An Integrated Modeling Approach for Predicting Process Maps of Residual Stress and Distortion in a Laser Weld: A Combined CFD–FE Methodology

Abstract

Laser welding has become an important joining methodology within a number of industries for the structural joining of metallic parts. It offers a high power density welding capability which is desirable for deep weld sections, but is equally suited to performing thinner welded joints with sensible amendments to key process variables. However, as with any welding process, the introduction of severe thermal gradients at the weld line will inevitably lead to process-induced residual stress formation and distortions. Finite element (FE) predictions for weld simulation have been made within academia and industrial research for a number of years, although given the fluid nature of the molten weld pool, FE methodologies have limited capabilities. An improvement upon this established method would be to incorporate a computational fluid dynamics (CFD) model formulation prior to the FE model, to predict the weld pool shape and fluid flow, such that details can be fed into FE from CFD as a starting condition. The key outputs of residual stress and distortions predicted by the FE model can then be monitored against the process variables input to the model. Further, a link between the thermal results and the microstructural properties is of interest. Therefore, an empirical relationship between lamellar spacing and the cooling rate was developed and used to make predictions about the lamellar spacing for welds of different process parameters. Processing parameter combinations that lead to regions of high residual stress formation and high distortion have been determined, and the impact of processing parameters upon the predicted lamellar spacing has been presented.

Corrosion Susceptibility and Functionally Graded Properties of Ti-35Nb-4Sn Alloy Processed by Laser Remelting

“…Although crystallinity of fusion zone and HAZ is partially improved with recrystallization, significant lattice distortion can be seen along fusion boundary. These results are in full agreement with those reported by Turner et al 25 , in which residual stresses induced by the solidification of a keyhole laser weld are higher in fusion zone than in HAZ or base metal and are maximum at the very edge of the weld bead. Therefore, the higher content of interstitials seems to be a primary cause for the abrupt increase in microhardness of fusion zone, while the higher concentration of lattice distortions is a secondary cause.…”

A new method for simulating electron beam welding process of niobium sheets with beam oscillation

“…For EBW simulation, Liang et al [33] employed an equivalent mapping algorithm. Turner et al [34] replicated the dimensions and geometrical characteristics of the molten pool obtained by CFD method to the SYSWELD software for mechanical analysis. Bakir et al [35] used polynomial function to fit the profile of the weld pool calculated by CFD method to generate a two half-ellipses heat source for FEM thermal analysis.…”