Gas-assisted laser single-pulse heating: study of thermal stresses

Pulsed laser heating of metals causes an excessive temperature gradient acr oss the heated zone, which in turn results in thermal stresses developing i n the heated region. In the present study, gas-assisted pulsed laser heatin g of steel is simulated. The governing flow, energy and thermal stress equa tions are solved numerically. The low Reynolds number k-epsilon model is in troduced to account for the turbulence. In the analysis, temporal variation in heating and stress development are considered. In order to examine the material response to the heating pulse, constant and variable properties of the workpiece are taken into account. It is found that the thermal stresse s are highly concentrated in the surface region of the substrate. The radia l component of the stress is compressive while the axial component is tensi le. The maximum equivalent strain is of the order of 10(-3). The maximum eq uivalent stress occurs below the surface along the z axis, where the radial intersection is the centre of the heated spot.