PSI - Issue 53

Camilla Ronchei et al. / Procedia Structural Integrity 53 (2024) 112–118

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Camilla Ronchei et al. / Structural Integrity Procedia 00 (2023) 000 – 000

works by Romano et al. (2018), Solberg et al. (2019) and Hu et al. (2020). To such an aim, the Kitagawa-Takahashi diagram (Kitagawa and Takahashi (1976)) is usually employed in order to establish a relationship between fatigue limit and defect size, which is expressed in terms of Murakami’s area parameter (Murakami, 2002). In such a context, the present paper aims to investigate the defect effect on the fatigue limits of an AM aluminium alloy (Sausto et al. (2022)) by exploiting a novel analytical procedure (Vantadori et al. (2023)). Such a procedure is based on the joint application of: (i) the Kitagawa-Takahashi diagram, formulated by employing the modified El-Haddad model (Beretta and Romano (2017)), for the fatigue limit calculations; (ii) the fatigue criterion by Carpinteri et al. (2015), based on the critical plane approach, for the fatigue strength assessment and the lifetime estimation.

Nomenclature max n area

square root of the expected maximum area of the defect under cyclic axial loading

El-Haddad parameter

0, EH area

tangential components of the stress vector w S related to the critical plane normal component of the stress vector w S related to the critical plane

C N

amplitude and mean value of N equivalent amplitude of N experimental fatigue lifetime

a N and m N

eq,a N

exp N

f N

theoretical fatigue lifetime

fatigue ratio

R

th K 

threshold stress-intensity factor range

experimental fatigue limit under cyclic normal loading equivalent uniaxial stress amplitude related to the critical plane

, 1 af  −

eq,a 

material ultimate tensile strength

u 

fatigue limit under cyclic normal loading fatigue limit of the defect free material

w 

0 w 

experimental fatigue limit under cyclic shear loading

, 1 af  −

fatigue limit under cyclic shear loading

w 

2. Experimental fatigue data The examined fatigue data are related to an experimental campaign recently performed by Sausto et al. (2022) on AM metallic specimens subjected to cyclic loading. More precisely, such specimens were produced by using a Laser-Beam based Powder Bed Fusion machine, and the material employed in the manufacturing process was the aluminium alloy AlSi10Mg powder with a mean particle size of 37 μm. T he specimens were printed with an orientation of 90° with respect to the building plate.

10 4

Tensile, R=-1 Torsional, R=-1 Torsional, R=0.1

STRESS RANGE, [MPa] 10 3

10 3

10 4

10 5

10 6

10 7

N exp , [cycles]

Fig. 1. Experimental curves in terms of stress range and number of loading cycles to failure for cyclic axial and torsional loading.