Due to increases in computational power, the finite-element (FE) method is now widely used to predict the thermal, material, and mechanical effects of welding. Welding simulations can provide important information about component distortions and residual stresses. This facilitates a reduction in lead-time and cost associated with the process planning. Moreover, welding is generally performed in combination with other manufacturing processes such as stress relief heat treatment. This article presents a simple method where welding and post weld heat treatment operations are combined using an uncoupled plasticity—creep model. Two FE codes, welding-function-specific SYSWELD and the general-purpose FE package, ABAQUS, were used to perform butt joint welding and post weld heat treatment simulations of two Inconel 718 plates. The predicted results obtained from the two FE codes, such as thermal histories, residual stresses, nodal displacements, and stress relaxation, are compared. Based on the results presented, some useful benchmarking comments on the use of the two FE codes for welding simulation are given.
Finite element modelling of the experimentally obtained parametric envelopes for stable keyhole plasma arc welding was performed using a three-dimensional conical Gaussian heat source. Uncoupled steady-state and transient heat transfer analyses were performed to predict fusion zones and thermal histories. The heat source definition was validated against the experimentally obtained macrograph and thermal history for a representative stable keyhole condition. The paper investigates the relationships between the primary welding parameters, i.e. current, traverse speed, plasma gas flow rate and the weld efficiency, using inverse finite element modelling. The effect of the change of plasma gas flow rate on weld efficiency was estimated by iteratively changing the efficiency to match the experimental results. The numerical–experimental approach is proposed to establish relationships between welding parameters and weld efficiency which can be utilised to understand the underlying physics of keyhole plasma arc welding. The inversely identified relationships between key welding parameters can be useful in selecting the appropriate combination of weld parameters for stable keyhole welding.
This paper describes high temperature cyclic and creep relaxation testing and modelling of a high nickel-chromium material (XN40F) for application to the life prediction of superplastic forming (SPF) tools. An experimental test programme to characterise the high temperature cyclic elastic-plastic-creep behaviour of the material over a range of temperatures between 20°C and 900°C is described. The objective of the material testing is the development of a high temperature material model for cyclic analyses and life prediction of superplastic forming (SPF) dies for SPF of titanium aerospace components. A two-layer visco-plasticity model which combines both creep and combined isotropic-kinematic plasticity is chosen to represent the material behaviour. The process of material constant identification for this model is presented and the predicted results are compared with the rate-dependent (isothermal) experimental results. The temperature-dependent material model is furthermore applied to simulative thermo-mechanical fatigue (TMF) tests, designed to represent the temperature and stress-strain cycling associated with the most damaging phase of the die cycle. The model is shown to give good correlation with the test data, thus vindicating future application of the material model in thermo-mechanical analyses of SPF dies, for distortion and life prediction.
Finite element (FE) simulation of welding processes enables the prediction of component distortions which significantly reduces the need for physical trials. This facilitates reduction in lead time and costs associated with process planning. In this paper, FE modelling of tungsten inert gas welding is performed using SYSWELD for a butt joint between 2 mm thick stainless steel 304 (SS304) sheets. A three-dimensional double ellipsoid (Goldak) heat source is used to model the heat flow during welding. The heat source definition as validated against an experimentally obtained grain structure (macrograph) and thermal history. The isotropic hardening material behaviour model is used in the mechanical analysis and the annealing is considered at 1300 uC. FE-predicted distortion for an unclamped situation is compared with an experimental trial. The FE-predicted fusion zone, thermal histories, and residual distortion are found to be in reasonably good agreement with experimental results. The validated FE methodology is further used to perform a parametric study on the effect of natural and forced cooling, clamp release times, and welding sequence on distortion.
SPF tool distortion due to the thermal cycling can lead to the forming of faulty SPF parts. In addition, thermo-mechanical fatigue and creep can cause cracking, which eventually lead to un-repairable damage to the tool. The aim of this paper is to investigate the thermo-mechanical distortion behaviour of a representative large SPF tool under realistic forming conditions using finite element analysis. Platen-tool contact and clamping pressure along the edges of the tool during the dwell time are modelled. The effects of heating and cooling cycles on tool distortion are analysed using different thermal histories with different heating and cooling rates. The effect of batch size on tool distortion is evaluated to optimise the batch size.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.