Institute for Systems Research Technical Reports
Permanent URI for this collectionhttp://hdl.handle.net/1903/4376
This archive contains a collection of reports generated by the faculty and students of the Institute for Systems Research (ISR), a permanent, interdisciplinary research unit in the A. James Clark School of Engineering at the University of Maryland. ISR-based projects are conducted through partnerships with industry and government, bringing together faculty and students from multiple academic departments and colleges across the university.
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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.Item A Stochastic Modeling for the Characterization of Random Tool Motion during Machining(1992) Hwang, Tsu-Wei; Zhang, G.M.; ISRThis paper presents the development of a new stochastic approach to characterize random tool motion during machining. The complexity of cutting mechanism is represented by a random excitation system related to physical properties of the material being machined. A Markov-chain based stochastic approach is developed to model the random tool motion as the response of a machining system under the random excitation. In considering a turning operation, a concept of group distributions is introduced to characterize the global effect on the cutting force due to the variation of a certain material property. A model of segment excitation is used to describe its micro function within an individual revolution. A distribution pattern observed in the material property is represented by a transition model. The simulation of random tool motion during machining resembles the generation of Markov chains. Microstructure analysis and image process are used to collect data, calculate relevant statistics, and estimate the system parameters specified in the developed stochastic model. As illustrated in this paper, the developed stochastic model can be effectively used to simulate the random tool motion and to learn rich information on the performance measures of interest such as machining accuracy and finish quality. The new approach represents a major advance to create a fundamental scientific basis for the realization of a reliable and effective prediction system for information processing in sensor-based manufacturing.Item Dynamic Visualization of the Surface Texture Formed During Machining(1991) Zhang, G.M.; Hwang, Tsu-Wei; Song, J.F.; ISRThis 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.Item Analysis and Control of Dimensioning and Geometric Tolerancing through Surface Topography Generation(1990) Zhang, G.M.; Hwang, Tsu-Wei; ISRA general quality assurance system to perform in-process inspection through on-line monitoring is proposed in this paper. Technical issues related to the model based indirect measuring approach to retrace the quality control target are discussed. This research analyzes the dynamic characteristics of dimensioning and geometric tolerancing through surface topography generation through incorporation of random tool motion analysis in the evaluation of machining accuracy. Statistical methods for estimating metrological indices, such as roundness and straightness, have been developed to assist in the determination of control limits designed for on-line detection of disturbances external to the normal machining process.Item Analysis of the Cutting Dynamics in Microscale(1990) Zhang, G.M.; Hwang, Tsu-Wei; ISRThis paper presents a new approach to the study of cutting dynamics in microscale. The manipulation of the cutting force generated during machining is based on the characteristics of microstructures within the workpiece material being machined. Mathematical modeling of the hardness variation around the circumference of the workpiece reveals the cohesiveness between the macroscale and microscale analyses. The case study presented in this paper illustrates the procedures used to evaluate the cutting force through the microscale analysis. A model-based indirect tool wear monitoring methodology has been developed to show the potential of applying the cutting dynamics in microscale for the design of on-line quality and process control systems.Item Control of Surface Topographies Formed During Machining(1990) Zhang, G.M.; Hwang, Tsu-Wei; Harhalakis, George; ISRThis paper presents a new approach from a systems engineering perspective to integrate tool path control and surface topography generation for the quality control of machined surfaces. This approach is based on a strategic link "variability of material properties - cutting mechanics in microscale - structural dynamics of machine tools - integration of tool fibratory and geometric motions - surface topography generation. "By combining experimental and analytical work, this research provides manufacturing industry with a computer-based method to control machined surface topographies.