Loading biaxiality and crack tip curvature effects on plastic stress intensity factor behaviour at small-scale and extensive pla

https://doi.org/10.3221/IGF-ESIS.78.16

An elastic–plastic finite element analysis (FEA) was performed for a Mode I plane-strain center-cracked plate (CCP) made of a titanium alloy and subjected to biaxial tension/compression loading. Two crack-tip configurations were considered: a mathematical notch (MN) and a finite radius of curvature (FRC). In the present study, both the J-integral and the plastic stress intensity factor (plastic SIF) were employed to characterize the elastic–plastic stress fields near the crack tip. The distributions of the J-integral and the plastic SIF were evaluated as functions of loading biaxiality and applied stress level. The analysis covered a biaxial stress ratio range extending from equibiaxial tension–compression to equibiaxial tension and included both small-scale yielding (SSY) and extensive plasticity conditions. The results reveal a pronounced coupling between loading biaxiality and crack-tip configuration effects on the fracture parameters. Opposite trends in the variation of the J-integral and the plastic SIF with respect to the biaxial stress ratio and crack-tip geometry were observed. In addition, a comparative assessment of SSY and extensive plasticity regimes was carried out for both crack-tip configurations. It was found that under extensive plasticity conditions the plastic SIF becomes dependent on the crack-tip radius of curvature, whereas under SSY conditions it remains essentially independent of crack-tip geometry.