In-situ SEM observation and crystal plasticity finite element simulation of fretting fatigue crack formation in Ni-base single-crystal superalloys

Fretting fatigue behavior of Ni-base single crystal (NBSX) superalloys was investigated based on in-situ scanning electron microscope (SEM) observations. Evolutions of slip lines and initiations of cracks were observed. Slip lines were found on specimen free surface along three typical directions. Short cracks were observed to initiate along the slip line. Crystal plasticity constitutive model considering cyclic hardening effect was employed. Crystal plasticity finite element method (CPFEM) simulation showed the activations of crystallographic slip systems at contact region. The slip plane with the maximum plastic slip was determined as dominate slip plane. Equivalent plastic strain was proved effective to predict crack initiation. The simulation results including predicted slip lines, crack initiation locations and orientations were in good agreements with observations.