Analytical modeling of temperature evolution and bend angle in laser forming of Al 6061-T6 sheets and its experimental analysis

Abstract

This paper presents a physics-based analytical model to analyze the temperature field and bend angle in a material irradiated by a moving laser heat source. The solution for temperature field involves use of integral transform technique to solve the three-dimensional governing heat transfer equation with consideration of heat transfer due to conduction and convection from laser-heated region to the surrounding material. Based on the strain difference caused by the developed temperature and forces under the laser-irradiated area due to laser heating, the bend angle of the sheet is calculated. The proposed analytical model considers the influence of residual heat in the previous laser scan for predicting the bend angle in multiple scans. Al 6061-T6 aluminium alloy sheet is chosen to demonstrate the efficacy of the proposed model. The results obtained with the analytical model are validated with the experimental investigation at different process conditions. The predictions of the analytical model in terms of temperature and bend angle are in good agreement with the experimental results by obtaining inversely estimated the absorption coefficient. A three-dimensional finite element model is also developed to verify the temperature field along the sheet thickness and bend angle predicted by the analytical model. By comparison, it is observed that the analytical model has promising advantage in computational efficiency compared to FEM simulations with comparable prediction accuracy, which can also broader the application of this analytical modelling method. To extend the applicability of the proposed analytical model, the influence of different process parameters such as sheet thickness, line energy, and number of passes on the laser forming process are also studied. Apart from this, microhardness, flexural strength and microstructure of laser-irradiated sheets are studied experimentally, under different parameter combinations in order to assess the applicability of Al 6061-T6 aluminium alloy sheet. The findings of the present study demonstrate the effectiveness of the proposed analytical model as an effective tool to estimate the temperature field and bend angle in laser heating process precisely and accurately, which reduces the need for time-consuming finite element model simulations and high experimental costs.