Dynamics of the heat affected zone and induced strains in laser machining below ablation threshold

Abstract

Abstract The Heat Affected Zone - HAZ of a laser irradiated AISI H-13 steel workpiece, is investigated via numerical simulations and experimental measurements. A three-dimensional transient thermo-structural finite element model is developed to simulate the machining process. A Gaussian laser beam is employed as the heat source. The developed finite element material model considers the effects of plastic strain, strain rate and temperature, along with a fracture model. The experiments are carried out with a laser of 1-4 W power and with a scanning speed of 100 mm/min. Thermocouple sensors are used for the temperature measurements, while the surface roughness is measured using white light interferometry and related experimental diagnostics. A parametric numerical analysis regarding the average absorptivity of the workpiece is performed and is compared to the experimental findings. The depth and width of HAZ and the induced strains are studied for the plastic and melting regimes. The influence of the surface roughness of the metal workpiece on the dynamics of HAZ is also experimentally demonstrated. The findings of this study highlight the role of the absorption coefficient and the surface roughness on the HAZ below the ablation threshold and can be applied to related laser machining processes.