Hypervelocity Penetration Research Articles

A multi-scale model for use in hydrodynamic simulations of impacts and hypervelocity penetrations into porous silica aerogel

Low-density silica aerogel is an ideal material for capturing hypervelocity interplanetary dust. To investigate the behavior of hypervelocity shock waves at different particle velocities using silica aerogel densities ranging from 80 kg/m3 to 320 kg/m3, a multi-scale Smooth Particle Hydrodynamics (SPH) approach is employed. The simulation results demonstrate a good agreement with the macroscopic experimental findings across a wide range of particle velocities, from 0.5 km/s to 20 km/s, while considering the shock wave velocities of the porous material and their linear variation. In addition, simulations of pressure-specific volume curves were conducted using the microscopic model. According to the simulation results, we present a novel compression model of silica aerogel materials regarding the classical form of the P−V relationship for porous materials. Building upon the microscopic model, we propose a macroscopic equivalent model for dynamic compression of low-density aerogel, which is subsequently incorporated into the hydrodynamic calculation of interplanetary dust hypervelocity penetration into aerogel. The results of the simulation of hypervelocity penetration indicate that the multi-scale model presented in this work can be used to simulate the macroscopic mechanical behavior of aerogels in a non-uniform field.

Experimental and theoretical study on cavitation of concrete targets penetrated by hypervelocity long rod projectiles

The cavitation phenomenon can seriously decrease the strike performance of military weapons. As military terminal-ballistic activities have turned to hypervelocity attacks, the cavitation effect existing in the hypervelocity penetration deserves more attention. In terms of long-rod hypervelocity penetration into concretes, this study presents an analytical cavity model for the prediction of the cavity diameter based on the two-stage cavitation mechanism and the u-v relationship. The two-stage mechanism involving mushrooming and radial momentum expansion is used to describe the cavitation modes and the penetration parameters for the projectiles used in the analytical model are determined by numerical simulations empirically. Besides, the three modes including rigidity, deformation and erosion are introduced into the cavity model to elucidate the projectile state. Moreover, the hypervelocity impact experiments on the long rods into semi-infinite concrete targets at velocities of 2117 ∼ 3086 m/s are carried out to observe the cavitation effect of concrete targets and for further validating the model through comparing with the experimental cavity profiles, where the cavity profile is quantified with silica gel, and the cavity diameter is found to be more than five times the projectile diameter. The cavitation effect is observed significantly and quantified from the experiment results. The cavity model is compared with the experimental cavity profiles, showing that the model has good applicability.

The maximum penetration depth of hypervelocity projectile penetration into concrete targets: Experimental and numerical investigation

With the employment of the Kinzhal hypervelocity missile in warfare, evaluating the penetration damage effect especially the penetration depth of hypervelocity weapons has become a hot topic. The maximum penetration depth is one of the most important concerns for protective engineers, however, which is still an open question due to the lack of penetration data. A combined experimental and numerical investigation on projectile hypervelocity penetration into concrete targets is presented in this study. Hypervelocity penetration tests were first carried out by launching projectiles with various length-to-diameter (L/D) ratios penetrating concrete targets, where the striking velocities ranged from 1462 m/s to 2891 m/s. Combined with our previous penetration data, a complete variation tendency of penetration depth is depicted, demonstrating the existence of the maximum penetration depth. Then the corresponding numerical models are developed and validated. Based on the numerical results, the three stages during hypervelocity penetration are identified, and the variation tendency of the penetration depth is clarified. After that, the influence of the properties of projectile and target on the maximum penetration depth and corresponding critical striking velocity are numerically investigated. Finally, empirical formulas are established to quantify the influences of these parameters on the critical striking velocity and penetration depth. The research results can provide important references for designing protective structure against hypervelocity weapons.

Flow field analysis of long rod hypervelocity penetration into semi-infinite concrete target

An ovoid of Rankine was used to describe the flow field shape, and a flow field analysis model was constructed to depict the penetration process. The depth of penetration, tunnel radius, change in the long rod length, and penetration velocity was calculated using this model. The calculation results were in good agreement with experimental data from previous studies. The influence of long rod material parameters on penetration was also analyzed. The following results were obtained: the depth of penetration increased slowly with increasing impact velocity at hypervelocity penetration, the erosion rate of the long rod was constant during the penetration process, and the length of the long rod was the most sensitive parameter affecting the depth of penetration, and the hole radius and long rod diameter had an approximately linear relationship and both increased with rod density.

Simulation Study on Hypervelocity Penetration of Lab Scaled Shape Charge Mechanism

Shaped charge (SC) is a mechanism used by defence industries as anti-armored weapon to penetrate armored plates. Numerous studies have been conducted on the shaped charged effects. However, experimental studies are limited due to great safety requirement and limited access to high grade explosive. Due to these limitations, an experimental study on a small-scale shaped charge mechanism (SCM) penetration blast test was conducted against five (5) types of target materials. The experimental data is then verified by simulation to proof that it can be used to predict the SC penetration data. This paper intent to present a comparative study on the effect of shaped charge blast conducted by simulation with the actual experimental results. In order to conduct this study, a 2D AUTODYN software were used to develop the SC blast model against five (5) types of target materials. This study concludes that the 2D AUTODYN simulations results can predict the hypervelocity penetration for all target materials compared to the experimental test with an average difference of 9.1 %.

Hypervelocity penetration behavior and fireball radiation characteristics of tungsten-zirconium reactive projectile

Reactive damage elements has the dual properties of kinetic energy penetration and strong combustion/explosion and thus enhanced damage ability potentially. At present, research on the damage characteristics of reactive projectile is mostly limited to the velocity of projectile impacting target below 2km/s, and there are few reports on hypervelocity impact. The damage ability of high-density and high-strength tungsten-zirconium (W/Zr) alloy projectiles is enhanced in hypervelocity impact, because the degree of material being fragmented is high, the particle size is small, and the flying speed of particles is fast, which are all conducive to the combustion of reactive components to form continuous high-temperature fireballs. In order to investigate the hypervelocity penetration behavior of W/Zr reactive projectile and the radiation characteristics of fireball, the failure characteristics of W/Zr reactive projectile impacting titanium alloy plate with velocities of 1.842-4.039km/s were obtained by hypervelocity impact test. The effects of projectile impact velocity and ambient gas pressure on the combustion characteristics of impact fireball are analyzed. The evolution characteristics of equivalent radiation temperature and equivalent radiation area are obtained by fitting experimental data. The effects of environmental gas on radiation characteristics under different impact conditions are identified and analyzed.

Experimental and Analytical Study on the Penetration Depth of Mortar Targets Subjected to Projectile Impact in the Hypervelocity Regime

A projectile may be deformed and eroded due to the high pressure generated by hypervelocity penetration, which makes it difficult to describe the penetration mechanism for protection engineering by existing theories at such high velocities. To analyze the penetration depth of concrete-like targets subjected to hypervelocity impact by kinetic energy weapons, experiments with ogive-nosed steel projectiles penetrating mortar targets are conducted, where the average uniaxial compressive strength of the mortar targets is 41.8[Formula: see text]MPa and the impact velocities range from 1[Formula: see text]225[Formula: see text]m/s to 2[Formula: see text]392[Formula: see text]m/s. The experimental results show that the crater diameter and crater depth have a linear relationship with the striking velocity. The depth of penetration (DOP) increases linearly first and then decreases sharply and increases slowly again. Three penetration regimes are observed in turn with increasing velocity, i.e. rigid projectile penetration, abrasive projectile penetration and semifluid projectile penetration. Furthermore, based on a study of the dynamic compression behavior and penetration resistance function of concrete, a hydroelastoplastic-frictional penetration model is established. The velocity range is divided into solid penetration, semifluid penetration and fluid penetration, which correspond to [Formula: see text], [Formula: see text] and [Formula: see text], respectively. Then, the rigid and abrasive projectile penetration models, which consider the projectile mass loss, are verified by the present test data. Finally, the semifluid projectile penetration model is evaluated with the existing test data. These results can provide support for research on the damage effect of hypervelocity kinetic energy weapons and the design of underground strategic protection engineering.

An approximate compressible fluid model of long-rod hypervelocity penetration

Long rods are expected to experience higher impact velocities in the future as a result of the further development of new launching systems and ultra-high-energetic materials. It is therefore of considerable importance to investigate the compressible fluid theory of long-rod hypervelocity penetration. Based on the compressible fluid theory and the quasi-steady penetration assumption, an integrated approximate compressible fluid model of long-rod hypervelocity penetration that ignores the influence of shockwaves is established in this study. By comparing the solutions of this theoretical model with the Alekseevskii-Tate model (Alekseevskii (1966), Tate (1967, 1969)), experimental data, and numerical simulations, the validity of the model is verified. Subsequently, we present a compressible hydrodynamic limit after further analyzing the similarities and differences between our model, the Alekseevskii-Tate model, and the hydrodynamic theory. Finally, based on analyses of different projectile–target combinations, the influence of the compressibility of projectile/target materials on the penetration efficiency is discussed. Meanwhile, the proposed model is deemed appropriate for velocities from 1.5 km/s to 12 km/s. In addition, under the conditions that either the projectile and target are similar or both are weakly compressible, we demonstrate that the applicable velocity range of the Alekseevskii-Tate model can be appropriately extended.

Mechanism on hypervelocity penetration of a tungsten alloy projectile into a concrete target

To investigate the hypervelocity impact mechanism of a tungsten alloy projectile on a concrete target, a new dynamic plasticity-based failure model for metal was developed by introducing Lode angle, dynamic enhancement factor, temperature softening term and stress triaxiality, and a new constitutive model for concrete was proposed by introducing strain rate effect, pressure dependence, Lode angle and free water effect. The advanced measurement technologies were introduced to determine the dynamic mechanical behaviors of materials, then the materials parameters were used to numerically simulate the hypervelocity penetration of a tungsten alloy projectile into a concrete target. Based on a 57/10 two-stage light gas gun, the experiments were carried out on the hypervelocity impact of the tungsten alloy projectile on the concrete target. And according to the computed tomography scanning images of the damaged concrete targets, the crater characteristics in the targets were analyzed. Then the relationships of the total penetration depth and the residual length of the projectile with the initial impact velocity of the projectile were obtained. The penetration of the projectile and the stress wave propagation in the concrete target were analyzed by the theoretical method. The achieved results are as follows. (1) By utilizing the new constitutive models for the metal and concrete, the failure morphology of the concrete derived from numerical simulation is consistent with that from the experiment. (2) The craters are structured by spalling areas and projectile holes, the transverse failure effect shows a significant advantage over low-velocity penetration, and the volume of craters is approximately proportional to the kinetic energy of projectiles. (3) The penetration depth increases at first and then decreases with the increase of the impact velocities, the decrease of the penetration depth under high velocity is due to the decrease of the rigid penetration stage after the erosive penetration stage. (4) A theoretical penetration model is proposed, which can be used to predict the depth of penetration, the residual length of the projectile and the diameter of the mushroom-like head, et al. (5) A theoretical stress wave propagation model is developed and the theoretical results of stress waves are in good agreement with the experimental ones.

Hypervelocity penetration of concrete targets with long-rod steel projectiles: experimental and theoretical analysis

Hypervelocity penetration experiments were performed on semi-infinite concrete targets with 7 mm-diameter 40CrNiMo steel long-rod projectiles at impact velocities ranging from 2117 m/s to 3086 m/s by using a two-stage combustion light-gas gun. After the experiments, the crater dimensions and penetration depth were carefully measured, also the residual projectiles were recovered. The depth of penetration was found to be greater than the hydrodynamic limit penetration depth. Numerical simulation was conducted to analyze the penetration process, and combined with the experimental results, it was obtained that the head of the long-rod projectile eroded and deformed into a hemisphere during hypervelocity penetration. According to the experimental and numerical simulation results, the penetration model of long-rod projectiles penetrating concrete targets at hypervelocity was constructed based on the Alekseevskii-Tate model. The penetration model was compared with the experimental depths of penetration, showing that the model had good applicability.

Experiment research and crater analysis of long rodhypervelocity penetration into concrete

With the development of hypervelocity kinetic energy weapons, the mechanism of long rod hypervelocity penetration into concrete target was a research highlight. To study the penetration mechanism and the crater law of long rod hypervelocity penetration into concrete, two kinds of long rods, TU1 and Q235, hypervelocity penetration into concrete with initial velocity of 1.8−2.4 km/s were experimented. Dimensional analyses of crater diameter and crater volume were performed based on the experiment data from this paper and references. Prediction formula of crater depth was derived from the bowl shape contour of crater section. The crater size of hypervelocity penetration was obviously larger than that of low and medium velocity penetration, and so the crater phase was non-negligible during the penetration mechanism researches. The length of the long rod was severely shortened until the long rod was completely eroded, the radius of the hole was obviously larger than that of long rod, and these results can be used to verify that the mechanism of long rod hypervelocity penetration into concrete was semi-fluid penetration. At the same time, it can be seen from the experimental results that the length of the long rod was the most important parameter affecting the penetration depth. The penetration depth increased with the increase of the length and density of the projectile, but was not affected by the strength of the long rod.

Effective velocity range of theoretical hypervelocity penetration models

This study attempted to improve the applicability of existing penetration models. First, the correlation of three existing hypervelocity penetration models of Birkhoff et al. (Birkhoff), Abrahamson and Goodier (A-G), and DiPersio, Simon and Merendion (DSM) was analyzed. The A-G model predicted the same penetration depths as Birkhoff and DSM models for jets of uniform and linear velocity distributions. Second, the accuracy of each penetration model was verified to check the differences in the experimental results. Finally, the penetration of jet elements with various velocity distributions was analyzed with finite element analysis. The effective velocity ranges of the analytical models were identified to be approximately 4 km/s for uniform velocity jets, and above 3 km/s for linear velocity profiled jets. This study is expected to provide efficiency to the study of hypervelocity penetration.

Dynamic hardness of rock materials under strong impact loading

There have been numerous methods to test the hardness value of a piece of material. However, these methods are invalid when the target is under hypervelocity penetration. The physical nature of dynamic hardness is discussed and a new method to calculate the dynamic hardness values of rock materials under hypervelocity penetration is given. The mathematical expressions of dynamic hardness are derived based on the ideal elastoplastic model and the internal friction model, respectively. The results show that under hypervelocity penetration the dynamic hardness is proportional to the dynamic shear strength, and the coefficient is a function of the bulk modulus and the shear modulus of the target itself. The results also show great agreement with test data.

Research on Dynamic Test of Hyper-Velocity Impact Penetration Acceleration Signal

In recent years, with the development of hyper-velocity weapon, the research focus of penetration effect has switched gradually from high-velocity to hyper-velocity, with insufficient studies on penetration effect and its internal mechanism. Besides, the study on penetration effect of hyper-velocity weapon depends on the measurement of mechanical signal during penetration of projectile. In this paper, dynamic test of hyper-velocity impact penetration acceleration signal is studied in depth. Firstly, the penetration velocity and acceleration of projectile under the impact load are analyzed, the influence of the movement of the testing unit on the measured acceleration signal is studied, and the factors to be considered when measuring the hyper-velocity impact load are given. Further, this paper designs a measurement circuit and dynamic models of each measurement module, details the influence of dynamic characteristics of power delivery network on test accuracy, and provides a method to obtain dynamic characteristics of power delivery network by virtue of S parameter. Finally, to extract the real penetration overload signal, a superior noise reduction algorithm adopting Modified Ensemble Empirical Mode Decomposition (MEEMD) is proposed, taking dynamic uncertainty and degree of approximation as evaluation indicators, and the measured sensor data is analyzed and processed with the proposed superior noise reduction algorithm. The experiment results show that, this method has a better noise reduction effect, and can be adopted to effectively extract real penetration overload signal. The results have theoretical research and application value to evaluate the reasonableness and effectiveness of measurement method of hyper-velocity penetration overload signal, and seek for a superior processing method for the noisy penetration overload signal.

Analytical model of hypervelocity penetration into rock

The results of dynamic compression tests of the rock revealed that the actual working pressure ranged from 5 GPa to 20 GPa when the penetration velocity ranged from 1000 m/s to 4000 m/s. The region is exactly the transition area where the compression state changes from elastoplasticity to hydrodynamics, and the rock is subject to restricted internal friction. Also the region lacks accurate representation in existing penetration theories. A study of the hydrodynamic was performed by using the internal friction theory. Equations were systematically presented which covered and linked up the elastoplasticity-semifluid with internal friction and hydrodynamic pressure. And the essential connections and differences between the penetration of hypervelocity kinetic energy bombs and common penetrating bombs were illuminated. Furthermore the velocity region of hypervelocity was demarcated theoretically, illuminating the transformation of the target medium with the increased penetration velocity from elastoplasticity to semifluid with internal friction and hydrodynamics. The calculations revealed the characteristic phenomenon that the decrease of penetration depth in that the abrasion of the bomb mass and the existence of a limitation depth. In conclusion the formulas to calculate the depth and diameter of the crater were presented.

Dynamic spherical cavity expansion analysis of concrete using the Bingham liquid constitutive model

High pressure exists in concrete targets during hypervelocity penetration. An incompressible concrete material under large deformation can be represented by a liquid constitutive model. The present work modifies the cavity expansion theory by characterizing incompressibility using the Bingham liquid constitutive model, in which the viscosity of an incompressible material is considered according to Cleja-Tigoiu's work. An analytic expression is derived for the relationship between the pressure on a cavity boundary and the velocity of cavity expansion. Then, the effects of material parameters in the modified model are studied, which is the basis of the calculation of the drag force in hypervelocity penetration. The viscosity coefficient (μ0) is the most sensitive parameter for the radial stress on the cavity surface. As μ0 increases, the dimensionless stress on the cavity surface (S) increases and the quadratic relation between S and the velocity of cavity expansion (a˙) becomes weaker. Finally, the penetration depths of long rod hypervelocity penetration into a concrete target are predicted based on the modified model, the results are in good agreement with experimental results.

A simplified approximate model of compressible hypervelocity penetration

A simplified approximate model considering rod/target material’s compressibility is proposed for hypervelocity penetration. We study the effect of shockwaves on hypervelocity penetration whenever the compressibility of the rod is much larger, analogously, and much less than that of the target, respectively. The results show that the effect of shockwaves is insignificant up to 12 km/s, so the shockwave is neglected in the present approximate model. The Murnaghan equation of state is adopted to simulate the material behaviors in penetration and its validity is proved. The approximate model is finally reduced to an equation depending only on the penetration velocity and a simple approximate solution is achieved. The solution of the approximate model is in agreement with the result of the complete compressible model. In addition, the effect of shockwaves on hypervelocity penetration is shown to weaken material’s compressibility and reduce the interface pressure of the rod/target, and thus the striking/protective performance of the rod/target is weakened, respectively. We also conduct an error analysis of the interface pressure and penetration efficiency. With a velocity change of 1.6 times the initial sound speed for the rod or target, the error of the approximate model is very small. For metallic rod–target combinations, the approximate model is applicable even at an impact velocity of 12 km/s.

Tensile behavior of C/SiC composites plate after hypervelocity penetration: Residual strength and fracture mechanism

The damage and tensile mechanical behavior of C/SiC composites plate after hypervelocity penetration are studied in this paper. Hypervelocity penetration is applied along the out-of-plane direction by an electrical gun at 3.5 km s-1, and the target is recovered for damage observation and tension test. Quasi-static tensions on the recovered targets and the slices cut from damage zone are examined along with high-speed photography. Moreover, corresponding numerical simulations are carried out. The damage zone in the vicinity of the penetration hole is small (∼10 mm), and the damage mode involves SiC matrix fracture, delamination, fiber bundle splitting and fiber breaking. The simulation results suggest that the degree of damage decreases exponentially with the increasing distance from the penetration hole center of the target plate. As the degree of damage increases, the tensile strength of C/SiC composites decreases and the corresponding fracture mode changes from shear failure to tensile breakage. Additionally the fracture surface becomes smoother, the quantity and length of fiber pullout also increases. Since the decrease of elastic modulus induced by damage weakens the stress concentration effect of the penetration hole, the residual strength of recovered target plate is only reduced from 241 MPa to 175 MPa.

Effect of compressibility on the hypervelocity penetration

We further consider the effect of rod strength by employing the compressible penetration model to study the effect of compressibility on hypervelocity penetration. Meanwhile, we define different instances of penetration efficiency in various modified models and compare these penetration efficiencies to identify the effects of different factors in the compressible model. To systematically discuss the effect of compressibility in different metallic rod-target combinations, we construct three cases, i.e., the penetrations by the more compressible rod into the less compressible target, rod into the analogously compressible target, and the less compressible rod into the more compressible target. The effects of volumetric strain, internal energy, and strength on the penetration efficiency are analyzed simultaneously. It indicates that the compressibility of the rod and target increases the pressure at the rod/target interface. The more compressible rod/target has larger volumetric strain and higher internal energy. Both the larger volumetric strain and higher strength enhance the penetration or anti-penetration ability. On the other hand, the higher internal energy weakens the penetration or anti-penetration ability. The two trends conflict, but the volumetric strain dominates in the variation of the penetration efficiency, which would not approach the hydrodynamic limit if the rod and target are not analogously compressible. However, if the compressibility of the rod and target is analogous, it has little effect on the penetration efficiency.

Stress-wave propagation and damage formation associated with hypervelocity penetration into polycarbonate

Hypervelocity impact experiments have been performed on polycarbonate to observe the impact-induced damage process progressing inside polymer material. Impact experiments have been conducted by impacting a sphere made of several kinds of materials using a two-stage light-gas gun. The damage evolution and stress wave propagation associated with hypervelocity impact have been observed via shadowgraphy using an ultra-high-speed camera. Recoded images clearly demonstrate how damages form during the hypervelocity impact event. The obtained time evolution of penetration show that the behavior of stress wave propagation associated with impact vary according to the penetrating motion, and the impact velocity dependence of penetration length and shape change depending on the deformation and fracture behavior of impactor during penetrating process. From these results, it is indicated that not only the mechanical characteristics of impactor material but also the change of penetrating motion associated with the deformation and fragmentation of impactor are key factors for impact-damage formation.