Study on damage mechanism and damage distribution of the rear plate under impact of debris cloud

The debris cloud generated by the hypervelocity impact(HVI)of orbiting space debris directly threatens the spacecraft.A full understanding of the damage mechanism of rear plate is useful for the optimal design of protective structures.In this study,the hypervelocity yaw impact of a cylindrical aluminum projectile on a double-layer aluminum plate is simulated by the FE-SPH adaptive method,and the damage process of the rear plate under the impact of the debris cloud is analyzed based on the debris cloud structure.The damage process can be divided into the main impact stage of the debris cloud and the structural response of the rear plate.The main impact stage lasts a short time and is the basis of the rear plate damage.In the stage of structure response,the continuous deformation and inertial motion of the rear plate dominate the perforation of the rear plate.We further analyze the damage mechanism and damage distribution characteristics of the rear plate in detail.Moreover,the connection between velocity space and position space of the debris cloud is established,which promotes the general analysis of the damage law of debris cloud.Based on the relationship,the features of typical damage areas are identified by the localized fine analysis.Both the cumulative effect and structural response cause the perforation of rear plate;in the non-perforated area,cratering by the impact of hazardous fragments is the main damage mode of the rear plate.

Debris cloud structure and hazardous fragments distribution under hypervelocity yaw impact

This study investigates how the debris cloud structure and hazardous fragment distribution vary with attack angle by simulating a circular cylinder projectile hypervelocity impinging on a thin plate using the finite element-smoothed particle hydrodynamics(FE-SPH)adaptive method.Based on the comparison and analysis of the experimental and simulation results,the FE-SPH adaptive method was applied to address the hypervelocity yaw impact problem,and the variation law of the debris cloud structure with the attack angle was obtained.The screening criterion of the hazardous fragment at yaw impact is given by analyzing the debris formation obtained by the FE-SPH adaptive method,and the distribution characteristics of hazardous fragments and their relationship with the attack angle are given.Moreover,the velocity space was used to evaluate the distribution range and damage capability of asymmetric hazardous fragments.The maximum velocity angle was extended from fully symmetrical working conditions to asymmetrical cases to describe the asymmetrical debris cloud distribution range.In this range,the energy density was calculated to quantitatively analyze how much damage hazardous fragments inflict on the rear plate.The results showed that the number of hazardous fragments generated by the case near the 35°attack angle was the largest,the distribution range was the smallest,and the energy density was the largest.These results suggest that in this case,debris cloud generated by the impact had the strongest damage to the rear plate.

Characteristics of Polyimide Debris Clouds Produced by Hypervelocity Impact

Polyimide is a typical complex high-molecular polymer of imide monomers,which is widely used in the manufacture of parts for aerospace engineering.The hypervelocity impacts between the spacecraft and orbital debris can induce great damage to the spacecraft.In order to improve the safety of spacecraft,the characteristics of polyimide debris clouds produced by hypervelocity impact should be studied.Firstly,a Mie-Grüneisen equation of state based on the shock adiabat for polyimide,which describes the mechanical behavior in the numerical simulation,was obtained from hypervelocity impact experiments,then a 3-dimentional smoothed particle hydrodynamics program was compiled to numerically simulate the hypervelocity impact between aluminum projectiles(orbital debris)and polyimide targets with different impact velocities(3.km/s,5.km/s,8.km/s)and angles(0°,30°,45°,60°),finally typical shapes of debris clouds produced in different impact velocities and angles were collected from simulation results,the characteristics of which were systemically discussed.

Dynamic modeling and damage analysis of debris cloud fragments produced by hypervelocity impacts viaimage processing

It is always a challenging task to model the trajectory and make an efficient damage estimation of debris clouds produced by hypervelocity impact(HVI)on thin-plates due to the difficulty in obtaining high-quality fragment images from experiments.To improve the damage estimation accuracy of HVIs on a typical double-plate Whipple shield configuration,we investigate the distributive characteristic of debris clouds in successive shadowgraphs using image processing techniques and traditional numerical methods.The aim is to extract the target movement parameters of a debris cloud from the acquired shadowgraphs using image processing techniques and construct a trajectory model to estimate the damage with desirable performance.In HVI experiments,eight successive frames of fragment shadowgraphs are derived from a hypervelocity sequence laser shadowgraph imager,and four representative frames are selected to facilitate the subsequent feature analysis.Then,using image processing techniques,such as denoising and segmentation techniques,special fragment features are extracted from successive images.Based on the extracted information,image matching of debris is conducted and the trajectory of debris clouds is modeled according to the matched debris.A comparison of the results obtained using our method and traditional numerical methods shows that the method of obtaining hypervelocity impact experimental data through image processing will provide critical information for improving numerical simulations.Finally,an improved estimation of damage to the rear wall is presented based on the constructed model.The proposed model is validated by comparing the estimated damage to the actual damage to the rear wall.

Research and development on hypervelocity impact protection using Whipple shield:An overview

Whipple shield,a dual-wall system,as well as its improved structures,is widely applied to defend the hypervelocity impact of space debris(projectile).This paper reviews the studies about the mechanism and process of protection against hypervelocity impacts using Whipple shield.Ground-based experiment and numerical simulation for hypervelocity impact and protection are introduced briefly.Three steps of the Whipple shield protection are discussed in order,including the interaction between the projectile and bumper,the movement and diffusion of the debris cloud,and the interaction between the debris cloud and rear plate.Potential improvements of the protection performance focusing on these three steps are presented.Representative works in the last decade are mentioned specifically.Some prospects and suggestions for future studies are put forward.

Analysis of the stress wave and rarefaction wave produced by hypervelocity impact of sphere onto thin plate

Shock wave is emitted into the plate and sphere when a sphere hypervelocity impacts onto a thin plate.The fragmentation and phase change of the material caused by the propagation and unloading of shock wave could result in the formation of debris cloud eventually.Propagation models are deduced based on one-dimensional shock wave theory and the geometry of sphere,which uses elliptic equations(corresponding to ellipsoid equations in physical space)to describe the propagation of shock wave and the rarefaction wave.The“Effective thickness”is defined as the critical plate thickness that ensures the rarefaction wave overtake the shock wave at the back of the sphere.The“Effective thickness”is directly related to the form of the debris cloud.The relation of the“Effective thickness”and the“Optimum thickness”is also discussed.The impacts of Al spheres onto Al plates are simulated within SPH to verify the propagation models and associated theories.The results show that the wave fronts predicted by the propagation models are closer to the simulation result at higher impact velocity.The curvatures of the wave fronts decrease with the increase of impact velocities.The predicted“Effective thickness”is consistent with the simulation results.The analysis about the shock wave propagation and unloading in this paper can provide a new sight and inspiration for the quantitative study of hypervelocity impact and space debris protection.

Experimental Study of Hypervelocity Impact on Multi-Shock Structure

Hypervelocity impact tests on multi-shock shields are carried out in order to develop space structures (against) space debris impacts. Sheets of LY12 aluminum were used as bumpers. The total thickness of shield structure, which consists of several sheets with various thickness, is 3.0 mm or 2.0 mm. Results of the tests show that the type 0.5 mm+0.5 mm+0.5 mm+0.5 mm is a better choice of spacecraft shield structure.

EXPERIMENTAL INVESTIGATIONS OF HYPERVELOCITY IMPACT ONTO ALUMINIUM DUAL-PLATE STRUCTURE

Dual-plate structure is very effective in the protection of space vehicle from hypervelocity im- pact.The experiments of A1 projectile impacting A1 dual targets at the velocity ranging over 2.5—7.0 km/s were systematically conducted.The damage effects were examined,including the perforation of the shield, the development of debris cloud and the general damage characteristics of the subplate.Many valuable experi- mental data and phenomena have been obtained

SPH Simulation of Hypervelocity Impacts

The smooth particle hydrodynamics (SPH) method is a very important tool to resolve hypervelocity problems. The basic principle of SPH method and how to generate a proper SPH mesh is described. The results of SPH simulations of hypervelocity impacts on thin or thick aluminum plates, performed by using the LS-DYNA 3D computer code, are also reported. The forming process and composition of the debris clouds simulated are identical with the experiment results. It can be concluded that the simulation is reasonable and SPH method is an ideal method for hypervelocity impact simulation..