Abstract:
Conventional manufacturing processes often require a large amount of
machining and cannot satisfy the continuously increasing requirements of a
sustainable, low cost, and environmentally friendly modern industry. Thus,
Additive Manufacturing (AM) has become an important industrial process for the
manufacture of custom-made metal workpieces. Among the different AM
processes, Wire and Arc Additive Manufacture (WAAM) has the ability to
manufacture large, low volume metal work-pieces due to its high deposition
rate. In this process, 3D metallic components are built by depositing beads of
weld metal in a layer by layer fashion.
However, the non-uniform expansion and contraction of the material during the
thermal cycle results in residual stresses and distortion. To obtain a better
understanding of the thermo-mechanical performance of the WAAM process, a
study based on FE simulation was untaken in this thesis. The mechanism of the
stress generation during the deposition process was analysed via a 3D transient
thermo-mechanical FE model which is verified with experimental results. To be
capable of analysing the thermo-mechanical behaviour of large-scale WAAM
components, an efficient FE approach was developed which can significantly
reduce the computational time. The accuracy of this model was validated
against the transient model as well as experimental measurements.
With the help of the FE models studies on different deposition parameters,
deposition sequences and deposition strategies were carried out. It has been
proved that the residual stresses and the distortions are possible to be reduced
by using optimised deposition parameters and sequences. In addition, a robot
path generation prototype has been developed to help efficiently integrate these
optimised process settings in the real-wold WAAM process.
