Abstract
Post-build rolling can mitigate residual stress (RS) and distortion in large-scale components built by wire arc additive manufacturing (WAAM). In this study, based on numerical simulations that considered both WAAM deposition and vertical rolling, the mechanisms of rolling-enabled mitigation of RS and distortion in a WAAM-built steel wall are elucidated. The influences of process configuration and condition, such as roller design (flat, profiled and slotted rollers), rolling load (25–75 kN) and roller-to-wall friction coefficient (0–0.8) on the distributions of plastic strain (PS) and RS were investigated. It is found that the slotted roller is most effective to introduce tensile PS for counteracting the compressive PS generated by the WAAM deposition, thereby reducing the tensile RS in the clamped condition and the final distortion after removal of clamps. Higher rolling load increases the rolling-induced tensile PS, which leads to more extensive mitigation of the WAAM-generated tensile RS. The simulations also demonstrate that the friction coefficient significantly affects the PS and RS when the slotted roller is employed. However, the efficacy of the flat/profiled roller is insensitive to friction coefficient. This study could underpin the development of an optimal post-build rolling process for efficient mitigation of RS and distortion in WAAM components.
Highlights
Popularity in aerospace, automotive, military, and petroleum industries [1]
Longitudinal tensile residual stress (RS) was generated in the wall after the thermal deposition cycles, and it was converted to compressive RS in the core of the wall by the rolling
The produced RS profile at higher rolling loads could be unfavourable in terms of fatigue performance of the component. This modelling study investigated post-build rolling as an efficient method for mitigation of RS and distortion in a WAAMbuilt steel wall component
Summary
Popularity in aerospace, automotive, military, and petroleum industries [1]. WAAM allows building of components with various dimensions, from relatively simple walls [2] and cylindrical structures [3], to complex parts with variable deposit features [3]. Parts with medium geometric resolution and surface quality [4] have been built using steel [2,5], aluminium alloy [6], titanium alloy [7,8], nickel superalloy [9], tantalum [10] and tungsten [11] This new technology is based on sequential deposition of metallic layers with a wire consumable, an arc heat source, and a robotic manipulator under precise computer control. Colegrove et al [21] and Martina et al [7] investigated interlayer rolling with flat and profiled rollers on WAAM Ti-6Al-4V components For both types of rollers, the distortion decreased with the increase of the rolling load. Hönnige et al [22] investigated the effect of inter-layer rolling on intersections based on ‘‘inverted” roller (i.e., roller with convex surface), and reported that the inverted roller can improve the microstructure, it does not affect RS distributions at the intersections, presumably because the thermal influence of WAAM deposition dominated over the rolling [22]
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