Laser machining has been widely used in additive as well as subtractive manufacturing process for over a decade. It is considered a thermal process which facilitates addition or subtraction of the material depending on the need in the machining process. Laser cutting, a subtractive manufacturing process, is considered a thermal separation process. This is used mostly in contour operations, shaping and forming. The recent developments of the different types of the laser as well as the reduction in the pulsing time has shed light on new potential approaches which can facilitate the process. Also, it has become a more complex thermal problem than before. Lasers with femto and pico-second pulse time has changed how materials behave when thermally induced with a high-power laser in a very small timeframe (picoseconds or femtoseconds) namely coulombic explosion. This mechanism is still having areas to be explored and explained to understand the conglomeration of dynamics of the processes of melt pool and assist gas, physical phenomenon that take place as well as the cut quality during the process. The paper focuses on mimicking a scenario of continuous width laser cutting in a simulation to understand the process better as well as verifying the results with that of the experimental. The cut surface in the simulation process is also further discussed to provide in depth understanding on the gas-assisted laser cutting process as well as the kerf shape. Traditional simulation approaches are not used to understand the scenario of the laser cutting. Rather, a full 3D modelling is developed that includes the variation of assist gas pressure from 9 to 11 bar, both liquification and evaporation of the stainless steel during the process, flow of the melt materials as well thermal stress in the material. Striation or Striation marks are important quality factors in the laser cutting process, which refers to the periodical marks on the cut surface of the material. It can be attaining to the surface roughness, geometry and appearance of the material. Parameters to reduce the striation marks are studied in detail to understand the relapse of the marks. The volume-of-fluid or TrueVoF method used by Flow3D simulation software has helped in producing comprehensive scenarios mimicking the experimental results. Moreover, ray-tracing algorithm to incorporate multiple reflection during the cutting process as well as Fresnel’s reflection model is added in the simulation process to enhance the laser material interaction close to real world. Recoil pressure of the assist has, and surface tension of the liquid phase was also included. The two-phase problem has additional degree of freedom which are the melt pool depth, the flow of the fluid and also the temperature in the two-phase boundary. The laser power is being simulated as a gaussian beam which predicts a modular frequency to attain the actual results observed in the experiment. The assist gas is used as a measure of removing the melt material during the cutting process. It had two separate quantitative measurements in the simulation process, namely the gradient of pressure and shear stress it caused in the liquid material surface. This paper used the same parameters used in the experimental approach and compared the results to understand the interactions between the material and the laser.

 

 


Analysis of Laser Cutting of 1.2mm Thick Austenitic Stainless Steel

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

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