Study On Technology Of Laser Forming Of Thin Aluminum-Lithium Alloy Sheet Metal

Laser forming is a new sheet metal forming process and it has long been a hot research internationally. It has wide application prospects in the field of aerospace, automobile, shipbuilding, instruments, microelectronics and so on. The research on laser forming has mainly focused on stainless steel, carbon steel and other materials. According to the demand of reducing the weight of the produces in the field of aerospace, thin aerospace aluminum-lithium alloy AA2090 sheet metal (which has many remarkable advantages, such as low density, significantly higher elastic modulus and so on) laser forming was studied.Through experimental study, the influence law of principal factors that influence laser forming, including laser power, scan speed, beam diameter, number of scan, scan line from the free end, sheet width and sheet thickness, was obtained respectively in the natural cooling and water cooling conditions.By means of the theory of orthogonal experimental design method, design of experiment and optimization were carried out respectively on process parameters, in the natural cooling and water cooling conditions. The results showed that, in the natural cooling condition, the effect of the four process parameters related to the energy of laser beam on bending angle was ranked in order of laser power, scan speed, number of scan and beam diameter; and in the water cooling condition was ranked in order of laser power, number of scan, scan speed, beam diameter. The optimum process parameters were obtained respectively, and experiment verifications were carried out respectively, verification results were very good. In addition, three kind of scan paths which scan along curves were also conducted to verify the correctness of optimum process parameters, the result were very good, too.Different scan paths and three-dimensional shapes were experimental studied, by controlling the scanning path. And it was found that when the ratio between the spacing (S, the spacing was the distance between two adjacent parallel scan lines) and the beam diameter (D) was different, distribution uniformity of thermal stress in that part of the board had different sensitivity to the scan direction of the two adjacent parallel scan lines. And what's more, the relationship between the size of the ratio (S/D) and the uniformity of scan direction was achieved, which solve the problem that the sheet metal generated distortion before that.Finally, in order to explore new scan methods, several new scan methods which scan along different curves (square wave, sawtooth-shaped, S-shaped tangent arc, spiral, parallel line method) to replace the original scan line path were proposed. It was found that the deformation of the sheet metal was uniform after scanning along those curves paths. Particularly, the bending corner was very smooth and round by scanning using parallel line method. Compared with scanning along straight line, more smooth and round corner can be achieved by using parallel line method.The studies in this thesis lay a solid theoretical foundation for the practical application of Aluminum-lithium alloy laser forming. It has great practical values and significance to promote and realize the industrial application of sheet metal laser forming.