Multiaxial fatigue life prediction for titanium alloy TC4 under proportional and nonproportional loading

Both proportional and nonproportional tension-torsion fatigue tests were conducted on titanium alloy TC4 tubular specimens. Six multiaxial fatigue parameters are reviewed and evaluated with life data obtained in the tests. It is found that the effective strain, the maximum shear strain and the Smith-Watson-Topper (SWT) criteria tend to give non-conservative results under nonproportional loading. The shear strain-based critical plane approaches, especially Wu-Hu-Song (WHS) approach show better life prediction abilities. The prediction results based on WHS parameter are all within a factor of two scatter band of the test results.