Thermal losses in the process of gas-assisted laser cutting of metals

Hydrodynamical phenomena in the process of laser welding and cutting

“…Experiment is carried out to observe the moving humps phenomenon in LW process. 8 A similar phenomenon pertaining to EBW is also reported. 13 Other experimental and theoretical observations also validate the existence of shelf and hump phenomena in the LW process.…”

“…4,5,7 Investigations of non-stationary hydro-and gas dynamic phenomena in laser materials processing (LMP) are urgent, since the existing models of these processes have so far traditionally relied on the concept of diffusive heat and mass transfer or on laminar convection. 1,6,8,9 The consideration of non-stationary, non-linear and turbulent hydro-and gas dynamic phenomena involves changes in the values of process parameters from tens of per cent to orders of magnitude. Hence, through the development of adequate models for LMP processes, allowing non-stationary hydro-and gas dynamic phenomena accompanied with experimental studies, these phenomena will make it possible to eliminate the procedures for engineering design of LMP process.…”

“…1,4,5 It has discussed the shelf instability in their attempt to establish the prevailing LC mechanism at low cutting velocities. 8 At P e .P ecrm >2-3, the melt layer on the frontal KH wall may exhibit small scale capillary waves with wavelength scale spanning 10 23 -10 22 cm. These waves get excited by capillary evaporative instability of the liquid surface.…”

“…Similar phenomenon also manifests in the case of moving humps. 4,8,17 The displacement of the liquid by the moving shelf to the melt pool is accompanied with an injection of submerged streams of the liquid. The flow in these streams manifests as non-stationary 3D whirls in the bottom of the KH with average velocities of the order of 1 m s 21 .…”

“…The driving force for stream injection arises from impulsive vapour pressure bursts caused by evaporating microdroplets. 8,20 Yet another hydrodynamic phenomenon in laser material processing stems from splashing from the melt pool. It may occur in the process of KH formation in a fixed specimen where the rate of laser beam power buildup is too high and does not match the velocity of radial expansion of the melt zone, i.e.…”