In ductile fracture, the cup and cone fracture that occurs at the neck of a specimen is produced by the coalescence of internal voids which in turn grow by plastic deformation under the influence of a prevailing stress triaxiality. In this work, our concern is with regard to hydrogen embrittlement phenomena, where the presence of hydrogen influences the ductile fracture. We correlate the micro-scale void growth to the macro-scale deformation at the center part of the tensile test model of α-Iron to simulate the hydrogen effects on macro- and micro-scale model simultaneously. The tensile test model is used to determine the hydrogen effects at the macro-scale while the internal void model is used to determine the influence of hydrogen on the void growth. Loads in micro-scale are imported from the displacement results at the center part of the macro-scale tensile model. Our findings show that the proposed approach is feasible and can be implemented to correlate the micro-scale void growth to the macro-scale deformation at the center part of the tensile test model of α-Iron in the presence of hydrogen. Due to limitations of experimental data for hydrogen-material interaction, only α-Iron is considered in this study.

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The procedure for the head check initiation life prediction of railway rails has been developed. It is mainly performed by three-dimensional finite element (FE) analyses that account for the local material response generated by the contact load between wheel and rail. Both wheel and rail are modeled by FE mesh, and the wheels are loaded then rotated to the rolling direction on the rails repeatedly. The Chaboche and Lemaitre model is used to simulate the material response that is important in rolling contact situations. The results obtained from FE analyses are combined with the theory of critical distance and the critical plane approach to predict fatigue crack initiation life in the railhead. Parametric studies are performed to investigate the influence of several factors on the crack initiation life. Finally, the predictions are compared with the data obtained from the investigation in the field.

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This paper aims at building up a computational procedure to study the bio-mechanism of pressure ulcer using the finite element method. Pressure ulcer is a disease that occurs in the human body after 2 hours of continuous external force. In the very early stage of pressure ulcer, it is found that the tissues inside the body are damaged, even though skin surface looks normal. This study assumes that tension and/or shear strain will cause damage to loose fibril tissue between the bone and muscle and that propagation of damaged area will lead to fatal stage. Analysis was performed using the finite element method by modeling the damaged fibril tissue as a cutout. By varying the loading directions and watching both tensile and shear strains, the risk of fibril tissue damage and propagation of the damaged area is discussed, which may give new insight for the careful nursing for patients, particularly after surgical treatment. It was found that the pressure ulcer could reoccur for a surgical flap treatment. The bone cut and surgical flap surgery is not perfect to prevent the bone-muscle interfacial damage.

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