Institute for Systems Research
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Item Mathematical Modeling of the Uncertainty for Improving Quality in Machining Operations(1993) Zhang, G.M.; Hwang, Tsu-Wei; Ratnakar, R.; ISRThe difficulty in quality improvement of machining performance comes from the uncertainty about the cutting force generated during the material removal process. This paper presents the results from the research aimed at developing a new approach to capture the uncertainty through mathematically modeling the physical machining system. a case study is used to demonstrate the procedure to interpret the cutting force variation through a three stage process. By integrating deterministic and stochastic approaches, an observed cutting force variation, which was recorded from an experiment, can be explained satisfactorily. The reduction of uncertainty allows an accurate prediction of the cutting force variation and forms a basis for developing a control strategy for improving the machining performance.Item Analysis of Elastoplastic Deformation Observed on Machined Surfaces(1993) Hwang, Tsu-Wei; Zhang, G.M.; ISRIn this paper, the study of material removal mechanism is focused on a non-linear quasi-static analysis of the elastoplastic interaction between a single-point cutting tool and the material being cut. An updated Lagrange procedure is applied to solve the large strain elastoplastic deformation problem which generates part of the irregularities observed on machined surfaces. A unique three-dimensional finite element model is developed to simulate the single-point metal cutting process. The effects of cutting parameter settings and workpiece material on the elastoplastic deformation of machined surfaces are investigated. The validity of this analysis is verified by experiments. The results of this analysis can be applied as a surface texture modification model to enhance the accuracy of a computer-aided surface texture simulator, an important part of a computer integrated manufacturing system.Item Analysis of Surface Quality in Machining of Metals and Advanced Ceramics(1992) Hwang, Tsu-Wei; Zhang, Guangming; ISROf all the processes used to shape metals, it is machining in which the conditions of operation are most varied. Good dimensional accuracy and surface quality from machining processes should be maintained such that the product's function and customer's satisfaction are assured. On the other hand, advanced ceramics have emerged as an important class of materials with uses in a variety of high performance applications such as aerospace, engines, and cutting tools. Many of these applications require the machining of ceramic component surfaces with tight dimensional accuracy and surface finish.Among the many of possible causes which can tarnish the machined surface quality, the most important ones, such as tool vibration and elastoplastic deformation, are identified. This research is, therefore, focused on the analyses of these identified factors in order to have a better understanding of their roles in the surface texture formation process during machining, which in turn can improve the efficiency and quality of machining processes.
The irregularities of a machined surface due to random tool vibration are investigated through a Markov-chain based stochastic approach. The dynamic characteristics of the metal cutting processes, especially the variation of material properties such as the microhardness, are modeled as a Markov- chain type random tool motion during machining.
An updated Langrange method is applied for the analysis of elastoplastic deformation observed on machined surfaces. A three dimensional finite element model is built to simulate a single-point metal cutting process. The results of the analysis could be applied as surface texture modification model to enhance the accuracy of the prediction of a machined surface texture.
By combining the aforementioned analytical work, a computer-based surface topography simulator, which can predict the surface topography formed under a given machining process, is developed. Experimental work is also performed to verify the results predicted by the simulator.
The study of machining of advanced ceramics (such as aluminum oxide and DICOR) is focused on the fundamental material removal mechanisms during machining. Based on the study, a cost- effective, chemical-assisted novel machining process is proposed to improve the surface quality.
Item Chemo-Mechanical Effects on the Efficiency of Machining Ceramics(1992) Zhang, G.M.; Hwang, Tsu-Wei; Anand, Davinder K.; ISRThis 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.