Fatigue Crack Growth Behaviour in Friction Stir Welded Aluminium–Lithium Alloy Subjected to Biaxial Loads

Abstract

In the present paper, biaxial load fatigue crack growth tests are reported. Specimens were made of an advanced aluminium-lithium alloy AA2198-T8 joined by the friction stir welding process, capable of producing advanced integral metallic structures that can offer significant cost and weight savings over the current joining methods. Two material rolling directions are considered in relation to the 1 welding and crack growth direction. Welding-induced initial distortion was measured before the experiment for better result interpretation.Test specimens are representative of two different weld orientations, i.e. longitudinal weld parallel to the material rolling direction and circumferential weld perpendicular to the material rolling direction for investigating the inherent material anisotropy of aluminium-lithium alloys. In all tests the fatigue crack was initiated in the thermo-mechanical process zone of the weld and propagated parallel to the weld joint line.It is shown that the rolling direction of the selected aluminium alloy strongly affects the crack growth path. The specimens welded orthogonally to the rolling direction exhibit a shorter fatigue crack growth life than the specimens welded parallel to the rolling direction.

Mixed mode fatigue and fracture in planar geometries: Observations onKeqand crack path modelling

“…Another specimen for planar tests is the cruciform specimen. Richter‐Trummer presents a review of this type of specimen. No standard cruciform specimen geometry exists, thus making comparison of results obtained by different researchers difficult .…”

“…Cruciform test specimen, V. Richter‐Trummer (in mm), [Colour figure can be viewed at wileyonlinelibrary.com]…”

“…Figure 12 shows a specimen used by Richter Trummer for tests on FCG in friction stir welded (FSW) joints,. 41,42…”

“…B, Central notch on constant thickness specimen, crack length 2a and fatigue crack propagation angle ß (in mm)49 Cruciform test specimen, V. Richter-Trummer (in mm),41,42 [Colour figure can be viewed at wileyonlinelibrary. com]…”

The effect of residual stress on mixed‐mode crack propagation behaviour in friction stir welded 7075‐T6 aluminium alloy panel under biaxial loading

“…In order to study the crack propagation behaviour under biaxial loading conditions, many researchers have done lots of works 11–18 . Misak et al 11,12 investigated the mixed‐mode FCGR in cruciform specimens with a 45° inclined centre notch under various mixed‐mode biaxial loading conditions.…”