Due to the sensitivity of the shaped charge jet to standoff and the complexity of its impact under lateral disturbances, this study aims to investigate the dynamic impact evolution of the jet influenced by standoff and lateral disturbances. A finite element model for the dynamic impact of shaped charge jets was established. Dynamic impact experiments were designed and conducted to validate the effectiveness of the numerical simulations. Utilizing dimensional analysis, a predictive model was developed for jet dynamic impact considering the combined effects of target plate strength, standoff and lateral disturbances. The results indicate that as the standoff varies between 90 mm and 225 mm, the dynamic impact depth of the jet decreases approximately linearly with increasing standoff. Meanwhile, for lateral disturbance velocities ranging from 100 m/s to 400 m/s, the impact depth decreases exponentially with increasing lateral relative velocity of the target. The lateral disturbance velocity is identified as the primary factor influencing jet impact, while the standoff is a secondary factor. The agreement among computational results, numerical simulations, and experimental outcomes confirms the accuracy and effectiveness of the predictive model and simulations, providing a basis for evaluating the dynamic impact potential of shaped charges.
The jet generated through PTFE based inert material liner has the characteristics of low energy, low density, and large aspect ratio, which can effectively achieve the "penetration without explosion" of explosive reactive armor. PTFE/Cu composite material liner with various densities is prepared, to research the roles of preparation procedure and density in the destroy effect of jet on reactive armor. Through numerical simulation research, it was found that there was no reaction at all in the explosive layer penetrated by the jet generated by the sinter liner molded, while the explosive layer penetrated by the jet generated through the hot-pressing sintering and extrusion molding liner experienced local reactions on the jet impact channel, and the overall explosive layer did not undergo any reaction. Through experimental verification, it has been proven that all three types of jets have achieved "penetration without explosion" on explosive reactive armor.
Abstract In this study, a new damage mode for the explosive reactive armour (ERA) of a shaped charge jet was proposed. The response characteristics of polytetrafluoroethylene (PTFE) and polyamide (PA) polymer jet impact on the ERA were analysed. The expansion degree and the diameter of the PTFE jet are larger than those of the PA jet, but the compactness of the PTFE jet head is lower than that of the PA jet, resulting in different impact pressures of the different polymer expansive jets on the target. The PTFE jet achieved the penetration without initiation of the ERA at different standoffs, while the PA jet directly detonated the sandwich charge when impacting the ERA vertically and failed to penetrate the front plate when impacting the ERA at 68°. With the increase of standoff, the reaction degree of the PTFE jet to the ERA decreased gradually, and the aperture of the front plate did not change.
The multi-layer tandem EFP warhead is one of the new concept warheads in the context of attacking new armor, such as composite armor, explosive reactive armor and soon. In this paper, a triple-layer sub-caliber hemispherical liner warhead is designed, and the forming process is studied by using ANSYS / LS-DYNA simulation software. Taking the velocity of the EFP and the length to diameter ratio as the performance indexes, the effect law of penetrator formation with structural parameters of curvature radius, the thickness of hemispherical liner and the height of shaped charge are analyzed, which provides a reference for the multi-layer EFP warhead. The results show that the effects of the various shaped charge structural parameters on the formation of independent EFP are different. Among them, the radius of curvature mainly affects the shape of each EFP; The bigger of the thickness of each layer liner, the faster of each layer liner separate; The influence of charge height on the EFP velocity and the length-diameter ratio of each layer is similar to that of the single layer liner, and the EFP velocity can be increased by increasing the charge height.
Three-dimensional printing is becoming increasingly popular because of its extensive applicability. However, printing materials remain limited. To determine the mechanical properties of polylactic acid (PLA) and copper powder-filled polylactic acid (PLA-Cu) materials subjected to static and dynamic loading, stress-strain curves were obtained under the conditions of different strain rates using a universal material testing machine and a separated Hopkinson pressure bar experimental device. Scanning electron microscopy (SEM) was used to analyze the micro-morphology of the quasi-static compression fracture and dynamic impact sections. The results revealed that the yield stress and elastic modulus of the two materials increased with increasing strain rate. When the strain rate reached a critical point of 0.033 s-1, the rate of crack propagation in the PLA samples increased, resulting in the material undergoing a change from ductile to brittle. The strength of the material subjected to dynamic loading was significantly higher than that subjected to quasi-static loading. The SEM image of the PLA-Cu material revealed that copper powder was evenly distributed throughout the 3D-printed sample and that stress initially began to concentrate at the defect site corresponding to the interface between the copper powder and PLA matrix; this resulted in comparatively lower toughness. This finding was consistent with the photographs captured via high-speed photography, which confirmed that the destruction of the specimen was accompanied by an explosive crushing process. Additionally, a Zhu-Wang-Tang constitutive model was used to fit the experimental results and establish a viscoelastic constitutive model of the material. By comparing the dynamic stress-strain curve to the theoretically predicted curve, we found that the established constitutive model could predict the mechanical properties of the PLA-Cu material with reasonable accuracy when the strain was below 7%.
Abstract The damage to the back of the target plate is a phenomenon that occurs when concrete is subjected to high-speed impact. In order to study the motion parameters of prefabricated spherical fragments penetrating finite thickness concrete targets at high speeds and the occurrence rules of concrete damage, as well as the impact of target back damage on the motion of fragments, experiments were conducted on 100 mm finite thickness concrete targets with prefabricated spherical fragments. The concrete model parameters in LS-DYNA were modified based on the residual velocity of fragments, and numerical simulations were conducted on the penetration of prefabricated fragments with different impact velocities and concrete target plates with different thicknesses. By analyzing the location of concrete target plate damage, the relationship between concrete thickness and concrete damage was obtained; Combining the motion parameters of fragment penetration process, the phenomenon of concrete collapse was linked to fragment motion, and the influence of concrete thickness on fragment motion parameters was analyzed. The results indicate that the thickness of the finite thickness concrete target plate and the penetration speed of fragments have a significant impact on the damage state of the target back, and further affect the motion change response stage during the penetration process of prefabricated fragments.
Abstract The temporal-spatial evolution process of fragment power field is the basis for calculating the state of fragment-target encounter and damage assessment. In order to accurately describe the temporal-spatial evolution process of the fragment power field of the axial preformed fragment warhead, the numerical simulation method is used to analyse the fragment dispersion characteristics of different warheads, and the fragment velocity attenuation model is established by programming. The numerical simulation results are used as the initial value to substitute into the model to obtain the temporal-spatial evolution process and the hitting target process of the fragment power field. The results show that the multi-layer fragments will collide many times under the action of detonation load, and the collision will lead to the decrease of the average velocity of the same fragment layer and the increase of the scattering angle. After increasing the number of fragments, the outer fragments are more concentrated, but the average velocity is significantly reduced, and the fragment miss rate increases. This study can provide a calculation basis for the state of fragment-target encounter and the static and dynamic explosion test of fragment warhead.
Abstract To explore the penetration behavior of jets under dynamic impact conditions and to predict and assess the dynamic penetration power of shaped charge jets, finite element methods were employed to numerically simulate shaped charge warheads under various impact conditions. Combined with theoretical analysis, the simulations analyzed the variations in perforation and dynamic penetration depth of the jet into target plates. Using a random forest algorithm, the influence weights of different factors on the dynamic penetration depth of the jet were obtained. Furthermore, an engineering model for predicting the dynamic penetration depth of shaped charge jets was established through a linear regression model. The research results indicate that the impact velocity is the most critical factor affecting the dynamic penetration depth of shaped charge jets. The dynamic penetration depth of the jet into targets within a certain range of impact velocities is approximately linear. The established engineering model can effectively predict the penetration power of jets under dynamic impact conditions.
An ideally shaped charge warhead is an effective weapon against armored targets. The use of the gathering energy effect generated by the explosion drives the liner to form a shaped charge jet, which can penetrate the armored target. Existing shaped charge warheads often use a metal liner. Herein, we discuss the characteristics of polymer liners. To study the characteristics of the expansive jet formed by the polymer liner, three polymer materials with different properties-polytetrafluoroethylene (PTFE), nylon (PA), and polycarbonate (PC)-were selected. Using the smooth particle hydrodynamics (SPH) method and the AUTODYN finite element software, the expansive jet formation by the polymer liners was simulated and verified by experimental data. The polymer jets of the different materials exhibit a certain degree of expansivity; however, due to differences in the material properties, the expansive diameter of the jet and the degree of head compaction differed. The expansive diameter of the PA jet was the smallest, and that of the PTFE jet was larger than that of the PA jet, but with a smaller compactness. The PC jet exhibited the largest expansive diameter and the highest degree of compactness.
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