Car manufacturers are very much concerned with thermal fatigue damage that may cause Diesel engine to fail after a few thousand cycles on the test bench and under severe operating conditions. The alternative heating and cooling of the operative Diesel engine generates fatigue cracks, initiating from the fire deck of the cast aluminum cylinder head, which can lead ultimately to engine failure. We present here the modelling of the fatigue damage in aluminum cylinder heads : we describe the constitutive equations and the results of fatigue crack growth rate measurements. These results are used with the weight function approach to predict crack propagation lifetime of cylinder heads.
Titanium alloys are key materials in aeronautics due to their low density, their high mechanical properties and their good resistance to corrosion and oxidation. However, these alloys are generally manufactured by traditional processes that do not offer the possibility to generate the just and best design for applications.For this reason, and in the context of continuously designing parts more robust and lighter, the direct manufacturing processes become necessary. Indeed, these processes give the opportunity to address the design of parts in a complete different way and can significantly reduce development and production costs but also design and manufacturing cycles.LBM and EBM constitute two major processes addressed in Safran. We propose to present their specificity, the resulting microstructures and mechanical properties in comparison with forged and cast parts. Post-finishing techniques will be also addressed, because surface roughness is a major issue of these processes depending on final application.
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