Study On Characteristics And Penetration Performance Of The Large Central-fragment In Debris Cloud Produced By Hypervelocity Impact

Debris cloud can be produced by hypervelocity impact of a projectile with a thin plate,then the kinetic energy of projectile would be dispersed into a large number of small fragments and reduce its penetration performance,which has been used in protection against meteoroid/orbital debris.This paper was mainly based on numerical simulations,to analyze the relationship between characteristics and penetration performance of the large central debris in debris cloud with impact conditions,and tried to calculate the penetration limit of the entire debris cloud using a single debris.In this paper,the study of formation process,distribution characteristic,modeling and penetration performance of debris cloud was reviewed firstly.This paper tried to associate those research directions,emphasize the understanding of physical processes and mechanisms,and remind attentions to emerging technologies.We believed the researches should be promoted to the mass and phase distribution and try to observe single debris.The debris cloud penetration performance is closely related to the engineering demand,the explicit quantitative calculation of penetration limit quantification should be focused.Based on the review we determined the central ideas:looking for the single "most dangerous fragment",and quantitatively calculate the penetration limit of entire fragment cloud based on that debris only.This paper focused on the shatter range of projectile,during which the large central-fragment was most likely the most dangerous debris.The purpose of this paper is analyzing the feasibility and deviation of the thought above.To observe a single fragment based on SPH method,an examination of the material model in pre-processing and the fragment identification and measurement skill in post-processing were required.This paper inspected the selection of failure model in terms of debris cloud velocity,mass distribution and maximum fragment size,the computations were consistent with the experimental on the overall distribution of debris.Besides,this paper used material failure model to simulate material failure behavior,to analyze the relationship between the stress state history of material and the velocity,mass distribution and penetration properties of debris cloud,then summarized the correlation between material failure difficulty and performances above.This part was also the analysis basis for the formation and characteristics of large central-fragment.Based on simulations the relationship between the equivalent size,original position of the material,velocity,temperature,mass of the large central-fragment and the impact velocity,the thickness of the plate was analyzed.This paper discussed the mechanism of characteristics changes meticulously,and derived the fragmentation velocity formula form theoretically,and the temperature data were rare and also important for analysis below.Finally,the penetration limits of the large central-fragment and entire debris cloud were compared,computing results proposed the large central-fragment to be the most dangerous fragment before its melting,and the large central-fragment penetrated subsequent target plate independently.So it could instead of the entire debris cloud to calculate the penetration limit.Characterizing the penetration performance of the large central-fragment using its kinetic energy,its relationship with impact velocity was basically consistent with the entire debris cloud penetration limit.Quantify the penetration performance of large central-fragment based on an empirical formula,found that the more complete of the material broken,the greater the difference to the debris cloud penetration limit,which agreed to the basic understanding.Finally,the quantified formula of the large central-fragment penetrating performance and the corresponding available range were given.