Mechanical Properties Of Lunar Soil Research Articles

An elastoplastic constitutive model of lunar soil simulant considering shear dilatancy and softening characteristics

The study of the constitutive relationship of lunar soil is the key to a deep understanding of the mechanical properties of lunar soil and the subsequent construction of lunar bases. Previous models mostly focused on the strengthening behavior before the peak, while rarely reflected the post-peak softening and residual deformation stages during shear deformation. A new elastoplastic constitutive relation is derived with combining kinematic hardening model and initial shear stress, which effectively compensates for the shortcomings of existing constitutive models, and the validity of the model is verified by comparing with existed laboratory test results. The developed constitutive model not only effectively captures the shear dilatancy and softening characteristics of lunar soil simulant, but also requires fewer parameters to be easily determined by simple initial loading curves from direct shear tests, Furthermore, the influences of some key parameters on shear strength and softening behavior of lunar soil simulant can be easily obtained based on this constitutive model.

Lunar soil-analogue VI-75 for large-scale experiments

At the present stage of the Moon study and exploration, the lunar soil model for large-scale field experiments is one of the most relevant for drop tests of lunar landing spacecraft, to develop test sites for testing self-propelled or manned lunar rovers, for designing and testing elements of lunar infrastructure, and so on. We analyzed the basic requirements for raw materials and lunar soil models for large-scale field experimental studies. The main physical and mechanical properties of the lunar soil for the verification of soil-analogues and the selection of raw materials for modeling mixtures are considered. We present the method of developing of the lunar soil-analogue, the measured physical and mechanical properties of the soil-analogues are given, including the deformation characteristics, and the technology of laying the soil-analogue in the test bench is considered. It is shown that our lunar soil analogue VI-75 fully imitates physical and mechanical properties of an original lunar soil at loose and compact state. Experiments confirmed its high operational properties and qualities.

Research on a lunar mobile spiral surface-soil sampler

This article presents the design of a spiral sampling device to perform lunar soil sampling and packaging, considering the special lunar environment and the physical and mechanical properties of the lunar soil. Combining the mechanical properties of lunar soil and the geometrical characteristics of the sampling device, the contact model between particles and the contact parameters between device and particles were adjusted. Through a discrete element simulation of the sampling process, the particles’ streamline, which is between the screw conveying modules and the sampling bailer, is derived. This result provides a theoretical foundation for the structural optimization of the device. Finally, a sampling experiment in simulated lunar soil verifies the feasibility of the sampling device.

Analysis and DEM Simulation on the Interaction Characteristics between Lunar Soil and Coring Drill

The interaction characteristic between lunar soil and coring drill is studied in this paper. According to the failure forms of lunar soil, the stress area is divided into two parts, central failure area and lateral failure area. The impacts of different drill parameters on cutting force are obtained by a rotary cutting model. And the process of lunar soil coring is simulated basing on a special built DEM (discrete element method) model, which accord to the special mechanical properties of lunar soil. By analyzing the simulation results, the correctness of the cutting model is proved.

Experimental investigation on deformation behavior of TJ-1 lunar soil simulant subjected to principal stress rotation

The knowledge of mechanical properties of lunar soil is of fundamental importance for the coming exploration of the Moon. This paper aims to investigate the fundamental deformation behavior of lunar soil and the effects of the intermediate principal stress coefficient, deviatoric stress ratio, and mean stress during the principal stress rotation. First, an improved technique was proposed to generate homogeneous samples based on the Multi-layer Undercompaction Method. Second, three series of tests on TJ-1 lunar soil simulant under the principal stress rotation were performed with a hollow cylinder apparatus at Tongji University, China. In each series of tests, only one value of the three variables mentioned above was changed while the others were kept constant. The test results demonstrate that the rotation of principal stress can result in significant plastic deformation, volumetric strain, and non-coaxiality (non-coincidence of the increment direction of principal plastic strain with the principal stress direction) of TJ-1 lunar soil simulant. In addition, it is found that the intermediate principal stress coefficient, deviatoric stress ratio, and mean stress have different influences on the four strain components, i.e. εz,εr,εθ and γzθ, volumetric strain, and non-coaxiality during the principal stress rotation. The influence of deviatoric stress ratio is relatively stronger than the others. Therefore, the influence of principal stress rotation on the deformation behavior of lunar soil should be taken into account carefully in the design and construction of facilities on the lunar surface in the future.