FEM model of impacts on blades

University essay from KTH/Kraft- och värmeteknologi

Author: Lore Ricquemaque; [2016]

Keywords: ;

Abstract: In-service support engineers often have to answer derogations requests regarding impacts on compressor blades. The stress concentration factor is a physical quantity helping them to take the decisions : it is a measure of the local increase of the stress due to the impact. Several techniques already exist to derive it like Petersons' abaci giving it regarding the geometrical parameters of the impact. They are user friendly but conservative in practice. The most accurate method is zoom-calculation : a Finite Element Model is created to precisely measure the stress concentration factor. This effective approach is however very time-consuming. In between, Snecma engineers developed a few years ago a law on the form of abaci derived from a zoom-calculation results database. The main purpose of this thesis is to create laws regarding new geometrical parameters and increase the size of the database following on from the work already carried out. FEM models depending on various parameters are thus created to derive stress concentration factors. A deep difference from what has been done before rests on the method : a calculation chain is developed to get results on different sets of impact parameters. It enables to easily and quickly update the mesh on the models and thus to consider numerous defect geometries. The final results of the study are a set of abaci giving the stress concentration factor due to the impact regarding its geometrical parameters.

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