PSI - Issue 37

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Mohammed Algarni et al. / Procedia Structural Integrity 37 (2022) 676–683 Author name / Structur l Integrity Procedia 00 (2019) 000 – 00

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Figure 2: Experimental results of 3D AM PLA fatigue life - notch effect with (a) R = -1, (b) R = 0.1, and (c) R = 0.3 and mean stress effect of (d) LN specimen, (e) MN specimen, and (f) SN specimen. 4. Fatigue Life Prediction 4.1. Effect of notch factor on the fatigue life model The notch factor influence on fatigue life is traditionally defined by the fatigue notch factor K f , as in Equ. (1) (Algarni, 2019), quantifying the fatigue strength reduction due to the existing notch (or stress concentration). The fatigue notch factor K f is a function of the notch sensitivity factor q and stress concentration factor K t (Peterson, 1974; Pilkey & Pilkey, 2008). The notch sensitivity factor q is described in Equ. (1), where w is material characteristic length (in mm) and r is the radius of the notch (in mm). The material characteristic length for thermoplastics is suggested by Amjadi & Fatemi (2020). The KV fatigue life model in Equ. (2) is used for reinforced epoxy composite materials (Kohout & Vechet, 2001) and is extensively used in many civil structures, including bridges. This model predicts the fatigue life based on the material’s fatigue degradation. Many studies have used the KV mod el to predict fatigue behavior for LCF and HCF. However, this research investigated the prediction capability of this model in the HCF regime only with the influence of notches with different radius on zero mean stress load.