Very often in the open literature the crack propagation simulation is based on the linear elastic fracture mechanics. This article describes a novel application of the cyclic crack tip opening displacement (ΔCTOD) method for evaluation of the cyclic nonlinear energy release rate under large plasticity and cyclic loading conditions. In order to consider the cyclic loading in the Hutchinson-Rice-Rosengren (HRR) solution, the monotonic plastic deformation of the material behaviour needs to be replaced by its cyclic counterpart. During cyclic loading conditions, a reverse plasticity occurs and leads to a crack closure effect via blunting of the crack tip. As a result, crack flanks are in contact during compression. This effect is determined from the effective difference between the maximum and minimum crack deformation. Then, the cyclic crack tip opening displacement is evaluated by applying the Shih rule. The proposed extension of the HRR solution in application to cyclic loading conditions via stress and strain transformation as well as accounting for the crack closure effect is validated in a good agreement with Dowling and Begley Compact Tension (CT) experiment. Potential crack closure due to crack surface roughness is neglected in current modeling. The proposed methodology extends the existing HRR solution for the reliable lifetime prediction.
CTOD Application to Elastic-Plastic Fracture Mechanics Using Cyclic Ramberg-Osgood Law and HRR Solution
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Bednarz, P, Fedorov, I, & Szwedowicz, J. "CTOD Application to Elastic-Plastic Fracture Mechanics Using Cyclic Ramberg-Osgood Law and HRR Solution." Proceedings of the ASME Turbo Expo 2012: Turbine Technical Conference and Exposition. Volume 7: Structures and Dynamics, Parts A and B. Copenhagen, Denmark. June 11–15, 2012. pp. 99-107. ASME. https://doi.org/10.1115/GT2012-68161
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