Laser nanosecond pulse heating of surfaces and thermal stresses

Laser pulse beating of metallic surfaces finds wide application in industry because of the precision of operation and localized heating of the substra te material. The thermal stresses are developed because of the high tempera ture gradient generated in the region irradiated by a Laser beam. The level of stresses developed becomes important during the laser surface treatment and annealing process. In this study, the laser nanosecond pulse heating o f a metallic substrate is considered. Energy transport and thermal stress e quations are solved numerically for step input intensity pulses. Because th e heating process is axisymmetric, the cylindrical coordinate system is emp loyed. The temperature and stress fields inside the substrate material are computed. It is found that in the early heating period, the temperature ris es rapidly in the surface vicinity of the substrate material. As the heatin g progresses, diffusional energy transport becomes important, in which case the rise of temperature in the surface vicinity attains almost a steady va lue. The axial stress component is tensile, the radial stress component is compressive, while the tangential stress component is compressive in the re gion close to the symmetry axis and it becomes tensile as the distance from the symmetry axis increases.