【作者】 廖国江；

【导师】 龚兴龙； 宣守虎；

【作者基本信息】 中国科学技术大学 ， 固体力学， 2014， 博士

【摘要】 磁流变弹性体(MRE)是一种主要由微米级的铁磁性颗粒和橡胶类基体构成的智能复合材料,其性能(模量、阻尼、变形、电阻抗等)可以由外加磁场快速、连续和可逆地控制,因此MRE在工程实践中具有广泛的应用前景。目前对MRE力学性能的研究主要集中在其剪切力学性能上,对法向力学性能的研究较少。此外,MRE在剪切状态下的承载能力较差,而在压缩状态下能承受较大的载荷。因此,MRE在压缩状态具有更好的工程应用价值。针对MRE可能的工程应用,本文首先对MRE的法向力和高应变率下的压缩性能进行了研究。在此基础上,结合前人的研究成果,针对MRE在振动控制应用中存在的问题,对MRE在吸振和隔振方面的应用展开了讨论,解决了MRE在振动控制应用中面临的器械设计和控制算法问题,初步实现了MRE的工程应用。本文的主要内容如下：1.采用安东帕MCR301流变仪研究了MRE在压缩状态、准静态剪切状态和动态剪切状态下的法向力,得到了MRE的法向力与外加磁场、剪切应变、温度和颗粒分布等的关系。在压缩状态下,MRE的法向力随着外加磁场的增大而增大,当铁颗粒达到磁饱和时,法向力也表现出饱和的趋势。此外,预压力、颗粒分布、外界环境温度和磁场的循环加载对MRE的法向力行为均有影响。在准静态剪切下,MRE的法向力与剪切应变密切相关。低磁场时,法向力随着剪切应变的增大而减小；高磁场时,法向力随着剪切应变的增大而增大。法向力的这种变化趋势与预压缩方向的弹性模量和颗粒链在外加磁场下受到的力矩相关。这两个因素的共同作用导致了MRE在准静态剪切下的法向力行为。在振荡剪切下,MRE的法向力与振荡剪切的幅值密切相关。当应变幅值低于7%时,法向力随剪切应变的变化趋势与准静态时类似。但是,当剪切应变幅值大于7%时,法向力随着剪切应变的增加急剧地减小,这与MRE内部铁颗粒链的断裂密切相关。该部分的研究工作为MRE在作动器和减振器等工程器械方面的应用奠定了基础。2.采用改进的SHPB测试系统研究了MRE在高应变率条件下的动态压缩力学性能,得到了MRE的动态压缩力学性能与外加磁场和应变率的关系,并提出了相应的本构方程。在屈服前的阶段,MRE的动态压缩力学性能具有明显的磁场相关性和应变率相关性。随着外加磁场的增加,杨氏模量增加,屈服应力增加,而屈服应变减小。随着应变率的增加,杨氏模量增加,屈服应力增加,而屈服应变减小。为了描述MRE在屈服前的动态压缩力学性能,提出了一个由超弹性、粘弹性和磁致应力组成的本构模型。实验和理论的对比表明,所提出的本构模型可以很好地描述MRE在高应变率下的动态压缩力学性能。在屈服后的阶段,当应变大于屈服应变时,MRE的应力表现出逐渐减小的趋势。随着应变的进一步增加,应力达到最小值。当应变大于0.2时,应力表现出逐渐增加的趋势。MRE屈服后的过程可以看作是其内部铁颗粒链逐渐被破坏和MRE逐渐被压实的过程。该部分的研究工作为MRE在抗冲击方面的应用提供了实验基础。3.在传统MRE吸振器的基础上,通过增加主动力控制,设计了移频范围宽且阻尼小的MRE主动自调谐式吸振器。主动自调谐式吸振器采用音圈电机作为阻尼补偿元件,通过主动力控制使得所设计的吸振器在保留传统MRE吸振器固有频率快速可调特点的同时又克服了传统MRE吸振器阻尼大、减振性能差的缺点。该部分研究对于解决工程实践中振动控制相关的问题具有一定的意义。4.为了提高半主动吸振器刚度控制的精度和速度,设计了一种基于相位差的MRE吸振器刚度控制算法。该算法不依赖于吸振器控制量与固有频率的精确模型,具有调整时间快、稳定性好和易实现等优点。实验和仿真的结果都验证了算法的可行性和有效性。该部分研究不仅可用于MRE吸振器的刚度控制,对所有的半主动吸振器均具有较好的控制效果,对于提高半主动吸振器刚度控制的速度和精度具有重要的意义。5.采用MRE作为变刚度元件,音圈电机作为变阻尼元件设计了刚度和阻尼实时可控的MRE隔振器原理样机及其控制算法。实验结果表明在ON-OFF控制下,MRE隔振器具有较好的隔振效果,可以有效地减小负载的振动响应。尤其对负载在固有频率附近的振动也具有较好的隔振效果。该部分研究对于解决工程实践中振动控制相关的问题具有一定的意义。更多还原

【Abstract】 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.更多还原