Multiaxial low cycle fatigue life of Ti-6Al-4V under non-proportional loading with mean strain

The mean strain effect on the multiaxial low cycle fatigue behavior of Ti-6Al-4V was investigated. Strain-controlled multiaxial low cycle fatigue tests at room temperature were carried out using a tubular specimen in tension and torsion loadings. Strain paths employed were four types of proportional and non-proportional loadings. Failure lives are affected by not only the non-proportionality of stress and strain histories but also the mean stress and strain. This study discusses the failure life properties based on the test results obtained and also shows strain parameters for the life evaluation under non-proportional loading with mean strain. The proposed strain parameters, where Findley and Walker models were applied within a non-proportional strain range, were suitable parameters to evaluate the life for Ti-6Al-4V under non-proportional straining with mean strain.