PSI - Issue 57

Nesrine Majed et al. / Procedia Structural Integrity 57 (2024) 502–509 Nesrine Majed et al./ Structural Integrity Procedia 00 (2019) 000 – 000

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The material is cast aluminium alloy A357-T6 according to the ASTM standard and AS7G06 as defined by the AFNOR standard. Its chemical composition is shown in the table 1. Its monotonic tensile properties and the fatigue limits for a cast alloy A357 with SDAS= 38 ±6 (μm ) are presented in Table 2 as it has been indicated by Mu et al (2014) and Serrano-Munoz (2020).

Fig. 1. Microstructure of cast alloy A357.

Table 1. Composition of the A357-T6 (wt.%).

Si

Mg

Ti

Fe

Mn

Cu

Ni

Sn

Zn

Pb

7.05 0.57

0.16 0.12 < 0.03

<0.015

<0.01

<0.01 <0.01

<0.003

Table 2. Mechanical properties and endurance limits of A357-T6 for N=5. 10 6 cycles. Mechanical properties values Young’s modulus E (GPa) 73 Poisson’s ratio ν 3 Monotonic yield strength 0.2 (MPa) 275 Tensile strength (MPa) 335 Tension defect-free fatigue limit ( = −1) 3 −8 1 (MPa) 91 Torsion defect-free fatigue limit ( = −1) 38−1 (MPa) 80

3. Crossland Criterion The analysis of the finite element (FE) results reveals that the stress state in front of the defect is characterized by multiple axes, although the applied loading is uniaxial . Iben Houria et al. (2015) explained that the Crossland criterion is the best-suited criterion to describe the fatigue limit trend of the A356-T6 alloy, which has properties close to those of the A357 alloy. Therefore, that criterion is applied in the present study. The Crossland criterion is defined by: = √ 2. + ≤ (1) √ 2. is the amplitude of the square root of the second stress deflector invariant. is the maximum hydrostatic pressure. , are two material parameters determined by two limits of fatigue in alternating tension and in alternating torsion.