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- Laser Machining of Structural Ceramics: An Integrated Experimental and Numerical Approach for Surface Finish
- This poster received 1st place in the 2013 Graduate Exhibition in the Engineering category. Abstract: High energy lasers emerged as an innovative and potential industrial tool to fabricate complex shapes on structural ceramics which is otherwise difficult using conventional machining techniques. However, obtaining a desired surface finish at higher material removal rate during laser machining of structural ceramics is still a critical issue. In this situation, the better understanding of various physical phenomena such as heat transfer, fluid flow, recoil pressure, Marangoni convection, and surface tension and its influence on the evolution of typical surface topography during laser machining could be more helpful. In light of this, this study was attempted to present the state of the art of laser machining of alumina using an integrated experimental and computational approach. A multistep computational model based on COMSOL™ Multiphysics was developed to study the effect of various physical phenomena on the generation of surface topography for various laser machining conditions. Furthermore, this process model can be used as a handy tool for the process engineers to configure the process variables (laser power, scanning speed, pulse rate, size of overlap) to obtain the specified quality characteristics. The surface topography of laser machined alumina was measured by an optical profilometer and the results were compared with the computationally predicted topographic parameters with reasonably close agreement.
- Temperature-dependent structural heterogeneity in calcium silicate liquids
- This article discusses temperature-dependent structural heterogeneity in calcium silicate liquids. X-ray diffraction measurements performed on aerodynamically levitated CaSiO3 droplets have been interpreted using a structurally heterogeneous liquid-state model. When cooled, the high-temperature liquid shows evidence of the polymerization of edge shared Ca octahedra. Diffraction isosbestic points are used to characterize the polymerization process in the pair-distribution function. This behavior is linear in the high-temperature melt but exhibits rapid growth just above the glass transition temperature around 1.2Tg. The heterogeneous liquid interpretation is supported by molecular-dynamics simulations which show the CaSiO3 glass has more edge-shared polyhedra and fewer corner shared polyhedra than the liquid model.