Mechanical Property Of Magnetorheological Elastomer And Its Application In Vibration Control

Magnetorheological elastomer (MRE) is a kind of smart composite consisting of micron sized ferromagnetic particles and rubber-like matrix. Its properties, such as modulus, damping, deformation, electric impedance and so on, can be controlled by the external magnetic field rapidly, continuously and reversibly. Due to these unique properties, magnetorheological elastomer can be used in many engineering fields. Recently, the study of magnetorheological elastomer is focused on the shear property, while few reports on the normal properties can be found. In addition, the magnetorheological elastomer can bear more loads in the compression status than that in the shear status. Therefore, the magnetorheological elastomer may be more proper to work in the compression status than in the shear status. The work in this dissertation first discussed the normal properties of magnetorheological elastomer, including the normal force and the compressive property under high strain rate. Then, based on the studies on the normal properties and the reported work by the other researchers, the work in this dissertation further discussed the application of magnetorheological elastomer in the vibration absorbing and vibration isolation. The details are as follows.1. The normal force of magnetorheological elastomer under compression status, quasi-static shear and oscillatory shear were studied using Anton Paar MCR301rheometer respectively. The relation among the normal force of magnetorheological elastomer, the external magnetic field, the temperature, the pre-compression force and the distribution of the iron particles were analyzed. It was found that the normal force of magnetorheological elastomer increased with increasing magnetic field under compression status. When the embedded iron particle reached magnetic saturation, the normal force reached the maximum value. Besides, the normal force of magnetorheological elastomer was influenced by the particle distribution, pre-compression force, environmental temperature and the loading process of magnetic field. Under quasi-static shear, the normal force of magnetorheological elastomer was related to the shear strain. When the external magnetic field was low, the normal force of magnetorheological elastomer decreased with increasing shear strain. When the external magnetic was high, the normal force increased with increasing shear strain. The complex relation between the normal force and the shear strain was resulted from the elastic modulus in the pre-compression direction and the magnetic torque applied on the iron chain in the magnetic field. Under oscillatory shear, the normal force of magnetorheological elastomer was influenced by the amplitude of the shear strain. When the strain amplitude was smaller than7%, the tendency of the normal force with increasing shear strain was similar to that in the quasi-static shear. However, when the strain amplitude was larger than7%, the normal force decreased sharply with increasing shear strain which was due to the change or break of the iron chain. The work in this part would provide the experimental data for the application of magnetorheological elastomer in vibration absorber, actuator and so on.2. The dynamic compression property of magnetorheological elastomer under high strain rate was investigated using modified SHPB technology. The relation among the dynamic compression property of magnetorheological elastomer, the magnetic field and the strain rate were discussed. In the pre-yield region, the compression property of magnetorheological elastomer was influenced by the external magnetic field and the strain rate significantly. With increasing magnetic field, the Young’s modulus and the yield stress increased while the yield strain decreased. With increasing strain rate, the Young’s modulus and the yield stress increased while the yield strain decreased. To characterize the compression property of magnetorheological elastomer, a constitute model consisting of hyperelasticity, viscoelasticity and a magnetic part was proposed. Calculation results showed that the proposed constitute model agreed well with the experimental data. In the post-yield region, the stress first decreased to a minimum value and then increased smoothly with increasing strain when the strain exceeded the yield strain, which was due to the change of the iron chain. The work in this part would provide experimental data for the application of magnetorheological elastomer in shock absorbing.3. A kind of magnetorheological elastomer based adaptive tuned vibration absorber, which was named magnetorheological elastomer based active adaptive tuned vibration absorber, was designed to overcome the disadvantage of large damping in the traditional magnetorheological elastomer vibration absorber. A voice coil motor controlled by the velocity feedback was incorporated into the vibration absorber to compensate the damping force so as to reduce the damping of the magnetorheological elastomer vibration absorber. Experimental results showed that the damping of the proposed vibration absorber was low. The frequency shift property and the vibration attenuation property were satisfying. The proposed vibration absorber in this part could be used in vibration control in engineering.4. A kind of phase based stiffness tuning algorithm was proposed for the magnetorheological elastomer tuned vibration absorber to improve the stiffness control effect and speed. The proposed stiffness tuning algorithm did not rely on the accurate description of the relation between the control signal and the nature frequency. Experimental results demonstrated that the proposed algorithm was efficient and fast for the magnetorheological elastomer based tuned vibration absorber to track the excitation frequency. The proposed stiffness tuning algorithm is efficient for not only the magnetorheological elastomer tuned vibration absorber but also the other semi-active dynamic vibration absorber.5. A vibration isolator prototype with real-time tunable stiffness and damping was proposed using magnetorheological elastomer as its tunable stiffness and voice coil motor controlled by the velocity feedback as its tunable damping. Experimental results demonstrated that the proposed vibration isolator showed satisfying isolation effect under the ON-OFF control strategy. The response of the payload was significantly suppressed in comparison to the passive system especially in the frequency band around the nature frequency. The proposed vibration isolator in this part could be used in vibration control in engineering.