3D Coupled Cellular Automaton (CA)–Finite Element (FE) Modeling for Solidification Grain Structures in Gas Tungsten Arc Welding (GTAW)

Abstract

A coupled Cellular Automaton (CA) -Finite Element (FE) model is proposed to predict the grain structure formation during Gas Tungsten Arc Welding (GTAW). The FE model solves the heat flow problem based on an adaptive meshing. This is done on a first FE mesh. The CA model simulates the development of the envelope of the grains in the liquid. For that purpose, a second FE mesh, referred to as CA mesh, is used. Fields can be interpolated between the adaptive FE mesh and the CA mesh. A CA grid made of a regular lattice of cubic cells is defined and superimposed onto the CA mesh. A new dynamic strategy for the allocation/ deallocation of the CA grid is proposed to reduce the computation and memory costs. This CAFE model is applied to partial melting of an initial grain structure and epitaxial growth in the undercooled zone of a liquid pool, thus simulating the formation of solidification structure during the GTAW process. Examples of single linear passes simulations for various processing conditions and a multiple pass simulation are presented.

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

“…A dynamic remeshing strategy is developed for the adaptation of the FE mesh as illustrated in Fig. 2 (b) [13,15,30]. This remeshing is based on a specific metric computed from three separated metrics.…”

“…A given volume of the metal defined by a cell of the CA grid can either remain solid, become liquid, or be partially melted. Once the temperature field is projected on the CA grid, the temperature of cell n, T n , being known, it is compared to the liquidus temperature of the alloy, T L , and linked to the state of its neighboring cells m to model melting [15]:…”

“…Recent progresses of the CAFE model were in the coupling with macrosegregation caused by thermosolutal convection [9e12], and optimization of computations by parallel algorithms [12e14]. Chen et al [15] then extended the 3D CAFE model to simulate the grain structure evolution during melting and solidification in Gas Tungsten Arc Welding (GTAW) processes. Recent progresses have also been reported in the literature for the grain structure prediction in laser welding [16].…”

Study of the effect of growth kinetic and nucleation law on grain structure simulation during gas tungsten arc welding of Cu-Ni plate

“…The initial average grain diameter of the base material is around 100 μm and the initial grain structure is equiaxed in the whole specimen. It means that the CA grid should contain billions of cells per cm 3 that is cumbersome to manage [5] even with increasing high-performance computing. A two-dimensional model will be developed.…”

“…Recently, Chen et al [5] adapted a three-dimensional cellular automata-finite element (CAFE) method for welding simulations and used it to predict grain structure. Based on a dendritic growth law derived from a Kurz Giovanola Trivedi (KGT) model [6], Chen et al [5] were able to predict epitaxial growth and grain growth selection even for multiple solidification/fusion cycles. In this important work, the nucleation phenomenon was not integrated despite its importance in CET prediction.…”