Determination of mechanical properties of non-linear coatings from measurements with coated beams

Abstract

a b s t r a c tCoatings are applied to structural components for several various reasons, such to protect against erosion or corrosion, as thermal barrier coatings, or to increase the energy dissipation. As determining the material properties of such coatings from homogeneous specimens is often difficult, it is sometimes necessary to conduct testing on coated specimens, with the properties of the coating then to be extracted from the results of testing. A methodology for doing this is given here. While applicable to other materials, the properties of such coatings as ceramics, metallics, or compounds to be applied to rotating and static components of gas turbines are of special interest. Such materials present a special challenge as the mechanical properties have generally been found to display a strong dependence on the amplitude of cyclic strain. Application of the methodology requires careful measurement of specimen dimensions, weights, natural frequencies, and system loss factors before and after coating. From these, the storage (Young's) modulus, the loss modulus, and the loss factor can be extracted. The methodology is demonstrated through the use of data taken on flat specimens of titanium with plasma-sprayed coatings of NiCrAlY and a titania-alumina blend ceramic, vibrating in a cantilever mode.

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

“…Moreover, there has been very little emphasis placed on the development of an effective micromechanical constitutive model that can explain the damping characteristics of hard coatings based on the physical insights from the few experimental studies and microstructural characterizations that exist in the literature on the nonlinear damping of thermal barrier atomic equilibrium separation at maximum potential energy k cr atomic critical separation at maximum interaction force B + , B À positive and negative sides of an interfacê e 1 ;ê 2 ;ê 3 unit vectors n normal to the interface d, d N , d T total, normal, and tangential displacement jumps across the interface d e T ; d p T elastic and plastic tangential displacement jumps t, t N , t T total, normal, and tangential conjugate tractions applied strain-amplitude E 0 and E 00 storage and loss moduli ceramic coatings (e.g. Shipton and Patsias, 2003;Patsias et al, 2004;Reed, 2007;Reed et al, 2007;Pearson, 2008;Torvik, 2009). To the authors' best knowledge, there have been only two attempts to model the nonlinear damping behavior of plasma sprayed TBCs.…”

A Hysteretic Energy Method for Determining Damping Properties of Hard Coatings

“…12 The guideline is as follows: the quality factor of a bare specimen should be at least an order of magnitude greater than the quality factor of the same beam with a coating to ensure that the net damping addition to the system is due to the coating material itself. 13 Combining this guideline with the bounds of modern coatings, a range for acceptable bare specimen quality factors can be determined via Eq. 4.…”

Damping Properties of Arc Ion Plating NiCrAlY Coating with Vacuum Annealing

“…The annealing experiment employed a JKQF-13000 tube annealing furnace (Jinan Precision Scientific Instrument and Meter Co. Ltd., Jinan, China). Some researchers have reported much work on this [16][17][18]. Ghidelli [19,20] studied the measurement method of residual stress and fracture mechanics of the coating.…”