| Laser forming is a recently developed and highly flexible metal forming process. It uses laser-induced thermal distortion to shape a metal workpiece without hard tooling or external forces. A number of issues concerning laser forming are not yet fully understood. Understanding these aspects of laser forming is a challenging problem of considerable academic interest and practical applications. Efforts are made to advance knowledge in these areas. Numerical simulation models using finite element analysis are developed. The simulation results are compared to, and are consistent with, the experimental observations under a wide range of conditions. The laser forming process is investigated under the condition of constant line energy. Under this condition, the effects of velocity on temperature, net energy input, strain rate and internal flow stress are studied. Their collective effects on deformation and microstructure are presented. The influence of the strain rate in laser forming is investigated. To isolate and effectively study the strain rate effects, which are temperature dependent, a “constant peak temperature” method is developed with the aid of the numerical modeling and solution. Under the constant peak temperature condition, the effects of strain rate on forming efficiency, residual stress and hardness of the formed parts are studied. A new laser-scanning scheme is postulated to obtain convex forming insensitive to the initial state. This postulate is validated by experimental and numerical results. Effects of the scanning scheme parameters on the certainty of the convex forming, and dependence of the bending angle on the Fourier number, laser power, and velocity are further investigated. Mechanisms of the process of laser bending of tubes are examined to better understand the deformation characteristics such as wall thickness variation, cross-section ovalization, bending radius, and asymmetry. Factors important to these characteristics are experimentally and numerically investigated. Temporal and spatial distributions of temperature and stress/strain obtained from experimentally validated simulation models are also used to better understand additional phenomena accompanying the process, and to help devise ways to improve the process. The process effects on hardness and microstructure variations are also investigated. |
