Experimental Observations in Stress Intensity Factor Determination Considering Plasticity‐Induced Crack Closure

This paper revisits the effects of plasticity‐induced crack closure on the experimental determination of the stress intensity factor using an experimental–numerical approach based on the displacement field measurements obtained via digital image correlation (DIC). The study focuses on the application of the CJP model, an advanced linear‐elastic crack‐tip stress‐field model that incorporates plasticity‐induced shielding effects into fatigue crack propagation analysis. For comparison, a second approach based on the J‐integral method was employed. The experimental stage involved fatigue crack growth tests under constant‐ΔK conditions, a key requirement for isolating crack‐shielding effects and validating crack growth models. For this purpose, disk compact tension (DC(T)) specimens made from 6351‐T6 aluminium and AISI 1020 steel were used. Two different loading conditions were examined, including a low‐high ΔK block loading sequence. The findings highlight the importance of incorporating crack‐shielding effects through advanced analytical models like the CJP for more accurate fatigue crack growth assessments.