Institute for Systems Research

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Author: search.filters.author.Zhang, G.M.Subject: search.filters.subject.materials properties

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    Control of Machining Induces Edge Chipping on Glass Ceramics
    (1996) Ng, S.J.; Le, Dung T.; Tucker, S.R.; Zhang, G.M.; ISR
    Edge chipping is a phenomenon commonly observed during the machining of ceramic material. Characterization of edge chipping, both in macro and in micro scale, and correlating its formation to machining parameters form a basis for developing new and innovative technologies for controlling in machining induced damage. An experimental-based study using glass ceramic material is performed. Three types of edge chipping are identified. The SEM-sterephotography method and the finite element method are used to evaluate the edge chipping effect under a set of machining conditions. Significant findings are obtained and guidelines for controlling edge chipping during machining are suggested.
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    Study of the Formation of Macro-and-Micro-Cracks during Machining of Ceramics
    (1993) Zhang, G.M.; Anand, Davinder K.; Ghosh, Subrata; Ko, Wing F.; ISR
    This paper presents an experimental study on the formation of macro- and micro- cracks formed during the machining of ceramic materials. Aluminum oxide (Al2O3) was used as the testing material and polycrystalline diamond tipped carbide inserts were used for material removal. The cutting force was recorded during machining and surface finish was measured after machining. an environmental SEM was used to obtain high-magnification images of macro- and microcracks induced by machining. With the assistance of a computer-based vision system, qualification of fracture surfaces with respect to crack nucleation, growth, and cleavage was attempted. Results from this research provide an insight into the prevailing mechanisms of material removal during the machining of ceramics, and suggest the development of crack- controlled machining technologies.
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    Chemo-Mechanical Effects on the Efficiency of Machining Ceramics
    (1992) Zhang, G.M.; Hwang, Tsu-Wei; Anand, Davinder K.; ISR
    This paper presents an experimental study of the turning of a ceramic material - aluminum oxide (A12O3). Emphasis is given to gain a comprehensive understanding of the cutting mechanism. This study explores the utilization of cutting fluids with chemical additives to develop a novel machining process. The machining tests were performed on a CNC lathe. Polycrystalling diamond compact tools were used. The cutting force during machining was measured using an instrumented tool holder as a dynamometer. The surface finish was inspected using a profilometer. SEM technique was used to study the mechanism of the surface formation in microscale. Results from this experimental study provides rich information on the cutting mechanisms during ceramics machining and the chemo-mechanical effects on the machining efficiency.
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    A Hidden Markov Model Approach to the Study of Random Tool Motion during Machining
    (1991) Zhang, G.M.; Lin, Chien; ISR
    This paper presents a new approach to the study of random tool motion during machining. Theory of the hidden Markov model is applied to formulate a comprehensive random excitation system present during machining. Based on the microstructural analysis, characteristics of the hardness distribution in the material being machined are identified for analyzing the cutting dynamics in microscale. The machining action within one revolution of the workpiece and the relation between the machining actions in consecutive revolutions are interpreted as a double stochastic process. Computer simulation based on the hidden Markov model approach is used to predict values of surface roughness characterization indices under given machining conditions. The predictions are compared with the data obtained from direct measurements, showing good agreements. The developed approach has brought new light on a better understanding of vibration control during machining.
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    Dynamic Visualization of the Surface Texture Formed During Machining
    (1991) Zhang, G.M.; Hwang, Tsu-Wei; Song, J.F.; ISR
    This paper presents a new methodology to study the properties of machined surfaces. A conceptual framework designed for dynamically visualizing the surface texture formed during machining is proposed. By integrating material science, machining science, and metrology science, the framework provides a systematic approach to investigate the mechanism of surface irregularity formation during machining. Studying the variability of basic material properties in micro-scale and relating this information to the surface texture formation during machining, this research provides a computer-based and comprehensive metrological system for industrial control and diagnostics of the surface quality during machining.