The studies related to metals damage under cyclic loading as the dominant form of structural failure is reviewed. The early approaches including stress-based and strain-based as well as the later approaches of energy-based, critical plane-based and damage mechanics-based are briefed on. Recent methods including thermography, finite element, and microstructural are summarized and explained. Different phenomenon occurring under cyclic loading are explained including fatigue crack initiation, crack propagation, fretting, and buckling. This review provides insight on the underlying mechanisms of different fatigue damage types and related proposed models. In addition, it explains the different aspects of each model along with their methodology.
In the present research work, constrained groove pressing as one of the sheet's severe plastic deformation is employed at elevated temperature to investigate the influence of this technique on the microstructural evolutions and mechanical properties of 2024 aluminum and AZ91D magnesium alloy sheets. With this regard, three cycles of constrained groove pressing have been conducted on these alloys' annealed sheets. Optical microscopy and X-ray diffraction were used to discuss the microstructure and crystallographic texture evolution. Results demonstrated that the average grain size of the annealed specimens was decreased to 11 µm and 14 µm after one pass at 300°C for 2024 Al and AZ91D Mg alloys, respectively. By measuring the microhardness, it was found that the annealed sample has the highest homogeneity with the minimum inhomogeneity factor 5.80 and 1.86 for the 2024 Al and AZ91D Mg alloys, respectively. The ultimate tensile strength of the annealed sheet was respectively increased up to 21% and 7% for these alloys by performing the first constrained groove pressing pass. Also, all of the mechanical properties variations are changed based on crystallographic texture evolutions.
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