Fatigue Crack Growth Rate (FCGR) is altered by a single anomalous load exceeding cyclic maximum (Overload) or compressive load below cyclic minimum (Underload). The authors study fatigue crack acceleration due to a single compressive Underload using residual stress mapping (by synchrotron XRD) and crack closure analysis (by DIC). The relative influence and duration of these two principal causes of FCGR alteration are revealed. Validated FEA model is used for parametric analysis of the effect of baseline cyclic loading ratio and magnitude of Underload on the cyclic J-integral.
