Design of a Mixed Mode MR Damper with Reduced Off-State Damping
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Publisher:The Ohio State University
Series/Report no.:The Ohio State University. Department of Mechanical Engineering Honors Theses; 2005
Magnetorheological (MR) fluid, a suspension of iron particles in oil, is a ‘smart fluid’ whose yield stress changes with the application of a magnetic field. MR fluid is used in dampers to provide variable damping to systems. A damper in mixed mode, a common mode of damper design, consists of a piston in a cylinder with the surrounding volume filled with MR fluid. The critical parameter in this design is the gap distance between the piston and cylinder. An advantage of mixed mode dampers is that they are capable of producing very high damping forces (when a strong magnetic field is applied). However, they also have very high off-state force (when no magnetic field is applied). The goal of this research is to lower the off- state damping forces. This is achieved by placing semi-circular cutouts around the piston circumference. Cutouts lower the off- state damping force and still maintain a high on-state holding force by varying the gap distance between the piston and the cylinder, therefore allowing more fluid to flow through in the off state. The damping forces were modeled using the Bingham plastic flow model. The design of an MR damper with cutouts and the advantages that cutouts provide were then analyzed. The size and numbers of cutouts were varied. Trends of dampers with cutouts were studied. Based on the analysis, a prototype damper was designed, built, and tested.
Mechanical Engineering Department
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