Evolution of residual stresses with fatigue crack growth in a variable polarity plasma arc-welded aluminum alloy compact tension specimen

The evolution of the residual stresses during fatigue crack growth in a welded compact tension C(T) specimen was measured using neutron diffraction. The measurements were performed by growing a fatigue crack in a sample in situ on a neutron diffractometer. The stresses were found to be unaffected by crack growth through the compressive part of the initial residual stress field. The residual stresses at the crack tip increased when the crack entered the tensile residual stress field to maintain residual stress equilibrium. Finite element (FE) modeling of the evolution of the residual stresses showed good correlation with the experimental results. The residual stress evolution was found to be governed by redistribution of the initial stress field and only slightly affected by fatigue-induced effects at the measured spatial resolution (2 mm × 2 mm × 7 mm).