Low cycle fatigue of steels under biaxial straining

Abstract

A cruciform test specimen and a loading rig are described, by which any combination of biaxial strains can be applied to a specimen. With the pressurizing equipment so far available, three states of strains have been investigated for two steels. In the mild steel used, large inclusions oriented in the roll direction aided fracture propagation when a maximum shear plane coincided with the roll direction. When not influenced by inclusions, fatigue life is related to total strain range by Coffin's law         ∊ N a = C The values of α and C are different for different states of strains. Empirical formulae are given to predict results for other states of strains.