Issue 37

V. Anes et alii, Frattura ed Integrità Strutturale, 37 (2016) 124-130; DOI: 10.3221/IGF-ESIS.37.17 126 Multiaxial cycle counting Constant amplitude loadings are well characterized by its maximum damage parameter found within the loading pattern. However, in cases of variable amplitude loadings the maximum value of a given damage parameter do not captures the overall damage. In order to overcome this drawback, the present authors developed the virtual cycle counting method, which is a non-Rainflow cycle counting method for multiaxial loading conditions [10]. The virtual cycle counting (vcc) is based on the time evolution of the SSF equivalent shear stress and is given through Eq. (4).        , ssf,max, 2 ssf peak valley Block abs vcc (4) Where vcc can be understood as a virtual loading cycles calculation. In order to estimate the fatigue life of a given loading block using the SSF criterion, it is necessary to divide the fatigue life estimate, obtained with the maximum SSF equivalent stress found within the loading block, by the virtual cycle counting yield by Eq. (4). Multiaxial loading path Fig. 1 depicts the normal and shear stress time evolution of the loading path studied here, as well as, its representation on the von Mises stress space. This loading path is a non-proportional loading block made of 360 proportional loading paths loaded sequentially with a 1º degree gap between them. Figure 1: FRI loading path [11, 12]: a) normal stress time evolution, b) shear stress time evolution c) loading path depicted in the von Mises stress space.