Wenwu Zhang

Micro Scale Laser Shock Processing of Metallic Components

Laser shock processing of copper using focused laser beam size about ten microns is investigated for its feasibility and capability to impart desirable residual stress distributions into the target material in order to improve the fatigue life of the material. Shock pressure and strain/stress are properly modeled to reflect the micro scale involved, and the high strain rate and ultrahigh pressure involved. Numerical solutions of the model are experimentally validated in terms of the geometry of the shock-generated plastic deformation on target material surfaces as well as the average in-depth strains under various conditions. The residual stress distributions can be further influenced by shocking at different locations with certain spacing. The potential of applying the technique to micro components, such as micro gears fabricated using MEMS is demonstrated. The investigation also lays groundwork for possible combination of the micro scale laser shock processing with laser micromachining processes to offset the undesirable residual stress often induced by such machining processes.

Laser forming: Industrial applications

Laser forming is currently a laboratory technique that is beginning to see industrial applications. In this paper, we discuss practical concerns and review the progress of laser forming at GE Global Research. Two applications, 3D shape tuning and precision tube bending, are presented. Topics include considerations for industrial applications, methods for qualifying a process window, materials characterization, path planning, and system integration.Laser forming is currently a laboratory technique that is beginning to see industrial applications. In this paper, we discuss practical concerns and review the progress of laser forming at GE Global Research. Two applications, 3D shape tuning and precision tube bending, are presented. Topics include considerations for industrial applications, methods for qualifying a process window, materials characterization, path planning, and system integration.

Combined research and curriculum development of nontraditional manufacturing

Nontraditional manufacturing (NTM) is becoming increasingly important in modern engineering. Therefore, it is important to develop up-to-date pedagogic materials for the area. This paper reports collaborative efforts among three universities in such a development sponsored by National Science Foundation of USA. The features of the development include systematic introduction, recent research results, and web implementation with interactive capabilities. This paper is based on an extensive web based course with animations, including Java applets, Shockwave animations, VRML animations, and QuickTime movies. The development is aimed at upper level undergraduate and introductory graduate students. Areas of focus include Laser Material Processing, Electrical Discharge Machining, Electro-Chemical Machining, and Abrasive Water Jet Machining. Cross process innovation are also presented. Needs for further pedagogic developments are discussed.

Effects of scanning schemes on laser tube bending

Four laser scanning schemes for tube bending, including point-source circumferential scanning, pulsed line-source axial procession, line-source axial scanning without and with water cooling are investigated in numerical simulation. The coupled thermo-mechanical model established using the finite element method is validated and applied to predict the bending deformation and help better understand bending mechanisms under different schemes. The influence of important parameters such as beam coverage, scanning velocity and cooling offset on the deformation is investigated in detail. Parametric studies are carried out to determine proper processing windows at which the largest bending can be obtained. The deformation characteristics, including the wall thickness variation and the cross-section distortion produced by different scanning schemes are analysed, along with the processing efficiency.Four laser scanning schemes for tube bending, including point-source circumferential scanning, pulsed line-source axial procession, line-source axial scanning without and with water cooling are investigated in numerical simulation. The coupled thermo-mechanical model established using the finite element method is validated and applied to predict the bending deformation and help better understand bending mechanisms under different schemes. The influence of important parameters such as beam coverage, scanning velocity and cooling offset on the deformation is investigated in detail. Parametric studies are carried out to determine proper processing windows at which the largest bending can be obtained. The deformation characteristics, including the wall thickness variation and the cross-section distortion produced by different scanning schemes are analysed, along with the processing efficiency.

Practical issues in laser micro/nano machining

Laser has become an important tool for micro/nano machining. To enable the successful application of laser micro/nano machining in manufacturing, requirements on geometry, speed and quality have to be fulfilled. In this paper, we review several representative applications of laser micro/nano machining, and discuss ways of solving the practical issues simultaneously.Laser has become an important tool for micro/nano machining. To enable the successful application of laser micro/nano machining in manufacturing, requirements on geometry, speed and quality have to be fulfilled. In this paper, we review several representative applications of laser micro/nano machining, and discuss ways of solving the practical issues simultaneously.