Zatsarna O. Anisotropy of brittle strength of deformed polycrystalline metals with b.c.c. lattice

Findings on experimental investigations of the effect of tensile and compressive prestrain on the level of brittle strength of deformed metal are presented in the thesis. Analysis is carried out for steel 30, steel 10G and betta-titanium alloy. Technique of experimental determination of the value of brittle strength of deformed material is developed. It is ascertained experimentally that prestrain can give rise to both increase in the level of brittle strength and to it decrease. The effect of texture sharpness on the level brittle strength of deformed metal is examined. Existence of critical values for angles of texture component smearing, starting from which the effect of texture on brittle strength appears, is established. It is found that above values depend on material and texture. Model of brittle fracture of deformed metal is offered, according to which crystallographic texture and residual microstresses are main reasons influencing the level of brittle strength of deformed metal. The effect of crystallographic texture on brittle strength is due to change in orientations of the crack nuclei opening relatively to the applied stress direction. Dependence of brittle strength on the level of microstresses is because of their effect on the CN stability and is characterized by the "orientation" effect.