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

Abstract

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 (λCO2 = 10.6 μm) results in lower roughness on the kerf walls, compared to the surface quality obtained by using lower wavelength (λNd-YAG = 1.06 μm). A good accordance with the experimental observations is concluded.

Formation Mechanism and Physical Properties of Particle Ejection during Laser Cutting of Metal Alloys

“…Kheloufi et al [21] and Amara et al [22] have both simulated the laser cutting process through this approach and achieved great agreement with experimental observation on cutting kerf. Their studies were further explored by investigating the impact of laser wavelength [23]. Although the flow of molten metal at the cutting kerf has been well studied using FV models, there has not been any work that considered the formation mechanism and physical properties of particle ejection in the laser cutting process.…”

“…The final term 𝑆 ℎ in Eqn. (23) represents the additional heat source terms applied to the surface of the molten film, which can be expressed in terms of the convection heat dissipation 𝑆 𝑐𝑜𝑛 , radiation heat dissipation 𝑆 𝑟𝑎𝑑 , vaporization heat dissipation 𝑆 𝑣𝑎𝑝 and Gaussian beam heating 𝑆 𝑙𝑎𝑠𝑒𝑟 as:…”