Laser micro-processing and thermomechanical modeling of plasticity for dieless wire drawing

A novel dieless drawing technique using laser micro-processing is presented to make fine metal wires. It is a promising process for fabrication of fine wires that are difficult to draw with the conventional processes or that require high quality surface excluding any contamination. The engineering purpose of the present work is to develop a new method to produce continuous fine metal wires of less than 100 μm in diameter (microwires), for which the conventional die drawing technique becomes very difficult.; A prototype experimental setup is designed and constructed. Nickel 200 and Au-Ag-Cu alloy wires are used as sample materials in laser dieless wire drawing experiments. The initial wire diameter of the nickel wires ranges from 50 to 500 μm. Effects of process parameters on wire drawability are experimentally investigated. The chemistry and microstructure of the wires are investigated at different conditions to understand the mechanisms of the effects of process parameters on drawability.; A thermomechanical model is developed to understand the laser dieless wire drawing process. In this model, a one-dimensional quasi-steady state heat conduction problem is coupled with a plastic deformation problem. An analytical solution is obtained for case of constant wire diameter. Numerical approach to the solution of the coupled thermomechanical problem is presented. The model allows predicting all the thermomechanical parameters of the wire in the deformed region and can be used to analyze other process related problems and to optimize the process. A method to evaluate the plastic flow parameters of the wire is presented based on temperature and deformation measurement of the wire in the deformation region.; The wire drawing process relies on the plasticity of the wire. However, plasticity is influenced by the dislocation motion in the material. Quantum mechanics provides a means of analyzing such dislocation motion. For a basic understanding of plasticity, especially how strain rate changes with stress and temperature, a dislocation motion model is presented based on quantum mechanical description of kink formation rate in the smooth kink regime.