The Evaluation of the Damping Characteristics of a Hard Coating on Titanium

Abstract

Engine failures due to fatigue have cost the Air Force an estimated $400 million dollars per year over the past two decades. Damping treatments capable of reducing the internal stresses of fan and turbine blades to levels where fatigue is less likely to occur have the potential for reducing cost while enhancing reliability. This research evaluates the damping characteristics of magnesium aluminate spinel, MgO+Al2O3, (mag spinel) on titanium plates from an experimental point of view. The material and aspect ratio were chosen to approximate the low aspect ratio blades found in military gas turbine fans. In the past, work has generally been performed on cantilever supported beams, and thus the two-dimensional features of damping were lost. In this study plates were tested with a cantilevered boundary condition, using electrodynamic shaker excitation. The effective test area of each specimen was 4.5 in × 4.5 in. The nominal plate thickness was 0.125 in. Mag spinel was applied to both sides of the plate, at a thickness of 0.01 in, and damping tests were run at room temperature. The effect of the coating was evaluated at the 2nd bending mode (mode 3) and the chord wise bending mode (mode 4). A scanning laser vibrometer revealed the frequency and shape of each mode for the plates. Sine sweeps were used to characterize the damping of the coated and uncoated specimens for the modes tested. The coating increased damping nonlinearly for both modes tested in which the general outcome was similar to that found in beams.Nomenclature σ = stress E = Young's modulus ε = strain δ = displacement v = velocity ω = frequency (radians/sec) ζ = damping ratio ∆ω = bandwidth (ω 2 − ω 1 )

Micromechanical theoretical and computational modeling of energy dissipation due to nonlinear vibration of hard ceramic coatings with microstructural recursive faults

“…Engine failures due to high-cycle fatigue during severe dynamic vibration have cost the US Air Force an estimated $400 million dollars per year over the past two decades (Blackwell et al, 2007). Therefore, structural materials that exhibit high damping capacities are desirable for mechanical vibration (which may lead to fatigue failure) suppression and acoustic noise (which may lead to health concerns) attenuation.…”

“…doi:10.1016/j.ijsolstr.2010.04.016 thermal barrier coatings (TBCs) to protect engine components from high temperatures and corrosion. In fact, recent research have indicated that ceramic TBCs can also provide some degree of vibration damping (Shipton and Patsias, 2003;Patsias et al, 2004;Tassini et al, 2006Tassini et al, , 2007Blackwell et al, 2007;Reed, 2007;Reed et al, 2007;Lauwagie et al, 2008;Pearson, 2008). However, constitutive modeling of this damping has been very limited in the literature due to the complex nonlinear damping behavior of these TBCs and due to the absence of a microstructural understanding of the origin of such nonlinear damping behavior.…”

Damping Properties of Arc Ion Plating NiCrAlY Coating with Vacuum Annealing

“…However, the low working temperature and the vulnerability limit its further application. Therefore, research into the damping properties of hard coatings has gradually aroused the interest of researchers [5]. Representative hard coatings include NiCrAlY coating and other ceramic coatings [6][7][8].…”

A New Finite Element Formulation for Nonlinear Vibration Analysis of the Hard-Coating Cylindrical Shell

“…Blackwell et al [8] experimentally studied the damping effects of hard-coating coated on the titanium plate and found its significant nonlinear damping characterization. Several research works, e.g., [9,10], indicated that both the elastic and damping properties of hard-coatings exhibit obvious nonlinearity, as well.…”