Microscopic contact model of lunar regolith for high efficiency discrete element analyses |
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| Affiliation: | 1. Dept. of Geotechnical Engineering, College of Civil Engineering, Tongji University, Shanghai 200092, China;2. School of Civil Engineering, Tianjin University, Tianjin 300072, China;3. Dept of Civil and Environmental Engineering, University of Surrey, Guildford, Surrey GU2 7XH, UK;1. School of Mechanical and Electric Engineering, Guangzhou University, Guangzhou 510006, China;2. School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001, China;1. State Key Laboratory of Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, China;2. Department of Geotechnical Engineering, Tongji University, Shanghai 200092, China;3. Department of Civil Engineering, Tianjin University, Tianjin 300072, China;4. School of Chemical Engineering, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK;1. School of Civil Engineering, Tianjin University, Tianjin 300072, China;2. State Key Laboratory for Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, China;3. Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Tongji University, Shanghai 200092, China;1. State Key Laboratory for Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, China;2. Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Tongji University, Shanghai 200092, China;3. Department of Geotechnical Engineering, College of Civil Engineering, Tongji University, Shanghai 200092, China;4. Department of Geotechnical Engineering and Geo-Sciences, Polytechnic University of Catalonia (UPC), Barcelona, Spain |
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| Abstract: | The grains of lunar regolith are characterized with rough surfaces, angular shapes and mutual adhesions due to short-range interactions. These features control the macroscopic mechanical behavior of lunar regolith but have not been completely captured by contact models in previous Discrete Element Method (DEM) analyses. In this paper, a simplified two-dimensional microscopic contact model is proposed for high efficiency DEM analyses of lunar regolith. The model consists of three components in the normal, tangential and rolling directions respectively, plus two new parameters. A shape parameter is used to control the rolling resistance ability at the contact area between two particles to capture the features of grain shape and interlocking. The second parameter, micro-separation, which denotes the nominal minimum distance between the molecules of the two contacting particles, is introduced to account for van der Waals force as the major component of the short-range interactions that contribute to the adhesion of regolith grains in lunar environment conditions. The novel model has been implemented in a two-dimensional DEM code for numerical simulations of biaxial compression tests on lunar regolith. The effects of interparticle friction, grain shape, lunar environment conditions and void ratio on the strength of lunar regolith were numerically investigated. The results show that soils in the simulated lunar environment exhibit greater strength and more apparent strain-softening and shear dilatancy than on the Earth. The proposed model can capture the main features of the mechanical behavior of lunar regolith (apparent cohesion and high peak friction angle) and a wide range of strength indices can be obtained by the contact model. |
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| Keywords: | Lunar regolith Discrete Element Method Contact model Rolling resistance Van der Waals force |
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