The effects of low‐plasticity burnishing (LPB) on the fatigue life of friction‐stir‐processed (FSP) Al 7075‐T6 plates were examined experimentally and numerically. Aluminum samples were taken from plates to test fatigue response in the presence of heat‐affected zone (HAZ) at different loading magnitudes. Finite element method was employed to numerically evaluate fatigue life of FSPed samples by means of the Smith–Watson–Topper (SWT) model. Through numerical analysis, the FSP and its cooling procedure were modelled on the basis of the arbitrary Lagrangian–Eulerian technique, and then, the effect of the LPB to assess fatigue response of samples was examined. Aluminum samples undergoing friction‐stir process presented lower‐fatigue life as stresses were highly concentrated within FSP regions. Involvement of LPB regained fatigue durability through compressive residual stress induced on the aluminum samples. The higher applied force over the LPB promoted compressive residual stress on the sample surface and improved fatigue life of samples. The predicted life results were found twice more in magnitude than those of experimentally obtained.

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In this study, a three-dimensional finite element model was developed to predict the fatigue life of composite bolted joints. In this model, progressive damage theory was used. The fatigue characterization was based on Hashin’s failure criteria which recognize the failure modes. To decrease the number of unidirectional tests, the effects of load ratio were considered based on Kawai’s criterion. A modified form of Miner’s rule was proposed to calculate the damage parameter. This equation corrected the effects of the fatigue failure cycles and included the effects of different load ratios. Also, this model could decrease the overestimation of the fatigue life predictions. All of the formulations were combined and used in a step-by-step solution. In this respect, a new iterative algorithm was developed so that at each step of solution, the material properties of all failed layers of each element were reduced according to the failure mode and sudden degradation rules. The estimated fatigue life was compared to the experimental data, and an excellent correlation between the results was observed. This model could monitor the damage propagation in fabricated joints.

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The main aim of the present study is to investigate the fatigue behavior of single friction stir spot welds (FSSW) using strain-based modified Morrow's damage equation. The correlation between microhardness, cyclic material constants, and mechanical strength of different zones around the FSSW are assumed to be proportional to the base material hardness. Experimental fatigue tests of friction stir spot welded specimens have been carried out using a constant amplitude load control servo-hydraulic fatigue testing machine. ANSYS finite element code has been used to simulate a single tensile shear friction stir spot welded joint, and non-linear elastic-plastic finite element analysis has been employed to obtain the values of local equivalent stress and strain near the notch roots of the joints. The results based on the numerical predictions have been compared with the experimental fatigue test data. It has been shown that the strain-based approach does a very good job for estimating the fatigue life of friction stir spot welded joints.

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