Determining thermal conductivity, specific heat capacity and absorptivity during laser based materials processing

Abstract

In this work, an inverse method is proposed to estimate the thermal conductivity, absorptivity and specific heat capacity for a laser irradiated sheet by measuring the data for transient-temperature distribution at two locations. The corresponding data is also obtained using a finite element method based direct model that takes the average thermal properties of the material as input. The inverse estimation of thermal conductivity, absorptivity and specific heat capacity is carried out by minimizing the difference between actual and direct model predicted data. For this purpose, a novel heuristic algorithm is developed. The efficacy and accuracy of the method is ascertained by carrying out simulation-experiments considering temperature-dependent properties in a finite element package. Later on, shop floor experiments were also conducted, which revealed that inversely obtained parameters are sufficiently accurate in predicting the temperature distribution at changed operating conditions. The effect of measurement errors on the inverse estimated results is also discussed.