Influence of Errors in Young’s Modulus on Fatigue Life Predictions of Notched Round Bars Under Bending-Torsion Loading

Abstract

Elastic constants are fundamental to characterise the stress-strain behaviour of materials which is essential for an accurate design of mechanical components against fatigue failure. In this paper, the first objective is to address recent patents on the determination of elastic constants and on fatigue life prediction methods. The second objective aims at studying the effect of errors in elastic constants on fatigue life prediction. Elastic constants are determined using dynamic and static methods, namely the Impulse Excitation Technique (IET) and the Three-Point Bending Test (3PBT). Then, high-cycle fatigue tests in notched round bars subjected to different bending-torsion loading scenarios are conducted to obtain experimental fatigue lives. Finally, experimental fatigue lives are compared with fatigue life predictions obtained for the different Young's moduli obtained previously. Results demonstrated that predictions based on the IET are more accurate than those obtained from the 3PBT. Recent patents on the determination of elastic constants and on fatigue life prediction methods are also addressed.