Optimization And Characterisation Of A CF850 Magnetorheological Mount Of The Automobie Engine

With the rapid development of the economy,automobiles have become indispensable for today’s people,who have higher expectations of them than ever before.For better comfort and lower prices,lightweight and vibration-damping designs are required.Generally,conventional automotive mounts are passive ones such as rubber mounts and hydraulic mounts,which provide vibration isolation within limits.Currently,magnetorheological mounts are widely studied and applied because they can improve the vibration isolation performance of mounts in a wide range of frequencies.In this thesis,a magnetorheological mount in the squeeze mode was designed.The structural parameters of the mount were designed and optimised in three dimensions: damping,magnetic circuit,and static stiffness.The optimal parameter combination was obtained through simulations and emulations,and verified through experiments,making the mount relevant to practical engineering applications.The main efforts of this thesis are as follows.(1)The rheological properties,working mode,and working principles of the magnetorheological fluid were interpreted.The magnetorheological mount in the squeeze mode was designed based on conventional hydraulic mounts.The rubber mainspring,magnetic circuit,and damping force designs were also carried out.After the specific parameters of the rubber mainspring were determined,its hardness was calculated using ANSYS,and the magnetic circuit of the mount was simulated using MAXWELL,from which the damping force and adjustable coefficient of the mount were derived.(2)The damping design of the magnetorheological engine mount was optimised.A series of tests were established using Design expert.The structural parameter combinations from these tests were substituted into the simulation model and solved separately at different values of current.Afterwards,the relationship between the damping force and the dynamic adjustable coefficient was fitted by quadratic regression equations to establish a response model and then to achieve the structural parameter combination leading to optimal damping.(3)The magnetic circuit design of the magnetorheological engine mount was optimised.Based on the fundamental theories of electromagnetic field,the magnetic circuit of the mount was analysed.A two-dimensional model of the magnetic circuit of the mount was constructed using MAXWELL,and a 4-factor,4-level orthogonal test was designed: the flow channel width in the squeeze mode,the gap between the squeeze channel plates,the height of the excitation coil,and the height from the bottom of the magnetic core to the excitation coil were selected as four influencing factors and the magnetic flux density as an evaluation index.The test results were subjected to range analysis to obtain the optimal structural parameter combination for the mount.(4)The static stiffness design of the magnetorheological engine mount was optimised.Based on the working principles of hydraulic mounts,a formula for calculating the static stiffness of the magnetorheological mount was derived,which was used to establish a model for optimising the static stiffness of the mount.According to the formula,three structural parameters were selected as the design variables,and the static stiffness of the mount was taken as the objective function.Based on engineering applications of the mount and the simulation data,the constraints were determined,and the optimisation model was solved in MATLAB Simulink,leading to optimal static stiffness and optimal structural parameter combination for the mount.(5)Static and dynamic stiffness tests were carried out on the performance of the magnetorheological mount.The principles,objectives,and methods of the tests were discussed,and the corresponding test results were obtained.Through analysis of the results,the optimised structural design of the mount was verified to be valid,and the results in this thesis to be universally applicable.