Experimental investigations, modeling, and optimization of multi-scan laser forming of AISI 304 stainless steel sheet

Abstract

Laser forming experiments were conducted on AISI 304 stainless steel flat sheet to study the effects of process parameters and for developing an empirical model of bending angle, which could be useful to produce a class of developable surfaces from it using multiple parallel laser scans. Central composite design of experiments was used to perform the experiments, input–output relationships were established, and optimization of laser forming process under temperature gradient mechanism was carried out using a response surface methodology based on the experimental data. Laser power, scan speed, spot diameter, scan position, and number of scans were taken as input variables, and bending angle was considered as the output. The performance of the developed model was validated through a set of experimental data. The optimum process parameters for obtaining the maximum bending angle were determined, and those were verified through the real experiments. The effect of work-piece geometry on bending angle and that of multiple laser irradiations on bending rate were also investigated. Bending angle was found to be influenced by the work-piece geometry. Bending angle increased with the number of laser scans, but the bending rate decreased. Metallurgical changes at the laser irradiated zones of the laser formed samples, that is, micro-structures and micro-hardness were also studied using scanning electron microscope and Vickers’ micro-hardness tester, respectively. Microstructures were found to be refined and micro-hardness of the bent zone got improved due to the laser forming.