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Abstract: In this research, fracture of dissimilar friction stir welded (FSWed) joint made of Al 7075‐T6 and Al 6061‐T6 aluminum alloys is investigated in the cracked semi‐circular bend (CSCB) specimen under mixed mode I/II loading. Due to the elastic‐plastic behavior of the welded material and the existence of significant plastic deformations around the crack tip at the propagation instance, fracture prediction of the FSWed specimens needs some failure criteria in the context of the elastic‐plastic fracture mechanics which are very complicated and time‐consuming. For this purpose, the Equivalent Material Concept (EMC) is used herein by which the tensile behavior of the welded material is equated with that of a virtual brittle material. By combining EMC with the 2 brittle fracture criteria, namely the maximum tangential stress (MTS) and mean stress (MS) criteria, the load‐carrying capacity (LCC) of the FSWed CSCB specimens is predicted. Comparison of the experimental results and theoretical predictions from the 2 criteria showed that both criteria could accurately predict the LCC of the cracked specimens. Moreover, as the contribution of mode II loading increases, the size of the plastic region around the crack tip at failure increases, leading to increasing the LCC. [ABSTRACT FROM AUTHOR]

This paper investigates the effects of the first non-singular stress terms on the fracture assessment of sharp V-notches under mixed mode loading. First, numerical studies have been performed on a fracture test configuration called single V-notched ring (SVR) specimen. Then, the notch stress intensity factors as well as the coefficients of the first non-singular stress terms, which are vital parameters in brittle fracture of V-notched components, were calculated via a finite element over-deterministic algorithm for a wide range of loading and geometry conditions. The obtained results demonstrate that the SVR specimen is able to provide a complete range of mode mixities from pure mode I to pure mode II loading conditions. The numerical results, next, have been converted to dimensionless parameters and are illustrated in several graphs. Indeed, these graphs can be easily employed by the engineers for rapid calculation of the corresponding notch stress intensity factors and the coefficients of the first non-singular stress terms in the SVR specimen. The obtained fracture parameters are then submitted to the maximum tangential stress criterion to assess the effects of the first non-singular terms on fracture behaviour of the specimen. Finally, an experimental study has been performed on the SVR specimen made of Nayriz Marble rock for two notch angles with a complete range of mode mixities. The obtained experimental data confirm the significant role of the first non-singular stress terms. In fact, these results show that considering only the singular stress terms may induce an average error of 38% in the predicted fracture loads, which can be decreased to about 12% just by adding the contribution of the first non-singular terms to the maximum tangential stress criterion. [ABSTRACT FROM AUTHOR]

Mixed-mode fracture parameters were determined numerically for a cracked straight-through flattened Brazilian disk (CSTFBD) specimen containing an angled center crack and subjected to diametral-distributed uniform compressive loading. The stress-intensity factors ( and ) and the -stress were calculated from finite-element analysis for different values of the crack angle, crack length, and specimen height. The fracture parameters (, , and ) decreased by reducing the height of the CSTFBD specimen. Furthermore, the pure Mode II crack inclination angle decreased in the CSTFBD specimen for larger crack lengths and smaller specimen heights. The -stress was always negative for all mode mixities. Also, the influence of the specimen height on the fracture parameters was more pronounced than the other affecting parameters, such as crack length. [ABSTRACT FROM AUTHOR]

Different laboratory experiments are usually conducted to characterize the fracture behaviour and integrity properties of newly developed structural materials. However, the reported fracture tests data for an improved high strength cement mortar (HSCM) under combined tension-shear loading are not in agreement with theoretical predictions obtained from well-known fracture criteria. It is shown in this paper that the significant difference existing between the experimental and theoretical results is due to ignoring the effect of T-stress on the processes of crack growth in the HSCM test specimens. A modified fracture model is then used to show that the theoretical predictions can be corroborated by the experimental results when the effect of T-stress is taken into account. [ABSTRACT FROM AUTHOR]