Research On Filling Model And Characteristic Of Lunar Soil Simulant

One of the purposes of the lunar soil deep-sampling mission is to obtain samples of lunar soil with original bedding information. Considering this purpose, this reseach compared traditional soil mechanics with discrete element method (DEM). Via DEM, the filling model and characteristic of lunar soil simulant in lunar soil deep-sampling with turnover flexible membrane was studied. Moreover, the impact of main structural parameters and drilling regulation parameters upon lunar soil simulant bedding information was analysed. This research has important significance for implementation of the lunar soil deep-sampling, design and development of drilling device, the formulation of the lunar soil deep-sampling regulation.Based on physical and mechanical properties of lunar soil and DEM elastic spheres model, contact mechanics model and flow model of spherical and non-spherical lunar soil simulant were established.With two-dimensional DEM software, PFC2D, simulation and analysis of the impact of particle diameter upon precision of model, the size effect was performed, grounded on which variable diameter modeling method was proposed. On this basis, lunar soil deep-sampling simulation model with turnover flexible membrane was established in three-dimensional DEM software, EDEM, with moving plane.According to the requirement of bedding information, the method and index of quantitative evaluation for it were proposed. Comparing the bedding information of direct penetrability sampling tube with that of turnover flexible membrane sampling tube shows that the turnover flexible membrane sample has better bedding information.Grounded on lunar soil deep-sampling simulation model with turnover flexible membrane, the impact of diameter of sample tube, friction coefficient of turnover flexible membrane, feed rate, excitation frequency upon bedding information in lunar soil deep-sampling were simulated and analyzed. The results show that the bigger sample diameter and the particle-membrane friction coefficient are or the smaller feed speed is, the better bedding information will be, and vibrant frequency should be kept away from the the natural frequency of lunar soil stimulant, which provide a reference for design and development of drilling device and the formulation of the lunar soil deep-sampling regulation.