2015 Vol. 35, No. 1
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2015, 35(1): 1-8.
doi: 10.11883/1001-1455(2015)01-0001-08
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Abstract:
Based on the dynamic Rigid-Linear Hardening Plastic-Rigid Unloading (D-R-LHP-R) model of foam materials and starting from the displacement continuity equation, the momentum conservation equation and the motion equation of rigid part, the relation between the critical position for shock disappearanceXs' the yield stress Y, the shock velocity cp as well as the impact boundary strain εi can be determined as follows: \begin{document} $\frac{X_{\mathrm{s}}}{L_{0}}=\exp \left(-\frac{\rho_{0} c_{\mathrm{p}} v_{\mathrm{i}}}{Y}\right)=\exp \left(1-\frac{\sigma_{\mathrm{i}}}{Y}\right)=\exp \left(-\frac{\rho_{0} c_{\mathrm{p}}^{2} \varepsilon_{\mathrm{i}}}{Y}\right)$ \end{document} Among the parameters in the above equation, the specimen density ρ0, the boundary stress σi, the impact velocity vi, the undeformed length of the specimen Xs, and the original length of the specimen L0, can be easily measured from the Taylor cylinder-Hopkinson bar impact experiments. Therefore, the constitutive parameters strees and strain of the R-LHP-R model can be finally reversely determined for the tested aluminum foam by using the above experimental parameters and Eq(a). The comparison of stress-strain between the quasi-static compressive curve and the R-LHP-R model indicates the strain rate sensitivity of the tested aluminum foams.
Based on the dynamic Rigid-Linear Hardening Plastic-Rigid Unloading (D-R-LHP-R) model of foam materials and starting from the displacement continuity equation, the momentum conservation equation and the motion equation of rigid part, the relation between the critical position for shock disappearanceXs' the yield stress Y, the shock velocity cp as well as the impact boundary strain εi can be determined as follows:
2015, 35(1): 9-15.
doi: 10.11883/1001-1455(2015)01-0009-07
Abstract:
A non-intrusive polynomial chaos method was introduced, and the main procedure of uncertainty quantification for JWL-EOS parameters was given. The method was implemented for the uncertainty quantification of the input parametersR1 and R2 of JWL-EOS to the detonation of plane and divergence. The results show that the methods of non-intrusive polynomial chaos can provide a valuable tool for the simulation of propagation of uncertainties, and uncertainty quantification for modeling and simulation in complex engineering.
A non-intrusive polynomial chaos method was introduced, and the main procedure of uncertainty quantification for JWL-EOS parameters was given. The method was implemented for the uncertainty quantification of the input parametersR1 and R2 of JWL-EOS to the detonation of plane and divergence. The results show that the methods of non-intrusive polynomial chaos can provide a valuable tool for the simulation of propagation of uncertainties, and uncertainty quantification for modeling and simulation in complex engineering.
2015, 35(1): 16-21.
doi: 10.11883/1001-1455(2015)01-0016-06
Abstract:
In order to clarify the influence the base materials have on aluminium honeycombs and to explore the difference of the buckling modes between dynamic and static compression, research of honeycombs with different base materials (3003H18 and 5052H18 aluminium alloy) was done. Test on specimens cut from aluminium honeycombs was conducted to investigate the uniaxial tension mechanical properties of base materials in this study. Both quasi-static and dynamic experiments on aluminium honeycombs with same geometry but made of different base materials were conducted. The quasi-static test was performed using universal tester with the loading speed of 0.1 mm/s and an "SHPB" system with large diameter PMMA bars was adopted in dynamic test with two average impact speeds (10 m/s and 28 m/s). High speed camera was applied in "SHPB" test to capture the image of the dynamic deformation of aluminium honeycomb structure. The test results showed that three stages can be divided in the compression of honeycombs and the buckling modes of different aluminium honeycombs under different loading speeds were the same. Dynamic enhancement existed in two kinds of aluminium honeycombs but with different enhancement ratios. The dynamic enhancement of 3003H18 honeycombs was more remarkable than that of 5052H18. Inertia theory can explain the enhancement. With the analysis of the result of base-material experiment, consumption was made that Honeycombs with a higher strain hardening rate tend to have a more remarkable enhancement.
In order to clarify the influence the base materials have on aluminium honeycombs and to explore the difference of the buckling modes between dynamic and static compression, research of honeycombs with different base materials (3003H18 and 5052H18 aluminium alloy) was done. Test on specimens cut from aluminium honeycombs was conducted to investigate the uniaxial tension mechanical properties of base materials in this study. Both quasi-static and dynamic experiments on aluminium honeycombs with same geometry but made of different base materials were conducted. The quasi-static test was performed using universal tester with the loading speed of 0.1 mm/s and an "SHPB" system with large diameter PMMA bars was adopted in dynamic test with two average impact speeds (10 m/s and 28 m/s). High speed camera was applied in "SHPB" test to capture the image of the dynamic deformation of aluminium honeycomb structure. The test results showed that three stages can be divided in the compression of honeycombs and the buckling modes of different aluminium honeycombs under different loading speeds were the same. Dynamic enhancement existed in two kinds of aluminium honeycombs but with different enhancement ratios. The dynamic enhancement of 3003H18 honeycombs was more remarkable than that of 5052H18. Inertia theory can explain the enhancement. With the analysis of the result of base-material experiment, consumption was made that Honeycombs with a higher strain hardening rate tend to have a more remarkable enhancement.
2015, 35(1): 22-28.
doi: 10.11883/1001-1455(2015)01-0022-07
Abstract:
First, the experiments that the steel balls impact to 2D-C/SiC composite under velocity of 79~ 219 m/s are investigated by using the air gun. Second, material parameters of 2D-C/SiC are obtained based on an orthotropic constitutive material model in Autodyn, and numerical simulation corresponding to experimental conditions are conducted based on smooth particle hydrodynamics(SPH) solver. The comparisons between the calculation results and experimental data of the debris cloud structure, the B scan results and the axis velocity of debris cloudvalidate the ability of this model for describing the brittle characteristics and the softening behaviour of 2D-C/SiC under impact load. Finally, the limit penetration depth of 2D-C/SiC under the impact of steel ball is predicted.
First, the experiments that the steel balls impact to 2D-C/SiC composite under velocity of 79~ 219 m/s are investigated by using the air gun. Second, material parameters of 2D-C/SiC are obtained based on an orthotropic constitutive material model in Autodyn, and numerical simulation corresponding to experimental conditions are conducted based on smooth particle hydrodynamics(SPH) solver. The comparisons between the calculation results and experimental data of the debris cloud structure, the B scan results and the axis velocity of debris cloudvalidate the ability of this model for describing the brittle characteristics and the softening behaviour of 2D-C/SiC under impact load. Finally, the limit penetration depth of 2D-C/SiC under the impact of steel ball is predicted.
2015, 35(1): 29-35.
doi: 10.11883/1001-1455(2015)01-0029-07
Abstract:
A two-dimensional mathematical model of viscous aluminum/air two-phase detonation is established. The flow field inside the detonation tube was calculated by the method of conservation element and solution element. And the distribution of physical parameters is analyzed. Numerical results show that in the early stages of the deflagration-to-detonation transition process in the tube, pressure change obviously along the radius and significant reflection wave is collided off the wall. In the later period, pressure along the axis changes obviously, but the radial effect still can't be ignored. The reflection wave from the collision is important on the formation of steady detonation wave. Numerical results also show that the initial radius of the aluminum powder particles have certain influence on the formation and propagation of detonation wave. And certain influence of gas viscosity on flow field near the wall in the detonation tube was exerted. The results of the study can be utilized to reveal the mechanism of the deflagration-to-detonation transitim.
A two-dimensional mathematical model of viscous aluminum/air two-phase detonation is established. The flow field inside the detonation tube was calculated by the method of conservation element and solution element. And the distribution of physical parameters is analyzed. Numerical results show that in the early stages of the deflagration-to-detonation transition process in the tube, pressure change obviously along the radius and significant reflection wave is collided off the wall. In the later period, pressure along the axis changes obviously, but the radial effect still can't be ignored. The reflection wave from the collision is important on the formation of steady detonation wave. Numerical results also show that the initial radius of the aluminum powder particles have certain influence on the formation and propagation of detonation wave. And certain influence of gas viscosity on flow field near the wall in the detonation tube was exerted. The results of the study can be utilized to reveal the mechanism of the deflagration-to-detonation transitim.
2015, 35(1): 36-42.
doi: 10.11883/1001-1455(2015)01-0036-07
Abstract:
To investigate the influences of temperature, impact velocity and fiber volumetric fraction on dynamic compressive strength and impact toughness of basalt fiber reinforced concrete (BFRC), dynamic compressive experiments were carried out on BFRC after different elevated temperatures by using a 100 mm diameter split Hopkinson pressure bar (SHPB) equipment. The results demonstrate that the dynamic compressive strength and impact toughness increase approximately linearly with the increase of average strain rate under the same temperature. At a fixed impact velocity, the rising of temperature results in a decrease in dynamic compressive strength and impact toughness as well as their strain rate sensitivities. For a given working condition, the dynamic compressive strength and impact toughness of BFRC are generally higher than those of plain concrete. The strengthening and toughening effect are relatively the best when the fiber volumetric fraction is 0.2%. Consequently, changes in dynamic compressive properties of BFRC after elevated temperatures are the combining effects of temperature, impact velocity and fiber volumetric fraction. The adding of basalt fiber can significantly decrease the thermal deterioration of BFRC.
To investigate the influences of temperature, impact velocity and fiber volumetric fraction on dynamic compressive strength and impact toughness of basalt fiber reinforced concrete (BFRC), dynamic compressive experiments were carried out on BFRC after different elevated temperatures by using a 100 mm diameter split Hopkinson pressure bar (SHPB) equipment. The results demonstrate that the dynamic compressive strength and impact toughness increase approximately linearly with the increase of average strain rate under the same temperature. At a fixed impact velocity, the rising of temperature results in a decrease in dynamic compressive strength and impact toughness as well as their strain rate sensitivities. For a given working condition, the dynamic compressive strength and impact toughness of BFRC are generally higher than those of plain concrete. The strengthening and toughening effect are relatively the best when the fiber volumetric fraction is 0.2%. Consequently, changes in dynamic compressive properties of BFRC after elevated temperatures are the combining effects of temperature, impact velocity and fiber volumetric fraction. The adding of basalt fiber can significantly decrease the thermal deterioration of BFRC.
2015, 35(1): 43-50.
doi: 10.11883/1001-1455(2015)01-0043-08
Abstract:
According to the uncertainty of rock burst intensity prediction and the incompatible problem of the single index which mainly influences the rock burst, a method combining variable weight theory with the degree of target approaching is proposed to make prediction of rock burst intensity. First, considering the preference degree of the judge, a variable weight model is given to calculate the weights of indexes based on a balance function. Second, this method constructs an interval incidence function, and the maximum value of incidence function for single index is used to be the target, so the rock burst intensity can be predicted based on the degree of approaching between samples and targets-the larger degree of the target approaching, the higher intensity of the rock burst. Finally, this method is applied to Dongyu rock mine in Lingbao, Dongguashan rock mine and Qinling Tunnel rock burst, and the results show that it can predict the rock burst intensity correctly and reasonably. What's more, compared with other methods like Bayes discriminant analysis method and distance discriminant analysis method(DDA), it doesn't need any prior knowledge, and so is very direct and convenient for calculation. Therefore, this method is worthy of promotion and application.
According to the uncertainty of rock burst intensity prediction and the incompatible problem of the single index which mainly influences the rock burst, a method combining variable weight theory with the degree of target approaching is proposed to make prediction of rock burst intensity. First, considering the preference degree of the judge, a variable weight model is given to calculate the weights of indexes based on a balance function. Second, this method constructs an interval incidence function, and the maximum value of incidence function for single index is used to be the target, so the rock burst intensity can be predicted based on the degree of approaching between samples and targets-the larger degree of the target approaching, the higher intensity of the rock burst. Finally, this method is applied to Dongyu rock mine in Lingbao, Dongguashan rock mine and Qinling Tunnel rock burst, and the results show that it can predict the rock burst intensity correctly and reasonably. What's more, compared with other methods like Bayes discriminant analysis method and distance discriminant analysis method(DDA), it doesn't need any prior knowledge, and so is very direct and convenient for calculation. Therefore, this method is worthy of promotion and application.
2015, 35(1): 51-56.
doi: 10.11883/1001-1455(2015)01-0051-06
Abstract:
The uniaxial compressive properties of aviation polyurethane were investigated experimentally by using a modified aluminum split Hopkinson pressure bar apparatus. The obtained stress-strain curves presented distinct non-linear viscoelastic characteristic.Based on the constitutive theory and the experimental data, a hyper-viscoelastic constitutive model that incorporated a strain-dependent relaxation time was proposed to describe the large compressive deformation response of incompressible aviation polyurethane at high strain rates. The proposed model was made up of two parallel mechanical elements-one component to characterize quasi-static hyperelastic behavior, and the other to define rate-sensitivity and strain history dependence. The predictions of the mechanical behavior using a hyper-viscoelastic constitutive model based on strain energy functions and hereditary approach had a good agreement with experimental results.
The uniaxial compressive properties of aviation polyurethane were investigated experimentally by using a modified aluminum split Hopkinson pressure bar apparatus. The obtained stress-strain curves presented distinct non-linear viscoelastic characteristic.Based on the constitutive theory and the experimental data, a hyper-viscoelastic constitutive model that incorporated a strain-dependent relaxation time was proposed to describe the large compressive deformation response of incompressible aviation polyurethane at high strain rates. The proposed model was made up of two parallel mechanical elements-one component to characterize quasi-static hyperelastic behavior, and the other to define rate-sensitivity and strain history dependence. The predictions of the mechanical behavior using a hyper-viscoelastic constitutive model based on strain energy functions and hereditary approach had a good agreement with experimental results.
2015, 35(1): 57-64.
doi: 10.11883/1001-1455(2015)01-0057-08
Abstract:
For the internal-combustion engine, super knock produced by new combustion system may cause detonation in combustion chamber, which may damage the piston. 2D numerical simulation which is conducted by Ansys Fluent is used to investigate the propagation and reflection of detonation wave produced in combustion chamber with cone type roof. The overpressure distribution on top piston surface is obtained. Numerical simulation showed that the detonation wave could converge in special zone because of the shape of combustion chamber, which made the overpressure there much higher than that in the other zones. The numerical results were compared with the experimental damaged pistons, and it's found that the converging of the detonation wave found in numerical simulation could be the reason that causes the piston local region damaged under super knock. The results obtained in the study provided an important reference to the shape design of combustion chamber in order to avoid piston from being damaged by the detonation wave.
For the internal-combustion engine, super knock produced by new combustion system may cause detonation in combustion chamber, which may damage the piston. 2D numerical simulation which is conducted by Ansys Fluent is used to investigate the propagation and reflection of detonation wave produced in combustion chamber with cone type roof. The overpressure distribution on top piston surface is obtained. Numerical simulation showed that the detonation wave could converge in special zone because of the shape of combustion chamber, which made the overpressure there much higher than that in the other zones. The numerical results were compared with the experimental damaged pistons, and it's found that the converging of the detonation wave found in numerical simulation could be the reason that causes the piston local region damaged under super knock. The results obtained in the study provided an important reference to the shape design of combustion chamber in order to avoid piston from being damaged by the detonation wave.
2015, 35(1): 65-69.
doi: 10.11883/1001-1455(2015)01-0065-05
Abstract:
A simple method was developed for measuring the impulse current waveform produce by a small high-voltage exploding device. The model of impulse current was determined by attenuation coefficient. To estimate the attenuation coefficient from the actual discharge voltage curve, the Levenberg-Marquarat algorithm was applied based on the equivalent circuit of discharge circuit and its differential equations. Compared with the direct measuring methods such as using shunt or Rogowski coil, this method overcomes the distortion of impulse current waveform caused by additional measuring circuit. The results show that the simulation current waveform fits the actual current waveform well. The method can be used for optimum matching design of electronic safety, arming device of in-line fuse or low-energy slapper detonator.
A simple method was developed for measuring the impulse current waveform produce by a small high-voltage exploding device. The model of impulse current was determined by attenuation coefficient. To estimate the attenuation coefficient from the actual discharge voltage curve, the Levenberg-Marquarat algorithm was applied based on the equivalent circuit of discharge circuit and its differential equations. Compared with the direct measuring methods such as using shunt or Rogowski coil, this method overcomes the distortion of impulse current waveform caused by additional measuring circuit. The results show that the simulation current waveform fits the actual current waveform well. The method can be used for optimum matching design of electronic safety, arming device of in-line fuse or low-energy slapper detonator.
2015, 35(1): 70-75.
doi: 10.11883/1001-1455(2015)01-0070-06
Abstract:
A solid traveling charge concept which can be used in high muzzle velocity gun firing is proposed based on differential principle. This concept can effectively overcome disadvantage of traditional traveling charge which increases projectile velocity and projectile base maximum pressure at the same time. A main character of the concept is to realize automatic compression of energy storage chamber and continuous injection of traveling working medium toward the in-bore space through speed difference between different components. Therefore the concept can effectively fill pressure drops of the projectile bottom and improve the utilization rate of gun working volume. The kinetic model of different components of differential traveling projectile and the physical quantity distribution of missile-borne working medium are deduced. With fixed maximum bore pressure, maximum projectile base pressure, projectile mass and travel, etc., and traveling charge mass 10.2 kg, calculation of some large caliber gun indicates that the projectile muzzle velocity increases by 26% and the utilization rate of gun working volume increases by 44%. This study provides a new technological approach for increasing gun muzzle velocity and realizing ultra-long distance firing.
A solid traveling charge concept which can be used in high muzzle velocity gun firing is proposed based on differential principle. This concept can effectively overcome disadvantage of traditional traveling charge which increases projectile velocity and projectile base maximum pressure at the same time. A main character of the concept is to realize automatic compression of energy storage chamber and continuous injection of traveling working medium toward the in-bore space through speed difference between different components. Therefore the concept can effectively fill pressure drops of the projectile bottom and improve the utilization rate of gun working volume. The kinetic model of different components of differential traveling projectile and the physical quantity distribution of missile-borne working medium are deduced. With fixed maximum bore pressure, maximum projectile base pressure, projectile mass and travel, etc., and traveling charge mass 10.2 kg, calculation of some large caliber gun indicates that the projectile muzzle velocity increases by 26% and the utilization rate of gun working volume increases by 44%. This study provides a new technological approach for increasing gun muzzle velocity and realizing ultra-long distance firing.
2015, 35(1): 76-81.
doi: 10.11883/1001-1455(2015)01-0076-06
Abstract:
It is hard to performe measurement of breech system under condition of gun shooting. The idea, treating the system separately to establish shock test platform, is presented. With the design principle determined, the principle model of the shock test platform was established through the improvement on automatic breechblock operating virtual prototype model. The minimum force for shock test platform to open breechblock is determined based on the conservation theorem of kinetic energy. Under the minimum breechblock operating force, the simulation tests are performed based on the principle model when the mass of the breechblock operating cam has original values ofm, 10m, 50m or 100m separately. The results show that it is impossible to operate breechblock under the four working conditions. However, as the mass of breechblock operating cam increases, the losing energy du to the work of the force decreases and the rotation angle of the crank lever increases, which makes the open breechblock easier. The research provides theory support for test platform establishment.
It is hard to performe measurement of breech system under condition of gun shooting. The idea, treating the system separately to establish shock test platform, is presented. With the design principle determined, the principle model of the shock test platform was established through the improvement on automatic breechblock operating virtual prototype model. The minimum force for shock test platform to open breechblock is determined based on the conservation theorem of kinetic energy. Under the minimum breechblock operating force, the simulation tests are performed based on the principle model when the mass of the breechblock operating cam has original values ofm, 10m, 50m or 100m separately. The results show that it is impossible to operate breechblock under the four working conditions. However, as the mass of breechblock operating cam increases, the losing energy du to the work of the force decreases and the rotation angle of the crank lever increases, which makes the open breechblock easier. The research provides theory support for test platform establishment.
2015, 35(1): 82-88.
doi: 10.11883/1001-1455(2015)01-0082-07
Abstract:
To obtain low detonation velocity explosive, commercial attenuant was blended into the emulsion explosive. The detonation velocity of compound explosive changes from 2 550 m/s to 1 450 m/s. Through analyzing the result of mechanical properties test and microstructure test of the Al/316L composite tubes which were fabricated by explosive welding of compound explosives, the appropriate detonation velocity (1 950~2 150 m/s) for the explosive welding of composite tube is obtained, and the combination quality of the composite tubes meet the subsequent processing requirement. The shape of the interface waveform is between line and wave. Interfacial wave also has poor rule of periodic variation. The reasons are that detonation velocity is important to the process, the explosion product does not scatter in the direction of tube diameter and the time that detonation products inside the tube affect to the flyer tube is longer than the flyer plate in the explosive welding process.
To obtain low detonation velocity explosive, commercial attenuant was blended into the emulsion explosive. The detonation velocity of compound explosive changes from 2 550 m/s to 1 450 m/s. Through analyzing the result of mechanical properties test and microstructure test of the Al/316L composite tubes which were fabricated by explosive welding of compound explosives, the appropriate detonation velocity (1 950~2 150 m/s) for the explosive welding of composite tube is obtained, and the combination quality of the composite tubes meet the subsequent processing requirement. The shape of the interface waveform is between line and wave. Interfacial wave also has poor rule of periodic variation. The reasons are that detonation velocity is important to the process, the explosion product does not scatter in the direction of tube diameter and the time that detonation products inside the tube affect to the flyer tube is longer than the flyer plate in the explosive welding process.
2015, 35(1): 89-93.
doi: 10.11883/1001-1455(2015)01-0089-05
Abstract:
To study the effect of water on charge mass for demolishing steel plate, the relationship of charge mass between steel plate backing on air and backing on water is analyzed. The results show that the charge mass for backing on water is 3.68 times the charge mass for backing on air. The charge mass is calculated with FEM method for explosions with steel plate backing on air and water. The results show that the charge mass for steel plate backing on air is 3.5 times the charge mass for steel plate backing on water, which is accordant with theoretical analysis. So the medium that steel plate backs on is the key factor for determing charge mass of cutting steel plate. The impulses on steel plate are almost equal for backing on air and backing on water, which indicates that the water constraining force on the detonation products can not afeect the charge mass much.
To study the effect of water on charge mass for demolishing steel plate, the relationship of charge mass between steel plate backing on air and backing on water is analyzed. The results show that the charge mass for backing on water is 3.68 times the charge mass for backing on air. The charge mass is calculated with FEM method for explosions with steel plate backing on air and water. The results show that the charge mass for steel plate backing on air is 3.5 times the charge mass for steel plate backing on water, which is accordant with theoretical analysis. So the medium that steel plate backs on is the key factor for determing charge mass of cutting steel plate. The impulses on steel plate are almost equal for backing on air and backing on water, which indicates that the water constraining force on the detonation products can not afeect the charge mass much.
2015, 35(1): 94-100.
doi: 10.11883/1001-1455(2015)01-0094-07
Abstract:
In order to investigate the influence of secondary combustion for base flow field, a mathematical and physical model about base flow with chemical non-equilibrium for base bleed equipment is conducted. H2-CO combustion model which consists 10 components and 25 reactions is used for secondary combustion. Two-dimensional axisymmetric equations are solved using a set of uniform numerical process methods. Simulation results agree with experiment data well. based on this, base flow field and combustion characteristics are numerically predicted. The results show that heat energy released from secondary combustion is far more than heat energy from bleed gases. Secondary combustion has a huge contribution to increase base pressure. It changes the temperature distribution of base region. Bleed gases flow into the shear layer, then combustion occurs. Some mixed gases which flow into the bottom region burn incomplete, because the oxygen is not sufficient near the bottom. Some mixed gases which flow into the downstream and main recirculation zone burn complete, because the oxygen is sufficient. The results can be used as reference for further improvement of the base bleed.
In order to investigate the influence of secondary combustion for base flow field, a mathematical and physical model about base flow with chemical non-equilibrium for base bleed equipment is conducted. H2-CO combustion model which consists 10 components and 25 reactions is used for secondary combustion. Two-dimensional axisymmetric equations are solved using a set of uniform numerical process methods. Simulation results agree with experiment data well. based on this, base flow field and combustion characteristics are numerically predicted. The results show that heat energy released from secondary combustion is far more than heat energy from bleed gases. Secondary combustion has a huge contribution to increase base pressure. It changes the temperature distribution of base region. Bleed gases flow into the shear layer, then combustion occurs. Some mixed gases which flow into the bottom region burn incomplete, because the oxygen is not sufficient near the bottom. Some mixed gases which flow into the downstream and main recirculation zone burn complete, because the oxygen is sufficient. The results can be used as reference for further improvement of the base bleed.
2015, 35(1): 101-107.
doi: 10.11883/1001-1455(2015)01-0101-07
Abstract:
To explore the breakage mechanism of rocks around the blasthole and to accurately predict the size of the crushed zone in drilling and blasting, an improved calculation model for calculation the size of the crushed zone was presented. The four-region model was established with hoop compressive stress in the inner part of fractured zone and cavity expansion effect taken into account. The material in the crushed zone is assumed to be granular medium without cohesion but with internal friction. On this basis, the formula for the crushed zone radius in drilling blasting is derived by elastic-plastic mechanics theory. The analysis shows that the size of the crushed zone ranges from 1.2 to 5.0 times of the blasthole radius, and there are notable discrepancies among rock types. Compared with other models, the improved model is in better agreement with the experiment data.
To explore the breakage mechanism of rocks around the blasthole and to accurately predict the size of the crushed zone in drilling and blasting, an improved calculation model for calculation the size of the crushed zone was presented. The four-region model was established with hoop compressive stress in the inner part of fractured zone and cavity expansion effect taken into account. The material in the crushed zone is assumed to be granular medium without cohesion but with internal friction. On this basis, the formula for the crushed zone radius in drilling blasting is derived by elastic-plastic mechanics theory. The analysis shows that the size of the crushed zone ranges from 1.2 to 5.0 times of the blasthole radius, and there are notable discrepancies among rock types. Compared with other models, the improved model is in better agreement with the experiment data.
2015, 35(1): 108-115.
doi: 10.11883/1001-1455(2015)01-0108-08
Abstract:
The main objective of this study is to establish the quantitative relationship between overpressure and flow speed in the open-end square tube by the numerical simulation. It is found that the numbers of the peak value of overpressure and flow speed at the same measured point are different. The peak overpressure always appears earlier than peak flow speed in time scale. In mast cases, larger side lenth of square tube corresponds to smaller peak overpressure, and the peak flow speed goes down slowly along the propagation direction. The peak overpressure decreases with the increasing of the distance far from ignition end. However, the peak flow speed increases with the stream wise distance. When normalized distance is less than 125, the peak overpressure and peak flow speed always presents an inverse relationship. Otherwise, the relationship is piecewise-linear. The results may provide reference for the study on evaluating the dust lifting ability behind shock wave in the limited spaces.
The main objective of this study is to establish the quantitative relationship between overpressure and flow speed in the open-end square tube by the numerical simulation. It is found that the numbers of the peak value of overpressure and flow speed at the same measured point are different. The peak overpressure always appears earlier than peak flow speed in time scale. In mast cases, larger side lenth of square tube corresponds to smaller peak overpressure, and the peak flow speed goes down slowly along the propagation direction. The peak overpressure decreases with the increasing of the distance far from ignition end. However, the peak flow speed increases with the stream wise distance. When normalized distance is less than 125, the peak overpressure and peak flow speed always presents an inverse relationship. Otherwise, the relationship is piecewise-linear. The results may provide reference for the study on evaluating the dust lifting ability behind shock wave in the limited spaces.
2015, 35(1): 116-123.
doi: 10.11883/1001-1455(2015)01-0116-08
Abstract:
In order to explore the design method of sandwich bulkhead subjected to the close blast load of missile-warhead, experiments were carried out to investigate the damage effect of sandwich bulkhead subjected to combined impact of shock and fragments using cast TNT and prefabricated fragments. The combined impact load of the shock and high-velocity fragments were analyzed. The failure modes of surface plate and sandwich core of the bulkhead were pointed out, and the protective mechanism of sandwich bulkhead were analyzed. Results show that the impact energy acted on the structure by the prefabricated fragments is far larger than that of shock under the close blast of cast TNT and prefabricated fragments, and should be the main load in the design of the bulkhead. Under combined impact of close-impact waves and high-velocity fragments, the deformation and failure modes of the front plate is large deformation, combined with large amounts of perforation holes, including large shearing plug caused by the dense fragments, perforation and craters caused by individual fragments. Large deformation is the main failure modes of back plate. Al2O3 tiles are badly fragmented. Part of the tile fragments splashed reversely and impact on the front plate. Fiber-reinforced composite laminates will generate large deformation including damage like fibers fracture and matrix cracking. In the design of sandwich bulkhead, the front plate should avoid transverse shearing failure and collision on the bullet-resistant core, the bullet-resistant core should avoid perforation failure, and the back plate should have enough strength to absorb the residual impact energy.
In order to explore the design method of sandwich bulkhead subjected to the close blast load of missile-warhead, experiments were carried out to investigate the damage effect of sandwich bulkhead subjected to combined impact of shock and fragments using cast TNT and prefabricated fragments. The combined impact load of the shock and high-velocity fragments were analyzed. The failure modes of surface plate and sandwich core of the bulkhead were pointed out, and the protective mechanism of sandwich bulkhead were analyzed. Results show that the impact energy acted on the structure by the prefabricated fragments is far larger than that of shock under the close blast of cast TNT and prefabricated fragments, and should be the main load in the design of the bulkhead. Under combined impact of close-impact waves and high-velocity fragments, the deformation and failure modes of the front plate is large deformation, combined with large amounts of perforation holes, including large shearing plug caused by the dense fragments, perforation and craters caused by individual fragments. Large deformation is the main failure modes of back plate. Al2O3 tiles are badly fragmented. Part of the tile fragments splashed reversely and impact on the front plate. Fiber-reinforced composite laminates will generate large deformation including damage like fibers fracture and matrix cracking. In the design of sandwich bulkhead, the front plate should avoid transverse shearing failure and collision on the bullet-resistant core, the bullet-resistant core should avoid perforation failure, and the back plate should have enough strength to absorb the residual impact energy.
2015, 35(1): 124-129.
doi: 10.11883/1001-1455(2015)01-0124-06
Abstract:
The simulation of the explosion of expanded graphite bums agent requires the determination of the parameters in the JWL EOS of expanded graphite bums agent. The JWL EOS of expanded graphite bums agent are fitted through the differential evolution method taking condensed explosives isentropic line EOS as the target equation. The cylinder test results show that the maximum error between the theoretical value and experimental value is less than 3.3%, meeting the needs of the expanded graphite bums agent explosion simulation research.
The simulation of the explosion of expanded graphite bums agent requires the determination of the parameters in the JWL EOS of expanded graphite bums agent. The JWL EOS of expanded graphite bums agent are fitted through the differential evolution method taking condensed explosives isentropic line EOS as the target equation. The cylinder test results show that the maximum error between the theoretical value and experimental value is less than 3.3%, meeting the needs of the expanded graphite bums agent explosion simulation research.
2015, 35(1): 130-134.
doi: 10.11883/1001-1455(2015)01-0130-05
Abstract:
One method is offered for calculating small difference of fracture time of cylinder shell in contrast experiments. The fracture strain of cylinder shell was measured by high-speed photography, and simultaneously the velocity-time curve and displacement-time curve were measured by Velocity Interferometer System. The difference of fracture time is calculated by two kinds of measurement results. The difference of fracture time of 45 steel cylinder shell unloaded by JO-9159 and JOB-9003 explosive is 0.45 μs, and the difference of fracture time of W alloy is 0.39 μs. The method can be used to measure more accurately the fracture time of cylinder shell unloaded by detonation.
One method is offered for calculating small difference of fracture time of cylinder shell in contrast experiments. The fracture strain of cylinder shell was measured by high-speed photography, and simultaneously the velocity-time curve and displacement-time curve were measured by Velocity Interferometer System. The difference of fracture time is calculated by two kinds of measurement results. The difference of fracture time of 45 steel cylinder shell unloaded by JO-9159 and JOB-9003 explosive is 0.45 μs, and the difference of fracture time of W alloy is 0.39 μs. The method can be used to measure more accurately the fracture time of cylinder shell unloaded by detonation.
2015, 35(1): 135-139.
doi: 10.11883/1001-1455(2015)01-0135-05
Abstract:
Multiple explosively formed projectile (MEFP) can effectively raise the utilization rate of explosive and the hit rate. The forming process of groove type MEFP and the process of penetrating double nonseptate steel target based on LS-DYNA are studied. The results show that the forming process of groove type MEFP should pass through five stages: overturn, the head extrusion fracture, the rear tensile fracture, cross flying and stable flying. The cross flying is caused by the radial force which comes from detonation wave. Penetration process should pass through three stages: Spud in, united penetration and breakthrough stage. The simulated results are consistent with the experimental results.
Multiple explosively formed projectile (MEFP) can effectively raise the utilization rate of explosive and the hit rate. The forming process of groove type MEFP and the process of penetrating double nonseptate steel target based on LS-DYNA are studied. The results show that the forming process of groove type MEFP should pass through five stages: overturn, the head extrusion fracture, the rear tensile fracture, cross flying and stable flying. The cross flying is caused by the radial force which comes from detonation wave. Penetration process should pass through three stages: Spud in, united penetration and breakthrough stage. The simulated results are consistent with the experimental results.
2015, 35(1): 140-144.
doi: 10.11883/1001-1455(2015)01-0140-05
Abstract:
In order to examine the overloading resistance performance and adaptability of primary explosive in detonator used for fuse, several typical primary explosives' mechanical conditions, failure character and overloading resistance capability in the simulating bomb was analyzed by the penetration experiment on concrete target. Results from test and calculation showed: The overloading value of tested bullet is 8.7×104g, time is 2 ms, the maximal velocity is 708 m/s, penetrating depth is 0.57 m; The maximal transient acting force of primary explosives in inertial load is 85.34 N; Impulse is 70.17 mN·s; The maximal transient action energy is 0.466 8 J; The total energy is 18.656 1 J. Under this mechanical condition, the actual acting force aroused for acceleration is less due to primary explosive' less mass, and it is comparative to impact sensitivity potential energy at static state of primary explosive. No damage and failure of the primary explosive were found in the tested bullet.
In order to examine the overloading resistance performance and adaptability of primary explosive in detonator used for fuse, several typical primary explosives' mechanical conditions, failure character and overloading resistance capability in the simulating bomb was analyzed by the penetration experiment on concrete target. Results from test and calculation showed: The overloading value of tested bullet is 8.7×104g, time is 2 ms, the maximal velocity is 708 m/s, penetrating depth is 0.57 m; The maximal transient acting force of primary explosives in inertial load is 85.34 N; Impulse is 70.17 mN·s; The maximal transient action energy is 0.466 8 J; The total energy is 18.656 1 J. Under this mechanical condition, the actual acting force aroused for acceleration is less due to primary explosive' less mass, and it is comparative to impact sensitivity potential energy at static state of primary explosive. No damage and failure of the primary explosive were found in the tested bullet.
