Forming Mechanism of Bump Shape in Pulsed Laser Melting of Stainless Steel

Abstract

Laser surface topography has great applications in mechanical, medical, and electrical industries. This paper proposes a mechanism for the shape formation of stainless steel by pulsed laser melting. A 2D axisymmetric finite element model considering the temperature-dependent surface tension is developed, in which the melt flow and free surface deformation are analyzed by using the normal and shear surface forces. The numerical results show that the molten flows toward the place of the greatest surface tension and the free surface deformation are dominated by the shear force (Marangoni effects), generated by the surface tension gradient during heating phase, and the normal stress, generated by the surface tension at the curved surface during the cooling period.

The Effect of Spot Size Combination Mode on Ablation Morphology of Aluminum Alloy by Millisecond-Nanosecond Combined-Pulse Laser

“…To describe the influence of the spot size combination mode on the molten pool, a two-dimensional (2D) axial symmetry physical model (Figure 7) has been developed based on the following assumptions [25,26]:The material is considered to be isotropic and homogenous.The flow of liquid metal in the molten pool is treated as incompressible Newtonian laminar flow.The thermo-physical properties related to aluminum alloy depend on the temperature in solid and liquid phase.…”

Numerical Simulation of Effect of Different Initial Morphologies on Melt Hydrodynamics in Laser Polishing of Ti6Al4V

“…In this paper, the model is based on the energy equation (Equation ( 1)), momentum equation (Equation ( 2)) and continuity equation (Equation ( 3)) as the theoretical guidance [22][23][24][25][26].…”

“…where ρ is the density, t is the laser radiation duration, T is the the variation of surface temperature with t, → u is the melt velocity, k is the thermal conductivity, → u m is the mesh velocity, p is the pressure, I is the identity matrix, µ is the dynamic viscosity, F V is the body force of buoyancy and gravity of the molten pool [23].…”

“…where C p is the specific heat, L m is the latent heat of melting, the definition of liquid fraction f L as follow [22][23][24][25][26]…”

“…(1) Heat transfer boundary condition Equation ( 7) describes the laser beam radiation which induces the thermal convection and surface to surface ambient radiation heat loss whiles the thermal insulation in boundary 4 is expressed in Equation ( 8) [22][23][24][25][26].…”