J. L. Seichepine, F. Peyraut, H. I. Faraoun, University of Technology of Belfort-Montbeliard, Belfort Cedex, France; C. Coddet, University of Technology Belfort-Montbeliard, Belfort Cedex, France
Abradable seals are located on the statical parts of gas turbines, in front of blades, allowing them to cut a track, but this has to be achieved with minimum wear, in order to control the over-tip leakage. These coatings are usually validated by rig tests, where samples are rubbed by the contact of a dummy blade with given running speed and incursion rate, simulating actual working conditions in an aircraft engine. The aim of this work was to develop a finite element model of abradable coating rig tests, allowing extensive studies on the influence of coating properties and test conditions on their performances. The FE code ANSYS was used to simulate a single contact between a blade and a part of the abradable coating. Target and contact elements were used to model the contact between both parts. The coupling of thermal and mechanical analyses is allowed by these elements, where the heat generation due to frictional dissipated energy is computed. For the coating, an elastic linear orthotropic law of behaviour was set up, with the parameters issued from previous works on abradable materials modelling. The motions of the two parts during the tests were simulated by dynamical displacements. An initial incursion of the blade into the coating was taken into account by an initial distortion of the mesh, resulting from a preliminary static calculation. Relevant algorithms and pertinent parameters were chosen for the contact analysis, the non-linear analysis and the dynamical analysis. The results obtained for reference coatings were dynamical fields of stresses and temperatures, for several sets of inlet parameters. Comparisons between the maximum computed values in each studied case and the corresponding blade wear measurements showed some consistency. Furthermore, these results contribute to explain why different test rigs work sometimes differently.
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