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The aim of the current work was to study the effect of laser shock peening (LSP) when applied to 2‐mm thick 2024‐T351 aluminium samples containing scratch‐like defects in the form of V‐shaped scribes 50 to 150 μm deep. The scribes decreased fatigue life to 5% of that of the pristine material. The effect of laser peening on fatigue life was dependent on the specifics of the peen treatment, ranging from further reductions in life to restoration of the fatigue life to 61% of pristine material. Fatigue life was markedly sensitive to near‐surface tensile residual stress, even if a compressive residual stress field was present at greater depth. Fatigue life after peening was also dependent on sample distortion generated during the peening process. Sample distortion modified local stresses generated by externally applied loads, producing additional life changes. Models based on residual stress intensity and crack closure concepts were successfully applied to predict fatigue life recovery. [ABSTRACT FROM AUTHOR]

Measurements are made of the stress developed in near-spherical elastic inclusions in an elastic plastic matrix under both tension and compression loading. Two experimental conditions are reported. The first case is where no thermal mismatch exists between the inclusions and the matrix, so that the stress in the inclusion is purely a result of the misfit in the elastic moduli and of the distortion of the plastic slip-line field around the inclusion. The observations are believed to be the first such and are in qualitative agreement with finite-element modelling for idealised inclusion distributions. The second case is the more usual one where a thermal misfit stress exists and observations are reported of the stress relief effects caused by the interaction of the plasticity-induced stress with the thermal and elastic misfit stresses. [ABSTRACT FROM AUTHOR]

Laser shock peening has become a commonly applied industrial surface treatment, particularly for high-strength steel and titanium components. Effective application to aluminum alloys, especially in the thin sections common in aerospace structures, has proved more challenging. Previous work has shown that some peening conditions can introduce at-surface tensile residual stress in thin Al sections. In this study, we employ finite element modeling to identify the conditions that cause this to occur, and show how these adverse effects can be mitigated through selection of peen parameters and patterning. [ABSTRACT FROM AUTHOR]

• Residual stress mapping provides an efficient alternative to welding process simulations. • Upper bound distributions of experimental data secure conservatism in integrity assessments. • Internal equilibrium in the FE model play important role in residual stress mapping. Residual stress is a factor which potentially affects the integrity of welded components. We have developed a methodology of assessment to establish the state of residual stress in a butt-welded plate by using a limited set of experimental measurements obtained using neutron diffraction. The unique longitudinal and transverse residual stress components, as a result of the welding process, are measured across the weld in three depths through the thickness. The measured residual stresses are then used to estimate a stress distribution for each stress component. The estimated stress distribution is then mapped to a finite element model of the weld plate, before adopting an iterative solution to reconstruct the residual stress fields. In addition, a traditional welding simulation is performed using the same weld plate details to predict and compare the residual stress distributions. It is shown that accurate residual stress field reconstruction is possible in and around the area of measurement using the limited measurement data from the neutron diffraction technique. In the estimated stress profiles, an upper-bound distribution is implemented in the weld and Heat Affected Zone (HAZ). This increases the efficiency and reduces the complexity of modelling. In the meantime, conservatism in the estimated stress is secured. [ABSTRACT FROM AUTHOR]

This paper presents results of fatigue crack growth testing of aluminium alloy 2624-T351 reinforced by bonded crack retarders made of GLARE fibre-metal laminate. Specimens were tested at room temperature, 70 °C and −60 °C. Better performance of the crack retarders in terms of increased fatigue life was achieved at room temperature than at the two temperature extremes. This is attributed to a combined effect of change in the fatigue crack growth rate at temperature in the substrate material, and residual stress generated at temperatures above or below room temperature. The change in fatigue crack growth rate was measured, and the substrate deformation and the stress intensity factors at temperature were calculated by Finite Element Analysis. In addition, the effect of thermal cycling on fatigue crack growth rate was investigated by exposing the specimens to repeated thermal cycles between 70 °C and −60 °C prior to fatigue testing. It is concluded that the pre-test thermal cycling has little effect on the fatigue crack growth rate. [ABSTRACT FROM AUTHOR]