A new equivalent stress approach based on complex invariants: The COIN LiWI method.

In this paper, a new equivalent stress approach is presented, which builds on the basic ideas of linear wave interference (LiWI) and thus leads to physically valid signals. Complex invariants (COIN) were introduced for the derivation, whereby a generalized calculation method with consideration of the tension shear strength ratio could be derived following the formulation of Mertens (1988). The LiWI approach was also applied to an equivalent stress formulation from the German FKM guideline (Rennert et al., 2021). Both approaches were tested and compared with signed von-Mises using existing experiments with a wide range of different loads, e.g. nonproportional, variable, frequency superimposed. • Revises the linear wave interference (LiWI) equivalent stress method. • Extends the approach by introducing complex invariants. • Considers different material ductilities and influence of the phase shift. • Encompasses variable, non-proportional, multi-frequency loads. • Approach was validated against experimental results. [ABSTRACT FROM AUTHOR]