Dynamic Perturbation of A Propagating Crack: Implications for Crack Stability
A general perturbation solution for the stress-intensity factors at the edge of a propagating crack whose surface is slightly undulating and whose edge is not quite straight is briefly reviewed, in the case that the medium through which the crack propagates is viscoelastic. This solution (which was generated in collaboration with A B Movchan) has already been exploited to demonstrate the persistence of “crack front waves” in the high-frequency limit, as well as to find the lowest-order corrections (which induce dispersion and attenuation) when the frequency is large but not infinite. So far, crack front waves have been studied, allowing only in-plane perturbation of the crack edge. Here, the corresponding formulae are summarised for a general three-dimensional perturbation, together with the forms to which they reduce in the high-frequency limit. Such formulae are expected to form the basis for an explanation of “Wallner lines”. At finite frequency, they provide a base for conducting a general study of the linear stability of a rectilinear propagating crack. Such a study has been completed in the special case of two-dimensional perturbation (plane strain), reported by O Obrezanova in these Proceedings.
KeywordsCrack propagation viscoelastic medium crack front waves crack stability
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