Numerical and Experimental Analysis of Foreign Objects Impact into the Surface with TBC Coating

Abstract

While the plane is maneuvering before start or landing, some solid particles (e.g. sand, dust, soil) can be sucked into an engine with the air. Their vast majority is stopped on the compressor blades, but the smaller ones are able to get into a hot part of the engine and cause erosion. Erosion is widely recognized as the second mechanism, after corrosion that reduces the TBC coating thickness. In many cases, erosion can completely remove it. Furthermore, TBC coatings are more susceptible to erosion due to their porous structure than full dense ceramic materials. In order to investigate the phenomenon of particles impact with diameter of 4mm, the pneumatic driven laboratory work station was built. The work station has an adjustable pressure, so that the foreign object may possess different kinetic energies. The pressure can be read on a digital pressure gauge and the shot release is done electrically. In addition, the work station has a universal cross table that provides precise positioning of the sample so as to be able to perform a dozen or so impacts in predetermined distance intervals. However, the most important component is the velocity measurement system which is used to determine the impact energy. The paper presents the results of 11 impacts made with different energies. The effect of complete destruction of the ceramic layer as well as indents without visible damage was achieved. Numerical simulations allowed to define the zones of stress influence of the individual indents. The brittle cracking model in Abaqus allowed the virtual representation of damage due to impact load.