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Proceedings Paper

Fret wear mediation of NIRCam filter wheel assembly
Author(s): Béla I. Privári
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Paper Abstract

We will discuss a fret wear solution developed for the James Webb Space Telescope NIRCam filter wheel assembly by implementation of a hard coating. With mechanisms and structures designed for space flight application, titanium is often selected as the choice material of construction. Titanium offers a low-density high strength material that is good for use with many optical instruments due to its' favorable thermal properties. An important factor to consider with titanium mechanisms and structures are component fits and the vibration environment that must be survived during launch. In many instances, small (slip) fits between titanium components can cause fret wear during launch induced vibration. Titanium is particularly susceptible to fret wear, although other materials also demonstrate the fret wear. Fretting is adhesive failure of a material that experiences impact and micro-slip with an adjacent part. The mechanism of fret wear involves small particles that are pulled from the surface of parts that turn into hard oxides that further accelerate the wear between the parts. To mitigate fret wear, the mechanism or structure can be designed to eliminate all slip fits altogether, lubricants may be added to the wear surfaces or hard coatings can be applied to the wear surfaces when the other approaches are not feasible. For the NIRCam filter wheel assembly, which must operate at 35K and remain optically clean, only hard coatings are feasible. A discussion of several coating alternatives and associated wear testing will be presented along with the selection of an optimal solution.

Paper Details

Date Published: 30 September 2011
PDF: 8 pages
Proc. SPIE 8150, Cryogenic Optical Systems and Instruments XIII, 81500K (30 September 2011); doi: 10.1117/12.896547
Show Author Affiliations
Béla I. Privári, Lockheed Martin Space Systems Co. (United States)

Published in SPIE Proceedings Vol. 8150:
Cryogenic Optical Systems and Instruments XIII
James B. Heaney; E. Todd Kvamme, Editor(s)

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