Investigation of thermal behaviour of structural steel S235N under laser cutting process: Experimental, analytical, and numerical studies

Abstract

Laser cutting represents an appealing solution for high machining speed and precision in steel constructions. To control the efficiency of laser cutting, the effects of laser heating must be understood; and to investigate thermal effects on a steel workpiece, a methodological approach for analytical modeling of laser cutting heat source is proposed herein. The proposed model takes into account laser source geometry variation along the cut edge thickness. Given the complexity of the analyzed process, there is no accurate mathematical formulation capable of modelling both heat flux and temperature distribution. Therefore, to model heat flux with an accurate temperature distribution field and both calibrate and validate solid phases of a cut specimen, the paper proposes a modified heat source based on a Gaussian distribution. The study focuses on mild structural steel S235N and relevant commonly used laser cutting parameters for structural applications. More precisely, the model allows the laser cutting process to be simulated as a function of laser beam diameter, cutting speed, laser power and element thickness. Thus, to simulate the thermal process by means of a proper heat source, a model was implemented in the FE software Abaqus. Model parameters were both calibrated and validated through experimental results provided by online monitoring of laser cutting process with a thermal camera and location of microconstituents. In particular, the temperature profiles obtained from the proposed FE model, exhibit a good agreement with experimental results. Finally, the distribution of microconstituents along the depth agrees with predicted temperature profiles.