Design of a yield stress characterizing platform for magnetorheological fluid magnetized by permanent magnets
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TECHNICAL PAPER
Design of a yield stress characterizing platform for magnetorheological fluid magnetized by permanent magnets Ping-Hsun Lee1 • Jen-Yuan Chang1 Received: 13 December 2019 / Accepted: 25 May 2020 Ó Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract In this paper we proposed a platform for measuring shear force of magnetorheological (MR) fluid by which the relationship of yield stress and magnetic flux density of specific materials can be determined. The device consisted of a rotatable center tube placed in a frame body and the magnetic field was provided by two blocks of permanent magnets placed oppositely outside the frame body. The magnitude and direction of the magnetic flux were manipulated by changing the distance of the two permanent magnets from the frame body and rotating the center tube, respectively. For determining the magnetic field of the device, we adopted an effective method by fitting the finite element method result to the measured one and then rebuilt the absent components to approximate the magnetic field, which was hardly to be measured as different device setup were required. With the proposed platform and analytical methods, the drawing shear force and the corresponding yield stress contributed by MR fluid in respect to the magnitude and direction of given magnetic flux density could be evaluated effectively for specific designing purposes without the requirement of a large, complex, and expensive instrument.
1 Introduction A magnetorheological (MR) fluid is a smart material that consists of micro-sized magnetic particles dispersed in a carrier fluid such as oil. In the absent of external magnetic field, it appears as normal viscous fluid. When external magnetic field exists the magnetized particles link as chains thus restrict the movement of the fluid, making the MR fluid resistive to shear force. This reaction is reversible and responses in several tens of millisecond (Kciuk and Turczyn 2006; Olabi and Grunwald 2007; Spaggiari 2013). Several devices such as damper, brake, clutch, etc. employed this MR fluid effect such that their properties can be controlled by changing magnetic fields (Carlson et al. 1996; Jolly et al. 1999; Wang and Meng 2001). In addition to traditional machineries, many novel devices such as soft gripper (Nishida et al. 2016; Tsugami et al. 2017), haptic interface (Song et al. 2018) were also developed by
& Jen-Yuan Chang [email protected] Ping-Hsun Lee [email protected] 1
Department of Power Mechanical Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
leveraging the controllable semi-solid and rheological properties of MR fluid. Since the performances of these devices depends on the mechanical properties of MR fluid itself, it is essential for a designer to acquire the fundamental properties of MR fluid, especially on how they are related to the alteration of magnetic field. Although the datasheets of specific MR fluid were provided by their vendors, it is
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