Investigation of plasticity–induced fatigue crack closure

Abstract

Plasticity-induced crack closure and constraint effects due to finite plate thickness are both fundamental aspects in the mechanics of fatigue cracks. Moreover, plasticity-induced crack closure provides an effective first-order correction to the crack driving force, as used in the correlation and prediction of fatigue crack growth. The approach developed in this study utilises the distributed dislocation technique to model fatigue cracks growing under constant amplitude loading infinite thickness plates. Numerical results are obtained through the application of Gauss-Chebyshev quadrature and are presented for the crack opening stress ratio. An excellent agreement is observed with previous three-dimensional finite element studies.

Keywords:

• Crack closure
• crack opening stress
• crack tip plasticity
• distributed dislocation technique
• edge dislocation
• plate thickness effect
• through-the-thickness crack.

Additional information

Notes on contributors

J Codrington

John Codrington completed his Bachelor of Engineering (Mechanical) with honours at the University of Adelaide in 2005, and is currently studying for a PhD at the same institution. John received an Australian Postgraduate Award for his studies into non-linear individual and interaction phenomena in fatigue crack growth. This study involved the theoretical investigation of fatigue crack growth based upon the popular mechanism of plasticity-induced crack closure. From these studies, new techniques for predicting fatigue crack growth have been developed based on the distributed dislocation technique. The effects of plate thickness were directly included by utilising first-order plate theory. A thesis by publication was submitted in mid-July and is currently under examination. In association with these publications, John was a winner of a postgraduate travel award for a paper presented at an ACAM conference in 2007.

General research interests include fracture mechanics, fatigue, structural health monitoring, biomechanics and composites. Some current projects that John is involved with include the development and investigation of a slurry spray based method for thermal barrier coatings (sponsored through the Asian Office of Aerospace Research and Development), the development of a new strain compatibility based method for crack detection and consultant work for ASC. In conjunction with his research interests, John is actively involved in teaching and tutoring undergraduate students in Stress Analysis and Design, Aerospace Structures, Solid Mechanics, and Fracture Mechanics at the School of Mechanical Engineering within the University of Adelaide. John is also a member of Engineers Australia.

A Kotousov

Dr Andrei Kotousov completed his PhD study at the Russian Academy of Sciences in 1993, and is currently Senior Lecturer at the School of Mechanical Engineering, University of Adelaide. He teaches the Solid Mechanics, Fracture Mechanics, and Stresses in Plates and Shells courses at the School, supervises PhD and Master Degree Students, and is actively involved into a number of large research projects.

Andrei has broad experience in theoretical and experimental fracture mechanics, biomechanics, structural health monitoring and composite materials, having produced more than 100 peer reviewed publications in these areas. He has developed strong collaborative relationships within both the Australian and international defence industries. The Australian Submarine Corporation, the US Air Force and the Australian Defence Science and Technology Organisation all currently support his work through research grants. In the past three years, Andrei has been actively involved in biomedical studies. This work has resulted in the development of new and growing collaborations between the fracture mechanics group at the University of Adelaide headed by Andrei and the Institute of Medical and Veterinary Science, Royal Adelaide Hospital, Queensland University of Technology and the University of Sydney. Andrei was recently awarded an ARC Discovery grant in fracture mechanics. He serves as a regular reviewer for international journals, conferences, and national and international grant applications.