Successful 3D-printing of steel structures requires optimisation of the printing process which in this project consists of wire-arc additive manufacturing (WAAM). The project will investigate the influence of weld track spacing and overlapping, scanning sequence, heat input, wire feed rate and pause time between track depositions. Test specimens will be 3D-printed for selected combinations of process parameters, and weld residual stresses will be measured in-situ on the neutron strain scanner at ANSTO, allowing the residual stress evolution to be investigated. The development of the residual stresses will be then modelled using finite element (macroscale) simulations that predict the overall residual stress field and distortion of WAAM-printed components. After verifying the accuracy of the numerical predictions against experimental results, the models will be used to uncover the interdependency between the weld process variables, including voltage, amps, speed, patterning, dwell time and interpass temperature, and the mechanical properties and residual stress fields, thereby enabling the rapid optimisation of WAAM-process variables.
Further, to understand the microstructure of WAAM-printed materials, optical, Scanning Electron Microscopy (SEM) and Electron Back-Scatter Diffraction (EBSD) procedures will be used for identification of microstructure, and neutron radiography and imaging will be used to study the efficiency of the printing process and the formation of volumetric defects such as porosity and inclusions. Based on these observations, a parameter set that minimises defects and optimises for residual stress, required microstructure and strength will be identified. The project will provide the successful candidate with cutting-edge and industry sought-after knowledge about the material characterisation of 3D-printed steel structures. It is part of a larger project supported by the Australian Research Council which comprises multiple PhD projects including research on the crystal plasticity mechanisms that control microstructure and mechanical properties, and the macroscopic testing and analysis of structural connections.
Faculty of Engineering scholarship opportunities August 2021 (sydney.edu.au)