Original Article Journal of Intelligent Material Systems and Structures 1–11 Ó The Author(s) 2020 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/1045389X20906474 journals.sagepub.com/home/jim A magnetic screw pump for magnetorheological clutch durability enhancement Raphae ¨l Pilon , Alexandre Landry-Blais , Benoit Gillet, Anae ¨ le Pin , Jean-Philippe Lucking Bigue ´ and Jean-Se ´bastien Plante Abstract Magnetorheological clutches have great potential for demanding applications such as powertrains and aircraft primary flight controls. However, in such high-power applications (.1 kW), durability is a challenge because of the continuous slippage at the clutch shear interface. To improve durability, this research studies the potential of using a magnetic screw pump to promote fluid mixing within a magnetorheological clutch. The screw flights are made of magnetorheological fluid formed by the concentration of the magnetic field lines around helical grooves machined into the shear interface (drum) of the clutch. While the magnetic pump does not display a typical screw pump behavior, a semi-empirical yield screw pump model is proposed to better understand the macroscopic behavior. Experimental flow characterization results show that the pressure–flow relation is significantly affected by the number of grooves, magnetic field intensity, and rotational speed. For a clutch containing 50 mL of magnetorheological fluid, maximum flow rates of up to 25 mL/ min and a maximum pressure of 150 kPa are achieved. Finally, durability test results show that the magnetic screw pump can increase durability by up to 42% when compared to a standard magnetorheological clutch, confirming that such a device is a viable solution for promoting durability. Keywords Magnetorheological, clutch, magnetorheological fluid, durability, screw, pump, circulation 1. Introduction 1.1. Motivation Magnetorheological (MR) actuators rely on a single motor to power the input of several MR clutches, while the output is maintained in continuous slippage. During operation, the torque transmitted to the output of each clutch is controlled by the modulation of the magnetic field intensity. The fast dynamics of MR clutches (Viau et al., 2017) coupled with their fundamental robustness and reliability due to the absence of metal–metal contacts make MR actuators of interest to the aerospace industry, for applications such as aircraft primary flight control (Chouinard et al., 2015). However, given the dissipative nature of MR clutches, magnetorheological fluid (MRF) durability represents an important challenge. This is espe- cially true in applications where significant power ( .1 kW) is dissipated in a limited amount of MRF ( \100 mL). 1.2. Background and literature Multiple failure modes regarding MRF durability have been identified in the literature. In-use-thickening (IUT) was the main failure mode observed in MR dam- pers, where iron particles would break down into smaller particles, causing an increase in off-state viscos- ity until the device is unusable (Carlson, 2002). In high- temperature applications, iron particles were shown to oxidize, resulting in reduced MRF shear stress propor- tionally to the oxide layer of the particles (Ulicny et al., 2007). Silicon oil–based MRFs were found prone to base oil polymerization, also resulting in viscosity increase (Carlson, 2002). With other types of base oil, such as polyalphaolefin and perfluorinated polyether (PFPE), polymerization is not an issue. However, petroleum-based MRFs have a tendency to outgas, resulting in a pressure build-up which can induce leaks Interdisciplinary Institute for Technological Innovation (3IT), Faculty of Engineering, Universite ´ de Sherbrooke, Sherbrooke, QC, Canada Corresponding author: Raphae ¨l Pilon, Interdisciplinary Institute for Technological Innovation (3IT), Faculty of Engineering, Universite ´ de Sherbrooke, 3000 Universite ´ Blvd, Sherbrooke, QC J1K 0A5, Canada. Email: raphael.pilon@usherbrooke.ca