Fracture mechanics assessment of large diameter wind turbine bearings

The structural integrity of large diameter wind turbine bearings have been investigated using the built-in “contour integral” tool in ABAQUS finite element software package by modeling three-dimensional penny-shaped cracks and evaluating the stress intensity factors. In order to sub-model a crack and investigate the fracture mechanics of the rolling contact between the rollers and the raceway, a python script was developed and implemented in the analysis. Important steps to build the crack model are detailed and recommendations are made for further use of the finite element modeling tool in compressive mixed mode fracture mechanics assessment of wind turbine bearings. Moreover, the influence of initial residual stresses due to induction hardening of the raceway is also investigated and discussed in this paper. For frictionless contacts between the two crack faces, “contour integral” in ABAQUS appears to be a suitable method to obtain accurate stress intensity factor solutions for modes II and III. The results from this study are validated through comparison with the analytical solutions available in the literature and are expected to facilitate numerical life assessment of wind turbine bearings.