Hypervelocity Research Articles

Research on discharge effect of solar array with power supply subjected to hypervelocity impact

Plasma-induced discharge is an important effect on the solar array of orbiting space vehicles subjected to hypervelocity impact, which will pose a serious threat to the power supply system of spacecraft. The paper investigates experimentally the process that the projectile in various impact velocities and incidence angles impact on solar array with sandwich structure comprising of a coverglass, a silica gel and a 2A12 aluminum liner at the different positions. The electron temperature and density of the plasma were diagnosed by applying in independent-constructed Triple Langmuir Probe diagnostic system, meanwhile, the charging and discharge test system were also constructed by ourselves. Three sets of experiments have been performed by two-stage light gas gun loading system and related measurement system. Especially, residual velocity was measured when projectile pierced through the solar array with composite structure. Experimental results revealed the discharge causes based on stress wave theory, and the discharge current characteristics of a primary and a secondary discharge of solar array induced by hypervelocity impact were given through hypervelocity impact experiments. Finally, it will provide a valuable benchmark for the construction of solar array against space debris.

Effects of head shape of projectiles on hypervelocity impact cratering on aluminum 5052 alloy targets at 7 km/s

A series of experiments was conducted to investigate the effect of projectile head shape on hypervelocity impact cratering. Aluminum 5052–H112 alloy thick targets were impacted by projectiles which had different heads at velocities of approximately 7.1 km/s. The head shape was classified into five types of head shape, i.e. flat-head and, two types of concave-head and two-types of convex-head. The effect of the head shape was evaluated by final morphology of craters, i.e. variables of the penetration depth, the crater diameter and the crater volume. The concave-head and convex-head projectiles produced shallow-shaped craters and deep-ones, respectively. The ratio of the crater penetration-to-diameter P/D increased as the head shape became more convex, and vice versa. The P/D ratio varied from 0.41 to 0.77. However, the penetration depth and the crater diameter had different dependencies based on the head shape. ‘Flat-head conversion’, in which the concave-head and the convex-head projectiles were imaginarily regarded as flat-head projectiles with a converted diameter, gave the consistent effect on the crater variables to the concave-head and the convex-head projectiles. A new coupling parameter of the point source solution was defined as a function of impact variables. The crater variables scaled by this coupling parameter was expressed as power laws of impact variables. The coefficient and the exponents of obtained relations were determined by using multiple regression analysis. Regression equations closely estimated the experimental results.

The development and ballistic performance of protective steel-concrete composite barriers against hypervelocity impacts by explosively formed projectiles

Explosively formed projectiles (EFP) are one of the most severe explosive and impact loading threats for civil infrastructure and military vehicles. Currently, there is no effective means of protection for military vehicles and infrastructure facilities from EFPs. This paper presents the experimental results of the hypervelocity impact of EFPs on steel-concrete (SC) barrier systems of finite dimensions. The SC barrier units tested were broadly representative of the type of protective SC units used in the expedient construction of barriers for mitigating improvised explosive device (IED) and EFP threats to critical infrastructure facilities. The response of non-composite, partially-composite, and fully-composite SC barrier units was studied. All studied protective systems were capable of terminating the high-velocity projectiles effectively through the combined action of the concrete core and steel faceplates. The data gathered from these tests are also intended to further the understanding of impacts on SC composite structures at speeds greater than 1000 m/s and for the calibration of numerical models of EFP interaction with SC targets. 3D numerical simulations were performed to better understand the various stages of EFP interaction with the SC composite barriers and develop recommendations for their design optimisation. No previously published results on the EFP terminal ballistic performance of SC composite structures of finite dimensions have been found in the open literature.

Hypervelocity impact response of CFRP laminates using smoothed particle hydrodynamics method: Implementation and validation

The current work investigates the hypervelocity impact response (HVI) of carbon fiber reinforced polymer composites (CFRP) and the produced secondary debris using smoothed-particle hydrodynamics methodology (SPH) in LS-DYNA. The aim of present study is to reproduce numerically the CFRP material response to hypervelocity impact and fragments cloud, to investigate the applicability of SPH modeling technique on composite materials and to determine the suitable numerical solution parameters. A verification procedure for modeling of composite laminate using SPH methodology is proposed. The investigation starts with baseline quasi-static tests, and the results are compared against the available theoretical ones to ensure the stability and efficiency of the SPH kernel function under quasi-static loading. Afterwards, the developed methodology is applied to hypervelocity impact response of CFRPs and the ballistic limit, the crater diameter as well as the secondary debris cloud are numerically calculated and correlated to the published HVI experimental results on CFRP plates.

An electrostatic method to model the expansion of hypervelocity impact plasma on positively biased surfaces

Spacecraft are a major component of infrastructure and are essential to modern society. Though launch opportunities are expected to become less expensive and more frequent through commercial launch providers, spacecraft design, manufacturing, and deployment processes are far from routine. In addition, a spacecraft's operational environment is riddled with numerous hazards that may jeopardize its performance, and with a cost to orbit of $10 000 per pound, there is a desire to protect our space assets and mitigate against damage. Meteoroids and orbital debris, which are components of the space environment, are two such threats to space vehicles. While larger objects endanger spacecraft mechanically, collisions are rare; however, bodies with masses smaller than a milligram impact frequently and at speeds up to 72.8 km s−1 if in solar orbit. Shortly after contact, projectile and spacecraft materials vaporize and ionize, resulting in an expanding plasma that may interfere with onboard sensors and equipment. These hypervelocity impacts have potentially been the source of unexplained electronic anomalies through arc discharge and electromagnetic emission mechanisms. To better understand the plasma structure, hypervelocity impact experiments were conducted at the Max Planck Institute for Nuclear Physics in Heidelberg, Germany. Using their Van de Graaff dust accelerator and vacuum chamber, iron dust particles impacted typical spacecraft material targets with surface potentials ranging from –1000 V to +1000 V, representing charging conditions experienced in orbit. During this experiment, a suite of sensors measured impact plasma properties; among these sensors are two distinct arrays of charge collecting plates, termed Faraday plate arrays, positioned to describe the plasma's range and azimuthal distributions. The work discussed here presents a multi-species plasma expansion model and compares its results to those obtained experimentally. The particle model uses a tree structure to reduce computational complexity. The agreement between the simulated output and the sensor measurements provides confidence in the model's ability to replicate the plume accurately. Consequently, the model is used to provide initial plasma temperature and bulk expansion speed estimates, to explore the sensitivity of our measurements to shifts in sensor position, and to identify potentially hazardous regions on spacecraft.

The influences of aramid fibre and its compound with ceramic on shielding performance of stuffed layer

Four kinds of aramid fibre and three compound modes of aramid with ceramic fibre were studied by hypervelocity impact tests respectively to probe the fabric layer with higher performance in space debris shield configuration. The aramid fibres include the Aramid-II manufactured in America, the Aramid-II, the Aramid-III and the PBO manufactured in China. Based on the above test results, the Aramid-III was chosen to compound with the basalt. The compound modes include hybrid weaving, affixing the Aramid-III and basalt fabric layers with the glue, and sewing them with the aramid thread. The configurations are impacted by the 5 mm-diameter Al projectile with the velocities of 4.5 km/s to 5.0 km/s. The test results show that the fabric layer containing Aramid-III fabric has equivalent shielding performance with the PBO fabric, and they are better than the other two stuffed layers containing Aramid-II fabric respectively under the equivalent areal density. The performance of stuffed layer is influenced by the adhesion degree of basalt and Aramid-III fibre. The three compound modes all improve the fabric adhesion degree, however, the over adhesion makes against dissipating the kinetic energy of debris cloud, which causes the performance to degrade.

Study of the shielding performance of a Whipple shield enhanced by Ti-Al-nylon impedance-graded materials

An improved meteoroid/debris shielding structure for spacecraft is presented, using a bumper constructed from impedance-graded materials. The hypervelocity impact performances of a shield enhanced by Ti-Al-nylon impedance-graded materials and an aluminum Whipple shield are investigated experimentally, using a two-stage light gas gun at velocities of 3.50 and 6.50 km/s. The impact characteristics, including debris clouds, penetration holes in the bumper, and damage patterns on the rear wall are studied. The results show that the shielding capability of a Ti-Al-nylon shield is greater than that of an aluminum Whipple shield where the bumper has the same areal density. A theoretical analysis and numerical simulation are performed to explore why Ti-Al-nylon shields achieve a better shielding performance. The results suggest that a Ti-Al-nylon bumper can generate higher shock pressures and induce a greater temperature increase, which is more effective for fragmenting a projectile. Furthermore, wave propagation in the projectile and bumper is discussed. It is found that the shockwave propagation is affected by the shock impedance mismatch in impedance-graded material bumpers, so that the shock heating effect and the expansion angle of the debris cloud are increased. Materials with lower melting and vaporization temperatures are helpful for improving the performance of a Ti-Al-nylon shield, thereby achieving a sharp increase in the protective capability for spacecraft meteoroid/debris shielding.

Combining dual domain material point method with molecular dynamics for thermodynamic nonequilibriums

The dual domain material point method (DDMP) combined with molecular dynamics (MD) is used to simulate a material undergoing a large deformation with a high strain rate. In the simulation, the continuum scale equation of motion is solved using DDMP, while the stresses required at the material points are obtained by performing MD simulations in small domains surrounding the material points following the entire history of the material deformation without reinitialization of the MD systems; therefore the history dependence, a common feature for thermodynamically nonequilibrium systems, can be tracked accurately.Two algorithms are introduced to avoid distortion of the MD domains and to ensure consistence in the energy density between the MD and macroscopic calculations. As an example, a hyper-velocity impact problem is simulated. The results of the combined DDMP–MD calculations are compared to a pure MD simulation. The method of the combined simulation is applicable to macroscopic systems, although the size of the simulation domain is only a few hundred nanometers in this example because of the limitation of the pure MD simulation.

Research on the Discharge and Mitigation Created by Ultra-high Velocity Impact on Solar Array With Applied Power Supply

Solar array is one of the core components of spacecraft exposed to space environment; it is vulnerable to the impact from space debris. Discharge of solar array induced by ultrahigh-speed collision will produce a serious threat to the power supply system of spacecraft in orbit. In order to mitigate discharge effect and simulate working state of solar array effectively during debris impacting on solar array, realizing charging through sunlight irradiance on the ground simulating experiments is very difficult. Therefore, the inverse process of solar energy generation is adopted by applied power supply to solar array. In addition, loading and measurement systems of discharge have been established in a laboratory. A two-stage light gas gun was used to launch the projectile to impact on solar array at the applied power supply voltage of 100 V, and the spacings among the cells of solar array were 0.6, 3, and 5 mm, respectively. The applied power supply system, the diagnostic system of plasma characteristic parameters, and the measuring system of discharge current and voltage were constructed to provide voltage for solar array, diagnosing characteristic parameters of plasma and measuring discharge parameters, respectively. Six sets of experiments have been performed to measure discharge current and voltage induced by plasma during 2A12 aluminum projectile impacting on the solar array with carbon fiber reinforced plastics Al honeycomb sandwich and 2A12 aluminum substrates, respectively. The experimental results showed that the discharge did happen during 2A12 aluminum projectile impacting on solar array, and the discharge current among the cells increased with the increase of the impact velocity under the given experimental conditions. Also, increasing spacings among the cells of solar array could indeed mitigate or inhibit plasma discharge effects created by hypervelocity impact on solar array at the same projectile incident angles and applied power supply.

Hydrocode simulations of a hypervelocity impact experiment over a range of velocities

This work investigates how the Eulerian hydrocode PAGOSA performs while simulating a hypervelocity impact experiment of stainless steel 304-L into aluminum 6061-T6. The specifications of the simulation were established in a paper detailing an experiment conducted at the Atomic Weapons Establishment (AWE) in the UK and the Centre d’Etudes de Gramet (CEG) in France. A variety of strength models and equations of state are employed under several different mesh sizes. The results display an excellent comparison with the experimental data and demonstrate dramatic differences in impacted crater geometries over various strength models and mesh sizes.

Three-dimensional characterization of debris clouds under hypervelocity impact with pulsed digital inline holography.

The increasing space debris poses a great threat to in-orbit spacecraft and satellites, because its hypervelocity impact can bring about fatal mechanical and electrical damage to them. This work applies pulsed digital inline holography (DIH) to measure three-dimensional (3D) positions and shapes of the debris clouds generated by the hypervelocity impact in the Whipple shield. Detailed operation procedures of synchronizing the pulse DIH system with the impact event and removing the strong plasma radiation are presented, ensuring the successful capture of the transient state of ultrafast ejecta. Experiments on a 2.25mm aluminum sphere impacting a 0.5mm thickness aluminum target plate with a velocity of 3.6 km/s are carried out at the Hypervelocity Impact Research Center of the China Aerodynamics Research and Development Center, and results show that the holographic fringes are clearly recorded and the debris fragments are reconstructed and located accurately, agreeing well with the results measured by laser shadowgraph. This work demonstrates the powerful capability and great potential of DIH in the diagnostics of hypervelocity impact.

Petrographic investigation of shatter cone melt films recovered from MEMIN impact experiments in sandstone and iSALE modeling of their formation boundary conditions

AbstractShatter cones are diagnostic for the recognition of meteorite impact craters. They are unambiguously identifiable in the field and the only macroscopic shock deformation feature. However, the physical boundary conditions and exact formation mechanism(s) are still a subject of debate. Melt films found on shatter cone surfaces may allow the constraint of pressure–temperature conditions during or immediately after their formation. Within the framework of the MEMIN research group, we recovered 24 shatter cone fragments from the ejecta of hypervelocity impact experiments. Here, we focus on silicate melt films (now quenched to glass) found on shatter cone surfaces formed in experiments with 20–80 cm sized sandstone targets, impacted by aluminum and iron meteorite projectiles of 5 and 12 mm diameter at velocities of 7.0 and 4.6 km s−1, respectively. The recovered shatter cone fragments vary in size from 1.2 to 9.3 mm. They show slightly curved, striated surfaces, and conical geometries with apical angles of 36°–52°. The fragments were recovered from experiments with peak pressures ranging from 46 to 86 GPa, and emanated from a zone within 0.38 crater radii. Based on iSale modeling and petrographic investigations, the shatter coned material experienced low bulk shock pressures of 0.5–5 GPa, whereas deformation shows a steep increase toward the shatter cone surface leading to localized melting of the rock, resulting in both vesicular as well as polished melt textures visible under the SEM. Subjacent to the melt films are zones of fragmentation and brittle shear, indicating movement away from the shatter cone apex of the rock that surrounds the cone. Smearing and extension of the melt film indicates subsequent movement in opposite direction to the comminuted and brecciated shear zone. We believe the documented shear textures and the adjacent smooth melt films can be related to frictional melting, whereas the overlying highly vesiculated melt layer could indicate rapid pressure release. From the observation of melting and mixing of quartz, phyllosilicates, and rutile in this overlying texture, we infer high, but very localized postshock temperatures exceeding 2000 °C. The melted upper part of the shatter cone surface cross‐cuts the fragmented lower section, and is accompanied by PDFs developed in quartz parallel to the {112} plane. Based on the overprinting textures and documented shock effects, we hypothesize shatter cones start to form during shock loading and remain an active fracture surface until pressure release during unloading and infer that shatter cone surfaces are mixed mode I/II fracture surfaces.

Behavior of Shear Thickening Fluid (STF) impregnated fabric composite rear wall under hypervelocity impact

On the contrary to previous researches on Shear Thickening Fluid (STF) impregnated fabric composites as a protection method against low to middle velocity impact such as stabbing or bulletproofing, the application of STF on space shields seems to be quite skeptical due to high-speed range of micro meteoroid and orbital debris (M/OD). However, the results of the eight types of fabric rear layers involving STF impregnated fabric of this study suggest that STF impregnated fabric can be a promising candidate for the improved rear wall of a space shield. After hypervelocity impact to the Al 6061-T6 frontal bumper, the all Heracron fabric rear wall was not fully penetrated against the hypervelocity fragments. However, a large hole was found in case of 2 mm Al 6061-T6 rear wall with the almost identical areal density and impact velocity. By replacing last 10 Heracron fabric layers from the rear side of the fabric rear wall to 6 layers of STF impregnated fabric, the trend in the number of undamaged layers was positively inversed. The study shows experimentally that the fabric rear wall of a space shielding system can be enhanced effectively by using STF impregnated layers.

Hypervelocity cratering and disruption of the Northwest Africa 869 ordinary chondrite meteorite: Implications for crater production, catastrophic disruption, momentum transfer and dust production on asteroids

Most asteroids for which porosities have been inferred have porosities from 20% to more than 50%, comparable to the range measured on chondritic meteorites. To investigate the effects of target porosity on cratering, impact disruption, momentum transfer and dust production we performed a series of hypervelocity impact experiments on targets of Northwest Africa (NWA) 869, a brecciated L3-6 ordinary chondrite, impacted by 1/16″ to ¼” Al-spheres at speeds ranging from 4.08 to 5.74 km/s at the NASA Ames Vertical Gun Range. These samples had a mean porosity of ∼6.4% and a mean unconfined compressive strength of ∼87 MPa. Ten hypervelocity disruptions demonstrated that these NWA 869 targets are significantly more resistant to disruption, i.e., they require more impactor kinetic energy per unit target mass to produce an equivalent disruption, than non-porous terrestrial basalt targets. The threshold collisional specific energy, Q*D, for these NWA 869 targets is ∼1795 J/kg, more than twice the literature value for non-porous terrestrial basalt, but significantly lower than the ∼2380 J/kg value we measured previously for highly-porous terrestrial pumice. Volatile-rich matrix was overrepresented in the ≤30 μm fraction of the dust while dust >30 μm in size was dominated by chondrule material in the disruption events. We measured the post-impact momentum of seven NWA 869 cratering events and found a mean momentum transfer of 2.7 times the momentum of the projectile, showing that the recoil from the crater ejecta exceeded the direct momentum transferred by absorption of the projectile by a factor of ∼1.7. We observed a two-stage development of the crater ejecta, with an initial release of high-speed, fine-grained material in a cone with an apex angle near 90°, followed by larger, lower-speed material directed nearly opposite the direction of the impactor.

Study on shield configuration stuffed with the integrated fabric layer and its bracing structure

Two alternative techniques to brace the fabric layers stuffed in high-performance shield configurations are evaluated by hypervelocity impact tests respectively. Al honeycomb core and Al mesh are proposed to brace the fabric layers separately. There are four types of stuffed layer structures. The first structure consists of two kinds of fabrics, one layer of basalt fabric followed with one layer of Aramid-III fabric repeatedly. The second type is the first one plus Al honeycomb core. The third type contains several layers of basalt fabric and one layer of Al mesh. The fourth type is similar to the third one, while the stuffed layer is sewed with the aramid thread. For the target configurations, the bumper and the rear plate are 1mm-thick Al plate and the stuffed layer is 100 mm from the bumper. The targets are impacted by Al projectile with the diameters about 5 mm, and the velocities range from 4 km/s to 5 km/s. According to the test results, the fixing and support structure weight of the fabric layer is lightened by using the Al honeycomb core. The Al honeycomb core absorbs and dissipates the kinetic energy of debris cloud effectively, however, its channel effect aggravates the perforation damage on the rear plate. For the fourth structure, the Al mesh plays the role of fixing and supporting basalt fabric, but the performance of stuffed layer intercepting debris cloud is reduced.

Hypervelocity impact flash and plasma on electrically biased spacecraft surfaces

Hypervelocity microparticles ( < 1 µg), traveling at speeds between 11 and 72 km/s with respect to the Earth, can impact spacecraft and form a small( ∼ 1 µm) and dense ( ∼ 1023 m−3) plasma. This plasma can generate a strong optical emission (impact flash) and electromagnetic pulse (EMP), which can lead to spacecraft electrical anomalies when the impacted spacecraft surface carries electrical potential due to various space weather effects. A parameter of the impact plasma that strongly determines its behavior is its temperature. In order to understand the microparticle hypervelocity impact plasma and their associated threat to spacecraft electronics, we need to determine the impact plasma temperature under different spacecraft charging conditions. A non-intrusive method to study the impact plasma is by measuring the optical emission spectrum. In this paper, we present a theory of how hypervelocity impact light flash is generated by the plasma, supported by experiments at a ground-based 3 MV electrostatic dust accelerator using three spectral photomultiplier tubes at 450, 550, and 600 nm. This paper is the first to present results on hypervelocity impacts with various target electrical biases as a control variable to study the relationship between the impact plasma and the impact flash. The impact flash continuum spectrum is suggested to be produced by the acceleration of charged particles via spacecraft surface electrical biases, the oscillating internal electric field, and/or the local recombination effects within the impact plasma. The impact flash was found to emit blackbody radiation in the early time after the impact ( ∼ 200 ns). Using blackbody spectrum to estimate the plasma temperature and optical thickness, we found that an impact velocity range of 15 to 40 km/s yielded average plasma temperatures between 3300 and 6000 K depending on the target biases. Our measurements demonstrated a strong dependence of plasma temperature on the bias, which serves as new experimental evidence to support that impact flash is produced by the impact plasma. The correlations between the impactor characteristics such as mass, velocity, and charge production are also connected with the temperature and optical thickness measurement.

Impact‐induced chemical fractionation as inferred from hypervelocity impact experiments with silicate projectiles and metallic targets

AbstractHypervelocity impacts are common in the solar system, in particular during its early phases when primitive bodies of contrasted composition collided. Whether these objects are chemically modified during the impact process, and by what kind of processes, e.g., chemical mixing or gas–liquid–solid fractionation, are still pending questions. To address these issues, a set of impact experiments involving a multielemental doped phonolitic projectile and a metallic target was performed in a 3–7 km s−1 range of impact speeds which are typical of those occurring in the asteroid belt. For each run, both texture and chemistry of the crater and the ejecta population have been characterized. The results show that the melted projectiles largely cover the craters at all speeds, and that melted phonolitic materials are injected into fractures in the crater in the metallic target. Ejecta are generally quenched droplets of silicate impact melt containing metal beads. Some of these beads are extracted from the target, but we propose that some of the Fe metal beads are the result of reduction of FeO. A thin FeO‐SiO2‐rich condensate layer is found at the edge of the crater, suggesting that a limited amount of vapor formed and condensed. LA‐ICP‐MS analyses suggest, however, that within analytical uncertainties, no volatility‐controlled chemical fractionation of trace elements occurred in the ejecta. The main chemical fractionation during impact at such velocities and energies are the result of projectile‐target mixing.

Nondestructive imaging of hypervelocity impact‐induced damage zones beneath laboratory‐created craters by means of ultrasound travel‐time tomography

AbstractSince the 1960s, hypervelocity impact experiments have been conducted to study the complex deformation mechanisms which occur in the subsurface of meteorite craters. Here, we present ultrasound tomography measurements of the damage zone underneath seven experimentally produced impact craters in sandstone cubes. Within the framework of the Multidisciplinary Experimental and Modeling Impact Research Network and the NEOShield Project, decimeter‐sized sandstone targets were impacted by aluminum and steel projectiles with radii of 2.5, 4, and 5 mm at velocities between ~3.0 and ~7.4 km s−1. The 2‐D ultrasound tomography clearly shows a correlation between impact energy and the damaged volume within the target blocks. When increasing impact energies from 805 to 2402 J, a corresponding increase in the damage radius from ~13.1 cm to ~17.6 cm was calculated. p‐Wave velocity reductions up to 18.3% (for the highest impact energy) were observed in the vicinity of the craters. The reduction in seismic velocity decreased uniformly and linearly with increasing distance from the impact point. The damage intensities correspond to peak damage parameters of 0.4–0.51 compared to undamaged target blocks. In addition to the damage zone below the crater, we could identify weakened zones at the sandstone walls which represent precursors of spalling. The volume of the damaged subsurface beneath experimentally produced craters determined through ultrasound tomography is larger than that obtained from previously reported p‐wave velocity reductions or to microscopic and microcomputed tomography observations of crack densities in experimentally produced craters.

TRAJECTORY BASED 3D FRAGMENT TRACKING IN HYPERVELOCITY IMPACT EXPERIMENTS

Abstract. Collisions between space debris and satellites in Earth’s orbits are not only catastrophic to the satellite, but also create thousands of new fragments, exacerbating the space debris problem. One challenge in understanding the space debris environment is the lack of data on fragmentation and breakup caused by hypervelocity impacts. In this paper, we present an experimental measurement technique capable of recording 3D position and velocity data of fragments produced by hypervelocity impact experiments in the lab. The experimental setup uses stereo high-speed cameras to record debris fragments generated by a hypervelocity impact. Fragments are identified and tracked by searching along trajectory lines and outliers are filtered in 4D space (3D + time) with RANSAC. The method is demonstrated on a hypervelocity impact experiment at 3.2 km/s and fragment velocities and positions are measured. The results demonstrate that the method is very robust in its ability to identify and track fragments from the low resolution and noisy images typical of high-speed recording.

Characterising primary fragment in debris cloud formed by hypervelocity impact of spherical stainless steel projectile on thin steel plate

Hypervelocity impact of a projectile on a thin plate generates a debris clouds. Largest chunk (mass) of the projectile material (called primary fragment) in the cloud poses significant ballistic threat to subsequent structure. Primary fragment characteristics (mass, velocity and exit angle) are used in assessing subsequent structure damage potential. Non-dimensional empirical equations are proposed in this paper for estimation of these characteristics. A set of simulations has been carried out using smoothed particle hydrodynamics (SPH) technique of Autodyn. Two stage light gas gun test data has been compared for validation of simulation. Simulation results for spherical projectile made of stainless steel impacting mild steel plate with impact velocity of 2–4 km/s and obliquity of 0°–60° has been analysed. Constants and radicals of the proposed equations are determined by multi variable regression of the simulation data. Comparison of the simulation data with the proposed equations shows a very good fit.