Thermo-mechanical analysis of wire and arc additive manufacturing process

Abstract

Conventional manufacturing processes often require a large amount of
\nmachining and cannot satisfy the continuously increasing requirements of a
\nsustainable, low cost, and environmentally friendly modern industry. Thus,
\nAdditive Manufacturing (AM) has become an important industrial process for the
\nmanufacture of custom-made metal workpieces. Among the different AM
\nprocesses, Wire and Arc Additive Manufacture (WAAM) has the ability to
\nmanufacture large, low volume metal work-pieces due to its high deposition
\nrate. In this process, 3D metallic components are built by depositing beads of
\nweld metal in a layer by layer fashion.
\nHowever, the non-uniform expansion and contraction of the material during the
\nthermal cycle results in residual stresses and distortion. To obtain a better
\nunderstanding of the thermo-mechanical performance of the WAAM process, a
\nstudy based on FE simulation was untaken in this thesis. The mechanism of the
\nstress generation during the deposition process was analysed via a 3D transient
\nthermo-mechanical FE model which is verified with experimental results. To be
\ncapable of analysing the thermo-mechanical behaviour of large-scale WAAM
\ncomponents, an efficient FE approach was developed which can significantly
\nreduce the computational time. The accuracy of this model was validated
\nagainst the transient model as well as experimental measurements.
\nWith the help of the FE models studies on different deposition parameters,
\ndeposition sequences and deposition strategies were carried out. It has been
\nproved that the residual stresses and the distortions are possible to be reduced
\nby using optimised deposition parameters and sequences. In addition, a robot
\npath generation prototype has been developed to help efficiently integrate these
\noptimised process settings in the real-wold WAAM process.