Non-local volumetric approach to analysis defect's shape influence on specimens durability subjected to bending and torsion

Abstract

The influence of defect features on fatigue behaviour is a complex trivial issue. Although the important advances over the last decades, the dialectical relationship between the defect orientation and durability is not clearly understood. The paper aims at studying the influence of the orientation of elliptical defects on the durability of samples made of C45 steel. Three types of samples with elliptical defects were subjected to cyclic bending and torsion (R = -1) in the form of a one-sided notch oriented at various angles, namely 45, 60 and 90°. The stress analysis was performed using local and non-local methods in order to determine an equivalent stress amplitude. The stress fields surrounding the defects were evaluated via three-dimensional numerical models. Then, the results were compared with the results obtained for smooth samples. The results show that the defect orientation has a higher effect under bending loading than under torsion and that the defects oriented perpendicularly to the longitudinal axis of the specimen are more detrimental.