Abstract
A slant plate flat throw test system for measuring the restitution coefficient of granular materials and a sliding friction test instrument for measuring the friction coefficient between discrete particles and continuum boundary surface materials are developed. The restitution coefficients of the glass bead particles, the glass beads relative to the glass plate, the composite of glass plate and the rubber membrane and the friction coefficients between the glass beads and the rubber film and the filter paper are measured by the designed methods. Based on the measured restitution coefficient and friction coefficient, the discrete element numerical simulation is carried out for triaxial test and plane strain test. Through comparing the experimental results and the discrete element numerical simulation results, the feasibility and rationality of the designed measurement methods and the discrete element numerical simulation are verified. The measuring methods developed in this paper can be further applied to the tests of other fine particles.
Highlights
In the process of discrete element numerical simulation, the contact relationship between particles and particles and the contact relationship between particles and boundary surfaces are often involved [1].When calculating the contact relation, the parameters of discrete element particles need to be input first, which involves the calibration of contact parameters
This paper developed a slant plate flat throw test system and a sliding friction test instrument for measuring the restitution coefficients and friction coefficients between the glass beads and the boundary surface respectively
The three-dimensional discrete element numerical simulation was performed according to the measured restitution coefficients and friction coefficients
Summary
In the process of discrete element numerical simulation, the contact relationship between particles and particles and the contact relationship between particles and boundary surfaces are often involved [1]. For the low-speed collision contact problem of a spherical near-rigid object, the restitution coefficient is the material correlation quantity, which indicates the ratio of the normal relative velocity before the collision of the contact point to the normal relative velocity after the collision [2] and in the discrete element simulation process, will affect the value of normal damping and time step. The free-falling body impact test was used to study and discuss the factors affecting the restitution coefficient of particle collision at low speed, including particle mass, falling height [14], characteristics of collision material, thickness [15], velocity of particle collision instantaneous relative to collision material, curvature of contact surface between two collision materials and collision history [16]. Measurement Methods of the Restitution Coefficient and Friction Coefficient for Particles
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