Research On The Characteristics Of Debris Clouds Produced By Hypervelocity Impacts Of Space Debris And The Design Of The Shielding Structure Based On SPH Method

Along with the quick development of aerospace sci-tech and sharply increment of aerospace mission, a great deal of space debris scatter on low earth orbit. This constitutes the complicated space debris environment which has been threatening the safety of the spacecraft seriously. How insure the safety of the spacecraft, which becomes a very important problem of the current spacecraft design. Because of the complexity of hypervelocity impacts, characteristics of debris clouds are not still clear. Therefore the design of spacecraft shielding structure still needs the further research.Smoothed particle hydrodynamics(SPH) method is the pioneer of meshless particle methods. Nowadays it has been applied to many realms with related fluid mechanics. It has simple logic, can avoid the mesh enlacement and distort of finite element method. So it is suitable for simulating hypervelocity impacts especially.SPH method is introduced systemically in this paper. And some kinds of problems related with numerical simulations are discussed deeply. The characteristics of debris clouds produced by hypervelocity impacts are studied using SPH method. Hypervelocity impacts of Whipple shields are simulated and analyzed.The main achievements and conclusions in this paper are presented in the following:1. Based on Cartesian coordinate system, the 2D and 3D SPH program is composed on one's own. Johnson-Cook tensile cumulative damage constitutive model, Johnson-Cook visco-plastic constitutive model and Steinberg-Cochran-Guinan (SCG) constitutive model are imported in the program successfully. The simulated results obtained by SPH program are in accord with the experiments. This shows that the SPH program is capable of simulating different impact dynamics problems, especially hypervelocity impacts.2. Five problems related with numerical simulations, such as the computational accuracy, tensile instability, ghost particle method, initial smoothing length and material interface made by different particle spacing, are studied. The three tensile instability treatment methods are compared. The calculated results show that Monaghan method and stable particle methods based on Lagrangian kernels are better than Conservative Smoothing Approach (CSA). The ghost particle method is an effective method to deal with the rigid boundary condition. But a low density region will be produced in the neighborhood of symmetric plane if the ghost particle method is used to deal with the symmetric boundary. This result is unreasonable. The research shows that the simulated results obtain some extent improvement by using the XSPH correction to the velocity of a particle. The effects of initial smoothing lengths on SPH simulated results are analyzed. The results show that the bigger initial smoothing length, the less rigid projectile. And the rational range of initial smoothing length is d0