模拟月壤可行驶性的离散元数值分析

Numerical analysis on travelability of lunar soil simulant by means of distinct element method

基于模拟月壤扫描电镜显微照片,建立土颗粒的几何模型,提出不规则形状颗粒群系统的生成策略,构建模拟月壤颗粒间接触的简化本构模型,并利用量纲分析法和双轴压缩试验离散元模拟,建立土宏观力学特性与细观模型参数的关系,结合模拟月壤的三轴压缩试验数据确定离散元模型参数.在月球重力环境下,对轮-土交互作用进行离散元模拟,推导土壤推力的细观表达式,定性分析不同滑转率时土颗粒的动态行为,定量分析模拟月壤的可行驶性.研究结果表明,土壤推力随滑转率的提高而增大;当车轮以高滑转率行驶时,土壤推力相对行驶时间存在瞬态和稳态2个阶段,并且瞬态值高于稳态值.

The geometric model of lunar simulant particles was built based on its scanning electron microscopic-photograph（SEM）, and a producing strategy for irregular-shape particle assembly was presented. A simplified contact reaction model of lunar particles was created. The relationship between soil macro-mechanical property and its meso-parameters was obtained by means of dimensional analysis and biaxial test simulation by distinct element method （DEM）. According to the relationship and triaxial test data of lunar simulant, the model parameters were determined numerically. Wheel-lunar simulant interaction was simulated by DEM under moon gravity, and the soil thrust expression in granular-scale was derived. The dynamic behavior of soil particles was quantitatively analyzed at different slip ratio, and lunar simulant＇s travelability was qualitatively estimated. Results show that soil thrust increases with higher slip ratio; there are transient period and steadystage period when wheel travels at high slip ratio, and soil thrust value is bigger in transient period than that in steady-stage period.