A level set approach for the simulation of the multipass hybrid laser/GMA welding process

Abstract

A new 3D finite element model, developed in a level set approach, is proposed to model hybrid gas metal arc / laser welding in multipass conditions. This heat and mass transfer model couples the resolution of the heat conservation equation, the momentum and mass conservation equations and the weld bead development. The arc welding total power is divided in two parts: one corresponding to the energy transferred to the fusion zone by droplets of melted filler material, the rest being transferred to the workpiece by the surrounding plasma. The droplets energy input is modelled as a volumetric heat source. Regarding the heat surface fluxes associated with plasma and laser heating, the "Continuum Surface Force" approach is used to model them as volumetric heat sources concentrated in the immediate neighbourhood of the metal-gas interface. A resolution scheme, consisting in ignoring high velocity fluid flow in the fusion zone, through the use of an augmented liquid viscosity, is proposed and discussed. Accordingly, the liquid thermal conductivity is enhanced to result in a realistic heat transfer to the workpiece. The formation of the weld bead is obtained through the introduction of a source term in the mass conservation equation, and the application of the normal component of surface tension forces, proportional to the mean curvature of the metal-gas interface. This approach is proposed to reduce computation time. The resolution scheme is applied to the simulation of hybrid welding of 18MND5 (ASME SA 533) steel grade. Results are compared to experimental measurements and observations operated in conditions close to industrial ones. The influence of the enhancement applied to the liquid conductivity coefficient is shown and discussed. A strong sensitivity evolution is demonstrated when varying it from the physical value to the value proposed in the welding literature. As proposed, the simplified resolution scheme leads to a good estimation of the weld bead surface development. Nevertheless, there are still noticeable differences with the whole set of experimental results that are discussed and can be explained by model limitations and insufficient knowledge of material and interfacial properties.

Three-dimensional cellular automaton-finite element modeling of solidification grain structures for arc-welding processes

“…This model, largely inspired from Ref. [18], thus overcomes the numerical difficulty inherent to a sharp interface tracking procedure of the metal/gas interface after successive passes in GMAW.…”

“…Thus the liquid pool is fed with a stable rate in the axial direction of the electrode. An efficient approach to model the time evolution of this interface was developed by Desmaison et al [18]. It is based on the LS method [19,20].…”

Metal additive-manufacturing process and residual stress modeling

“…When the transient thermo-mechanical simulations are carried out within an Eulerian approach, interface-tracking methods such as volume of fluid or level set are used. Desmaison et al developed a full transient thermo-mechanical model for multi-pass hybrid welding [65], a process easily comparable to wire feed additive manufacturing. In spite of advanced numerical tools (adaptive remeshing, Hamilton-Jacobi resolution algorithm among others), the finest of inherent numerical parameters make the approach too complex for the modeling of large and complex AM.…”

Finite element modeling of deposition of ceramic material during SLM additive manufacturing

“…These two domains are separated by an interface ߰ = 0, where ߰ = ‫,ܠ(߰‬ ‫)ݐ‬ is the signed distance (to the interface) function of position ‫ܠ‬ and time ‫.ݐ‬ Centered on this interface, we define a transition zone with half thickness ߳, in which property (density, conductivity, etc.) of each domain is averaged by a Heaviside function ℋ to get global property ߯ [12]:…”

“…Radiation of gas-material interface with ߳ ் = 0.6 is also taken into account. By means of the CSF method, following Desmaison et al [12], a contribution to the volumetric heat source term ‫̇ݍ‬ in Eq. (8) can be expressed.…”