A CFD-DEM-Wear Coupling Method for Stone Chip Resistance of Automotive Coatings with a Rigid Connection Particle Method for Non-Spherical Particles

The stone chip resistance performance of automotive coatings has attracted increasing attention in academic and industrial communities. Even though traditional gravelometer tests can he used to evaluate stone chip resistance of automotive coatings, such experiment-based methods suffer from poor repeatability and high cost. The main purpose of this work is to develop a CFD-DEM-wear coupling method to accurately and efficiently simulate stone chip behavior of automotive coatings in a gravelometer test. To achieve this end, an approach coupling an unresolved computational fluid dynamics (CFD) method and a discrete element method (DEM) are employed to account for interactions between fluids and large particles. In order to accurately describe large particles, a rigid connection particle method is proposed. In doing so, each actual non-spherical particle can he approximately described by rigidly connecting a group of non-overlapping spheres, and particle-fluid interactions are simulated based on each component sphere. An erosion wear model is used to calculate the impact damage of coatings based on particle-coating interactions. Single spherical particle tests are performed to demonstrate the feasibility of the proposed rigid connection particle method under various air pressure conditions. Then, the developed CFD-DEM-wear model is applied to reproduce the stone chip behavior of two standard tests, i.e., DIN 55996-1 and SAE-J400-2002 tests. Numerical results are found to be in good agreement with experimental data, which demonstrates the capacity of our developed method in stone chip resistance evaluation. Finally, parametric studies are conducted to numerically investigate the influences of initial velocity and test panel orientation on impact damage of automotive coatings.