Effect of mean shear stress on torsion fatigue failure behavior of 2A12-T4 aluminum alloy

• Fatigue test of 2A12-T4AA is conducted under torsion fatigue loading.
• A threshold is found to distinguish the mean shear stress effect in torsion fatigue.
• Macro- and micro-analysis are conducted to obtain the fracture characteristics.

Fatigue experiments with solid cylindrical bar specimens were carried out to investigate the effects of mean shear stress on the torsion fatigue failure behavior of 2A12-T4 aluminum alloy. The torsion S–N curves under different values of mean shear stress were obtained. Experiment results showed that fatigue life under the same shear stress amplitude gradually reduces with increasing the mean shear stress, when mean shear stress is lower than a threshold value. Macro-analysis and micro-analysis of specimen fracture appearance were conducted in order to obtain the fracture characteristics for different mean shear stress values under torsion fatigue loading.