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

The removal of information from working memory

What happens to goal-relevant information in working memory after it is no longer needed? Here, we review evidence for a selective removal process that operates on outdated information to limit working memory load and hence facilitates the maintenance of goal-relevant information. Removal alters the representations of irrelevant content so as to reduce access to it, thereby improving access to the remaining relevant content and also facilitating the encoding of new information. Both behavioral and neural evidence support the existence of a removal process that is separate from forgetting due to decay or interference. We discuss the potential mechanisms involved in removal and characterize the time course and duration of the process. In doing so, we propose the existence of two forms of removal: one is temporary, and reversible, which modifies working memory content without impacting content-to-context bindings, and another is permanent, which unbinds the content from its context in working memory (without necessarily impacting long-term forgetting). Finally, we discuss limitations on removal and prescribe conditions for evaluating evidence for or against this process