PSI - Issue 19

Fabian Becker et al. / Procedia Structural Integrity 19 (2019) 645–654 F. Becker et al. / Structural Integrity Procedia 00 (2019) 000–000

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Fig. 9. Damaged specimen surfaces after the fatigue testing with a target bolt load of 5 kN (T = Tension side; C = Compression side)

Fig. 10. Normalized S-N plot with reference test results and the 5 kN bolt load results

For intermediate equivalent bending strains, delamination initiation and growth are reflected in a loss of dynamic sti ff ness. However, compared to higher loaded specimens, delamination growth initiates at the end of the clamping section and remains confined at the surface. For low equivalent bending strains, a slow symmetrical delamination growth is visible, which lies on the surface of the specimen. The lives of the clamped specimens are significantly shorter than the reference testing series due to the introduction of additional failure modes due to additional fiber transverse stresses introduced by the clamping. The results show that a life estimation of a longitudinal leaf spring based on three point bending experiments on specimen level without considering the influence of a clamping will overestimate the fatigue life leading to a non-conservative fatigue design.