Finite element modeling of abradable materials – Identification of plastic parameters and issues on minimum hardness against coating's thickness

¹ M3M, Belfort-Montbéliard University of Technology, Belfort, France
² LERMPS, Belfort-Montbéliard University of Technology, Belfort, France
³ MTU Aero Engines GmbH, Dachauer Strae 665, 80995 München, Germany

Corresponding author: francois.peyraut@utbm.fr

Received: 30 October 2007
Accepted: 15 February 2008

Abstract

Abradable materials are used to decrease the gas consumption of aircraft engines by minimizing the gap between the blade tips and the stator. The key idea consists in using the blades themselves to machine the gap on the abradable coating. The best compromise between soft and hard coating properties has to be reached to avoid blades wear and prevent coating erosion by gas flux and particles. The plastic parameters of abradable coating were identified by using an optimization process directly connected to FEA. The first order optimization method (conjugate gradient strategy + golden section algorithm) was applied to achieve the optimal solution. A good agreement was found between experimental and numerical results. The plastic parameters were used to study the hardness variability of abradable materials with the coating thickness. Surprisingly, a minimum hardness value was found while it was expected that hardness should be always decreasing with thickness. It has been demonstrated that this minimum is produced by the boundary conditions influence on hardness measurement. This research work was completed within the Seal-Coat project funded by the European Commission under the FP5 Growth Program.