Title: Critical factors for MR fluids in vehicle systems

Authors: J. David Carlson

Addresses: Materials Division, Lord Corporation, 406 Gregson Drive, Cary, NC 27511, USA

Abstract: In developing and manufacturing MR fluids for use in vehicle systems, the greatest barriers to success have not been factors initially viewed as being most critical during the early R&D stages. While high yield strength and settling stability are certainly important, other factors such as low off-state viscosity, fluid durability and fluid manufacturability have often proven to be more challenging requirements. The present paper looks at conditions found in MR fluid devices operating in typical vehicle systems where shear rates may exceed 105 s–1 and devices are called upon to operate for many millions of cycles. The problem of ||in-use-thickening|| wherein an MR fluid that is subjected to long-term dynamic use and progressively thickens until it eventually becomes an unworkable paste is described. A guideline for estimating the life of MR fluid in a particular application is discussed.

Keywords: magnetorheological; MR fluid; life-testing; in-use-thickening; semi-active; damper; settling; durability; QS-9000.

DOI: 10.1504/IJVD.2003.003572

International Journal of Vehicle Design, 2003 Vol.33 No.1/2/3, pp.207 - 217

Published online: 19 Sep 2003 *

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