2009 Vol. 29, No. 1
Display Method:
2009, 29(1): 1-6.
doi: 10.11883/1001-1455(2009)01-0001-06
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Abstract:
Flames and inert gases past an cylinder obstacle were numerically simulated by using the immersed boundary method used in the 3D compressible viscous flow and the high-order accurate total variation diminishing (TVD) schemes based on the high-order piecewise parabolic method (PPM). In the turbulent calculation, the large eddy simulation (LES) was introduced and the eddy break-up(EBU) model was adopted to compute the chemical reaction rate. Comparison of the simulated and experimental results shows that the high-accuracy PPM schemes can used to simulate fame and inert gas past a cylinder obstacle effectively. The numerical computation of the flame past the cylinder obstacle indicates that before the flame passes the cylinder obstacle, the gas expansion due to combustion causes the unburned gases in front of the flame to flow and to form the inert gas past the cylinder obstacle. This is similar to the inert gas past the cylinder obstacle without combustion. But there are obvious differences between the fame and inert gas past the cylinder obstacle when and after the flame passes the cylinder obstacle.
Flames and inert gases past an cylinder obstacle were numerically simulated by using the immersed boundary method used in the 3D compressible viscous flow and the high-order accurate total variation diminishing (TVD) schemes based on the high-order piecewise parabolic method (PPM). In the turbulent calculation, the large eddy simulation (LES) was introduced and the eddy break-up(EBU) model was adopted to compute the chemical reaction rate. Comparison of the simulated and experimental results shows that the high-accuracy PPM schemes can used to simulate fame and inert gas past a cylinder obstacle effectively. The numerical computation of the flame past the cylinder obstacle indicates that before the flame passes the cylinder obstacle, the gas expansion due to combustion causes the unburned gases in front of the flame to flow and to form the inert gas past the cylinder obstacle. This is similar to the inert gas past the cylinder obstacle without combustion. But there are obvious differences between the fame and inert gas past the cylinder obstacle when and after the flame passes the cylinder obstacle.
2009, 29(1): 7-12.
doi: 10.11883/1001-1455(2009)01-0007-06
Abstract:
Materials such as steel and reinforced concrete are frequently used in blast-resistant structures. However, analytical procedures for those structures are limited to elastic or elastic-plastic small deformations. This paper aims to discuss the feasibility of the application of nonlinear elastic large deformation materials to blast-resistant structures theoretically. Based on the principle of the equivalent structural system and the representation of the transverse and longitudinal displacements of the beam supported with immovable pinned ends by triangular series, a simplified nonlinear analytical method is derived for the beam consisting of nonlinear elastic large deformation materials by Lagranges equations of the second kind. The effectiveness of the proposed analytical method is verified by ABAQUS finite element code, in which the nonlinear elastic large deformation materials are simulated by the hyperelastic model. The blast-resistant properties of the beams consisting of the nonlinear elastic material subjected to the typical blast loads are analyzed, and the discussions about the relationships among the dynamic magnification factor, material property, and the blast load are given. The analytical results show that the blast resistance of the beam consisting of nonlinear elastic large deformation materials is much better than that of the beam consisting of linear elastic small deformation materials, and the structural blast-resistance increases greatly with the increasing of the structural deformation.
Materials such as steel and reinforced concrete are frequently used in blast-resistant structures. However, analytical procedures for those structures are limited to elastic or elastic-plastic small deformations. This paper aims to discuss the feasibility of the application of nonlinear elastic large deformation materials to blast-resistant structures theoretically. Based on the principle of the equivalent structural system and the representation of the transverse and longitudinal displacements of the beam supported with immovable pinned ends by triangular series, a simplified nonlinear analytical method is derived for the beam consisting of nonlinear elastic large deformation materials by Lagranges equations of the second kind. The effectiveness of the proposed analytical method is verified by ABAQUS finite element code, in which the nonlinear elastic large deformation materials are simulated by the hyperelastic model. The blast-resistant properties of the beams consisting of the nonlinear elastic material subjected to the typical blast loads are analyzed, and the discussions about the relationships among the dynamic magnification factor, material property, and the blast load are given. The analytical results show that the blast resistance of the beam consisting of nonlinear elastic large deformation materials is much better than that of the beam consisting of linear elastic small deformation materials, and the structural blast-resistance increases greatly with the increasing of the structural deformation.
2009, 29(1): 13-17.
doi: 10.11883/1001-1455(2009)01-0013-05
Abstract:
Based on the thermal explosion theory, the security of loaded projectiles penetrating into concrete targets was investigated. By taking the hot-spot temperature (also called the critical initial explosion temperature) as the initial explosion criterion, the thermal conductivity model was introduced. The relationship between the dimensionless heat flow density Qm and the dimensionless peak temperature Tmax, which were located in the interface between explosive charge and cartridge case, was acquired. The dimensionless control parameter Qmc, which can be used as the engineering criterion, and the dimensionless parameter KⅠ, which denotes the proportion of the received heat energy between explosive charge and cartridge case, were obtained. The results show that the intense friction between explosive charge and cartridge case is an important factor for the formation of hot spots which can cause projectiles to explode ahead of schedule.
Based on the thermal explosion theory, the security of loaded projectiles penetrating into concrete targets was investigated. By taking the hot-spot temperature (also called the critical initial explosion temperature) as the initial explosion criterion, the thermal conductivity model was introduced. The relationship between the dimensionless heat flow density Qm and the dimensionless peak temperature Tmax, which were located in the interface between explosive charge and cartridge case, was acquired. The dimensionless control parameter Qmc, which can be used as the engineering criterion, and the dimensionless parameter KⅠ, which denotes the proportion of the received heat energy between explosive charge and cartridge case, were obtained. The results show that the intense friction between explosive charge and cartridge case is an important factor for the formation of hot spots which can cause projectiles to explode ahead of schedule.
2009, 29(1): 18-22.
doi: 10.11883/1001-1455(2009)01-0018-05
Abstract:
The paper characterizes the fault zone as an idealized interface with linear slip-weakening friction and investigates reflection and transmission of stress wave across two elastic half-spaces on the condition that the initial stress state of rock interface is taken into account. On this basis, the conditions of initial slip and unstable slip are revealed, and the occurrence of dynamic triggering is analyzed which depends on the balance between the incident wave and intrinsic mechanics of fault. The example shows that when the angle of incidence is given, the higher the frequency is, the larger the needed amplitude is.
The paper characterizes the fault zone as an idealized interface with linear slip-weakening friction and investigates reflection and transmission of stress wave across two elastic half-spaces on the condition that the initial stress state of rock interface is taken into account. On this basis, the conditions of initial slip and unstable slip are revealed, and the occurrence of dynamic triggering is analyzed which depends on the balance between the incident wave and intrinsic mechanics of fault. The example shows that when the angle of incidence is given, the higher the frequency is, the larger the needed amplitude is.
2009, 29(1): 23-28.
doi: 10.11883/1001-1455(2009)01-0023-06
Abstract:
The second-order manifold method was used to simulate the dynamic tension split process of a flattened rock Brazilian disc subjected to shock loading through introducing a criteria for crack initiation and crack growth. The split process caused by a reflected tension stress wave was reproduced. The simulated phenomena are in good agreement with the experimental results. The dynamic equilibrium stress distribution also agrees with the calculated results by the finite element method. Researched results show that the manifold method is effective for the simulation of the dynamic failure process under shock loading.
The second-order manifold method was used to simulate the dynamic tension split process of a flattened rock Brazilian disc subjected to shock loading through introducing a criteria for crack initiation and crack growth. The split process caused by a reflected tension stress wave was reproduced. The simulated phenomena are in good agreement with the experimental results. The dynamic equilibrium stress distribution also agrees with the calculated results by the finite element method. Researched results show that the manifold method is effective for the simulation of the dynamic failure process under shock loading.
2009, 29(1): 29-34.
doi: 10.11883/1001-1455(2009)01-0029-06
Abstract:
Ballistic tests were performed to investigate the anti-penetration properties of ultra-high molecular weight polyethylene fiber-reinforced laminated plates (UFRP) against high-speed cubic fragments. Energy absorption performances were compared among these fiber-reinforced laminated plates with the four different area densities of 7.11, 15.4, 20.6 and 30.8 kg/m2. Experimental results show that the relations of ballistic limit and area density for the thin UFRP are different from those for the thick ones. Vertical strips on the obverse sides of the thin UFRP and horizontal strips on their rear sides can be observed, but no trips can be seen from the thick UFRP. It is required to consider effects of stamp deformation of the fragments on energy absorption and deformation modes of the thick UFRP impacted by high-speed fragments.
Ballistic tests were performed to investigate the anti-penetration properties of ultra-high molecular weight polyethylene fiber-reinforced laminated plates (UFRP) against high-speed cubic fragments. Energy absorption performances were compared among these fiber-reinforced laminated plates with the four different area densities of 7.11, 15.4, 20.6 and 30.8 kg/m2. Experimental results show that the relations of ballistic limit and area density for the thin UFRP are different from those for the thick ones. Vertical strips on the obverse sides of the thin UFRP and horizontal strips on their rear sides can be observed, but no trips can be seen from the thick UFRP. It is required to consider effects of stamp deformation of the fragments on energy absorption and deformation modes of the thick UFRP impacted by high-speed fragments.
2009, 29(1): 35-40.
doi: 10.11883/1001-1455(2009)01-0035-06
Abstract:
According to the existing blasting vibration live data, the different-frequency-band energy distribution of the blasting vibration signals was attained by the wavelet analysis technology. Based on the characteristics of dynamic response from the controlled structures by blasting vibration, a multi-factor blasting vibration safety criterion was proposed, also called the response energy criterion, in which taking the total influence of the intensity, frequency and duration of vibration and the characteristics (natural frequency and damping ratio) of dynamic response from the controlled structures themselves into account. The feasibility of the proposed criterion was validated by the engineering examples. Results show that this response energy criterion can describe accurately the effect degree of blasting vibration on the controlled structures, and that it can reflect the essence of blasting vibration damage to the structures more comprehensively than the actual velocity-frequency safety criterion.
According to the existing blasting vibration live data, the different-frequency-band energy distribution of the blasting vibration signals was attained by the wavelet analysis technology. Based on the characteristics of dynamic response from the controlled structures by blasting vibration, a multi-factor blasting vibration safety criterion was proposed, also called the response energy criterion, in which taking the total influence of the intensity, frequency and duration of vibration and the characteristics (natural frequency and damping ratio) of dynamic response from the controlled structures themselves into account. The feasibility of the proposed criterion was validated by the engineering examples. Results show that this response energy criterion can describe accurately the effect degree of blasting vibration on the controlled structures, and that it can reflect the essence of blasting vibration damage to the structures more comprehensively than the actual velocity-frequency safety criterion.
2009, 29(1): 41-44.
doi: 10.11883/1001-1455(2009)01-0041-04
Abstract:
The nano-CeO2 powders were synthesized by detonation using the Ce(NO3)36H2O as the precursor. The detonation products were characterized by XRD and TEM.Influences of urea and NaNO2 in explosive on the morphology of detonation products were investigated. The three experimental results indicate that the obtained CeO2 crystals are cubic fluorite structure and their granule dimensions are 45, 64, 33 nm, respectively. The powders are spherical when urea is added and the sizes of the powders are small when Na(NO3)36H2O is added in the explosive.
The nano-CeO2 powders were synthesized by detonation using the Ce(NO3)36H2O as the precursor. The detonation products were characterized by XRD and TEM.Influences of urea and NaNO2 in explosive on the morphology of detonation products were investigated. The three experimental results indicate that the obtained CeO2 crystals are cubic fluorite structure and their granule dimensions are 45, 64, 33 nm, respectively. The powders are spherical when urea is added and the sizes of the powders are small when Na(NO3)36H2O is added in the explosive.
2009, 29(1): 45-48.
doi: 10.11883/1001-1455(2009)01-0045-04
Abstract:
A travelling wave acoustooptic switch based on Bragg diffraction was proposed according to the requirement for optical switches used in shock wave and detonation physics experiments. Some important parameters of this acoustooptic switch such as the switch waveform, extinction ratio, light damage threshold and energy availability were experimentally obtained. The results show that compared with electrooptic switches, the acoustooptic switch effectively eliminates the ringing phenomena existing on the top of light switch waveforms, reduces the instrument volume, and improves the working stability. The extinction ratio is about 5000∶1. The light damage threshold of the acoustooptic crystal is larger than 2.26 kW/cm2 and the energy availability of the switch reaches up to 70%. The inherent delay time and rising edge time are 900 ns and 440 ns, respectively, which meet the synchronism requirement of the measuring system. In addition, the duration of the switching time can be easily changed by the trigger signal to meet different test demands.
A travelling wave acoustooptic switch based on Bragg diffraction was proposed according to the requirement for optical switches used in shock wave and detonation physics experiments. Some important parameters of this acoustooptic switch such as the switch waveform, extinction ratio, light damage threshold and energy availability were experimentally obtained. The results show that compared with electrooptic switches, the acoustooptic switch effectively eliminates the ringing phenomena existing on the top of light switch waveforms, reduces the instrument volume, and improves the working stability. The extinction ratio is about 5000∶1. The light damage threshold of the acoustooptic crystal is larger than 2.26 kW/cm2 and the energy availability of the switch reaches up to 70%. The inherent delay time and rising edge time are 900 ns and 440 ns, respectively, which meet the synchronism requirement of the measuring system. In addition, the duration of the switching time can be easily changed by the trigger signal to meet different test demands.
2009, 29(1): 49-55.
doi: 10.11883/1001-1455(2009)01-0049-07
Abstract:
The cellular structures of closed-cell foams were modeled as tetrakaidecahedrons and their dynamic crushing behaviors were simulated by the finite element method. In the numerical simulation, all the tetrakaidecahedrons have the same sizes. Numerical calculations were carried out to investigate principally effects of different impacting velocities, relative densities and strain hardening moduli of solid materials on deformation modes, plateau stress and densification strain energy. Energy absorption capacities of foams were comprehensively described. Numerical results show that deformation modes are greatly affected by impacting velocity. Especially when the foams are subjected to high-velocity impact, the I-shaped mode can be observed near the impacting rigid platen, and this deformation mode propagates towards the supporting rigid platen. Relative density contributes to energy absorption capacity significantly. Densification strain energy varies parabolically with relative density. In addition, there is a linear relationship between the three parameters including impact velocity, relative density and ratio of hardening modul to elastic modul of solid material and the plateau stress respectively.
The cellular structures of closed-cell foams were modeled as tetrakaidecahedrons and their dynamic crushing behaviors were simulated by the finite element method. In the numerical simulation, all the tetrakaidecahedrons have the same sizes. Numerical calculations were carried out to investigate principally effects of different impacting velocities, relative densities and strain hardening moduli of solid materials on deformation modes, plateau stress and densification strain energy. Energy absorption capacities of foams were comprehensively described. Numerical results show that deformation modes are greatly affected by impacting velocity. Especially when the foams are subjected to high-velocity impact, the I-shaped mode can be observed near the impacting rigid platen, and this deformation mode propagates towards the supporting rigid platen. Relative density contributes to energy absorption capacity significantly. Densification strain energy varies parabolically with relative density. In addition, there is a linear relationship between the three parameters including impact velocity, relative density and ratio of hardening modul to elastic modul of solid material and the plateau stress respectively.
2009, 29(1): 56-60.
doi: 10.11883/1001-1455(2009)01-0056-05
Abstract:
Kinematic and dynamic analysis on underwater high-speed supercavitating projectiles were carried out and a mathematical model was proposed to establish coupling nonlinear differential equations. The equations were resolved to obtain the kinematical characteristics of the projectiles. The numerical simulation results show that the horizontal velocity of the flying projectile decreases rapidly because of the drag forces acting on the tip and the tail of the projectile. The angular velocity of the flying projectile decreases gradually in the fluctuating form, namely, a tail-slap phenomenon. Meanwhile, the vibration extent reduces gradually resulted from the lessening of the cavity dimension. The smaller the projectiles moment of inertia is, the less the changing range of the angular velocity and the tail-slap times are. The greater the launching depth or velocity is, the faster the tail slap attenuation is. The higher initial angular velocity can cause the angular velocity of the projectile to attenuate more rapidly.
Kinematic and dynamic analysis on underwater high-speed supercavitating projectiles were carried out and a mathematical model was proposed to establish coupling nonlinear differential equations. The equations were resolved to obtain the kinematical characteristics of the projectiles. The numerical simulation results show that the horizontal velocity of the flying projectile decreases rapidly because of the drag forces acting on the tip and the tail of the projectile. The angular velocity of the flying projectile decreases gradually in the fluctuating form, namely, a tail-slap phenomenon. Meanwhile, the vibration extent reduces gradually resulted from the lessening of the cavity dimension. The smaller the projectiles moment of inertia is, the less the changing range of the angular velocity and the tail-slap times are. The greater the launching depth or velocity is, the faster the tail slap attenuation is. The higher initial angular velocity can cause the angular velocity of the projectile to attenuate more rapidly.
2009, 29(1): 61-66.
doi: 10.11883/1001-1455(2009)01-0061-06
Abstract:
While elastic waves propagates along structures, all kinds of information can be carried, in-cluding damage information, which offers possibility for detection of damaged structures. For the sake of carrying on local control and health safety monitoring, a damaged continuous beam by applying square pulses was investigated by the reverberation-ray matrix method. The local damage in the continuous beam was modeled by the decreased Youngs modulus. Researched results show that while the square pulse is applied obliquely, the axial velocity wave at the receiving point can be detected, the detected velocity wave can be used to locate the damage position and to estimate the damage degree.
While elastic waves propagates along structures, all kinds of information can be carried, in-cluding damage information, which offers possibility for detection of damaged structures. For the sake of carrying on local control and health safety monitoring, a damaged continuous beam by applying square pulses was investigated by the reverberation-ray matrix method. The local damage in the continuous beam was modeled by the decreased Youngs modulus. Researched results show that while the square pulse is applied obliquely, the axial velocity wave at the receiving point can be detected, the detected velocity wave can be used to locate the damage position and to estimate the damage degree.
2009, 29(1): 67-72.
doi: 10.11883/1001-1455(2009)01-0067-06
Abstract:
The discrete wavelet threshold method was used to denoise the SHPB testing signals containing the high-frequency noise. Aimed at the short-duration and abrupt change of non-stationary SHPB testing signals, the Sym5 wavelet basis was chosen as the optimal one which has the lowest root mean square error (RMSE) among various wavelet basis reconstruction for the processing of SHPB testing signals. The unbiased estimation procedure SURE was used to determine the threshold value for each decomposition level, the signal was decomposed to six levels with the threshold values of 0.119, 0.085, 0.089, 0.102, 0.118, 0.116 from level 1 to level 6 respectively. Signal-noise ratio (SNR) and RMSE of the signals denoised by the discrete wavelet transform were compared with those by the conventional low-pass filters in dynamic strain indicators. SNR of the signal denoised by the discrete wavelet transform is greater than that by the low-pass filter, and RMSE of the signal denoised by the discrete wavelet transform is smaller than that by the low-pass filter. The results show that discrete wavelet transform not only has favorable denoising effects, but also can get more accurate reconstruction signals, it can replace the low-pass filters in dynamic strain indicators for the SHPB testing signal denoising.
The discrete wavelet threshold method was used to denoise the SHPB testing signals containing the high-frequency noise. Aimed at the short-duration and abrupt change of non-stationary SHPB testing signals, the Sym5 wavelet basis was chosen as the optimal one which has the lowest root mean square error (RMSE) among various wavelet basis reconstruction for the processing of SHPB testing signals. The unbiased estimation procedure SURE was used to determine the threshold value for each decomposition level, the signal was decomposed to six levels with the threshold values of 0.119, 0.085, 0.089, 0.102, 0.118, 0.116 from level 1 to level 6 respectively. Signal-noise ratio (SNR) and RMSE of the signals denoised by the discrete wavelet transform were compared with those by the conventional low-pass filters in dynamic strain indicators. SNR of the signal denoised by the discrete wavelet transform is greater than that by the low-pass filter, and RMSE of the signal denoised by the discrete wavelet transform is smaller than that by the low-pass filter. The results show that discrete wavelet transform not only has favorable denoising effects, but also can get more accurate reconstruction signals, it can replace the low-pass filters in dynamic strain indicators for the SHPB testing signal denoising.
2009, 29(1): 73-79.
doi: 10.11883/1001-1455(2009)01-0073-07
Abstract:
The scattering of SH-wave by the circular cavity near the bimaterial interface in a vertical half-space and dynamic stress concentration were explored based on the complex function method and the Greens function method. The solution of the present problem was given by the image method. Firstly, a suitable Greens function was constructed, which was the essential solution of displacement field for an elastic right-angle plane with a circular cavity subjected to anti-plane harmonic line source loading at the horizontal surface. Secondly, the conjunction method was used to develop the scattering model of SH-wave, then a series of Fredholm integral equations of the first kind for determining the unknown forces were established through the continuity conditions expressed in terms of the Greens function. Finally, the dynamic stress concentration was analyzed by numerical examples.The numerical examples show that the dynamic stress concentration depends on the incident frequency and angle of SH-wave, the geometrical position of the circular cavity, and the different media combination parameters. Compared with the scattering of SH-wave by the circular cavity in a complete space, the free boundary of the vertical half-space has great effect on the incident plane SH-wave and the dynamic stress concentration factors around the circular cavity are magnified obviously while the SH-wave disturbs from a rigid medium to a soft medium.
The scattering of SH-wave by the circular cavity near the bimaterial interface in a vertical half-space and dynamic stress concentration were explored based on the complex function method and the Greens function method. The solution of the present problem was given by the image method. Firstly, a suitable Greens function was constructed, which was the essential solution of displacement field for an elastic right-angle plane with a circular cavity subjected to anti-plane harmonic line source loading at the horizontal surface. Secondly, the conjunction method was used to develop the scattering model of SH-wave, then a series of Fredholm integral equations of the first kind for determining the unknown forces were established through the continuity conditions expressed in terms of the Greens function. Finally, the dynamic stress concentration was analyzed by numerical examples.The numerical examples show that the dynamic stress concentration depends on the incident frequency and angle of SH-wave, the geometrical position of the circular cavity, and the different media combination parameters. Compared with the scattering of SH-wave by the circular cavity in a complete space, the free boundary of the vertical half-space has great effect on the incident plane SH-wave and the dynamic stress concentration factors around the circular cavity are magnified obviously while the SH-wave disturbs from a rigid medium to a soft medium.
2009, 29(1): 80-84.
doi: 10.11883/1001-1455(2009)01-0080-05
Abstract:
A numerical analysis model for the bird-impact response of aircraft windshields was proposed by combining the dynamic explicit finite element code PAM-CRASH and the smoothed particle hydrodynamics (SPH) method. The dynamic response of an aircraft windshield to bird-impact loading was simulated by the proposed analysis model. The displacement-time curves for the four points on the medial axis of the aircraft windshield were calculated, the failure criterion for the aircraft windshield subjected to bird-impact loading was developed, and the failure state of the aircraft windshield under the given experimental conditions was numerically calculated. Numerical simulation results of the bird-impact process indicate that the SPH bird model can correctly model the breaking-up of the bird into debris particles. The good agreement between numerical and experimental results illuminates that the numerical simulation model developed in the present paper is valid.
A numerical analysis model for the bird-impact response of aircraft windshields was proposed by combining the dynamic explicit finite element code PAM-CRASH and the smoothed particle hydrodynamics (SPH) method. The dynamic response of an aircraft windshield to bird-impact loading was simulated by the proposed analysis model. The displacement-time curves for the four points on the medial axis of the aircraft windshield were calculated, the failure criterion for the aircraft windshield subjected to bird-impact loading was developed, and the failure state of the aircraft windshield under the given experimental conditions was numerically calculated. Numerical simulation results of the bird-impact process indicate that the SPH bird model can correctly model the breaking-up of the bird into debris particles. The good agreement between numerical and experimental results illuminates that the numerical simulation model developed in the present paper is valid.
2009, 29(1): 85-89.
doi: 10.11883/1001-1455(2009)01-0085-05
Abstract:
A excessively-conjugated heat assembly and a mechanical clamp device were used to achieve the radial pre-strain of disk-shaped LY12 samples. In the experiment, the LY12 samples were impacted by the flyer plates driven by a one-stage light-gas gun, and spall signals of the samples in several pre-strain states were measured by VISAR. The experimental results show that the spall strengths are 1.13, 0.935, 0.755 and 0.643 GPa respectively corresponding to the pre-strains of 0, 25110-6, 1 10810-6 and 1 88610-6 when the samples are impacted by the flyer plates with 500 m/s. The pre-stress (pre-strain) reduces the spall strength of LY12 aluminum obviously. It is confirmed that the spall strength is closely related to the initial stress. It is helpful for the future research on materials spallation in multi-dimensional strain states.
A excessively-conjugated heat assembly and a mechanical clamp device were used to achieve the radial pre-strain of disk-shaped LY12 samples. In the experiment, the LY12 samples were impacted by the flyer plates driven by a one-stage light-gas gun, and spall signals of the samples in several pre-strain states were measured by VISAR. The experimental results show that the spall strengths are 1.13, 0.935, 0.755 and 0.643 GPa respectively corresponding to the pre-strains of 0, 25110-6, 1 10810-6 and 1 88610-6 when the samples are impacted by the flyer plates with 500 m/s. The pre-stress (pre-strain) reduces the spall strength of LY12 aluminum obviously. It is confirmed that the spall strength is closely related to the initial stress. It is helpful for the future research on materials spallation in multi-dimensional strain states.
2009, 29(1): 90-94.
doi: 10.11883/1001-1455(2009)01-0090-05
Abstract:
By analyzing the performances and primary technical parameters of the APX-RS digital camera, the dynamic test was designed to shoot the aviation attitudes of the moving object in the three phases of high, medium, low speeds and to obtain its clear images and accurate motion velocities. Experimental results show that this camera can record effectively the aviation course of a high-speed moving object with any velocity less than 4 Mach number. This camera is helpful in the research field of explosion and shock.
By analyzing the performances and primary technical parameters of the APX-RS digital camera, the dynamic test was designed to shoot the aviation attitudes of the moving object in the three phases of high, medium, low speeds and to obtain its clear images and accurate motion velocities. Experimental results show that this camera can record effectively the aviation course of a high-speed moving object with any velocity less than 4 Mach number. This camera is helpful in the research field of explosion and shock.
2009, 29(1): 95-100.
doi: 10.11883/1001-1455(2009)01-0095-06
Abstract:
The constitutive descriptions of concrete materials idealize the pressure-volumetric strain relationship as the tri-linear equation of state and idealize the shear strength-pressure relationship as the Mohr-Coulomb yield criterion considering the tension cutoff and the shear saturation. The dynamic response expression of the spherical cavity expansion is derived by the self-similar methods, and the dynamic response numerical solution is given by the Runge-Kutta-Felberg method. The result shows that the cavity expansion pressures increase with the cavity expansion velocity and the shear saturation strength, and the cavity expansion pressures considering the shear saturation are less than those without considering the shear saturation in case of the high cavity expansion velocity.
The constitutive descriptions of concrete materials idealize the pressure-volumetric strain relationship as the tri-linear equation of state and idealize the shear strength-pressure relationship as the Mohr-Coulomb yield criterion considering the tension cutoff and the shear saturation. The dynamic response expression of the spherical cavity expansion is derived by the self-similar methods, and the dynamic response numerical solution is given by the Runge-Kutta-Felberg method. The result shows that the cavity expansion pressures increase with the cavity expansion velocity and the shear saturation strength, and the cavity expansion pressures considering the shear saturation are less than those without considering the shear saturation in case of the high cavity expansion velocity.
2009, 29(1): 101-104.
doi: 10.11883/1001-1455(2009)01-0101-04
Abstract:
A one-dimensional Lagrangian backward integeration method was used to analyze VISAR records of isentropic compression experiments. The pressure history at the window-sample interface calculated by the interface velocity history was proved to be successful. A contrast calculation shows that the backward method is as accurate as the forward method. Analysis of the Z575 experiments shows that the isentropic compression curves of Al 6061-T6 are in good agreement with that by Hall C A.
A one-dimensional Lagrangian backward integeration method was used to analyze VISAR records of isentropic compression experiments. The pressure history at the window-sample interface calculated by the interface velocity history was proved to be successful. A contrast calculation shows that the backward method is as accurate as the forward method. Analysis of the Z575 experiments shows that the isentropic compression curves of Al 6061-T6 are in good agreement with that by Hall C A.
2009, 29(1): 105-108.
doi: 10.11883/1001-1455(2009)01-0105-04
Abstract:
An optical-fiber displacement interferometer was proposed on the basis of the optical Doppler effects and heterodyne technique. The proposed interferometer was assembled by using the components well developed in the telecommunication industry, which consisting of a fiber-pigtailed semiconductor laser, a three-port optical circulator, a fiber probe, a wideband detector, a high-sampling-rate broadband oscilloscope, and so on. The coaxial configuration for the signal light and reference light is adopted so that the proposed interferometer can measure velocities of any reflecting surface and overcomes the effects of polarization-mode dispersion, and its work distance is up to 20 mm. The velocities of the explosively-driven metal plate were measured by the proposed interferometer and compared with those measured by the velocity interferometer system for any reflector. Measured results show the velocities by these two methods are accordant with each other.
An optical-fiber displacement interferometer was proposed on the basis of the optical Doppler effects and heterodyne technique. The proposed interferometer was assembled by using the components well developed in the telecommunication industry, which consisting of a fiber-pigtailed semiconductor laser, a three-port optical circulator, a fiber probe, a wideband detector, a high-sampling-rate broadband oscilloscope, and so on. The coaxial configuration for the signal light and reference light is adopted so that the proposed interferometer can measure velocities of any reflecting surface and overcomes the effects of polarization-mode dispersion, and its work distance is up to 20 mm. The velocities of the explosively-driven metal plate were measured by the proposed interferometer and compared with those measured by the velocity interferometer system for any reflector. Measured results show the velocities by these two methods are accordant with each other.
2009, 29(1): 109-112.
doi: 10.11883/1001-1455(2009)01-0109-04
Abstract:
A cook-off equipment was developed to explore influences of charge porosity on the cook-off response of explosives. The cook-off test was carried out by taking the TNT and JB-B explosives for examples. Experimental results indicate that with the increase of charge porosity, the lasting time from the beginning of self-acceleration decomposition reaction to the start of cook-off reaction is prolonged, the corresponding cook-off temperature is elevated, and the violence of the cook-off response is intensified.
A cook-off equipment was developed to explore influences of charge porosity on the cook-off response of explosives. The cook-off test was carried out by taking the TNT and JB-B explosives for examples. Experimental results indicate that with the increase of charge porosity, the lasting time from the beginning of self-acceleration decomposition reaction to the start of cook-off reaction is prolonged, the corresponding cook-off temperature is elevated, and the violence of the cook-off response is intensified.
