Development of a reaction-diffusion model for erosion and identification of the associated diffusion coefficient
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摘要: 提出了吸附作用(包括物理吸附和化学吸附)是引起空间材料原子氧腐蚀的主要机理.以此为依据,建立了相应的腐蚀量的反应-扩散方程.应用分子动力学经典碰撞理论的估算表明了方程中的物理作用项对于扩散效应为一小量,从而进一步简化了方程.在所建立的模型方程中,选用了基于Eyring绝对速率理论的扩散系数.对空间表面材料Kapton在近地轨道LEO(Low Earth Orbit)环境受原子氧侵蚀的过程进行了数值模拟,计算结果与飞行试验数据在误差允许的范围内符合得较好.Abstract: It was proposed that the adsorption (including both physical and chemical) was the principal mechanism for AO(atomic oxygen) in LEO(low earth orbit) interactingwith surface materials. The remaining secondary physical or chemical mechanisms could be included into the principal mechanism. The reaction-diffusion equation of erosion could thus be constructed. In addition, with the aid of the classical theory of collision dynamics molecules, one could verify that the physical erosion term in the reaction-diffusion equation happened to be higher order and could be neglected. The diffusion coefficient followed from Eyring’s theory of absolute rates. Numerical simulations of AO effects over the space material Kapton were conducted to validate the model. The numerical results on thickness losses and a 2-D undercutting of Kapton in LEO environment were presented. The simulation results fit NASA’s flight test data well within a proper error range.
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Key words:
- erosion /
- diffusion-reaction equation /
- free molecular flow /
- atomic oxygen
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