PSI - Issue 53

Andrea Zanichelli et al. / Procedia Structural Integrity 53 (2024) 3–11 Author name / Structural Integrity Procedia 00 (2019) 000–000

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In the present paper, an analytical methodology (Vantadori and Zanichelli (2021b), Vantadori et al. (2022b), Vantadori et al. (2022c), Zanichelli and Vantadori (2021)), recently proposed by the present authors for traditional metallic components subjected to fretting fatigue, is extended to the case of AM components. In particular, such a methodology is proposed to be used for the fatigue life estimation of additively manufactured metals subjected to cyclic loading, even in the presence of a stress concentration. An experimental campaign related to AM AISI 316L stainless steel, available in the literature (Wang et al. (2021)), is here considered. The fatigue life values of both plain and notched specimens, subjected to cyclic loading characterised by different degrees of multiaxialities, are determined by employing the above methodology. The present paper consists of the following sections: the methodology proposed for the fatigue assessment of AM metals is described in Section 2; then, the experimental campaign analysed for the verification of such a methodology is summarized in Section 3; subsequently, the results obtained by applying the above methodology to both plain and notched specimens are discussed in Section 4; finally, some conclusions are drawn in Section 5. 2. Analytical methodology for fatigue assessment of AM metals The analytical methodology proposed for the fatigue assessment of additively manufactured metals subjected to cyclic loading, even in the presence of a stress concentration (e.g. a notch), is detailed in the present Section. Such a methodology is based on the joint application of: • a multiaxial stress-based fatigue criterion, named Carpinteri et al. criterion (Carpinteri et al. (2015), Vantadori et al. (2020), Vantadori et al. (2021a)), which exploits the concept of the critical plane, for the fatigue parameter computation and the fatigue life assessment; • a stress averaging method, named Critical Direction Method (Araújo et al. (2017), Araújo et al. (2020)), for the determination of the orientation of the critical plane. Moreover, this methodology takes into account a parameter related to the material microstructure, that is, the average grain size of the material, d . The main steps of such a methodology are shown in Figure 1 and hereafter summarised.

Fig. 1. Flowchart of the analytical methodology for fatigue assessment of AM metals.

Firstly, some input data need to be defined, that is: the geometric sizes characterising the component, the loading conditions, and the mechanical and fatigue properties of the material. Then, the stress field within the structural component is computed, and the hot-spot is located on the surface of the component itself, that is, the crack nucleation location is defined.