ELASTIC-PLASTIC FRACTURE MECHANICS FOR INITIATION AND PROPAGATION OF NOTCH FATIGUE CRACKS |
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| Authors: | M. M. HAMMOUDA,R. A. SMITH&dagger ,K. J. MILLER&Dagger |
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| Affiliation: | Research Fellow, University of Sheffield;Lecturer, University of Cambridge;Professor, University of Sheffield |
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| Abstract: | Abstract Initiation and propagation are considered to be controlled by the extent of total plastic shear deformation φ. Crack initiation and crack propagation occur when φ, exceeds a critical threshold value which can be equated to threshold conditions determined from linear elastic fracture mechanics analyses. When a crack is in a plastically deformed zone φt=φ p +φ e . where φ p is the component of φ t due to notch bulk plasticity and φ e , is the component of φ t due to a linear elastic fracture mechanics (LEFM) analysis of the crack tip plasticity field.
When cracks initiate at notch roots φ t > φth. As the crack propagates in the notch plastic zone the rate of decrease of v p will be different from the rate of increase of φ e and it is possible for φ t to decrease to a level below φth thereby creating a non-propagating crack. |
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