Thermomechanical deformation behaviour of DH36 steel during friction stir welding by experimental validation and modelling

Friction stir welding is a solid state thermo-mechanical deformation process from which the plasticisation behaviour of the stirred material can be evaluated throuh the study of flow stress evolution. Flow stress data also supporting the development of a local microstructural numerical model have been generated. Hot compression testing of DH36 steel has been performed at a temperature range of 700ºC-1100ºC and strain rates from 10-³ s-¹ to 10² s-¹ to study the alloy's thermo-mechanical deformation behaviour in conditions which simulate the actual friction stir welding process. It has been found that the evolution of flow stress is significantly affected by the test temperature and deformation rate. The material's constitutive equation and constants have been calculated after analysis of these data. Preliminary numerical analysis results are in good agreement with experimental observations

Advances in friction stir welding of steel : Project HILDA

A microstructure and property evaluation of friction stir welded DH36 6mm plate has been undertaken. The study examined a wide range of process parameters and, from this, a process parameter envelope has been developed and an initial process parameter set established that gives good welding properties. Thermo-mechanical deformation studies were developed to generate flow stress regimes over a range of stain rates and temperatures and these data will support the on-going local numerical modelling development. A preliminary thermo-fluid model has been developed to predict temperature and material flow during the FSW of steel grade DH36. In this model, materials are considered as highly viscous incompressible fluid. The welded material is flowing around the rotating tool thanks to the modelling of the friction at tool/workpiece interface. In parallel, a global numerical model is being developed to predict the inherent residual stresses and distortion of FSW butt welded assemblies often in excess of 6m long plate

Multiphysics welding simulation model

The electron beam welding (EBW) process is extensively used for assembling titanium and other high strength components in the aircraft engine industry. For such applications, it is important to predict distortions and residual stresses after the welding process. In welding simulation, identifying the main physical phenomena is important to formulate reasonable hypothesis to capture the first order effect. A specific fluid flow model has been implemented in the in house CFD solver (ARGO). This model allows the simulation of the melt pool dynamics during welding by taking into account the influence of different convective terms. A single domain approach with an enthalpy-porosity formulation has been used. The influence of each term on the final melt pool shape has been studied

Powder bed fusion modelling based on Discontinuous Galerkin formulation

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