An evolutionary model for the accumulation of fatigue damage is developed as a functional of the time history of stress in a local volume not associated with plastic deformation. The model is generalized to account for rheonomic effects: the dependence of cyclic lifetime on loading frequency and dwell times at the maximum stress within a cycle. Material constants are identified for the two-phase titanium alloy VT6 (Ti-6Al-4V analogue), which exhibits cold creep and sensitivity of fatigue properties to temporal features of cyclic loading at room temperature. New fatigue test data with various frequencies and dwell times are used. The model accurately describes these data and predicts fatigue life over a wider range of loading conditions. A fatigue life assessment is performed for a gas turbine engine component under flight cycles with dwells at maximum and intermediate stress levels, revealing significant nonconservatism of life estimates obtained via program block simplification under the linear damage summation hypothesis.

Dmitry S. Petukhov, Leading Engineer; e-mail: petuhovds@mail.ru;

Ilya E. Keller, Doctor of Physical and Mathematical Sciences, Head of the Laboratory of Nonlinear Mechanics of Solids; e-mail: kie@icmm.ru; https://orcid.org/0000-0001-9914-8870; AuthorID: 11695