13th International Conference on Fracture June 16–21, 2013, Beijing, China -4- ElTobgy et al. [6] reported that single particle impact is insufficient to simulate the erosion process, three and more particles are needed to analyze multiple particle interactions. In this study, 5 particles are used to ensure the accuracy of the model. In general, the erosion rate (%) is used to describe the erosion wear performance of the substrate material. Our objective is to analyze the material erosion rate under various processing conditions. The erosion rate is defined as [7]: ݁ ݎ ݅ݏ ݊ ݁ݐ ܽݎ ൌ௨௨௧௩ ௦௦ ௦௦ ௦௨௦௧௧ ௧ ௧ ௧௦ ௪௧ (8) 2.2.1. Impact particle Two kinds of impact particle are used in the present simulation study, that is, spherical and irregular non-spherical particles. The purpose is to consider the effect of particle shape on material removal mechanism. The impacting material is steel with a density of 7800 kg/m3. In the finite element model, the impact particle material is modeled as a rigid body. The element for the impact particle is 3-node and 4-node bilinear quadrilateral rigid elements (R3D3 and R3D4). 2.2.2. Impact substrate The substrate is modeled as a deformable elastic plastic material, and the eight-node brick hexahedral element with reduced integration and hourglass control (C3D8R) is used to mesh the substrate. The accuracy of the material removal prediction is tested with different grid sizes for convergence test. In this study, mesh size is chosen to ensure neither time-consuming nor leading to unreasonable discrepancy. Figures 1 and 2 show the FE model of spherical and irregular particles. General contact is defined between the impacting particles and substrate material. The contact property is assumed to follow coulomb friction, and the friction coefficient between impact particle and substrate is assumed to be 0.2 [12], the boundary condition is applied to ensure that the substrate is fixed for bottom plane and the particles rotation are constrained in all three directions. Figure 1. Spherical particle FE model Figure 2. Irregular particle FE model When particles impact the substrate, some of impacts, depending on the impact velocity and angle, will only deform the material surface without causing material removal, leading to the hardening of substrate material. In the previous attempts of erosion wear process simulation, most of them do not consider such hardening effect. In practice, the influence of multi-particle impacts is obvious in erosion process since the impact contact may change after multiple impacts. Therefore, although ideal cases, in which particle impacts with the same velocity and angle are employed, it is still necessary to adopt the multiple particle impact model. Figure 3 shows the material removal after each spherical particle impact. It clearly shows that the material removal increases with increasing impact times under the same impact condition. ElTobgy et al. [6] showed that the erosion rate is affected by a number of system parameters, such
RkJQdWJsaXNoZXIy MjM0NDE=