Effect of Strain Gradients on Fatigue Life of C-Mn Steel Notched Tubes Under Axial and Torsion Loads: Tests and Analyses

Present study aims to investigate individual effects of strain gradient and peak equivalent strain amplitude on fatigue life of notched tubes of C-Mn steel. Remote pure axial and pure torsion strain-controlled tests have been performed for different strain gradients (owing to different hole diameter in tube specimen) subjected to same peak equivalent strain amplitude at hole tip. During the tests, local strains ahead of notch were measured using digital image correlation/strain gauge techniques. Measured strains have been compared with simulated strains using detailed finite element analyses. Additionally, fatigue life assessment has also been carried out using equivalent strain amplitude at (i) peak strain location and (ii) different distances from peak strain location. A critical distance parameter (d_c), in present study, has been deduced based on least scatter between predicted and test fatigue lives.