A compliance-based approach to measure fracture resistance curve for surface cracked steel plates

Abstract

This paper proposes a compliance-based approach to determine the fracture resistance \[J\]–\[R\] curve for surface cracks in high-strength steel (S690) plate specimens in a four-point-bend set up. This study extends the \[\eta \]-approach used in the fracture test for the typical specimens with a through-thickness crack, to the surface cracks in plate specimens in calculating the energy release rate from the area below the measured moment versus the crack-plane rotation. The energy release rate, computed from the detailed finite element models using the domain integral approach, confirms a constant \[\eta \] value for surface cracked steel plates. Coupled with the post-test sectioning, the unloading compliance method quantifies the extended crack-front profiles ahead of the fatigue pre-cracked surface notch, using the crack-size versus the compliance relationship derived from linear-elastic finite element analyses. The fracture resistance curves thus obtained remain similar at different locations along the crack front and comparable with the fracture resistance measured using a standard side-grooved compact tension specimen at a finite crack extension.