Wire + arc additive manufacturing (WAAM) is a modern manufacturing process that has opened new possibilities for rapid builds and reductions in material wastage. This paper explores residual stress in WAAM Ti-6Al-4V walls built using three different deposition strategies: single bead, parallel path, and oscillation path. The effect of interlayer hammer peening and interlayer temperature was investigated for the single bead walls. We also examined the residual stress in compact-tension (C(T)) coupons extracted from large builds (walls) with crack orientation either parallel with or perpendicular to the build direction. This type of sample is often used for the measurement of the fatigue crack growth rate. The contour method was used for experimental determinations of residual stress. In addtion, residual stress in the C(T) coupons was estimated by finite element (FE) analysis. A good agreement was achieved between the contour method and FE analysis. The oscillation-path wall had the lowest residual stress values. For the single bead walls built with various process conditions, residual stress was significantly reduced after removing the substrate. A interlayer temperature of 110 °C resulted in much higher residual stress values in the wall (both tensile and compressive) compared to the continuous build, with much higher interlayer temperature.

To meet the high demand for lightweight energy-efficient and safe structures for transport applications, a current state-of-the-art light rail vehicle structure is under development that adopts a multi-material design strategy. This strategy creates the need for advanced multi-material joining technologies. The compatibility of the adhesive with a wide range of material types and the possibility of joining multi-material structures is also a key advantage to its success. In this paper, the feasibility of using either epoxy or polyurethane adhesive joining techniques applied to the multi-material vehicle structure is investigated. Importantly, consideration is given to the effect of variation in bond thickness for both families of structural adhesives. Multi-material adhesively bonded single lap joints with different adhesives of controlled bond thicknesses were manufactured and tested in order to experimentally assess the shear strength and stiffness. The torsional stiffness and natural frequency of the vehicle were modelled using a global two-dimensional finite element model (FEM) with different adhesive properties, and the obtained vehicle performances were further explained by the coupon-level experimental tests. The results showed that the vehicle using polyurethane adhesive with a target bond thickness of 1.0 mm allowed for optimal modal frequency and weight reduction.