Combined tension and bending fatigue life assessment method of
blade-like specimen considering the effect of non-uniform
tension-bending stress distribution and multi-damages
Abstract
This paper proposes a novel combined cycle fatigue life prediction
method of a blade-like specimen considering the effect of multiple
damage modes and complex stress state. Combined tensile and bending
fatigue (CTBF) experiments were performed on a blade-like specimen at
850°C, using a novel biaxial tension-vibration test system. To account
for the effect of high stress ratio related creep on bending fatigue
damage, a creep damage factor was proposed and explicitly introduced
into Lemaitre-Chaboche model. In the framework of continuum damage
mechanics (CDM), the CTBF life was assessed considering the
geometry-stress gradient feature factor and multiple damage modes,
including the damage of LCF, high stress ratio bending fatigue and
oxidation. Finally, a novel CTBF life prediction model was proposed,
agreeing well with the experimental results. Compared with the existing
classical models, the proposed model provides the significantly higher
prediction accuracy.