THE PLASTIC COMPONENT OF THE DEFORMATION J-INTEGRAL FOR A STATIONARY CRACK - THE SMALL-SCALE YIELDING SITUATION

Against the background of the desirability of having a reliable methodology for quantifying a material's crack growth resistance, the paper derives a general expression which relates the plastic component J(p) of the deformation J integral (J(D)) for a stationary crack to the crack tip stress intensity, when the yielding is small-scale; J(p) can then be expressed in terms of the energy integral via a composite eta factor eta-COMP. It is thereby possible to examine the overall accuracy of eta factor descriptions of J(p), that are obtained on the basis of limit load considerations; the paper examines the accuracy for the compact tension specimen geometry. More generally, the small-scale yielding results can be coupled with those for the extensive yield state, so as to give a simple procedure for obtaining the two eta factors eta and eta-c appropriate to a two eta factor description of J(p).