Process simulation and optimization of laser tube bending

Abstract

A 3D thermomechanical finite element analysis model for laser tube bending is developed based on the software MSC/Marc. The processes of single- and multi-scan are analyzed numerically. The gradient and development of the temperature between the laser scanning side and the nonscanning side leads to the changing complexity of the stress and strain. Consequently, the length of the laser scanning side becomes shorter than that of nonscanning side after cooling. The length difference between both sides makes the tube produce the bending angle. The relationship between the number of scans and the bending angle is about in direct ratio. The bending angle induced by the first irradiated time is largest. Meanwhile, the finite element simulation is integrated with the genetic algorithm. Aiming at different process demands, corresponding objective functions are established. Laser power, beam diameter, scanning velocity, and scanning wrap angle are regarded as design variables. Process optimizations of maximum angle bending and fixed angle bending after single laser scan are realized. Groups of optimized process parameters can be obtained according to different optimization objectives. The bending angle can approach to the maximum when the laser power, spot diameter, scanning velocity, and scanning wrap angle are 381.24 W, 3.37 mm, 16.34 mm/s, and 123.1°, respectively. When the laser power, spot diameter and scanning velocity are 426.12 W, 4.9 mm, 14.31 mm/s respectively, a fixed angle bending can be achieved.