Thermodynamic Analysis Of Laser Welding Of Automobile Body Orienting Light Weight

Light Weight is the main development tendency of automobile industry in the future, as well as one of the important means to reduce energy consumption and environment pollution. The body weight accounted for the total weight of 40%, which is important to realize automobile light weight. The use of advanced materials and welding methods are important ways to realize the lightweight body. So it is put forward that adopting high strength steel and light alloy to replace traditional materials and using laser welding to take place of traditional welding methods like spot welding and arc welding. The main purpose of this paper is to make a research on laser welding process by using new vehicle body materials of high strength steel and light Al alloy, using finite element method to make a simulation and analysis on the distribution characteristic and variation of temperature field and stress filed in laser welding process, to make a further discuss about the influence of welding parameters like laser power and welding speed on temperature and stress, providing theoretical basis and reference to practical application of laser welding. And the main contents of the paper include:(1) Building a geometric model of roof and side body which is a typical weld position, adopting software of Hyper Mesh to establish a finite element analytical model and import to ANSYS software to make finite element analysis. Make a discuss and summary about different kinds of heat models, put forward the combined heat model of Gauss surface heat source and peak increasing cylindrical body heat source as the heat model in this paper, according to keyhole shape in deep penetration of laser welding and the characteristic of weld fusion lines. And realize the anomalous moving of heat source, weld generation in order, and the process of cyclic loading by sing programming language of ANSYS software and element birth and death.(2) Make a simulation of laser welding process of roof and side of body for their materials are BH steel and high strength steel of DP600, analyze the distributions and variation rules of weld zone, thermal field and stress field, reveals the influence of weld parameters on weld zone, thermal and stress fields. The result shows that the weld zone size and highest temperature rises with the increase of power and decline with the increase of weld speed, thermal stress of weld declines with the increase of power and rises with the increase of weld speed.(3) Make a simulation of laser welding process of roof and side of body for their materials are light 6061 Al alloy, analyze the distributions and variation rules of weld zone, thermal field and stress field, reveals the variation rules of temperature field and characteristic of fast cooling and thermal stress distribution along the weld centerline.(4) Build a thermal measurement system in laser welding process, to measure and record temperature of different position in process. The comparison between measured result and simulated result verified the reliability of finite element model and heat model, which could be applied as a theoretical basis for process design and numerical simulation of laser welding.