Modelling And Analysis Of Thermal Stress Field For Laser Cutting Corner In Steel Sheet

Laser cutting has many advantages such as good cutting quality andcutting speed and small heat-affected zone and little pollution. It has beenwidely used by industries. However, there is a certain degree fluctuation ofcutting movement due to the limit of cutting speed in cutting machinewhen laser cutting corner trajectory. And result in bad cutting quality suchas corner burnt and heat concentrated and stress concentrated and so on. Soit is in dire need of solving this problem to improve laser cutting efficiencyand extend application.The paper discusses the research status and development of thermalstress field analysis in laser cutting. A3-D model of laser cutting cornerwith a fluctuation cutting speed is established, and the physical process oflaser heat source moving along the corner trajectory is simulated. Then thevarying laws in thermal stress field is analyzed, and also the effects ofchanging cutting parameters such as corner size and cutting speed andlaser power are studied.At first based on heat transfer and thermodynamics theory and speed fluctuation model, the modeling approach of laser cutting corner with afluctuation speed is analyzed. The3-D simulation model is established bythe finite element software of ANSYS. Then the simulation process oflaser heat source movement and metal heat melting is realized by utilizingthe APDL programming language and the function of element birth anddeath in ANSYS. The phenomenon of heat and stress concentrated andcorner burnt are been found in the3-D simulation model. At the same time,the influence of fluctuation speed on laser cutting quality is confirmed.Secondly, the influence rule of laser cutting parameters in the3-Dsimulation model is carried out. It is found the corner concentrated moreserious and temperature changes more slowly and corner burnt moreobvious and thermal stress smaller when corner size is decreased. And ifthe cutting speed is decreased, the same phenomenon can also been found.However, if the laser power is decreased, the phenomenon is alien to thesituation of decreasing cutting speed.On the base of theoretical research, the paper carried out a series ofexperiments. The temperature distribution is got by thermocouple. And theresidual stress of workpiece surface is attained by X-ray diffraction.Besides, laser cutting surface quality is observation by microscope. Andexperiments show coincidence with simulations. In conclusion, the research in this dissertation enriches the theory andmethod of analysis of thermal stress field in laser cutting corner with afluctuation speed, and provides theoretical foundation and importantreference to laser cutting corner with good quality.Finally, the paper summarizes all the done work and views the studydirection in future.