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Proceedings Paper

Advanced simulation methods to detect resonant frequency stack up in focal plane design
Author(s): Craig Adams; Neil R. Malone; Raymond Torres; Armando Fajardo; John Vampola; William Drechsler; Russell Parlato; Christopher Cobb; Max Randolph; Surath Chiourn; Robert Swinehart
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Paper Abstract

Wire used to connect focal plane electrical connections to external electrical circuitry can be modeled using the length, diameter and loop height to determine the resonant frequency. The design of the adjacent electric board and mounting platform can also be analyzed. The combined resonant frequency analysis can then be used to decouple the different component resonant frequencies to eliminate the potential for metal fatigue in the wires. It is important to note that the nominal maximum stress values that cause metal fatigue can be much less than the ultimate tensile stress limit or the yield stress limit and are degraded further at resonant frequencies. It is critical that tests be done to qualify designs that are not easily simulated due to material property variation and complex structures. Sine wave vibration testing is a critical component of qualification vibration and provides the highest accuracy in determining the resonant frequencies which can be reduced or uncorrelated improving the structural performance of the focal plane assembly by small changes in design damping or modern space material selection. Vibration flow down from higher levels of assembly needs consideration for intermediary hardware, which may amplify or attenuate the full up system vibration profile. A simple pass through of vibration requirements may result in over test or missing amplified resonant frequencies that can cause system failure. Examples are shown of metal wire fatigue such as discoloration and microscopic cracks which are visible at the submicron level by the use of a scanning electron microscope. While it is important to model and test resonant frequencies the Focal plane must also be constrained such that Coefficient of Thermal expansion mismatches are allowed to move and not overstress the FPA.

Paper Details

Date Published: 12 September 2014
PDF: 6 pages
Proc. SPIE 9219, Infrared Remote Sensing and Instrumentation XXII, 92190A (12 September 2014); doi: 10.1117/12.2065901
Show Author Affiliations
Craig Adams, Raytheon Vision Systems (United States)
Neil R. Malone, Raytheon Vision Systems (United States)
Raymond Torres, Raytheon Vision Systems (United States)
Armando Fajardo, Raytheon Vision Systems (United States)
John Vampola, Raytheon Vision Systems (United States)
William Drechsler, Raytheon Vision Systems (United States)
Russell Parlato, Raytheon Vision Systems (United States)
Christopher Cobb, Raytheon Vision Systems (United States)
Max Randolph, Raytheon Vision Systems (United States)
Surath Chiourn, Raytheon Vision Systems (United States)
Robert Swinehart, Raytheon Vision Systems (United States)

Published in SPIE Proceedings Vol. 9219:
Infrared Remote Sensing and Instrumentation XXII
Marija Strojnik Scholl; Gonzalo Páez, Editor(s)

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