Collaborative Research:Investigation of Material Removal in Impact Machining by Loose Abrasives

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Existing nanomachining processes that rely on lithographic and energy beam based methods often need cleanroom environments and huge capital investments. Their shortcomings include limited choice of work materials, chemical hazards, and thermally induced defects on machined surfaces. This award supports a study of material removal in brittle materials by the impact of nano diamond particles. Research results can lead to a low cost alternative for nanomachining at room temperature without the shortcomings of existing nanomachining processes. The new process can improve the nanomachinability of a wide variety of both conductive and nonconductive materials, and may have applications in biomedical, electronic, automotive, energy, and metal working industries. Potential applications in these industries include nanostructured scaffolds for artificial tissue engineering, nanostructured switches and wireless transmitters, ultra-low friction layers for thermal barrier coatings, and nanostructured proton exchange membranes for fuel cells. The experimental platform for the new process is an atomic force microscope where workpiece is vibrated at the frequency of 20-160 kHz. Machining is achieved by the impact of loose nano diamond particles in liquid medium. The research objective is to understand effects of kinetic energy on material removal mechanism (plastic deformation or brittle fracture). The level of kinetic energy is determined by machining conditions (primarily diamond particle size and vibration frequency). The research plan consists of computer simulations and experimental studies. Extended finite element methods will be used to simulate the machining process. In these models, to mimic the impact given by the diamond particle on the workpiece at different kinetic energy levels, the workpiece is fixed and the diamond particle is treated as a vibrating rigid body (at the frequency of 20-160 kHz). Drucker-Prager constitutive law will be employed to describe the behavior of brittle materials. Finite element models will be validated by comparing model predictions with experimental results. Machining experiments using graphene, silicon, and glass samples will be performed at different levels of kinetic energy by varying the mean size of diamond particles (5, 10, 15 nm) and vibrating the workpiece at different frequencies in the range of 20-160 kHz. Machined surfaces will be examined using electron microscopy, and optical microscope to determine if the material removal is done by plastic deformation or brittle fracture.