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Department of Engineering
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An occasional cross-disciplinary seminar series
(Information and directions for visitors)
Abstracts
Extension of the J concept for significant crack growth in ductile fracture mechanics
Professor A.G. Atkins
University of Reading
The current difficulties of predicting load-displacement-crack length behaviour during elastoplastic crack propagation are briefly reviewed, particularly in terms of applying path-independent, displacement-reversible non-linear elastic fracture mechanics (on which the Rice J-integral is based) to practical elastoplastic structural integrity problems which are both path-dependent and displacement-irreversible. The meaning of so-called JR crack resistance curves and their transferability to other problems is used to illustrate the difficulties. It is shown that even under supposed HRR J-control within the first mm or so of crack propagation, a rising JR curve may not mean an increasing resistance to cracking.
The recent closed-form solution [Proc.Roy.Soc., A454, 1998, 815] for path-dependent, displacement-irreversible elastoplastic crack propagation in the double cantilever beam testpiece is examined. An algebraically exact connexion is revealed for this geometry between the elastoplastic solution and the non-linear elastic fracture mechanics solution. It suggests how the crack-tip work of fracture and the work of remote plasticity may be uncoupled in other types of testpiece to produce a crack-tip resistance curve independent of starter crack length. This is the crack resistance parameter that should become transferable. New experimental data and re-analysis of results in the literature are used to try out the idea.
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