Study On The Assist’s Braking Device For Oil Drill Rig With Stirring Magnetorheological Fluids

Magnetorheological(MR) fluids are a kind of smart materials whose reological properties may be rapidly varied by application of magnetic field. Therefore MR fluids have found extensive application in numerous fields such as clutch, brake. Now most auxiliary brakes used in drill rigs are water brake and eddy current electromagnetic brake. But they suffer from some disadvantages such as low braking power, large size and so on.The design scheme of agitated MR auxiliary brake and its brake principle was presented in this paper. Because of the rapidly increase of the viscosity of MR fluids with the application of magnetic field, resistance was produced to the rotor rotating in the fluids and accordingly brake torque was generated. In combination with the constitutive equation of MR fluids, calculation formula of brake torque was deduced theoretically. Based on the rheologic behavior of MR fluids and the basic parameters of drill rig, the framework of this new type of MR auxiliary brake was preliminarily devised. Meanwhile, various factors influencing MR fluids auxiliary brake torque were analyzed. Consequently, structural parameters of brake, magnetic circuit as well as materials used were determined. At last, with the brake prototype the experimentation of measuring brake torque was carried out on specially designed testing machine and brake performance and other properties of the MR fluids auxiliary brake were further summarized. It was found that the theoretical analysis was consistent with the experimental result and the MR fluids auxiliary brake possessed good brake performance.