2009 Vol. 29, No. 6
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2009, 29(6): 561-565.
doi: 10.11883/1001-1455(2009)06-0561-05
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Abstract:
The expanding gap-ring test was put forward and designed for studying the evolvement of damage in material under impact tensile. The impact tensile process of an expanding gap ring was studied by numerical simulation. The length of loading time for different positions in the gap ring is relative to the distances of these positions from the gap. However, the length of time cant be calculated by Mott-wave transmitting, but can be determined by the velocity histories of nodes in different positions of the gap ring.
The expanding gap-ring test was put forward and designed for studying the evolvement of damage in material under impact tensile. The impact tensile process of an expanding gap ring was studied by numerical simulation. The length of loading time for different positions in the gap ring is relative to the distances of these positions from the gap. However, the length of time cant be calculated by Mott-wave transmitting, but can be determined by the velocity histories of nodes in different positions of the gap ring.
2009, 29(6): 566-572.
doi: 10.11883/1001-1455(2009)06-0566-07
Abstract:
Based on the blasting construction of diaphragm wall in Puxi guiding section of East Fuxing Road crossing-river tunnel, the vibration monitoring project on the existing tunnel influenced by explosion construction was put forward, which included measure points arrangement, test method and vibration test system. Based on the monitoring data of explosion vibration, the vibration wave form, velocity, acceleration response, domain frequency and field of measure points were analyzed under the condition of three different locations and different detonators. Then according to the safety-judging criterion of explosion vibration, the conclusion that the existing tunnel could be in the base line of safety value under explosion vibration was drawn. Furthermore, the response spectrum characteristics of the existing tunnel subjected to three different explosion vibrations were concluded, these would provide references to the similar projects.
Based on the blasting construction of diaphragm wall in Puxi guiding section of East Fuxing Road crossing-river tunnel, the vibration monitoring project on the existing tunnel influenced by explosion construction was put forward, which included measure points arrangement, test method and vibration test system. Based on the monitoring data of explosion vibration, the vibration wave form, velocity, acceleration response, domain frequency and field of measure points were analyzed under the condition of three different locations and different detonators. Then according to the safety-judging criterion of explosion vibration, the conclusion that the existing tunnel could be in the base line of safety value under explosion vibration was drawn. Furthermore, the response spectrum characteristics of the existing tunnel subjected to three different explosion vibrations were concluded, these would provide references to the similar projects.
2009, 29(6): 573-578.
doi: 10.11883/1001-1455(2009)06-0573-06
Abstract:
The dynamic compression stress-strain relations of iron specimens with three sizes were obtained with a split Hopkinson pressure bar apparatus. Based on these experimental results, an empirical model was presented to quantitatively describe the influence of bar/specimen contact surfaces indentation on strain measurement in SHPB experiments. This research shows that the influence on elastic strain is obvious, even when the uneven stress states in specimens eliminated by using pulse shapers; while the influence on plastic strain is related to the hardening modulus and length of the specimen: the influence will be obvious when the hardening modulus is large and the size of the specimen is comparatively small, and the correction for plastic strain is needed.
The dynamic compression stress-strain relations of iron specimens with three sizes were obtained with a split Hopkinson pressure bar apparatus. Based on these experimental results, an empirical model was presented to quantitatively describe the influence of bar/specimen contact surfaces indentation on strain measurement in SHPB experiments. This research shows that the influence on elastic strain is obvious, even when the uneven stress states in specimens eliminated by using pulse shapers; while the influence on plastic strain is related to the hardening modulus and length of the specimen: the influence will be obvious when the hardening modulus is large and the size of the specimen is comparatively small, and the correction for plastic strain is needed.
2009, 29(6): 579-583.
doi: 10.11883/1001-1455(2009)06-0579-05
Abstract:
The SHPB compression and the reversed Taylor tests were accomplished for JOB-9003 to explore its dynamic properties under impact load and to provide the experiment data for its constitutive model. The stress-strain curves of JOB-9003 obtained in the SHPB experiment were analyzed. The analysis shows that there is a good linear relationship between strain rate and stress at low and middle strain rates. The photos of the deformed JOB-9003 cylinder in the reversed Taylor test display that damage and fracture can markedly affect the mechanical properties of JOB-9003. The constitutive model deduced from the SHPB experiment was checked by the experimental results of the Taylor test. It is indicated that this constitutive model cannot be used to describe the compressive deformation of JOB-9003 at high strain rates.
The SHPB compression and the reversed Taylor tests were accomplished for JOB-9003 to explore its dynamic properties under impact load and to provide the experiment data for its constitutive model. The stress-strain curves of JOB-9003 obtained in the SHPB experiment were analyzed. The analysis shows that there is a good linear relationship between strain rate and stress at low and middle strain rates. The photos of the deformed JOB-9003 cylinder in the reversed Taylor test display that damage and fracture can markedly affect the mechanical properties of JOB-9003. The constitutive model deduced from the SHPB experiment was checked by the experimental results of the Taylor test. It is indicated that this constitutive model cannot be used to describe the compressive deformation of JOB-9003 at high strain rates.
2009, 29(6): 584-589.
doi: 10.11883/1001-1455(2009)06-0584-06
Abstract:
According to the dimensionless depth-of-penetration formula for different targets penetrated by rigid projectiles, the present paper theoretically analyses the resistive force which the target exerts on the projectile during penetration. In particular, the impact velocity threshold, which is applicable for the assumption of constant resistive force, is formulated by impulse analysis. The impact velocity thresholds are calculated for different projectile/target combinations by the proposed formula and the calculated velocity thresholds are in good agreement with the relative numerical results.
According to the dimensionless depth-of-penetration formula for different targets penetrated by rigid projectiles, the present paper theoretically analyses the resistive force which the target exerts on the projectile during penetration. In particular, the impact velocity threshold, which is applicable for the assumption of constant resistive force, is formulated by impulse analysis. The impact velocity thresholds are calculated for different projectile/target combinations by the proposed formula and the calculated velocity thresholds are in good agreement with the relative numerical results.
2009, 29(6): 590-595.
doi: 10.11883/1001-1455(2009)06-0590-06
Abstract:
Traditional single core sandwich structures consist of two face sheets and one core. With an additional sheet, called internal sheet in this paper, inserted into the core, a two-core sandwich structure was then formed. Two-core sandwich structures with glass fiber/epoxy composite laminated face sheets and a thin internal sheet subjected to low velocity impact were studied, and attention was focused on the contact force responses of the two-core sandwich structures and effects of the locations of the internal sheet and levels of impact energy on the responses of the sandwich structures. A drop test was carried out and the contact force history between the projectile and the sandwich structures was then obtained. The results show that the contact force history of the two-core sandwich structures are affected significantly by the internal face sheet involved and the location of the internal face sheet.
Traditional single core sandwich structures consist of two face sheets and one core. With an additional sheet, called internal sheet in this paper, inserted into the core, a two-core sandwich structure was then formed. Two-core sandwich structures with glass fiber/epoxy composite laminated face sheets and a thin internal sheet subjected to low velocity impact were studied, and attention was focused on the contact force responses of the two-core sandwich structures and effects of the locations of the internal sheet and levels of impact energy on the responses of the sandwich structures. A drop test was carried out and the contact force history between the projectile and the sandwich structures was then obtained. The results show that the contact force history of the two-core sandwich structures are affected significantly by the internal face sheet involved and the location of the internal face sheet.
2009, 29(6): 596-600.
doi: 10.11883/1001-1455(2009)06-0596-05
Abstract:
Based on Motts statistical theory and Gradys energy balance theory, The Crack Opening Displacement model (COD model ), was used to describe the brittle fragmentation characteristic of TU1 ring. The formula of fragment size and number were derived from the COD model. The fragmentation experiments were carried out for brittle TU1 rings. The freely expanding ring specimens were electromagnetically driven at different stain rates. The experimental results are in agreement with the COD model, and provide an important reference for the description of the brittle metal fragmentation behavior.
Based on Motts statistical theory and Gradys energy balance theory, The Crack Opening Displacement model (COD model ), was used to describe the brittle fragmentation characteristic of TU1 ring. The formula of fragment size and number were derived from the COD model. The fragmentation experiments were carried out for brittle TU1 rings. The freely expanding ring specimens were electromagnetically driven at different stain rates. The experimental results are in agreement with the COD model, and provide an important reference for the description of the brittle metal fragmentation behavior.
2009, 29(6): 601-606.
doi: 10.11883/1001-1455(2009)06-0601-06
Abstract:
The discontinuity instability and wave front evolution of a cylindrical convergent shock wave propagating in gas were simulated by the CE/SE scheme. The evolution of the interface between the high-pressure driving gas and the low-pressure driven gas was revealed by the level set method. Both the typical spire and bubble discontinuity patterns due to Rayleigh-Taylor (RT) and Richtmyer-Meshkov (RM) instability, and the polygon and petal patterns developed from the initial sine convergent shock wave were obtained. Results demonstrate that the CE/SE scheme is feasible in numerical simulation involving convergent shock wave propagation.
The discontinuity instability and wave front evolution of a cylindrical convergent shock wave propagating in gas were simulated by the CE/SE scheme. The evolution of the interface between the high-pressure driving gas and the low-pressure driven gas was revealed by the level set method. Both the typical spire and bubble discontinuity patterns due to Rayleigh-Taylor (RT) and Richtmyer-Meshkov (RM) instability, and the polygon and petal patterns developed from the initial sine convergent shock wave were obtained. Results demonstrate that the CE/SE scheme is feasible in numerical simulation involving convergent shock wave propagation.
2009, 29(6): 607-612.
doi: 10.11883/1001-1455(2009)06-0607-06
Abstract:
Numerical fracture induced by neighbor particles moving out of the influencing domain of the kernel function may occur in the numerical simulation of hypervelocity impact problems by the standard SPH method. A new adaptive SPH method by adding and merging particles according to the distance between particles was developed to eliminate the numerical fracture. Numerical simulations were carried out on the Taylor and hypervelocity impact samples. Simulated results display that the new adaptive SPH method can effectively eliminate the numerical fracture in the computation and remarkably improve the computational precision.
Numerical fracture induced by neighbor particles moving out of the influencing domain of the kernel function may occur in the numerical simulation of hypervelocity impact problems by the standard SPH method. A new adaptive SPH method by adding and merging particles according to the distance between particles was developed to eliminate the numerical fracture. Numerical simulations were carried out on the Taylor and hypervelocity impact samples. Simulated results display that the new adaptive SPH method can effectively eliminate the numerical fracture in the computation and remarkably improve the computational precision.
2009, 29(6): 613-616.
doi: 10.11883/1001-1455(2009)06-0613-04
Abstract:
A sensitivity parameter design method for reliability of explosive initiators is presented. To meet the requirements of fire reliability and safety reliability, the reliability index is transformed to sensitivity distribution parameter and it may control reliability of explosive initiator by modulating sensitivity during its development. The mathematical expressions about reliability index and parameter of sensitivity distribution of explosive initiator with Normal distribution, Logistics distribution, LogNormal distribution and LogLogistics distribution are deduced. An application example shows that it is instructive for development of explosive initiators.
A sensitivity parameter design method for reliability of explosive initiators is presented. To meet the requirements of fire reliability and safety reliability, the reliability index is transformed to sensitivity distribution parameter and it may control reliability of explosive initiator by modulating sensitivity during its development. The mathematical expressions about reliability index and parameter of sensitivity distribution of explosive initiator with Normal distribution, Logistics distribution, LogNormal distribution and LogLogistics distribution are deduced. An application example shows that it is instructive for development of explosive initiators.
2009, 29(6): 617-624.
doi: 10.11883/1001-1455(2009)06-0617-08
Abstract:
The finite element code AUTODYN was used to numerically simulate the detonation processes of double layer shaped charges. The shock initiation of the inner layer charge was described by the Lee-Tarver ignition and growth model. Detonation wave propagation processes of the double layer shaped charges were discussed by the numerical results and the corresponding characteristic parameters were obtained. Jet formation processes of the typical single and double layer shaped charges were numerically presented, and jet parameters for the double layer charges with different detonation velocities in the inner and outer layers were numerically analyzed. Calculated results show that the jet head velocities of the double layer shaped charges are higher 20% than those of the single layer shaped charges. Double layer charges can effectively enhance the head velocity of a shaped charge metal jet, augment its penetration depth and increase explosive charge power.
The finite element code AUTODYN was used to numerically simulate the detonation processes of double layer shaped charges. The shock initiation of the inner layer charge was described by the Lee-Tarver ignition and growth model. Detonation wave propagation processes of the double layer shaped charges were discussed by the numerical results and the corresponding characteristic parameters were obtained. Jet formation processes of the typical single and double layer shaped charges were numerically presented, and jet parameters for the double layer charges with different detonation velocities in the inner and outer layers were numerically analyzed. Calculated results show that the jet head velocities of the double layer shaped charges are higher 20% than those of the single layer shaped charges. Double layer charges can effectively enhance the head velocity of a shaped charge metal jet, augment its penetration depth and increase explosive charge power.
2009, 29(6): 625-631.
doi: 10.11883/1001-1455(2009)06-0625-07
Abstract:
By adopting linear-focused photomultiplier tubes (PMT), an eight-channel radiation pyrometer was developed for shock temperature measurements. The dynamic linearity in each channel of the pyrometer, using the developed voltage divider circuit, exceeds 8 mA at the work voltage of -800 V. The saturated light intensity is better than the level of 100 W and the response time is less than 3 ns. The relative uncertainties of spectral radiances, which are measured by the pyrometer, are about 3% .The pyrometer was successfully used to measure the radiance history and shock temperature within 50 kK.
By adopting linear-focused photomultiplier tubes (PMT), an eight-channel radiation pyrometer was developed for shock temperature measurements. The dynamic linearity in each channel of the pyrometer, using the developed voltage divider circuit, exceeds 8 mA at the work voltage of -800 V. The saturated light intensity is better than the level of 100 W and the response time is less than 3 ns. The relative uncertainties of spectral radiances, which are measured by the pyrometer, are about 3% .The pyrometer was successfully used to measure the radiance history and shock temperature within 50 kK.
2009, 29(6): 632-636.
doi: 10.11883/1001-1455(2009)06-0632-05
Abstract:
The model was simulated by photo-elastic experiments according to the Lamb model, which included the propagation, interaction laws and interception effects of slot obstacle. The experimental results accord with the kinetics mostly: (1) There are P, S and Rayleigh waves under the action of oblique impact load. Only P and Rayleigh waves contribute to rock burst. (2) From the fringe patterns, the effects of inducing fracture and laws of propagation about pressure and Rayleigh are important factors for rock-burst mechanism, which can explain the space relationship between rock burst and face. (3) The slot on the model surface can effectively intercept stress waves, especially Rayleigh waves. So the method for controlling rock-burst is theoretically feasible.
The model was simulated by photo-elastic experiments according to the Lamb model, which included the propagation, interaction laws and interception effects of slot obstacle. The experimental results accord with the kinetics mostly: (1) There are P, S and Rayleigh waves under the action of oblique impact load. Only P and Rayleigh waves contribute to rock burst. (2) From the fringe patterns, the effects of inducing fracture and laws of propagation about pressure and Rayleigh are important factors for rock-burst mechanism, which can explain the space relationship between rock burst and face. (3) The slot on the model surface can effectively intercept stress waves, especially Rayleigh waves. So the method for controlling rock-burst is theoretically feasible.
2009, 29(6): 637-641.
doi: 10.11883/1001-1455(2009)06-0637-05
Abstract:
An experimental setup, containing the pure iron flyer and sample with the same thickness, was applied to carry out symmetric impact tests on pure iron. The free-surface velocities of the pure iron samples were obtained by VISAR. The X-ray diffraction and metallographic examination of the recovered samples exhibit that abnormal multiple spalling behaviors happen in the pure iron samples as the impact pressure is above the phase transition pressure 13 GPa. By referring the experimental results by L.R.Veeser, et al, the spalling mechanism was explored by analyzing the interaction process of stress waves. It is found that the shock-induced phase transition, release-induced reverse phase transition and rarefaction shock wave lead to the abnormal (secondary) spalling phenomena in the pure iron samples.
An experimental setup, containing the pure iron flyer and sample with the same thickness, was applied to carry out symmetric impact tests on pure iron. The free-surface velocities of the pure iron samples were obtained by VISAR. The X-ray diffraction and metallographic examination of the recovered samples exhibit that abnormal multiple spalling behaviors happen in the pure iron samples as the impact pressure is above the phase transition pressure 13 GPa. By referring the experimental results by L.R.Veeser, et al, the spalling mechanism was explored by analyzing the interaction process of stress waves. It is found that the shock-induced phase transition, release-induced reverse phase transition and rarefaction shock wave lead to the abnormal (secondary) spalling phenomena in the pure iron samples.
2009, 29(6): 642-647.
doi: 10.11883/1001-1455(2009)06-0642-06
Abstract:
A methodology for the numerical simulation of bird strike on a nose radome structure of an aircraft is presented. The simulation technique is based on a non-linear dynamic finite element analysis and is performed in two steps. The first step deals with the choice of suitable material models capable of representing the behaviors of the material systems used in the impact process. The second step deals with the numerical simulation of bird strike on aircraft radome structure. The influence on the numerical results of the critical modeling issues such as the mesh density, the substitute bird flexibility and contact interfaces parameters are discussed briefly, and the of strain rate effect of material is presented by comparing the calculations. Then, the analytical method is employed to predict the amount of energy absorbed by the radome structure. As the impact location varys, the tendency of the energy absorbed by the structure is given.
A methodology for the numerical simulation of bird strike on a nose radome structure of an aircraft is presented. The simulation technique is based on a non-linear dynamic finite element analysis and is performed in two steps. The first step deals with the choice of suitable material models capable of representing the behaviors of the material systems used in the impact process. The second step deals with the numerical simulation of bird strike on aircraft radome structure. The influence on the numerical results of the critical modeling issues such as the mesh density, the substitute bird flexibility and contact interfaces parameters are discussed briefly, and the of strain rate effect of material is presented by comparing the calculations. Then, the analytical method is employed to predict the amount of energy absorbed by the radome structure. As the impact location varys, the tendency of the energy absorbed by the structure is given.
2009, 29(6): 648-653.
doi: 10.11883/1001-1455(2009)06-0648-06
Abstract:
The explosion seismic source function in hard rock was numerically simulated with a one-dimensional spherical symmetric finite difference code. The following factors were calculated as the displacement and radial pressure at the elastic radius, the reduced displacement potential and source spectrum. These calculated results are in agreement with the existent results. And the relationship between seismic coupling strength and material shear strength was discussed. It is found that the seismic source strength of underground explosion decreases with the increase of material shear strength.
The explosion seismic source function in hard rock was numerically simulated with a one-dimensional spherical symmetric finite difference code. The following factors were calculated as the displacement and radial pressure at the elastic radius, the reduced displacement potential and source spectrum. These calculated results are in agreement with the existent results. And the relationship between seismic coupling strength and material shear strength was discussed. It is found that the seismic source strength of underground explosion decreases with the increase of material shear strength.
2009, 29(6): 654-658.
doi: 10.11883/1001-1455(2009)06-0654-05
Abstract:
Aluminum foam-filled tubes were prepared by filling open-cell aluminum foam into thin-walled aluminum alloy tubes. Quasi-static compression experiments were conducted to investigate the compressive deformation behaviors of the foam-filled tubes. Influences of the structural characteristic parameters both of the aluminum foam and the hollow tube on the compressive properties and energy absorption behaviors of the tubes with foam filler were explored. Experimental results show that the compressive load-displacement curves of aluminum tubes with foam filler exhibit a distinct characteristic of three deformation regions, namely, elasticity region，serrated plastic plateau region and densification region. The factors, which include the diameter-thickness ratio of the aluminum tube, the density and property of aluminum foam, remarkable affect the mean crushing load and energy absorption characteristics of the foam-filled tube. The aluminum foam filler can modify the compressive deformation pattern of the aluminum tube. The wall of the aluminum tube with foam filler just folds outward during compression deformation.
Aluminum foam-filled tubes were prepared by filling open-cell aluminum foam into thin-walled aluminum alloy tubes. Quasi-static compression experiments were conducted to investigate the compressive deformation behaviors of the foam-filled tubes. Influences of the structural characteristic parameters both of the aluminum foam and the hollow tube on the compressive properties and energy absorption behaviors of the tubes with foam filler were explored. Experimental results show that the compressive load-displacement curves of aluminum tubes with foam filler exhibit a distinct characteristic of three deformation regions, namely, elasticity region，serrated plastic plateau region and densification region. The factors, which include the diameter-thickness ratio of the aluminum tube, the density and property of aluminum foam, remarkable affect the mean crushing load and energy absorption characteristics of the foam-filled tube. The aluminum foam filler can modify the compressive deformation pattern of the aluminum tube. The wall of the aluminum tube with foam filler just folds outward during compression deformation.
2009, 29(6): 659-664.
doi: 10.11883/1001-1455(2009)06-0659-06
Abstract:
An apparatus for measuring explosion limit of combustible liquid vapor was designed. The explosion limits and detonation parameters, the least explosion suppressible concentration of RP-5 oil, RP-3 oil and alcohol air mixtures were measured respectively by using the apparatus and vertical detonation tube. The results indicate that the explosion limits and the least explosion suppressible concentration of the 1301 inert gas are (1.53~7.73)%, (0.82~7.17)% and (3.38~18.25)%, 6.75%, 6.8% and 5.56%, respectively, by volume, for RP-5 oil, RP-3 oil and alcohol air mixtures; the least explosion suppressible concentrations of N2, and CO2 are 49% and 45%, respectively, by volume, for RP-3 oil air mixtures. So the suppression effect of 1301 inert gas is better than CO2 and N2. The critical initiation energy, detonation velocity and pressure, the width of detonation wave cells are 2.11 MJ/m2, 1 609 m/s, 1 480 kPa, 14.5 mm, respectively, for alcohol-air mixture with equivalence ratio concentration.
An apparatus for measuring explosion limit of combustible liquid vapor was designed. The explosion limits and detonation parameters, the least explosion suppressible concentration of RP-5 oil, RP-3 oil and alcohol air mixtures were measured respectively by using the apparatus and vertical detonation tube. The results indicate that the explosion limits and the least explosion suppressible concentration of the 1301 inert gas are (1.53~7.73)%, (0.82~7.17)% and (3.38~18.25)%, 6.75%, 6.8% and 5.56%, respectively, by volume, for RP-5 oil, RP-3 oil and alcohol air mixtures; the least explosion suppressible concentrations of N2, and CO2 are 49% and 45%, respectively, by volume, for RP-3 oil air mixtures. So the suppression effect of 1301 inert gas is better than CO2 and N2. The critical initiation energy, detonation velocity and pressure, the width of detonation wave cells are 2.11 MJ/m2, 1 609 m/s, 1 480 kPa, 14.5 mm, respectively, for alcohol-air mixture with equivalence ratio concentration.
2009, 29(6): 665-668.
doi: 10.11883/1001-1455(2009)06-0665-04
Abstract:
Three kinds of ultrafine TATB with different microstructure were prepared, and 2% F2311 binder was added to make the TATB powder, and the TATB-based explosives were pressed with different densities. The influences of microstructure on the detonation-spreading performances of TATB-based explosives were studied by the modified floret test. The results show that the detonation-spreading performances are significantly influenced by TATB microstructures at the same short-duration shock initiation.
Three kinds of ultrafine TATB with different microstructure were prepared, and 2% F2311 binder was added to make the TATB powder, and the TATB-based explosives were pressed with different densities. The influences of microstructure on the detonation-spreading performances of TATB-based explosives were studied by the modified floret test. The results show that the detonation-spreading performances are significantly influenced by TATB microstructures at the same short-duration shock initiation.
2009, 29(6): 669-672.
doi: 10.11883/1001-1455(2009)06-0669-04
Abstract:
In order to improve the reliability assessment of an explosive initiator with small samples, the up-down test was studied. And a new arithmetic was put forward to transform the binary data into virtual complete samples. The simulation result shows that the estimate of the scale parameter from the virtual samples is better than that from the binary data while the estimates of the location parameters are approximately the same. Then using the estimates, a reliability assessment method for explosive initiator based on fiducial inference was proposed. The method was used for the reliability assessment of one explosive initiator, and was compared with the run-down method.
In order to improve the reliability assessment of an explosive initiator with small samples, the up-down test was studied. And a new arithmetic was put forward to transform the binary data into virtual complete samples. The simulation result shows that the estimate of the scale parameter from the virtual samples is better than that from the binary data while the estimates of the location parameters are approximately the same. Then using the estimates, a reliability assessment method for explosive initiator based on fiducial inference was proposed. The method was used for the reliability assessment of one explosive initiator, and was compared with the run-down method.
