DRUM :: Browsing by Author "Zhang, G.M."

Browsing by Author "Zhang, G.M."

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Analysis and Control of Dimensioning and Geometric Tolerancing through Surface Topography Generation
(1990) Zhang, G.M.; Hwang, Tsu-Wei; ISR
A 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.
Analysis of Elastoplastic Deformation Observed on Machined Surfaces
(1993) Hwang, Tsu-Wei; Zhang, G.M.; ISR
In 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.
Analysis of the Cutting Dynamics in Microscale
(1990) Zhang, G.M.; Hwang, Tsu-Wei; ISR
This 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.
Bridging the Gap and Preparing for Engineering
(1993) Zhang, G.M.; Dally, James W.; ISR
This paper presents the experience obtained from the 1992 summer program. Twenty-three female high school students participated. A laboratory demonstration course provided them with a comprehensive understanding of engineering disciplines. A design course introduced the product development cycle in engineering through a project approach. Applying the knowledge gained from the classroom, they designed a porch glider, then manufactured or procured the glider's components, and finally assembled them. During the six-week program, they were highly motivated and enthusiastic in learning engineering fundamentals and developing critical thinking skills. They experienced college life and gained confidence in choosing careers in science and engineering.
Building MRSEV Models for CAM Applications
(1993) Gupta, Satyandra K.; Kramer, Thomas R.; Nau, D.S.; Regli, W.C.; Zhang, G.M.; ISR
Integrating CAD and CAM applications, one major problems is how to interpret CAD information in a manner that makes sense for CAM. Our goal is to develop a general approach that can be used with a variety of CAD and CAM applications for the manufacture of machined parts.
In particular, we present a methodology for taking a CAD model, extracting alternative interpretations of the model as collections of MRSEVs (Material Removal Shape Element Volumes, a STEP-based library of machining features), and evaluating these interpretations to determine which one is optimal. The evaluation criteria may be defined by the user, in order to select the best interpretation for the particular application at hand.
Characterization of the Surface Cracking Formed during the Machining of Ceramic Material
(1995) Zhang, G.M.; Ng, S.; Le, Dung T.; ISR
This 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.
Characterization of the Surface Texture Formed During the Machining of Ceramics
(1995) Zhang, G.M.; Ng, S.J.; Le, Dung T.; Job, Lenox S.; ISR
This paper presents the development of a computer-based system to perform characterization of the surface texture formed during the machining of ceramic material. Techniques of image processing and computer graphics are employed to display vivid pictures of micro-scale details of the machined surfaces. Special attention is given to establishing the interrelations between the surface texture formation and the grain facet fracture induced by machining. Results obtained from microscopic analysis of the formed surface texture reveal that grain pullouts and cleavage, as a result of the progressive development of grain boundary micro-cracking, are two mechanisms responsible for the material removal process. The surface texture is an aggregation of macro and micro-scale fractured facets. A new performance index  cavity density is introduced to quantify the combinational effect of material microstructure and the dynamic loading during machining on the micro-mechanisms of the material removal process.
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.
Concurrent Evaluation of Machinability during Product Design
(1992) Gupta, Sandeep K.; Nau, D.; Zhang, G.M.; ISR
This paper presents a new methodology of evaluating the machinability of a machined part during the design state of the product development cycle, so that problems related to machining can be recognized and corrected while the product is being designed. Our basic approach is to perform a systematic evaluation of machining alternatives throughout each step in the design stage. This involves three basic steps: (1) generate alternative interpretations of the design as different collection of machinable features, (2) generate the various possible sequences of machining operations capable of producing each interpretation, and (3) evaluate each operations sequence, to determine the relevant information on achievable quality and associated costs. The information provided by this analysis can be used not only to give feedback to the designer about problems that might arise with the machining, but also to provide information to the manufacturing engineer about alternative ways in which the part might be machined.
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.
Control of Surface Topographies Formed During Machining
(1990) Zhang, G.M.; Hwang, Tsu-Wei; Harhalakis, George; ISR
This 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.
Development of Variant Designs in ISO 9000 Certification
(1993) Woo, M.; Zhang, G.M.; ISR
This paper will present the research results from developing a computer database system using a variant design approach to assist in the preparation of quality manuals. The basic principle is "the most common one of design assignments modifies or uses an existing design to make a 'new' component." Such an information flow mainly relies on a database, which stores all the information about ISO 9000 certification requested by a desired company. Integration of system architecture and communication protocol allows to accommodate different types of business (electronics, mechanical, etc.). A case study is presented to illustrate the process of generating quality manuals through an intelligent user-interface and to demonstrate a new and unique business strategy to enhance quality improvement and management.
Dynamic Generation of Machined Surfaces Part 1: Description of a Random Excitation System
(1990) Zhang, G.M.; Kapoor, S.G.; ISR
With increasing emphasis on the adaptive control for the purpose of quality and productivity improvement, it becomes necessary to develop models which can correlate the surface finish parameters with the machining conditions as well as workpiece material characteristics. This paper presents a study that leads to the development of a model for the dynamic generation of three- dimensional texture of machined surfaces. In Part I, the mathematical formulation of the random excitation system which is responsible for the random portion of a surface profile is developed. It is assumed that the random excitation system originates from the nonhomogeneous distribution of microhardness of workpiece material. Machining tests are also performed to verify the validity of such a model development. In Part 2, a procedure for the construction of three-dimensional topography will be developed and the relationship between the machining conditions and the surface finish parameters will be established.
Dynamic Generation of Machined Surfaces Part 2: Construction of Surface Topography
(1990) Zhang, G.M.; Kapoor, S.G.; ISR
In Part I of these two-part papers, a normal distribution model has been formulated to describe the random excitation system present during machining. Part 2 presents a methodology to dynamically generate the surface topography under the random excitation environment through computer simulation. The proposed methodology uses the tool vibratory motion along with the tool geometrical motion to construct the topography of a machined surface. Both experimental and simulation results confirm that when a small feed is used, the influence of the spiral trajectory of tool geometrical motion on the surface generation decays dramatically and the random excitation system, on the opposite, is strengthened playing a significant role in surface texture generation.
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.
Estimation of Achievable Tolerances
(1993) Gupta, Satyandra K.; Nau, D.S.; Zhang, G.M.; ISR
This report presents a new and systematic approach to assist decision-making in selecting machining operation plans. We present a methodology to estimate achievable tolerances of operations plan. Given an operation plan, we use variety of empirical and mathematical models to evaluate process capabilities of various machining operations and compute achievable tolerances using tolerance charting techniques.
Evaluating Product Machinability for Concurrent Engineering
(1992) Nau, D.S.; Zhang, G.M.; Gupta, Satyandra K.; Karinthi, Raghu R.; ISR
Decisions made during the design of a machined part can significantly affect the product's cost, quality, and lead time. Thus, in order to address the goals of concurrent engineering, it is important to evaluate the machinability of the proposed design, so that the designer can change the design to improve its machinability, To determine the machinability of the part, all of the possible alternative ways to machine the part should be generated, and their machinability evaluated. This chapter describes the techniques we have developed to do this automatically.
The information provided by these techniques will prove useful in two ways: (1) to provide information to the manufacturing engineer about alternative ways in which the part might be machined, and (2) to provide feedback to the designer identifying problems that may arise with the machining.
Experiences of Engineering Design for High School Women
(1992) Zhang, G.M.; Dally, James W.; ISR
This paper presents the experiences of teaching high school women during the 1991 Summer Study in Engineering Program. A project driven approach was employed in teaching the course to encourage talented women to pursue engineering careers. The course provided an introductory experience to the product development cycle by actually designing, building, and assembling a playground seesaw. Engineering concepts were taught in the classroom on an as needed basis during the design process. The students acquired computer skills through the preparation of technical reports and engineering drawings. The participating students were organized into groups and the aspects of teamwork and cooperative learning were highly stressed as the design project progressed. The women were motivated and satisfied with their academic achievements and personal development. Its impact on increasing enrollment of women students in engineering is far reaching.
A Freshman Engineering Design Course
(1992) Dally, James W.; Zhang, G.M.; ISR
This paper presents the structure of a new freshman engineering design course offered at the University of Maryland at College Park. Teaching engineering design through a project approach is the primary focus of this course. The design project involves the development of a product which is simple yet sufficiently challenging to motivate the students to learn basic engineering concepts. The design process consists of three phases, i.e., design manufacturing, and assembly. By actually building the product, the students are exposed to the product development cycle and gain important hands on experience. Teaching modern graphics is a second objective. In the course students acquire entry level skills in the application of computer software through practice and self-instruction with on-site assistance. Our experience in using this new structure to provide freshman a design experience early in the engineering curriculum has been extremely favorable. Evidence indicates that the students were highly motivated. They learned engineering fundamentals, developed critical thinking skills, and gained an educational experience that is relevant to the practice of engineering.
Generation and Evaluation of Alternative Operation
(1992) Nau, D.S.; Zhang, G.M.; Gupta, Satyandra K.; ISR
This paper presents a new and systematic approach to assist decision-making in selecting machining operation sequences. The approach is to produce alternative interpretations of design as different collections of machinable features, use these interpretations to generate alternative machining operation sequences, and evaluate the cost and achievable machining accuracy of each operations sequence. Given the operation sequences and their evaluations, it is then possible to calculate the performance measures of interest, and use these performance measures to select, from among the various alternatives, one or more of them that can best balance the need for a quality product against the need for efficient machining.

Browsing by Author "Zhang, G.M."

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