![]() Looking for the different situations present in cutting and trepanning, the formation of horizontal structures in the ripple pattern in the cut is discussed. Deflection and separation of a supersonic gas jet emanating from a nozzle and propagating into the cut kerf is investigated using Schlieren photography and theoretical analysis. Results of a detailed analysis of the momentum boundary layer of the gas flow is compared with numerical calculations using the Euler equations as well as the viscous effects described by the compressible Navier-Stokes equations. The interaction of the gas flow with the condensed phase is mediated by two quantities, namely the pressure gradient and the shear stress along the liquid surface. ![]() To find the properties of the gas flow leading to melt ejection is a fundamental task in cutting. Heat transport in thin film flow is investigated demonstrating howto control the error of reduced models by spectral methods. The dynamic model predicts a modulation frequency for the laser power that leads to almost complete suppression of adherent dross in contour cutting. The onset of evaporation and the increase in capillary forces are the two physical phenomena relevant to the build-up of adherent dross. The additional degrees of freedom are the melt film thickness, the mass flow and the temperature at the melt film surface. In discussion of what is known as the two phase problem the properties of the melt flow are included. The model reproduces details of the U-shaped ripples evolving at the cut surface. Solving inverse problems and the properties of the thermal boundary layers are discussed. Experimental findings about the morphology of ripple formation guide the modelling approach and motivate the investigation of what is known as the one phase problem. Asymptotic methods are used to identify the degrees of freedom, and integral methods are applied to derive their equations of motion. The existence of a finite dimensional inertial manifold means that the motion of a finite set of degrees of freedom can give a good approximation to the complete solution. In such dissipative dynamical systems a finite dimensional inertial manifold exists which contains the attractor of the system. ![]() ![]() The cutting process is described with a spatial three-dimensional Free Boundary Problem for the motion of one phase boundary. Diagnosis of ripple and dross formation is advanced to observe the melt flow and its separation simultaneously as well as the spatial shape of the cut kerf. This work describes the advances in fundamental physical modelling and process monitoring of laser cutting, as well as time varying processes such as contour cutting. There are, however, gaps in understanding the dynamics of the process, especially issues related to cut quality. Laser cutting is a thermal separation process widely used in shaping and contour cutting applications. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. Archives
January 2023
Categories |