Influence of low-angle grain boundaries on short fatigue crack growth studied by a discrete dislocation method

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Influence of low-angle grain boundaries on short fatigue crack growth studied by a discrete dislocation method

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Publication Conference Paper, peer reviewed
Title Influence of low-angle grain boundaries on short fatigue crack growth studied by a discrete dislocation method
Author(s) Bjerkén, Christina ; Melin, Solveig
Date 2008
English abstract
The growth of short fatigue cracks in or below the threshold regime are highly influenced by the local microstructure. In the present study, the influence of low-angle boundaries on the growth and arrest of microstructurally short edge cracks in crystalline material is investigated using a discrete dislocation method. The crack is modelled by boundary elements consisting of dislocation dipoles. An external load that is fully reversed during the fatigue cycle is applied to obtain a crack growth rate of a few Burgers vector per cycle. The crack growth and the developing plasticity are given by the emission, and eventual annihilation, of dislocations at the crack tip. The low-angle grain boundary is modelled as an array of aligned dislocations. It is found that the developing local plasticity, is crucial for the growth rates. Different stress ranges are used and both positive and negative low-angle grain boundaries are considered. It is found that depending on sign of the of the grain boundary, different growth behaviour are found. Generally, a positive low-angle grain boundary gives a low, rather stress range independent growth rate. A negative grain boundary results in increasing crack growth when the stress range is increased. The distance between the crack tip and the low-angle boundary is found not to significantly influence the crack growth characteristics, for the geometries and load ranges considered in this study.
Publisher VUTIUM Brno, Czech Republic
Host/Issue Proceedings 17th European Conference on Fracture, Brno 2008
Language eng (iso)
Subject(s) fatigue
short crack
low-angle grain boundary
crack growth
discrete dislocations
Technology
Research Subject Categories::TECHNOLOGY::Engineering mechanics
Handle http://hdl.handle.net/2043/7475 (link to this page)

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