Multiaxial fatigue rule applied to disc specimens with variable thickness subjected to an equibiaxial stress state

Assessing multiaxial fatigue theories requires experimental verification of a failure criterion, posing a significant challenge. This study aims to investigate the validity of a multiaxial fatigue method based on the Lagoda-Macha-Sakane (LMS) theory. The LMS theory links the critical strain energy density to the fatigue crack initiation cycles through a non-linear equation defined by a set of empirical parameters calibrated by a strain-controlled uniaxial fatigue test. This work adopts the LMS formulation, numerically calibrating the fatigue curve based on strain energy density from uniaxial fatigue experimental data and considering only the LMS theory for the critical strain energy density computation. This method avoids compatibility condition uncertainties and previous identification of material parameters. The study uses bi-axial bending tests on AISI 316 L steel plate specimens with 3D finite element analyses to support computational assessment. The predictive capability of the model and the effectiveness of the testing method are presented and discussed.