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Vehicle weight reduction through the use of components made of magnesium alloys is an effective way to reduce carbon dioxide emission and improve fuel economy. In the design of these components, which are mostly under cyclic loading, notches are inevitably present. In this study, surface strain distribution and crack initiation sites in the notch region of AZ31B-H24 magnesium alloy notched specimens under uniaxial load are measured via digital image correlation. Predicted strains from finite element analysis using Abaqus and LS-DYNA material types 124 and 233 are then compared against the experimental measurements during quasi-static and cyclic loading. It is concluded that MAT_233, when calibrated using cyclic tensile and compressive stress-strain curves, is capable of predicting strain at the notch root. Finally, employing Smith-Watson-Topper model together with MAT_233 results, fatigue lives of the notched specimens are estimated and compared with experimental results.

Interest in magnesium, as the lightest engineering metal, has increased in the automotive industry as a result of requirements for lighter and cleaner vehicles. Resistance spot welding (RSW) is already the predominant mode of fabrication in this industry, and the fatigue of spot welded magnesium sheet must be studied. In this study, the tensile and fatigue strength of resistance spot welded AZ31 Mg alloy was studied. Three sets of tensile shear spot welded specimens were prepared with different welding parameters to achieve different nugget sizes. Metallographic examination revealed grain size changes from the base material (BM) to heat affected zone (HAZ) to the fusion zone (FZ). Monotonic tensile and fatigue tests were conducted and the effect of nugget size on tensile shear and fatigue strength was discussed.

Fatigue durability of structural components depends on geometrical features, material fatigue properties, and service loading. The scatter of the three basic factors affects also the scatter of the fatigue durability of those objects. In order to estimate the scatter of predicted fatigue durability it is necessary to describe in a consistent way the variability of the input data, i.e. the scatter of the geometrical parameters and resulting stress concentration factors and the stress magnitude and distribution in critical regions, the scatter of the material properties, and the scatter of the applied load. The statistical data, mathematical tools and their practical use leading to the evaluation of fatigue reliability and durability of welded structures in earth moving machinery is the subject of the discussion presented below.

Results concerning Finite Element stress analysis and fatigue life predictions of various thin-walled structures designed according to the Statically Admissible Discontinuous Stress Fields (SADSF) method are presented and discussed in the paper. The SADSF method is one of a very few approaches enabling effective, from the load limit analysis viewpoint, design of geometrical shapes and spatial distribution of the material for prescribed geometrical and load boundary conditions. The resultant geometry of the structure is obtained by satisfying equilibrium conditions and maintaining the same equivalent stress in each of the discrete regions of the object. Such requirements can be satisfied if a relatively simple material model is used and as a consequence the ideal rigid-plastic material model is used when the system of discrete statically admissible stress field is looked for.

Computer simulations based on the Monte Carlo method are often used for the probabilistic assessments of fatigue lives of structures and mechanical components. This is due to relatively easy simulation and reliability calculation procedure, particularly if the direct Monte Carlo method is applied. The only disadvantage of such a method is the necessity of large number of repetitions required for a high level of reliability. Useful tips enabling the decrease of the number of samplings in the simulation procedure and preserving the required reliability level are the subject of the discussion presented below.