Analytical model for prediction of bend angle in laser forming of sheets

This paper covers an analytical approach for predicting the bend angle of a laser formed sheet with a single laser scan. The proposed approach is based on the strain energy stored under the laser-irradiated area that causes plastic deformation of sheet due to laser heating. With any particular intensity of laser, the temperature profile established across the sheet thickness is determined by employing a one-dimensional transient heat conduction equation and by considering the loss of heat to the surrounding material by thermal conduction. Based on the temperature gradient across the sheet thickness, thermal strain, strain-induced stress, and bending moment are evaluated. By equating the strain energy stored in the sheet material due to thermal stress and strain with the strain energy stored due to the bending moment, the angle of bend in the sheet is determined. The results obtained with the proposed model are validated with the experiments performed on AISI 304 stainless steel and AA 1100 aluminum alloy sheet material of different thickness using CO2 laser with varying power and scanning speed. A three-dimensional finite element model is developed to validate the temperature profile predicted by the proposed model. The effectiveness of the proposed approach is validated by comparing the predicted bend angle with those predicted by other analytical models. Apart from this, the effect of various process parameters on the laser formed sheet was studied using microstructure and microhardness analysis. Finally, with the application of the proposed model, a process map is generated to achieve pure bending during laser forming.