Influence Of Yield Stress Research Articles

The influence of yield stress on fracture of NaCl crystals

The critical force for crack initiation in NaCl crystals is measured as a function of yield stress (τy). Dislocation slip bands generated at the crack tip are observed. For τy > 1.5 MN/m2, the crack extends without generating dislocations. For τy < 1.5 MN/m2, dislocation slip bands are introduced on {110} planes obliquely backward from the crack tip, and the degree of the local plastic deformation is insensitive to the yield stress. With decreasing yield stress, the critical force for crack extention becomes smaller. Die kritische Kraft fur die Risausbreitung in NaCl-Kristallen wird im Zusammenhang mit der Fliesspannung (τy) gemessen, und die am Kopf des Risses hervorgerufenen Gleitbander werden beobachtet. Fur τy > 1,5 MN/m2 breiten sich die Risse sprode aus, ohne Versetzungen hervorzurufen. Fur τy < 1,5 MN/m2 werden Gleitbander in {110}-Ebenen schrag ruckwarts um den Riskopf hervorgerufen; die Grose der lokalen plastischen Verformung ist fast unabhangig von der Fliesspannung. Mit abnehmender Fliesspannung nimmt die kritische Kraft fur die Risausbreitung ab.

A model for the initiation of hydrogen embrittlement cracking at notches in gaseous hydrogen environments

A model for the initiation of hydrogen embrittlement cracking in gaseous hydrogen environments is presented. The model is based on the stress-induced diffusion of hydrogen atoms to the regions of high triaxial stress ahead of a plastically strained notch. The influence of yield stress and notch geometry on the apparent threshold stress intensity for embrittlement are considered and derived analytically. The time dependence for crack initiation for apparent stress intensities above the threshold is derived from a simple diffusion model. The results of the model are in agreement with reported hydrogen embrittlement phenomena.

Economy of High Strength Steel Structural Members

Several types of structural members are analyzed to determine how higher strength steels can be used to their greatest advantage; influence of yield stress, modulus of elasticity, and price on optimum proportioning of structural members; it is demonstrated that through optimum design, application of higher strength steels can lead to significant material-cost savings for lighter weight structures.

A study of the relation between the brinell hardness and the grain size of annealed carbon steels

When modelling the fracture toughness of the investigated AISI M2 high-speed steel, the stress-modified critical strain criterion was used. The very important influence of microstructural parameters such as the volume fraction of undissolved eutectic carbides, their mean diameter, and the mean distance between the carbides, as well as the volume fraction of retained austenite in the matrix, was also taken into account. The influence of yield stress and fracture ductility was expressed in terms of the hardness of the steel. It was found that the plastic zone which develops, during fracture toughness measurements, ahead of the fatigue crack tip, was, as a rule, smaller than the prior austenite grain size, so that, in the case of the investigated high-speed steel, the size of these grains did not have any influence on the measured fracture toughness value. However, importantly, the calculated fracture toughness values, which were derived using a newly developed semi-empirical equation, agreed well with the experimental results obtained by the authors, as well as with results obtained by other authors.