Extension and validation of the Finite Fracture Mechanics Coupled Criterion to V-notched specimens under small scale yielding conditions

We extend the Finite Fracture Mechanics Coupled Criterion (FFMCC) to V-notched specimens made of steels, where small-scale yielding occurs at the notch tip. By introducing a circular “plastic area” with a power-law degradation of the Young’s modulus, an asymptotic analysis is developed to compute the dissipated energy and failure load analytically. The coupled stress and energy release rate criteria are reformulated using matched asymptotic expansions, and tabulated functions enable straightforward failure prediction. The extended FFMCC is an easy method that requires simplified FE solutions, validated herein by four-point bending experiments (4PB) on AISI 4340 and H13 steel specimens with different V-notch angles and tempering treatments. The predicted failure loads and plastic area show very good agreement with experimental results, demonstrating the robustness and practicality of the proposed analytic extension for steels in the presence of small-scale yielding.