Numerical analysis of transient heat transfer and temperature response in a metal during a laser irradiation

Abstract

This paper describes numerical analysis of transient heat transfer in a metal specimen during high-power laser irradiation. Three-dimensional finite element models of the heat flow are developed and solved, where both the convection and the radiation effects from the surfaces and the temperature dependence of all thermo-physical properties are taken into account. In this calculation, properties of iron (SS400) are used. Continuous (CW) laser irradiation of which maximum heat input 320 W, corresponding to 4 kW laser power, is applied to metal with stationary and a constant moving velocity conditions. The laser beam shapes are assumed circular or elliptical. We investigate the effects of heat input on the temperature distribution and its response based upon the model. As a result of the simulation, the heat-conduction effects are the most significant factor affecting the heat transfer processes, but the convection and radiation effects from the surface are negligible under the present conditions. Only a very thin layer (less than 0.5 mm) near the surface heated by the heat input can be high temperature regions. Simulated temperature responses along the central axis are compared with experimental results of temperature distribution obtained by a two-dimensional infrared thermometer, and both results are in good agreement, which indicated the validity of the present models. The maximum cooling rate can be estimated in the heated region, where the cooling rates is typically 103 - 104 °C/s, linearly depending on the heat input. Experimental results of laser hardening on the iron (SS400) specimen are compared with the cooling rate of these simulated results. The dependency of the hardening on the cooling rate is obtained.This paper describes numerical analysis of transient heat transfer in a metal specimen during high-power laser irradiation. Three-dimensional finite element models of the heat flow are developed and solved, where both the convection and the radiation effects from the surfaces and the temperature dependence of all thermo-physical properties are taken into account. In this calculation, properties of iron (SS400) are used. Continuous (CW) laser irradiation of which maximum heat input 320 W, corresponding to 4 kW laser power, is applied to metal with stationary and a constant moving velocity conditions. The laser beam shapes are assumed circular or elliptical. We investigate the effects of heat input on the temperature distribution and its response based upon the model. As a result of the simulation, the heat-conduction effects are the most significant factor affecting the heat transfer processes, but the convection and radiation effects from the surface are negligible under the present conditions. Only a ver...