PSI - Issue 57

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

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In summary, a typical structural analysis of an exhaust manifold consists in a pre-load step (room temperature) followed by (at least) one heat-up/cool-down step that reflects the most damaging engine operating condition.

Fig. 16. Boundary conditions in the Structural Analysis

3.2. The Material Calibration Chaboche’s viscoplastic parameters can be determined from isothermal and non -isothermal complex low cycle fatigue tests (CLCF). Different strain amplitudes, strain rates, hold times and temperatures are employed in these tests in order to gather enough information to determine the material properties. Various optimization techniques can be used in the fitting of the plasticity parameters [20]. Isothermal CLCF tests are performed under temperature conditions that span from 25 to 500 Celsius. A typical enforced strain history is shown in figure 17, and the resulting stresses history is shown in figure 18, where stress relaxation is observed during hold times.

Fig. 17. Schematic Prescribed strain history for Isothermal CLCF test