Micromechanical removal processes during material processing technologies with fluid-coupled particle systems

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In this project, the interaction of solid particle systems and fluid flow is investigated on the micromechanical scale for wet material processing technologies with free movable abrasive particles as wire sawing, lapping or polishing. The interaction of sharp-edged three-dimensional particles among each other and with the deformable tools or workpiece are modeled by means of the discrete element method. The actual material removal mechanism caused by microscopic fracture processes is simulated and quantified. The phenomena in the shear gap and sawing kerf are experimentally investigated in special purpose built experimental devices by means of stereo-microscopy using high-speed cameras. The aim of the project is to understand the contact dynamics of particle systems in shear flows interacting with the surfaces at high velocities and rotations, which is affected by the roughness profiles and the material properties of particles and walls.In the second phase of the project we focus our experimental and numerical studies on the feedback of the particle motion onto the fluid flow. This will be achieved in the simulations by a complete coupling of the discrete element method and a fluid solver. In this way, such effects are captured like fluid interference by resting particles or particle clusters, local pressure variations in the fluid as well as separation of particles. Based on the planned fundamental research using a shear flow model with well-defined boundary conditions, we will apply the developed methods to the wire-sawing technique for silicon wafers to establish a correlation with the macroscopic technological parameters as removal rate and surface quality. Since these methods are widely distributed in materials processing technologies, a remarkable enhancement of efficiency and product quality are expected.