Laser forming of sheet metal offers the advantages of requiring no hard tooling and thus reduced cost and increased flexibility. It also enables forming of some materials and shapes that are not possible now. In single-axis laser bending of plates, the bending edge is found to be somewhat curved and the bending angle varies along the laser-scanning path. These phenomena are termed edge effects, which adversely affect the accuracy of the bending and result in undue residual stress. Numerical investigations are carried out to study the process transiency and the mechanism of the edge effects. Temperature dependency of material properties and strain-rate dependency of flow stress are considered in the numerical simulation to improve prediction accuracy. Numerical results are validated in experiments. Patterns of edge effects and resultant residual stress distributions are examined under a wide range of conditions. A more complete explanation for the mechanism of the edge effects is given.

A sensing and control system of process quality in C02 laser deep penetration welding has been developed, including plasma photo sensor (PS) and plasma charge sensor (PCS), signal processing circuit, personal computer, and optimization and control software. By using the information of plasma radiation and plasma charge, the focusing lens is adjusted to the optimum focal point position (at which the maximum penetration can be achieved ) and closed-loop control is realized to assure the focal point position and penetration depth constant. In laser welding of the workpiece aslant placed with larger angle, the variation offocal point position is less than 0.2mm and the fluctuation ofpenetration depth is less than 0.05mm. The control system has been preliminarily applied in laser precision welding of 2.5m long zircaloy fuel channel used in nuclear heat-supply reactor.

Laser forming has not been widely used due to limited understanding of its mechanism and immaturity of processing technology. In the study of single axis laser bending of plates, edge effects affect accuracy of the bending. Experimental and numerical studies are carried out to study the mechanism of the edge effects. Temperature dependency of material properties and strain-rate dependency of yield stress are considered in numerical simulation. Numerical results match well with experimental results. Patterns of edge effects are examined in terms of bending angle variation and curved bending edge under different conditions. A more complete explanation for the mechanism of the edge effects is given.

Recent developments in the study of the laser bending process are reviewed and presented to obtain new perspectives along the lines of dimensional characteristics and mechanical properties of the formed parts. Both numerical and experimental results are described and compared. The dimensional characteristics examined include bending angle variation and bending edge curving. The mechanical properties examined include residual stress, hardness and microstructural change.

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