Relaxation of residual stress in shot peened Udimet 720Li under high temperature isothermal fatigue

Assessment of surface hardening effects from shot peening on a Ni-based alloy using electron backscatter diffraction techniques

“…A previous study by Evans et al [3] has observed the effects of residual stress relaxation in alloy 720Li under high temperature isothermal fatigue. Included in their analysis is a study of residual stresses in a 6-8 A sample (with identical shot size and coverage) using x-ray diffraction techniques described in the introduction, without [3], predicted values of the shot peening affected zone [7], results from hardness testing and results from the EBSD misorientation tool in a nickel-based alloy subjected to shot peening at a 6-8 Almen intensity with 110H steel shot at 200 per cent coverage. in between the residual stress, and those of the EBSD misorientation tool, although they are closer to the depths determined using the EBSD misorientation tool.…”

“…Despite numerous measurements of residual stress to assess the effects of shot peening, a recent study by Guechichi and Castex [14] provides evidence that strain hardening and not residual stress is the primary contributor to fatigue resistance. Such claims are enhanced if residual stress relaxation is considered, as shown by Evans et al [3], who demonstrate that one cycle of high temperature isothermal fatigue is enough to reduce residual stress levels in a nickel-based superalloy by more than 50 per cent. More recent studies [15][16][17], have highlighted the ability of electron backscatter diffraction (EBSD) data to assess strain hardening levels in alloys, building on use of the focussed ion beam to look more carefully at surface and sub-surface features [18].…”

“…Shot peening is a process whereby many hard particles (typically steel or glass beads), known as 'shot', are directed towards the intended surface. The impact indentations of the shot induce local plastic deformation at the surface, increasing the dislocation population to impede potential crack growth, and inducing a compressive residual stress field as a result of the recovery of underlying material [1][2][3].…”

“…The method will be used at various shot peen intensities to demonstrate the ability of the tool to distinguish between these changes. A comparison with residual stress measurements using XRD for the same material presented by Evans et al [3] is made, and data are compared with predicted results from the Peenstress SM model and subsequent microhardness testing.…”

Thermal Relaxation of Residual Stresses in Shot Peened Surface Layer on TiB<SUB>2</SUB>/Al Composite at Elevated Temperatures

“…[5][6][7][8] However, there is little information on the relaxation behaviors in shot peened MMCs at elevated temperatures. The understanding of the residual stresses and work hardening states relaxations of the composite is crucial for the fatigue properties improvement.…”