Extension of the static equivalent stress hypotheses to linearly vibrating systems using wave interference – The LiWi approach

Abstract

This paper presents a damage-equivalent stress, to be related to uniaxial S-N curves for mechanical systems undergoing multiaxial stress cycles for evaluating fatigue strength. It covers variable and non-proportional loads, wherein the known static equivalent-stresses from von-Mises, Tresca and Rankine are extended to oscillating systems using wave interference. This novel approach is termed as LiWI (Linear Wave Interference) and leads to physically valid signal progressions, allowing for frequency content preservation, rotational invariance and application to static cases. Hence a unification of the equivalent stress descriptions in time, frequency and stochastic (power spectral density) domains for linear time invariant systems results.