Local Strain Energy Density Concept

Abstract

The local strain energy density (SED) approach is elaborated for strength assessments in respect of brittle fracture and high-cycle fatigue. Pointed and rounded (blunt) V-notches subjected to tensile loading (mode 1) are primarily considered, occasionally extended to multiaxial conditions (mode 3, mixed mode 1 and 2). The application to brittle fracture is related to PMMA flat bar specimens with U-notches. The application to high-cycle fatigue comprises fillet-welded joints, weld-like shaped and V-notched base material specimens as well as round bar specimens with V-notch. The relation of the local SED concept to comparable other concepts is investigated, among them the Kitagawa and Atzori diagrams, the Neuber concept of fictitious notch rounding applied to welded joints and the J-integral approach. Alternative details of the local SED concept such as a semicircular control volume, microrounded notches and slit-parallel loading are also investigated. Coarse FE meshes at pointed or rounded notch tips are proven to be acceptable for accurate local SED evaluations. The peak stress method, which is based on a special coarse FE mesh for the assessment of the fatigue strength of welded joints, is also suitable.