Browsing by Author "Ng, S."
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Item Characterization of the Surface Cracking Formed during the Machining of Ceramic Material(1995) Zhang, G.M.; Ng, S.; Le, Dung T.; ISRThis paper presents a method to characterize the surface cracking formed during the machining of ceramics material. Ceramic specimens are prepared under two different machining environments, dry and submersion. An environmental scanning electron microscope is used to obtain high-magnification images of machined surfaces. Reconstruction of the surface texture in a three-dimensional space is made by scanning the images and using graphics software to obtain detailed and informative spatial views of the machined surface. The visualized surface cracks provide quantitative information on their size and shape. Two performance indices are proposed to characterize the distribution of surface cracks induced by machining in terms of the density and crack depth with reference to the machined surface. As a case study, the developed nondestructive evaluation method is used to assess the effectiveness of using the submerged machining to process ceramic material. The obtained results present a clear picture illustrating the capability of controlling the crack formation during the submerged machining.Item Submerged Precision Machining of Ceramic Material(1995) Zhang, G.M.; Ko, Wing F.; Ng, S.; ISRThe brittle nature of ceramics makes them difficult to machine. This paper presents a study to explore a new method to machine ceramic material. The method is based on the stress-corrosion- cracking behavior of ceramic material under certain aggressive environments. An apparatus is designed to create a machining environment where workpiece and cutting tool are submerged in a bath filled with cutting fluids. Observations on the surface texture formed during machining have been made to investigate the effectiveness of submerged machining on quality and efficiency of the machining operation. The obtained results strongly suggest that the chemo-mechanical interactions occurred during machining have great influence on the stress distribution produced in the ceramic material being machined, thus have direct effects on crack initiation and propagation. By controlling the machining parameters, higher material removal rate with less surface damage can be achieved, showing the potential of submerged machining as an innovative technology for machining ceramic material.