INFLUENCES OF TEMPORAL AND SPATIAL DISTRIBUTION OF LASER RADIATION HEAT ON THE CRACK PROPAGATION FOR CUTTING HIGH THICK MATERIALS

The temporal and spatial distribution of irradiated heat on the material surface will affect the temperature gradient of the heated area and subsequently change the stress field distribution inside the material. To this end, the influence mechanisms of spatial and temporal distribution on the internal temperature and stress fields are deeply investigated numerically. The influence of laser process parameters on the stress field of internal material along the cutting path is also revealed. The simulation results show that as the laser radiation area increases, the tensile stress concentration area on the material surface will extend from the surface to the thickness. The stress gradient and extreme value inside the material irradiated by elliptical spot laser are larger than that by circular spot laser. Compared with the single laser, the stress and temperature on the whole profile of the material irradiated by double-sided asymmetric simultaneous laser are symmetrical. At the same time, high tensile stress areas in front of the laser spot on the upper and lower surfaces gradually extended to the middle area along the thickness direction. This results in the crack formation in the middle, propagation on the upper and lower surfaces, faster crack extension speed, and less delay fracture than that of a single laser. The results will contribute to controlling the maximum tensile stress perpendicular to the scanning path to expand along the thickness direction and will realize rapid thermal stress-controlled fracture cutting of high thick materials.