Impact Characterization Of Granuler Matter Under Different Gravitation Based On The Discrete Element Method

Particulate matter is closely related to human life and is widely used in various engineering fields.As the footsteps of human exploration gradually move toward the deep space environment,the rich dynamical behavior of particulate matter under different gravity and its mechanism increasingly become the key research problems in the field of current and future deep space exploration.Among them,studying the impact evolution process and the corresponding mechanical behavior of particulate matter under different gravity can provide insight into the complex physical laws related to particle collisions,thus guiding the scientific implementation of deep space exploration missions such as hard landing of vehicles and surface sampling of stars,and providing a theoretical basis for the engineering applications of particulate materials in deep space environment.Therefore,this paper establishes a discrete element model of the impact effect on granular materials under different gravity.The applicability and rationality of this discrete element model in the particle impact problem is verified by comparing the results with the impact test under Earth gravity.The discrete element numerical study of the process of a large ball impacting a granular bed under different impact velocities and gravitational accelerations is carried out using CUDA-GPU parallel computing.The main research contents of this thesis include.(1)The influence law of gravitational acceleration on the displacement,normal force and sustained collision time of the impactor is quantitatively analyzed,and the scalar relationship between the final penetration depth of the impactor and the impact velocity and total fall distance is also explored,based on which the penetration deceleration process of the impactor is distinguished.(2)The kinetic behavior of the granular medium after vertical impact is studied.The effects of impact velocity and gravitational acceleration on the impact cratering process are mainly analyzed,and the original three-dimensional impact crater data are converted into twodimensional contours,and the best-fit curve of the two-dimensional contours of the impact crater is given;the relationship between the impact crater radius and the dimensionless gravity scale is also discussed and compared with the results of laboratory tests.(3)The effects of gravitational acceleration and impact velocity on the kinetic characteristics of the ejected particles were analyzed,and the variation of the velocity of the ejected particles with the ejection position was studied;meanwhile,it was found that the gravitational acceleration had no effect on the ejection angle of the particles;after that,the effects of different impact velocities and gravitational accelerations on the ejection mass of the particles were analyzed,and finally the relationship between the velocity and mass of the ejected particles and the dimensionless gravitational scale was given.