Strain-concentration factor of circumferentially notched cylindrical bars under static tension

Abstract

A new definition of the strain-concentration factor (SCNF) has been proposed for circumferentially notched cylindrical bars under static tension. The average axial strain used in the definition of this new SNCF takes into consideration the triaxial state of stress at the net section. This is very different from the definition of the conventional average axial strain, which has been defined under uniaxial state of stress. This new average axial strain approaches rapidly 2ln( do/d) as plastic deformation develops from the notch root; this 2 In( do/d) is the average axial strain at the net section at deformation levels where elastic deformation is negligible compared with the plastic one. The value of the new SNCF increases with plastic deformation from the notch root and then decreases gradually. It becomes less than its elastic value at large deformations; however, it is larger than unity at any deformation level. This is consistent with the concave distributions of axial strain at the net section. On the other hand, the value of the conventional SNCF becomes less than unity after plastic deformation develops from the notch root. This is contradictory to the concave distributions of axial strain. The new SNCF is greater than the conventional value at any deformation level. The new SNCF approaches the conventional SNCF as the stress triaxiality decreases at the net section. The proposed SNCF is more reasonable than the conventional SNCF.