PSI - Issue 38

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Hubert Blondet et al. / Procedia Structural Integrity 38 (2022) 526–537 Hubert Blondet, Kamilia Barthoux/ Structural Integrity Procedia 00 (2021) 000 – 000

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NB: It is necessary to separate traction from compression because of the Cast Iron behaviour which allows much more stress in compression than in traction. Dividing the stress by the corresponding Rm will thus “increase” the tensile areas influence, and “decrease” the compressive areas. Temperature influence on material behaviour is not considered because for the Cylinder Head, the Rm does not highly depends of the temperature levels seen by the cylinder head. The “thermal” stress  th are removed from the “PCP” stresses  PCP because as explained before, these “PCP” stresses are calculated after PCP + thermal loads. To have only the impact of the PCP load it is then necessary to remove the contribution of the thermal stresses. 2.4 Participation Factor Computation Participation factors consist in translating the real duty cycle in terms of contribution of each engine Speed / Load pairs for which simulation results are available. Two ways of computing the Participation Factor for each engine Speed / Load pair are set up:

- An “instantaneous” participation, which will be used for PCP combinations. - A “damped” participation, which will be used for Thermal combinations - 2.4.1 Instantaneous Participation Factor computation

Because PCP loading is instantaneous, it will follow all the variations of the duty cycle. Computing the Participation Factors assumes that no extrapolation is performed. If points in duty cycle exist that are outside the FEM computed ENGINE SPEED/LOAD pairs, it has been showed it can lead to hazardous results: they will be then truncated at the boundaries of the domain. Hypotheses for computing the participation factor at a point are presented here: - Retrieve the RPM and LOAD of the current duty cycle point - Isolate the immediately four closest available FEM points - Compute the coordinates “X, Y” of this point on the coordinate system made of the four FEM points - Compute the contribution of each point, as described here: