PSI - Issue 24

Giovanni Zonfrillo et al. / Procedia Structural Integrity 24 (2019) 470–482 G. Zonfrillo and M.S. Gulino / Structural Integrity Procedia 00 (2019) 000–000

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Fig. 2. Distribution of σ u / σ y among the sample materials (Manson’s rule).

Fig. 3. Distribution of n among the sample materials (Landgraf’s rule).

Based on 47 materials, Daunys and Sˇ niuolis (2006) demonstrate how the cyclic behaviour of the alloy can be inferred from the parameters Ψ and σ u / σ y : if σ u / σ y > 1.8 the material hardens, if σ u / σ y < 1.4 and Ψ < 0.7 the material softens, when σ u / σ y < 1.4 and Ψ > 0.7 the material behaviour is stable; for 1.4 <σ u / σ y < 1.8 a transition zone can be highlighted in which, independently of Ψ , both softening, hardening or stabilization occur. To graphically explain the relations provided by Daunys, Figure 5 illustrates the distribution on the Ψ , σ u / σ y plane of the materials contained in the analysed database. Table 1 summarises, in an intelligible and complementary way to Figure 2-5, the results of the four proposed rules application to the available database of materials. As for the softening behaviour, Landgraf’s rule allows obtaining the best results, with a high number of correct predictions (81%) and reduced errors (1%); for the remaining 18% of the cases, a specific behaviour is not predicted. Considering only the hardening materials, the best performances are associated with Manson’s rule. For what regards mixed and stable materials, Zhang’s rule is inapplicable as it