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Proceedings Paper

A thermo-hydraulic wax actuation system for high force and large displacement applications
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Paper Abstract

An actuation system, making use of paraffin wax as a smart material, has been developed for high force, large displacement applications. Wax actuators exploit the significant volumetric expansion (typically between 10 and 15%) experienced during the solid to liquid phase change of paraffin wax. When contained, this expansion results in considerable hydrostatic pressure. Traditionally, wax actuators are designed such that the wax acts directly, via a compliant seal, on an output device such as a piston. We propose using an additional intermediate (passive) fluid to transmit pressure to a separate remote actuator. In essence, we propose a solid-state 'pump' for hydraulic actuation, with no moving parts and which requires no maintenance. The pump makes use of paraffin wax pellets, submerged in hydraulic fluid. The pellets are encapsulated in silicone rubber to prevent contamination of the hydraulic fluid. Upon melting, the volumetric expansion is used to displace the hydraulic working fluid, which is in turn used to drive a conventional hydraulic actuator. Making use of only 65g of paraffin wax, heated from room temperature to 80ºC, the pump generated a blocked pressure of 45MPa and displaced 15.7ml of hydraulic fluid. The pump was used to drive a commercial actuator, and achieved a free stroke of 24.4mm and a blocked force of approximately 29kN.

Paper Details

Date Published: 11 April 2007
PDF: 9 pages
Proc. SPIE 6527, Industrial and Commercial Applications of Smart Structures Technologies 2007, 652707 (11 April 2007); doi: 10.1117/12.714737
Show Author Affiliations
Craig S. Long, CSIR Material Science and Manufacturing (South Africa)
Philip W. Loveday, CSIR Material Science and Manufacturing (South Africa)

Published in SPIE Proceedings Vol. 6527:
Industrial and Commercial Applications of Smart Structures Technologies 2007
L. Porter Davis; B. K. Henderson; M. Brett McMickell, Editor(s)

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