Method for estimating normal contact parameters in collision modeling using discontinuous deformation analysis

This paper presents a contact parameter estimation method for collision modeling using discontinuous deformation analysis (DDA). Most DDA codes and discrete element method (DEM) codes use the viscoelastic contact model for contact-stress calculation. The contact parameters of the viscoelastic contact model, such as normal stiffness and damping constant, affect the computation results observably. Although the DDA method has been proposed for more than 20 years, the contact parameters in DDA modeling are still difficult to determine. In collision dynamics, the coefficient of restitution (COR) is considered the critical parameter for describing the changes of motion state after collision between two objects. In the proposed method, the normal COR is used for evaluating calculation results of rockfall modeling with three-dimensional DDA. The normal COR of the two-object model is obtained by tests or empirical methods. The relation curve of contact parameters and the normal COR is generated on the basis of a series of numerical computations according to the tests. Then, the reasonable combination of normal stiffness and damping constant can be calculated by matching the normal COR on this curve and used in other similar computations to obtain more practical results. An example based on laboratory tests is reported to validate the method.