Hypervelocity Impact Of Spherical Projectile Research Articles

Jetting and shock wave during oblique hypervelocity impact of spherical projectile

Abstract Space debris impacts on whipped shields are dominantly non-vertical. During the initial impact stage of a projectile on a target, wave propagation and evolution occur in their interior with co-dominant material fragmentation. In this study, the effects of the impact conditions (impact velocity and attack angle) on the critical conditions for jet generation were examined based on the asymmetric jetting theory. In the geometric propagation model (GPM), the effect of the attack angle was considered, and a wave front deflection angle parameter was introduced. The modified GPM could describe the geometric features and position of a wave front during an oblique impact. Combined with smoothed particle hydrodynamics numerical simulations, the interior of projectiles, fragmentation features and pressure attenuation were studied. It was found that in large attack angle cases, the projectile material is more likely to reach the critical conditions for jet generation. The modified GPM is an oblique elliptic equation that is a function of the equivalent speed, impact velocity, attack angle, time and deflection angle. It may be applicable to hypervelocity events involving any monolithic material as long as the equivalent speed and deflection angle can be provided from numerical simulations. The impact conditions exhibit a quantitative relationship with the pressure attenuation in a projectile, among which the impact velocity has a more significant effect. This study established a quantitative analysis method for the initial impact stage of the oblique hypervelocity impact of a spherical projectile on a flat plate.

Anisotropic debris cloud formation after hypervelocity impact into rolled magnesium alloy plates

Magnesium (Mg) alloys are attractive structural materials because of their high specific properties. However, their behavior under impact is complicated due to their anisotropic, hexagonal, close packed crystal structure and coupled deformation mechanisms of twinning and dislocation slip. Here we investigate the breakout and fragmentation of rolled AZ31B Mg alloy plates by the hypervelocity impact of spherical projectiles, using time-resolved and quantitative diagnostics. We find that the impact, subsequent penetration, and rupture of the rolled plate are followed in many cases by the development of a debris cloud that is not isotropic. We have quantified the degree of this asymmetry by employing multiple high-speed cameras, mounted along orthogonal directions, relative to the penetration axis of the projectile. A series of impact tests with velocities ranging from 1.2 to 3.6 km/s revealed that the formation and overall shape of the debris cloud were dependent on the projectile material and magnitude of the impact velocity. These salient features have also been captured in simulations of the impact event by incorporation of a simple anisotropic description of the material strength while retaining an isotropic model for material failure. Agreement between the experiments and model predictions suggests that the anisotropic strength response of Mg is primarily responsible for most of the observed anisotropy in the debris cloud formation, especially for impacts up to 3.0 km/s.

A numerical approach for response of whipple shields with coated and monolithic front bumper to hypervelocity impact by spherical projectiles

Orbital debris in space offers a constant threat to spacecraft, satellites, and the International Space Station (ISS). There is a growing concern as the number of satellites and other space objects keep increasing year-on-year with advancements in space exploration and orbital activities. The threat posed by the small debris or MMODs (micrometeoroid orbital debris) to satellites and spacecraft can be prevented using Whipple shields made of impact-resistant materials. In the current work, a numerical approach has been utilized to simulate hypervelocity impact of spherical projectiles of diameter 4 mm on monolithic and coated whipple shields to determine the extent of damage, and the deformation behaviour. The simulations were conducted at 3.5 km/s and 5.5 km/s. The computational work was carried out using AUTODYN® module of ANSYS® finite element software.

Failure mechanism of monolayer graphene under hypervelocity impact of spherical projectile.

The excellent mechanical properties of graphene have enabled it as appealing candidate in the field of impact protection or protective shield. By considering a monolayer graphene membrane, in this work, we assessed its deformation mechanisms under hypervelocity impact (from 2 to 6 km/s), based on a serial of in silico studies. It is found that the cracks are formed preferentially in the zigzag directions which are consistent with that observed from tensile deformation. Specifically, the boundary condition is found to exert an obvious influence on the stress distribution and transmission during the impact process, which eventually influences the penetration energy and crack growth. For similar sample size, the circular shape graphene possesses the best impact resistance, followed by hexagonal graphene membrane. Moreover, it is found the failure shape of graphene membrane has a strong relationship with the initial kinetic energy of the projectile. The higher kinetic energy, the more number the cracks. This study provides a fundamental understanding of the deformation mechanisms of monolayer graphene under impact, which is crucial in order to facilitate their emerging future applications for impact protection, such as protective shield from orbital debris for spacecraft.

Growth of hole in thin plates under hypervelocity impact of spherical projectiles

The paper presents an exhaustive analysis of experimental data on the strike of spherical projectile on thin metallic targets for prediction of hole-diameter in the target. The discrepancies in the test data have been highlighted. A non-dimensional model for the prediction of hole-diameter is presented, which incorporates the geometric and material properties of the target as well as the projectile and the angle of strike of the projectile. Most of the historical models perform well for one or two materials and for other materials their performance is far from satisfactory. The proposed model not only works well for these materials independently but also for all materials data of normal and oblique strike. The influence of the velocity of strike on the hole-diameter has been studied by extracting data sets with other parameters same. It is observed that most of the historical models either under-predict or over-predict the hole-diameter for some range of velocity, but the proposed model works well for the whole range of velocity.

Hydrocode modelling of hypervelocity impact on brittle materials: depth of penetration and conchoidal diameter

Summary The Johnson-Holmquist brittle material model has been implemented into the AUTODYN hydrocode and used for Lagrangian simulations of hypervelocity impact of spherical projectiles onto soda-lime glass targets. A second glass model (based on a shock equation of state and the Mohr-Coulomb strength model) has also been used. Hydrocode simulations using these two models were compared with experimental results. At 5 km s−1, the Mohr-Coulomb model under-predicted the depth of penetration, whilst adjustment of the Johnson-Holmquist model bulking parameter was required to match the experimental data to the simulation results. Neither model reproduced the conchoidal diameter; a key measured parameter in the analysis of retrieved solar arrays, so two failure models were used to investigate the tensile failure regime. A principal tensile failure stress model, with crack softening, when used with failure stresses between 100 and 150 MPa and varying bulking parameters, reproduced the conchoidal diameter morphology. Empirically-determined, power-law damage equation predictions for the range 5–15 km s−1 were compared with simulations using both models since no experimental data was available. The powerlaw velocity dependence of the depth of penetration simulations was found to be significantly lower than the 0.67 predicted by the empirically-determined damage equations.

Analytical Prediction of Hole Diameter in Thin Plates Due to Hypervelocity Impact of Spherical Projectiles

A first-principles-based model is presented for calculating the hole diameter resulting from the normal hypervelocity impact of a spherical aluminum projectile on a thin aluminum plate. One-dimensional shock theory is used to predict the creation and attenuation of Hugoniot pressures along the plate surface. Pressures are translated into the plate thickness by calculating intersecting positions of advancing shock fronts and centered-fan rarefaction waves. The radial position at which the shock pressure equals a predetermined value is defined to be the hole diameter. The model was calibrated by determining this critical value for aluminum-an-aluminum impacts using several hundred data points. A residuals analysis indicated some inherent problems with the model. Two empirical factors were added to account for thin plate and two-dimensional shock dissipation effects. The predictions of the adjusted model are shown to compare well with predictions of several empirical hole diameter models.

Analytical Prediction of Hole Diameter in Thin Plates Due to Hypervelocity Impact of Spherical Projectiles

A first-principles-based model is presented for calculating the hole diameter resulting from the normal hypervelocity impact of a spherical aluminum projectile on a thin aluminum plate. One-dimensional shock theory is used to predict the creation and attenuation of Hugoniot pressures along the plate surface. Pressures are translated into the plate thickness by calculating intersecting positions of advancing shock fronts and centered-fan rarefaction waves. The radial position at which the shock pressure equals a predetermined value is defined to be the hole diameter. The model was calibrated by determining this critical value for aluminum-an-aluminum impacts using several hundred data points. A residuals analysis indicated some inherent problems with the model. Two empirical factors were added to account for thin plate and two-dimensional shock dissipation effects. The predictions of the adjusted model are shown to compare well with predictions of several empirical hole diameter models.

Penetration and ricochet phenomena in oblique hypervelocity impact

An experimental investigation of phenomena associated with the oblique hypervelocity impact of spherical projectile on multisheet aluminum structures is described. A model that can be employed in the design of meteoroid and space debris protection systems for space structures is developed. The model consists of equations that relate crater and perforation damage of a multisheet structure to parameters such as projectile size, impact velocity, and trajectory obliquity. The equations are obtained through a regression analysis of oblique hypervelocity impact test data. This data shows that the response of a multisheet structure to oblique impact is significantly different from its response to normal hypervelocity impact. It was found that obliquely incident projectiles produce ricochet debris that can severely damage panels or instrumentation located on the exterior of a space structure. Obliquity effects of high-speed impact must, therefore, be considered in the design of any structure exposed to the meteoroid and space debris environment.