Material processing by laser radiation is well known in nowadays industrial applications. But, provided laser beam power is only partially absorbed from the work-piece. The reflected amount of radiation remains un-used. Especially simulations of laser beam processes are strongly influenced by the absorption coefficient.
In order to predict variations of the absorption coefficient multiple laser beam heating as it is used for laser beam bending of stainless steel sheets was carried out. Specimens were irradiated along a linear path. The amount of irradiation cycles was varied in several steps from one to 100. Absorption coefficient measurements were carried out prior and after laser processing using an integrating sphere. Additionally, roughness values of treated and untreated areas were compared.
It was found that roughness values increase with a larger amount of laser processing cycles. Simultaneously, increasing absorptivity was measured having rougher surfaces. Therefore, changes of the absorption coefficient can be correlated to the amount of laser processing cycles. As a linear function of the amount of cycles the calculation of an adaptive absorption coefficient was implemented in a numerical simulation. For simulations the calucation software simufact.welding was used.
Implementing an adaptive absorption coefficient results in significant changes of the resulting bending angle when simulating linear heat inputs. Compared to a static absorption coefficient an adaption during the simulation process results in a difference of 49.4 % when simulating 50 cycles. Therefore, a significant influence on resulting bending angles is shown when using an adaptive absorptivity value.