Fatigue Life Evaluation Using the Damage‐Equivalent Strain for 7075‐T6 Aluminum Alloy Under Bending and Torsion Bending Vibrations

ABSTRACT The vibrations caused by external factors (such as fluids) or internal factors often pose strength‐related problems in mechanical and structural components. Although several studies have investigated the material fatigue characteristics during vibration, reports on complex vibration modes such as torsion bending are limited. In this study, we addressed this gap by conducting experiments and finite element analyses on I‐ and L‐shaped aluminum alloy specimens under bending and torsion bending vibrations, respectively. We established a reliable method to estimate the strain at the notch by utilizing the strain measured at a position outside the notch and a ratio derived from finite element analysis. This method allows for accurate assessment of the critical strain history without interfering with crack observation. Using the strain range at the crack initiation site effectively unified the fatigue life evaluation for both specimens.