A SIMPLE TEST METHOD FOR ENERGY-DISSIPATION RATE, CTOA AND THE STUDY OF SIZE AND TRANSFERABILITY EFFECTS FOR LARGE AMOUNTS OF DUCTILE CRACK-GROWTH

Simple extensions to the standard deep notch bend test procedure are s uggested to allow the collection of data relevant to the energy dissip ation rate, D, crack opening angle, COA, and J, all for arbitrarily la rge amounts of growth in extensive plasticity. The methods of analysis are detailed for real elastic-plastic behaviour of a high strength lo w-hardening type metal with a view to encouraging use on a wider range of materials. A proposal is made, and equations given, that the parti cular version of J used for an R-curve derived from the area under the loading diagram, should correspond to the value of the far-held integ ral, J(ff). The relationship between the global measure of COA that em erges from D and the local crack tip opening angle, CTOA, as used in c omputational studies, is established. Transferability of CTOA data is examined in the light of effects of size and configuration. An explici t rule of the form CTOA root G=f (material and configuration) is propo sed for the modelling of ductile growth in finite element studies. It is applied to a set of data in the literature, for the variation of CT OA with size in the deep notch bend test and for the configurations, b ending, double edge and centre cracked tension.