Browsing by Author "Wang, F."
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Item Open Access Investigation of the benefits of plasma deposition for the additive layer manufacture of Ti-6Al-4V(Elsevier Science B.V., Amsterdam., 2012-07-01T00:00:00Z) Martina, Filomeno; Mehnen, Jorn; Williams, Stewart W.; Colegrove, Paul A.; Wang, F.With increasing emphasis on sustainability, Additive Layer Manufacturing (ALM) offers significant advantages in terms of reduced buy-to-fly ratios and improved design flexibility. Plasma Wire Deposition is a novel ALM technique in which plasma welding and wire feeding are combined. In the present work, a working envelope for the process using Ti–6Al–4V was developed, and regression models were calculated for Total Wall Width, Effective Wall Width and Layer Height. The Plasma Wire Deposition process is able to produce straight walls of widths up to 17.4 mm giving a maximum effective wall width after machining of 15.9 mm, which is considerably wider than competing processes. In addition, for Ti–6Al–4V the deposition efficiency averages 93% and the maximum deposition rate is 1.8 kg/h. Coarse columnar grains ofβphase grew from the base during deposition, which transformed into a Widmanstätten structure ofαlamellae on cooling. Bands were identified in the deposits, which had a repetitive basket-weave microstructure that varied in size. The strength measured by micro-indentation hardness of 387 HV on average is as much as 12% higher than the substrate. These preliminary results indicate that Plasma Wire Deposition is likely to be a suitable process for the ALM of large aerospaceItem Open Access Thermo-mechanical analysis of wire and arc additive layer manufacturing process on large multi-layer parts(Elsevier Science B.V., Amsterdam., 2011-12-01T00:00:00Z) Ding, J.; Colegrove, Paul A.; Mehnen, Jorn; Ganguly, Supriyo; Sequeira Almeida, P. M.; Wang, F.; Williams, Stewart W.Wire and Arc Additive Layer Manufacturing (WAALM) is gaining increasing popularity as the process allows the production of large custom-made metal workpieces with high deposition rates. The high power input of the welding process, causes significant residual stress and distortion of the workpiece. This paper describes the thermo-mechanical behaviour of the multi-layer wall structure made by the WAALM process. A 3D thermo-elastic–plastic transient model and a model based on an advanced steady-state thermal analysis are employed in this study. This modelling approach shows a significant advantage with respect to the computational time. The temperature simulations and distortion predictions are verified by comparing with the experimental results from thermo- couples and laser scanners, while the residual stresses are verified with the neutron diffraction strain scanner ENGIN-X. The stress across the deposited wall is found uniform with very little influence of the preceding layers on the following layers. The stress redistributed after unclamping with a much lower value at the top of the wall than at the interface due to the bending distortion of the sampl