Rod Penetration Research Articles

Theoretical Research Progress in High-Velocity/Hypervelocity Impact on Semi-Infinite Targets

With the hypervelocity kinetic weapon and hypersonic cruise missiles research projects being carried out, the damage mechanism for high-velocity/hypervelocity projectile impact on semi-infinite targets has become the research keystone in impact dynamics. Theoretical research progress in high-velocity/hypervelocity impact on semi-infinite targets was reviewed in this paper. The evaluation methods for critical velocity of high-velocity and hypervelocity impact were summarized. The crater shape, crater scaling laws and empirical formulae, and simplified analysis models of crater parameters for spherical projectiles impact on semi-infinite targets were reviewed, so were the long rod penetration state differentiation, penetration depth calculation models for the semifluid, and deformed long rod projectiles. Finally, some research proposals were given for further study.

Experimental research on the long rod penetration of tungsten-fiber/Zr-based metallic glass matrix composite into Q235 steel target

In the present paper, the long rod penetration experiments of tungsten-fiber/Zr-based metallic glass matrix composite (WF/Zr-MG) and tungsten heavy alloy (93W) into Q235 steel targets are conducted by employing H100 smooth bore artillery within the speed range from 765 m/s to 1809 m/s. The diameter of the long rods is 19 mm and its aspect ratio is 10. Different from the mushrooming of 93W rod nose, the self-sharpening phenomenon is observed in the nose of WF/Zr-MG rod. The experimental results indicate that the WF/Zr-MG rod has much better penetrating performance than the 93W rod when the penetration velocity exceeds 1000 m/s. Integrated with the metallographic analysis of the residual rods, the failure modes of WF/Zr-MG rod are identified systemically. The deformation and shear failure of WF/Zr-MG composite mainly occurs in the edge layer of the rod nose during the high-speed penetration and it displays the localizing and sharpening features. The thickness of the edge layer in the rod nose maintains a dynamic balance.

Research of the Penetration Process for Concrete Target Based on the Extended Finite Element Method

The extended finite element method (XFEM) is the most effective numerical method to solve discontinuous dynamic problems so far. It makes research within a standard finite element framework and needs not mesh repartition to geometric and physical interface, so it reserves all merits of the conventional finite element method (CFEM). The XFEM was applied to the penetration process for concrete target in the paper, and the displacement mode of elements with cracks and fracture criterion were presented. Then the weak solutions of control equations were discretized in different areas. The numerical examples for steel rod penetrating in the concrete target concluded that the method and program were reasonable and effective. The effect discipline of crack growth to the concrete material penetration process was summarized, and it would establish theoretic base for the further application of the XFEM.

An Examination of DOP Test of Ceramic Tile Subjected to Long Rod Penetration

Depth of penetration (DOP) test of ceramic tile subjected to long rod impact was analyzed by applying the Tate model. This paper investigated the influence of impact velocity and tile thickness on the ballistic performance measurement of the tested ceramic tiles. DOP test was simplified as an eroding rod penetrating a target composed of multilayered materials. Through applying the Tate model, the method of obtaining the numerical solution was proposed. For a constant impact velocity, it was found that the measured differential tile efficiency (DEF) was independent of the thickness of the ceramics tiles. But the measured DEF decreased as the impact velocity increased. These analytical conclusions were verified by the using of the results of DOP tests of SiC and Al2O3 tiles subjected to impact of long tungsten alloy rods at a nominal impact velocity of 1.3 km/s.

Rate dependent shear failure and the scaling effect in long rod penetration

Long rod penetration tests show a scaling effect that cannot be explained by rate dependent strength. We propose here that this scaling effect may be explained by rate dependent failure. We start by revisiting the well known result that long rod penetration efficiency depends on strain to failure of both projectile and target materials. We then make the strain to failure depend on strain rate, using the overstress concept. In this way the effective strain to failure increases with strain rate. As strain rate increases with decreasing scale, we get that penetration efficiency decreases with decreasing scale, as observed in tests. In the paper we show results of hydrocode runs that demonstrate the relation between strain rate sensitivity of strain to failure and the scaling effect in long rod penetration.

Computational Technique of the Sliding Interface in Numerical Simulations of 3D Penetration

Based on the Lagrange finite element method, a simplified computational technique for sliding interface in oblique penetration is proposed in the paper. By applying the 3D finite element program developed on this technique to numerical analog computation of ogive-noded steel rod penetrating in the aluminum target, a result which is consistent with that of A.J.Piekutowskis experiment can be reached. Hence it proves the rationality and validity of the program and method discussed in this paper and that the method is useful in the numerical study of penetration and perforation.

Predicting the penetration of long rods into semi-infinite metallic targets

Analytical equations are presented herein to predict the penetration of semi-infinite metallic targets struck normally by long rods at high velocities for Y p<S where Y p is the rod strength and S is the static target resistance. The equations are derived based on energy balance method. It is assumed that the kinetic energy loss of a long rod is related to the energy dissipated by the plastic deformations in the target, the energy consumed by the long-rod penetrator itself and the energy carried by the eroded rod debris. Secondary penetration is also examined in the present paper due to the fact that the eroded rod debris forms a tube which can penetrate the target further if the density of the rod is greater than that of the target and the impact velocity is high enough. The present analytical equation is found to be in good agreement with the experimental data for a wide range of impact velocities.

Application of the Extended Finite Element Method to the Penetration Problem for a Body with Cracks

The XFEM makes research within a standard finite element framework and needs not mesh repartition to geometric and physical interface, and it reserves all merits of the CFEM, therefore it is the most effective numerical method to solve discontinuous dynamic problems so far. The crack growth problem was studied in the XFEM computation, and the displacement mode of elements with cracks and fracture criterion were presented. The numerical examples for steel rod penetrating in the aluminum target concluded that the method and program were reasonable and effective. The crack growth discipline of penetration process for metal material was summarized, and it would establish theoretic base for the further application of the XFEM.

Modeling Experiments of Hypervelocity Penetration of Adobe by Spheres and Rods

The work described in this paper uses the Holmquist-Johnson-Cook equation of state and constitutive model for concrete and appropriate material parameters derived from mechanical test data to perform numerical simulations of penetration and perforation of adobe building material. Experimental results from the literature are modeled, and two-dimensional numerical simulations are carried out using the CTH Eulerian shock physics code. Two groups of simulations were performed in accordance with the experimental results. The first group is tungsten rod penetrators, with impact velocities ranging from 340 to 820 m/s, perforating adobe targets with thicknesses ranging from 71 to 497mm, and comparison of the residual velocities predicted by the numerical simulations with the available experimental results. The second group is steel spheres, with impact velocities ranging from 500 to 3230 m/s, penetrating into adobe targets of semi-infinite thickness, and comparison of the depths of penetration predicted by the numerical simulations with the available experimental results. The technique described in this paper for modeling and simulation of adobe penetration and perforation is able to adequately predict the residual velocities and depths of penetration for the conditions modeled.

Закономерности высокоскоростного проникания осесимметричных длинных стержней в прочное полупространство

Закономерности высокоскоростного проникания осесимметричных длинных стержней в прочное полупространство

BURN FISTULAS

We present an unusual case of hot metal rod penetration through anterior aspect of the right thigh near femoral triangle and exited posteriorly through the right buttock leading to burn fistula. The case is presented because of rarity of hot rod penetrating the thigh and subsequent anxiety for the surgeon in keeping an eye over the femoral vessels and restoring the function of the limb.

Simulation Analysis of Penetration Performance of Tungsten Alloy and Tungsten Carbide Rod Penetrator

In penetration mechanics, the material parameters of the rod penetrator are very important factors which influence the effect of penetration. The effect of each parameter changes with the impact velocity. Simulation analysis of two models filled with tungsten alloy and tungsten carbide separately penetrating semi-infinite armor steel target at medium to high velocities has been made to quantitatively analyze the key roles that the density and hardness play. Simulation results indicate that a dividing line of velocity exists between the penetrations of two materials. Above the line, tungsten alloy rod with greater density has a distinct advantage with increasing velocity. Below the line, the advantage of tungsten carbide rod with greater hardness is significantly more with the decreasing velocity. In the process of penetration, penetration velocity decreases rapidly from a high value to zero. The simulation result provides quantitative analytic basis which can be used to prove that the penetrator composed of two different materials is better than the one composed of homogenous material.

Stone and gravel contents of arable soils influence estimates of C and N stocks

Abstract Studies concerning the stoniness of arable soils are scarce since those soils are commonly regarded as composed mainly of fine earth. However, even the influence of lesser volumes of stones and gravel on estimates of nutrient stocks may be significant. Nutrient analyses are performed on the fine earth fraction. It is therefore necessary to determine the bulk density and the relative soil volume that is occupied by fine earth when expressing nutrient stocks per unit area and to a certain depth. In this study, relative volumes of stones and gravel were investigated in the top soils, i.e. down to 30 cm depth, of five Swedish arable sites. Bulk density and gravel volume were determined by soil coring and stone volume using the rod penetration method. A function for estimation of relative stone volume from mean penetration depth was developed. The function is suitable for soils with low stoniness, i.e. less than 10%. The results showed that although the relative volumes of stones and gravel were small, at most 8%, neglecting the volume occupied by rock fragments led to an overestimation of C and N stocks by 8–9%. The moderate volumes of stones and gravel also significantly affected comparisons between sites. It was concluded that the inclusion of stone and gravel volume of arable soils may be important if nutrient stocks of different sites are compared, or the effects of land use changes are scaled up to regional or global levels.

Nanocrystalline refractory metals for extreme condition applications

For the last decade, there has been research aimed at engineering plastic instability into the deformation behavior of body centered cubic (b.c.c.) metals. At dynamic strain rates, the adiabatic shear band deformation mode has been shown to improve the performance of kinetic energy penetrator materials. However, for some b.c.c. metals the transition to localized plastic deformation dominates at all strain rates. This limits the traditional engineering properties (e.g., ductility and toughness) and feasibility of incorporation into a long rod penetrator system. Recently, we demonstrated that nanocrystalline tantalum shows significant promise as it deforms via adiabatic shear bands in dynamic compression but shows significant tensile elongation in quasi-static deformation.

On the Failure and Dynamic Performance of Materials

Waves induced by impact initiate deformation mechanisms within a material that precede later flow. An impulse excites a cascade of deformation mechanisms starting with ultrafast and concluding with slower ones. In metals, brittle glasses and polycrystalline ceramics there are a combination of mechanisms with differing relaxation times that condition a loaded target. In the case of ballistic impact, once failure has occurred, long rod penetration can occur and the depth achieved within each target can be scaled with the deformation strengths recorded during the initial high pressure impulse. A review of material shock response and target preconditioning shows a correlation with the ballistic penetration of the target after loading. This indicates that the effect of an initial loading impulse upon material behaviour is a strong feature of the effects observed in many dynamic phenomena.

A combined numerical and theoretical study on the penetration of a jacketed rod into semi-infinite targets

A combined numerical and theoretical study is conducted herein on the penetration of semi-infinite targets by jacketed rods with different r j 0/ r c 0 ratios where r j 0 and r c 0 are the radii of the jacket and the core, respectively. The numerical results show that for smaller r j 0/ r c 0 ratios the u– v relationship changes only a little compared to that of unitary long rod penetrator of the same core material, hence, the u– v relationship of unitary (homogeneous) long rod penetration is also applicable for jacketed rod penetration. Model for cratering in semi-infinite targets by jacketed rods is then suggested by using the laws of conversation of mass, momentum and energy, together with the u– v relationship of unitary (homogeneous) long rod penetration and an analytical model for predicting the depth of penetration has also been given for jacketed long rods penetrating semi-infinite targets in co-erosion mode. A new criterion for transition from bi-erosion to co-erosion is proposed. It transpires that the present model is in good agreement with the experimental observations for EN24 steel jacketed tungsten alloy long rods penetrating semi-infinite armor steel targets in terms of crater diameter and penetration depth.

Development of a penetration model for an erosive long rod considering strength effects of colliding materials

In this article a simple penetration model for the terminal ballistic of long rod penetrators is developed. The model is to predict the crater depth of a projectile penetrating into a semi-infinite target. A principle objective was to take an account of strength properties of colliding materials using erosive phenomena. The entire velocity regime from low to hypervelocity is analysed. The effect of the penetrator aspect ratio is also considered in the model. The model developed here is based on the steady-state penetration process and is used to compare with existing experimental measurements. The results of the comparison show very good agreement with experimental investigations of other researchers in this field. The study shows that it is possible to construct a very simple model to predict crater depth for a large range of materials with sufficient accuracy without recourse to high cost of experimentation. In fact, the biggest advantage of this model is simplicity and direct applicability to design process. Historically, penetration mechanics has relied very heavily on experimental investigation. This work gives a quick and easy result with sufficient accuracy which may be useful for many applications. To validate the analytical solution, an experimental method is employed.

Analytical model for cratering of semi-infinite metallic targets by long rod penetrators

Analytical model is presented herein to predict the diameter of crater in semi-infinite metallic targets struck by a long rod penetrator. Based on the observation that two mechanisms such as mushrooming and cavitation are involved in cavity expansion by a long rod penetrator, the model is constructed by using the laws of conservation of mass, momentum, energy, together with the u-v relationship of the newly suggested 1D theory of long rod penetration (see Lan and Wen, Sci China Tech Sci, 2010, 53(5): 1364–1373). It is demonstrated that the model predictions are in good agreement with available experimental data and numerical simulations obtained for the combinations of penetrator and target made of different materials.

Resistance of the medium during high-velocity penetration of long rods and shaped-charge jets

We consider the high-velocity penetration of long rods and shaped-charge jets into semi-infinite targets with initial impact velocities of 2–4 km/sec. At these velocities, the mechanical characteristics of the target materials makes a great contribution to the final parameters of the process: penetration depth and critical velocity of the impactor (jet). The dynamic compressive stability threshold of the material, obtained in experiments with uniaxial dynamic loading of flat targets, is proposed as a parameter that determines the properties of the target in the penetration process.

Penetration of a copper rod into a sandy target

This paper presents the results of experimental and theoretical studies of high-velocity penetration of cylindrical copper rods into sand. The hydrodynamic Alekseevskii-Tate theory is modified to determine the penetration depth and wear velocity of the material of the rod penetrating into soil target in the plastic and hydrodynamic stages of penetration. The case where the target material is significantly less strong than the rod (impactor) material is considered.