PSI - Issue 57

Giovanni M. Teixeira et al. / Procedia Structural Integrity 57 (2024) 670–691 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

689

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Table 1. Chaboche Parameters

 1

 2

 3

Yield Stress at Zero Plastic Strain

Kinematic Hardening Parameter C1

Kinematic Hardening Parameter C2

Kinematic Hardening Parameter C3

Temp [Celsius]

204.735 121.17 71.0306 39.2758

461454 322687 107930 19823.8

2101.77 1889.38 1123.89 606.195

34790.3 1059.6 529.801 264.901

257.17 257.17 257.167 257.159

1239.56 725.275 418.681 75.8242

0 0 0 0

400 550 650 750

3.3. Thermomechanical Fatigue Results Figure 23 shows the stress distribution on the exhaust manifold at the end of the heat-up loading, which is the one where the largest stresses are found among the twenty analysis steps that were simulated. Some of the stress concentrations that arise in finite element analyses are caused by rigid couplings and boundary conditions and therefore can be disregarded. The area highlighted in figure 23, however, is a typical place where cracks nucleate in exhaust manifolds.

Fig. 23. Stress distribution at the end of the heating load

Figure 24 show the areas where fatigue cracks are expected to nucleate after 12 thousand hours of operation.

Fig. 24. Fatigue Life in Log(hours)

When oxidation is explicitly taken into account through equation 53 the hidden assumption is that some of the