate the dynamic mechanical property of the polyurethane foam aluminum complex material.Based on the test results, we analyzed the mechanical behaviors of the material through influencing factors including relative density, strain, strain rate and content of polyurethane.Then the dynamic constitutive model was established.It was shown that: the dynamic modulus of elasticity of the composite material is independent of the relative density; the yield strength and the flow stress of the composite material varies directly with the strain rate and the relative density; the yield strength of the composite material varies directly with the mass of the polyurethane foam.It was proved that in definite ranges of relative density and strain rate, the curves of constitutive model fit well with the curves of experimental data.So the dynamic constitutive model has some reference value to engineering applications.
2014, 34(3): 379-384.
doi: 10.11883/1001-1455(2014)03-0379-06
Abstract:
A new non-ideal explosive was obtained by adding aluminum fiber to RDX.Pressure-time curves were measured in different regions by underwater explosion experiments of aluminum fiber explosive and RDX.Peak pressure, impulse, shock wave energy, bubble impulsion period and bubble energy were obtained by analyzing the curves.The peak pressure of the new explosive is lower than that of RDX in same regions.The shock wave impulse becomes lager and the distance does not much affect the difference.Compared with RDX, the specific shock wave energy of the new explosive decreases by 2%~5.2%, the specific bubble energy rises by 9.4%~23.36%, the specific explosion energy increases averagely by 3.5%.The specific bubble energy is 55%~60% of explosion energy, which is higher than the ratio 50%~53% of RDX.The specific explosion energy is 74%~84% of explosion heat, which is lower than the ratio 89%~95%of RDX.
A new non-ideal explosive was obtained by adding aluminum fiber to RDX.Pressure-time curves were measured in different regions by underwater explosion experiments of aluminum fiber explosive and RDX.Peak pressure, impulse, shock wave energy, bubble impulsion period and bubble energy were obtained by analyzing the curves.The peak pressure of the new explosive is lower than that of RDX in same regions.The shock wave impulse becomes lager and the distance does not much affect the difference.Compared with RDX, the specific shock wave energy of the new explosive decreases by 2%~5.2%, the specific bubble energy rises by 9.4%~23.36%, the specific explosion energy increases averagely by 3.5%.The specific bubble energy is 55%~60% of explosion energy, which is higher than the ratio 50%~53% of RDX.The specific explosion energy is 74%~84% of explosion heat, which is lower than the ratio 89%~95%of RDX.
