Simulation by temperature gradient adaption of wavelength effect in metal laser cutting

Laser cutting of thick metal workpieces requires the use of low operating speeds which, however, will have an influence on the cut quality following the used laser wavelength. In this study, we develop a model which takes into account the Fresnel coefficients in order to determine the local laser absorbed energy as a function of the beam incidence angle on the surface workpiece. The deposited laser energy occurs on the metal/air interface which evolution is tracked by the volume-of-fluid multiphase model. In the simulation, in order to find the difference between the patterns obtained on the kerf walls when different laser wavelengths are used, an important number of cells must be used at the regions of interest, which are characterized by high gradients, but a larger number of cells will have the consequence to complete the calculation with much less computer time consumption. Therefore, a gradient adaption method was implemented in order to control the number of cells, by multiplying or reducing them when it is necessary, depending on the importance of the temperature gradients. It was found out in our results that processing with higher wavelength (lambda(CO2) = 10.6 mu m) results in lower roughness on the kerf walls, compared to the surface quality obtained by using lower wavelength (lambda(Nd-YAG) = 1.06 mu m). A good accordance with the experimental observations is concluded. (C) 2017 Laser Institute of America.