Influence of Errors in Young’s Modulus on Fatigue Life Predictions of Notched Round Bars Under Bending-Torsion Loading
Ricardo Branco, Jose D. Costa and Fernando V. Antunes
Affiliation: Department of Mechanical Engineering, ISEC, Polytechnic Institute of Coimbra, 3030-199 Coimbra, Portugal.
Keywords: Fatigue life prediction, Impluse Excitation Technique, resonant methods, three-point bending test, Young’s
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.
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