CRITICAL STRAIN AND DAMAGE EVOLUTION FOR CRACK GROWTH FROM A SHARP NOTCH TIP OF HIGH-STRENGTH STEEL

This paper proposes details of an approach that uses expressions of fracture strain and damage evolution as functions of stress triaxiality for notch-free specimens to predict their values for crack growth from a sharp notch tip of a single-edge-notched bend (SENB) specimen. Experimental testing and finite element (FE) modelling are used to determine the basic mechanical properties and deformation behaviour of those specimens, which are needed to calibrate model constants in the proposed approach and to validate prediction from the approach. Three types of mechanical testing were conducted, using standard smooth tensile, short-gauged tensile and standard SENB specimens. The FE modeling is to establish constitutive relationship between stress and strain for notch-free specimens so that the FE modeling can be used to determine parameters such as stress triaxiality and unloading modulus for the prediction of fracture strain and damage evolution at the sharp notch tip of SENB specimen. The study will then examine whether the proposed approach can predict the trend of variation for fracture toughness among three high-strength steels, which is an on-going study and the results will be presented in the conference.