I am working on impact of a high speed metal particle on a substrate by FEA using Abaqus. The model is axisymmetric as shown in figure 1. I am using Coupled Euler- Lagrangian method for simulation. The substrate and particle is modeled as a Lagrangian body and the particle is placed in a Eulerian domain. I have created a discrete field for material assignment using volume fraction tool. The particle is then excluded from the simulation. The analysis procedure is Dynamics, temperature, explicit. The particle size is 25 microns. When I am using mesh size 1.5 microns for the particle, substrate and eulerian domain I am getting expected results as shown in animation1. But whenever I am changing the mesh size (increasing or decreasing) I am getting results as the particle is scattered or broken and impacting the substrate very randomly as shown in animation 2. Does anyone have ideas why this is happening?