The newly designed abradable 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 model of abradable coating rig tests, allowing extensive studies on the influence of coating properties and test conditions on the thermal behaviour of the system. The proposed model includes several steps implementing different numerical tools. Firstly, a relevant structural description of an abradable coating is obtained from micrographs, using an original image analysis route. FE (Finite Element) calculations based on this description allow then to estimate the coefficients of an anisotropic elastic law of mechanical behaviour. Furthermore, a plasticity law is deduced from a FE simulation of the material HR15Y hardness. These parameters are used as input of a FE simulation of a single blade-to-coating rubbing hit, resulting in calculated stresses and temperatures. Finally a global approach of the complete abradability test, based on the results obtained from the simulation of a single hit and on various assumptions, provides predictions of the blade and coating temperature variations versus time during a complete abradability test.

Abradable coatings are widely used in aerospace turbine engines to improve seal performance between rotating and stationary parts and thus the engine efficiency. As they are elaborated by thermal spraying of composite powders, these materials are highly heterogeneous. Their behaviour in working conditions is quite complex and not fully understood. This study contributes to a better knowledge of the mechanical behaviour of a range of abradable coatings. Finite Element calculations were derived from the analysis of micrographs and allowed to estimate the coefficients of an anisotropic elastic law of behaviour. Several models were investigated in the case of an AlSi-PE (Polyester) coating. As the PE % appeared to be a determinant factor, its influence was quantified ranging from 0% to 100%, using virtual micrographs deduced from the original ones. The computed Young's moduli Ex (in coating longitudinal direction) were quite consistent, considering the hypotheses made. An empirical relationship giving the variation law of Ex versus the PE % was suggested and applied to predict the modulus Ex of a real coating, which was close to the measured value.