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Woodpecker-inspired shock isolation by microgranular bed

Sang-Hee Yoon1,3, Jin-Eep Roh2 and Ki Lyug Kim2

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This paper presents a woodpecker-inspired shock isolation (SI) using a microgranular bed to protect micromachined electronic devices (MEDs) for high-g military applications where mechanical excitations reach up to tens of thousands of gs and several hundreds of kHz. The shock isolating phenomenon in the microgranular bed within a metal housing, biomimetically inspired from a spongy bone within a skull of the woodpecker, controls unwanted high-frequency mechanical excitations so that their adverse effects on the embedded MEDs are kept within acceptable limit. The microgranular bed composed of close-packed microglass beads reduces the mechanical excitations transmitted to the MEDs through kinetic energy absorption. Two kinds of tests, a laboratory test and a 60 mm air-gun test, have been made. The laboratory test using a vibration exciter up to 25 kHz has demonstrated that the cut-off frequency (2.2–15.8 kHz) and roll-off steepness (−155.0 to −78.7 dB decade−1) are inversely proportional to the diameter of the close-packed microglass beads (68–875 µm), whereas the vibration absorptivity (0.23–0.87) is proportional. The 60 mm air-gun test under high-g environments of up to 60 000 g has verified that the woodpecker-inspired SI is superior in improving the shock survivability of the MEDs to the conventional one using hard resin.


PACS

85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices

81.40.Pq Friction, lubrication, and wear

62.65.+k Acoustical properties of solids

62.20.Qp Friction, tribology, and hardness

81.20.Wk Machining, milling

Subjects

Electronics and devices

Condensed matter: structural, mechanical & thermal

Nanoscale science and low-D systems

Dates

Issue 3 (7 February 2009)

Received 16 September 2008, in final form 3 November 2008

Published 18 December 2008



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