Experimental Study And Simulation On Laser Bending Of Tubes

With the rapid development of technology and industrial production, the bending tubes have been widely used in transportation, construction, power, petroleum, chemical industry, aviation, aerospace and other industrial departments. Most of the bending technology adopt bending modulus, long time use of bending modulus will reduce the accuracy of the bend tubes. Especially on materials of difficult to forming, some common failures, such as wall thinning, cracking in the outer of tube, wrinkling in the inner of tube and cross-section distortion, spring-back have become increasingly obvious. So it is necessary to study the new tube bending method.Laser forming is a flexible forming technology which forms workpiece by means of laser-induced non-uniform thermal stress. As a forming method of hot accumulation, in comparison with conventional metal forming process, it requires no dies and external forces, especially, it is suitable for the hard and brittle materials forming and low volume production. Laser bending tubes can effectively reduce the inadequacy of conventional methods. However, laser bending can not be applied in practice now, it needs further researching, the following contents have been done in this paper:(1) The analysis on laser bending process is done, and the tube forming characteristics is understanding; establishing the bending analytical model, getting the thermal distribution and the bending curvature; calculating the extreme laser power density of bending tubes by reasonable simplified heat conduction equation and boundary conditions.(2) Laser tubes bending experiment is done. Determine the scope and scanning process parameters. Through single factor test method we study the law of different laser parameters (including laser power and scanning speed, light spot diameter and the scanning angle), diameter size and the number of scanning to the bending angle.(3) Establishing the 3-D finite element model of laser bending of tubes, to simulate the bending process. Describing the mobile heat sources and automatically loading it by the use of APDL. Using a set of processing parameters to get the tube temperature, stress-strain field and bending angle changes and analyzes its deformation characteristics.(4) Based on geometric curvature, the path planning for laser bending tubes is researched, which contains two-dimension bending and three-dimension bending two manners. To laser bending tubes, the desirable surface is divided into several segments according to the extreme point and inflection point, regarding the extreme point as the initial place, the heating paths in every subsection are planned in accordance with the curvature variation. To three-dimensional bending, two two-dimensional curvatures from the projection was researched, the scanning paths and processing parameters are acquired respectively. Through combining two groups of data, the three-dimensions bending path is acquired.The work in this paper supplies experimental and theoretical foundation for application of laser bending, and this paper presents the laser scanning path planning method, which can play a certain role in promoting the development of laser bending.