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Taylor S.R.,University of Texas Health Science Center at Houston | Contu F.,University of Texas Health Science Center at Houston | Hunter C.N.,U.S. Air force | Fenzy L.,Techspace Aerospace
ECS Transactions | Year: 2010

This study examines the role of short-term changes in the coating-substrate interface as a means to predict the long-term coating performance. By introducing a through-coating defect, interfacial changes are quantified using EIS over short times of exposure to aqueous environments. The ability of these short-term measurements to predict long-term performance of coating systems was examined in two studies. In one study, 32 aerospace coating systems on AA2024-T3 substrates were exposed in a large volume cell to 0.1M (NH 4) 2SO 4 + 0.005M NaCl for 8 days. In a second study, 12 aerospace coatings systems on AA2024-T3 were exposed in a small volume cell (80 μ) to 0.5M NaCl for 4 days. Separate panels of the same coating systems were exposed to ASTM B117 salt spray for 3000 hours. A blind comparison of the EIS data to the 3000 h salt spray results showed an 80% correlation. EIS data acquired after the introduction of the defect was essential and the dominate factor in the prediction of 3000 h salt spray results. The results of this study reinforces the importance of coating-substrate interface stability in predicting field performance of inhibited coating systems, and provide a promising short-term method for the quantitative prediction of long-term coating performance for these materials. ©The Electrochemical Society.

Sans J.,Von Karman Institute for Fluid Dynamics | Brouckaert J.-F.,Von Karman Institute for Fluid Dynamics | Hiernaux S.,Techspace Aerospace
Proceedings of the ASME Turbo Expo | Year: 2015

The solidity in a compressor is defined as the ratio of the aerodynamic chord over the peripheral distance between two adjacent blades, the pitch. The choice of this parameter represents a crucial step in the whole design process. Most of the studies addressing this issue are based on low-speed compressor cascade correlations. In that prospect, aiming at updating those correlation data as well as improving the physical understanding of the solidity effect on compressor performance, both experimental and numerical high-speed cascade investigations have been carried out at the von Karman Institute. The profile is a state-of-the-art controlled diffusion blade, representative of a low pressure compressor stator mid-span profile. The performance in terms of total pressure losses and deviation have been measured in the high-speed C3 cascade facility for three different solidities at six incidences and two Mach numbers. Based on the experimental results, a numerical linear cascade model has been built and computations have been run with FINE/Turbo at the same conditions as the measurements. The quality of the numerical predictions is discussed over the whole incidence range and, in particular, big discrepancies are highlighted at off-design incidences. Focusing on the solidity effects at mid-span, both experimental and numerical results are compared with existing correlations. The establishment of updated correlations for such controlled diffusion profile is addressed for both deviation and total pressure losses and at both optimum and off-design conditions. Copyright © 2015 by ASME.

Bettaieb M.B.,University of Liege | Lenain A.,Techspace Aerospace | Habraken A.M.,University of Liege
Fatigue and Fracture of Engineering Materials and Structures | Year: 2013

This paper presents and discusses static (elastoviscoplastic and damage) and high-cycle fatigue characterization of two microstructures of the Ti5553 alloy. The difference between these two microstructures is related to their heat treatment and precisely to the temperature of the final aging. For each microstructure, several tests were carried out to identify their static and fatigue properties and the test results were correlated to the microstructure. A fractographic analysis of the rupture sections was performed in order to investigate the fracture mechanisms of the two microstructures. Finally, the fatigue properties of the two microstructures were compared with those found in results reported in the literature for two other classical titanium alloys used for aeronautical applications. © 2012 Wiley Publishing Ltd.

Cori J.-F.,Techspace Aerospace | Etienne S.,Ecole Polytechnique de Montreal | Garon A.,Ecole Polytechnique de Montreal | Pelletier D.,Ecole Polytechnique de Montreal
International Journal for Numerical Methods in Fluids | Year: 2015

This paper presents an approach to develop high-order, temporally accurate, finite element approximations of fluid-structure interaction (FSI) problems. The proposed numerical method uses an implicit monolithic formulation in which the same implicit Runge-Kutta (IRK) temporal integrator is used for the incompressible flow, the structural equations undergoing large displacements, and the coupling terms at the fluid-solid interface. In this context of stiff interaction problems, the fully implicit one-step approach presented is an original alternative to traditional multistep or explicit one-step finite element approaches. The numerical scheme takes advantage of an arbitrary Lagrangian-Eulerian formulation of the equations designed to satisfy the geometric conservation law and to guarantee that the high-order temporal accuracy of the IRK time integrators observed on fixed meshes is preserved on arbitrary Lagrangian-Eulerian deforming meshes. A thorough review of the literature reveals that in most previous works, high-order time accuracy (higher than second order) is seldom achieved for FSI problems. We present thorough time-step refinement studies for a rigid oscillating-airfoil on deforming meshes to confirm the time accuracy on the extracted aerodynamics reactions of IRK time integrators up to fifth order. Efficiency of the proposed approach is then tested on a stiff FSI problem of flow-induced vibrations of a flexible strip. The time-step refinement studies indicate the following: stability of the proposed approach is always observed even with large time step and spurious oscillations on the structure are avoided without added damping. While higher order IRK schemes require more memory than classical schemes (implicit Euler), they are faster for a given level of temporal accuracy in two dimensions. © 2015 John Wiley & Sons, Ltd.

Sans J.,Von Karman Institute for Fluid Dynamics | Resmini M.,Von Karman Institute for Fluid Dynamics | Brouckaert J.-F.,Von Karman Institute for Fluid Dynamics | Hiernaux S.,Techspace Aerospace
Proceedings of the ASME Turbo Expo | Year: 2014

Solidity in compressors is defined as the ratio of the aerodynamic chord over the peripheral distance between two adjacent blades, the pitch. This parameter is simply the inverse of the pitch-to-chord ratio generally used in turbines. Solidity must be selected at the earliest design phase, i.e. at the level of the meridional design and represents a crucial step in the whole design process. Most of the existing studies on this topic rely on lowspeed compressor cascade correlations from Carter or Lieblein. The aim of this work is to update those correlations for state-ofthe-art controlled diffusion blades, and extend their application to high Mach number flow regimes more typical of modern compressors. Another objective is also to improve the physical understanding of the solidity effect on compressor performance and stability. A numerical investigation has been performed using the commercial software FINE/Turbo. Two different blade profiles were selected and investigated in the compressible flow regime as an extension to the low-speed data on which the correlations are based. The first cascade uses a standard double circular arc profile, extensively referenced in the literature, while the second configuration uses a state-of-the-art CDB, representative of low pressure compressor stator mid-span profile. Both profiles have been designed with the same inlet and outlet metal angles and the same maximum thickness but the camber and thickness distributions, the stagger angle and the leading edge geometry of the CDB have been optimized. The determination of minimum loss, optimum incidence and deviation is addressed and com- Copyright © 2014 by ASME.

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