航天器损伤评估和安全管理中的多尺度力学问题

文章指出航天器的安全性涉及到材料、元件、器件、子系统、系统和整机6个层次。虽然预测和防止失效的任务是在整机层次,但是损伤却是起源于材料的微损伤这一最底层。损伤从原子层次到整机层次的在多个尺度层次上的演化诱致了整体的破坏。由此引入多尺度力学,即研究各种不同长度尺度和时间尺度相互耦合现象的科学。文章试图将力学的宏观运动方程和微结构转变的动力学方程组成统一的方程组,从而得到宏观标量损伤D与微损伤数密度n的关系。文章还指出对于航天器的抗辐射加固问题,微损伤成核和发展的特征时间,与宏观特征空间尺度,以及外加载荷的特征时间之间的耦合关系,即德博拉(Deborah)数,是判断这类损伤演化诱致失效问题的一个关键。

Multiscale Mechanical Problems in Damage Evaluation and Safety Management of Spacecraft

This paper points out that the spacecraft safety concerns a six-layer hierarchy problem, which consists of material, element, component, subsystem, system, and whole machine. Though the task of prediction and prevention of failure is on the top level, the initial damage may come from the lower microstructual level in materials. The damage evolution with coupling multi-levels, from atom level to whole machine level, may lead to eventual rupture at the whole level. Therefore, multi-scale mechanics is introduced to study the phenomena that couple various length and time scales. The paper suggests that the macroscopic equations of mechanics and the kinetic equations of microstructual transformations should form a unified set. Then, the relationship between macroscopic damage variable D and microdamage number density n can be obtained. Additionally, it is pointed out that the key point to judge the failure induced by the damage evolution in the radiation-resistance and reinforcement problems of spacecraft can be attributed to the coupling relationships among the characteristic time of nucleation and growth of microdamages, the macroscopic characteristic spatial scale, and the characteristic time of external loading, i.e., the Deborah numbers.