Photoelastic evaluation of stress fields and notch stress intensity factors for blunt V-notches

Abstract

Fracture loads of engineering components with blunt notches cannot be evaluated by the linear elastic fracture mechanics (LEFM) due to no stress singularity. In this study, an approach to determining stress fields and notch stress intensity factors (NSIFs) at blunt V-notches is developed using the photoelastic technique. To solve the nonlinear governing equations of the NSIFs derived from the Filippi’s stress equation, the overdeterministic least squares method combined with the Newton-Raphson method is applied. The NSIFs for a series of three-point-bending specimens with a blunt V-notch up to fracture are evaluated for different notch angles, tip radii, and notch lengths under mode I loading conditions. It is observed that the NSIFs obtained from photoelastic measurements agree well with the numerical values, and the notch fracture toughness is accordant to the mean stress (MS) criterion. The experimental results will be useful for the fracture characterization and strength evaluation of engineering components with complex notches.