Critical plane fatigue life models of materials and structures under multiaxial stationary random loading: The state-of-the-art in Opole Research Centre CESTI and directions of future activities

In the paper some fatigue life assessment models for materials and structures under triaxial random stress state in time and frequency domains developed over 25 years in Opole University of Technology are presented. The first stress models were formulated by generalization of the known models applied under cyclic loadings. The main operation of the calculation algorithm is reduction of the triaxial stress state to the equivalent uniaxial one. Such a reduction is performed with a criterion of multiaxial fatigue failure, suitable for a given material. Then, the determined equivalent stress history is processed, like in the case of uniaxial random fatigue. Later, the strain and energy models were formulated and developed. Also, the spectral method was presented. At the end of the paper some desired directions in future researches are proposed.