Comparative Analysis of Fatigue Life Predictions in Lateral Notched Round Bars under Multiaxial Loading

Abstract

The main objective of this study is to predict the multiaxial fatigue life for lateral notched round bars made of DIN 34CrNiMo6 high strength steel. In-phase bending-torsion tests for different stress amplitudes and different ratios of the normal stress to the shear stress were performed. Single torsion and single bending tests were also conducted for different stress amplitudes. In addition, the beach marking technique was used to mark crack fronts on fracture surfaces for the different loading paths studied. Experimental fatigue life was compared with predictions obtained by the Coffin-Manson model. The stress-strain state at the notch root was evaluated using the Theory of Critical Distances (TCD) and the Equivalent Strain Energy Density (ESED). Finally, a comparative analysis of the fatigue life predictions obtained by the two above-mentioned approaches was carried out. The former gave good results for higher lives but was too conservative for lower lives. The latter led to good correlations in the range studied here.