【作者】 刘旭辉；

【导师】 汪希平； 王文；

【作者基本信息】 上海大学 ， 机械设计及理论， 2010， 博士

【摘要】 磁流变液阻尼器作为一种半主动可控的阻尼器件,自磁流变现象发现后一直是学术界和工程界的研究热点。这种阻尼可控器件,其内部阻尼介质采用磁流变液,该液体主要由微米级尺寸大小的磁性颗粒与载液和稳定剂混合而成,通过调节不同强度的外加磁场,使阻尼通道中磁流变液的流动特性发生变化,从而控制阻尼力。目前高性能的磁流变液在市场上已可以购买,但价格昂贵,因此只有在一些重要或高端的技术领域,有可控磁流变液阻尼器的应用实例。传统的磁流变阻尼器由于是采用腔体充满磁流变液的设计方式,用量大,同时还需专门的密封装置,导致价格昂贵;另外在工作时,硬质的磁性颗粒极易进入到密封部位的间隙里,加剧了密封处的磨损,影响了阻尼器的寿命。本论文针对磁流变液阻尼器在工程应用中碰到的价格昂贵和使用寿命短的瓶颈问题,以现有的多孔海绵磁流变液阻尼器设计为模版,研究了采用多孔泡沫金属替代多孔海绵储存磁流变液并产生阻尼的新型磁流变液阻尼材料的可行性,对这种磁流变液阻尼材料产生阻尼效应的机理进行了理论和实验研究,并对该材料的动态响应和阻尼性能进行了测试和分析。本论文完成的主要工作有:1)提出多孔材料的结构参数选择原则,对相关参数进行了测试,为选择合适的多孔材料储存磁流变液并产生阻尼提供实验依据。研究了磁流变液在毛细管中的上升现象,得到磁流变液在毛细管中的上升高度与孔径的关系以及毛细管内的磁流变液性能变化情况,初步确定了保证磁流变液性能不产生较大变化的最小孔径;测试了不同种类和不同孔隙率的多孔材料储存磁流变液的能力,分析了磁流变液在通过多孔材料后的渗透情况。2)分析和测试了多孔泡沫金属的性能。针对选择的多孔泡沫金属(铜、铁、镍),利用石蜡熔融法,测出多孔泡沫金属的孔隙率,测试了在重力作用下,磁流变液通过多孔泡沫金属后的性能变化与多孔泡沫金属结构参数的关系;对不同种类多孔泡沫金属的相对磁导率及对磁场分布的影响进行了理论和实验研究。3)研究了磁流变液在磁场作用下的上升机理,建立了用于计算磁流变液上升高度的理论模型,搭建了测试磁流变液上升高度的装置,测试了磁流变液在不同强度外加磁场下的上升高度,实验验证了所建立的磁流变液上升高度计算模型的准确性,磁流变液上升高度的理论模型建立和实验验证工作为分析多孔泡沫金属磁流变液阻尼材料的阻尼效应提供了理论依据。4)搭建了多孔泡沫金属磁流变液阻尼材料的性能测试系统,研究了剪切转矩及其影响因素。介绍了性能测试装置的工作原理、主要结构和测试系统,采用计算、仿真和实验的方法分析了所设计装置的内部磁场分布。应用搭建的实验装置研究了不同多孔泡沫金属、剪切间隙、外加电流(磁场)及剪切应变等对多孔泡沫金属磁流变液阻尼材料剪切转矩的影响。结果表明,采用多孔泡沫金属铜储存磁流变液时产生的剪切转矩最大;对于多孔泡沫金属磁流变液阻尼材料,在外加磁场强度和剪切间隙相同的条件下,从多孔泡沫金属中析出磁流变液的量对剪切转矩的影响非常大。5)研究了多孔泡沫金属磁流变液阻尼材料的动态响应性能。定义了三个时间参数用于表征多孔泡沫金属磁流变液阻尼材料的动态响应性能,实验研究了剪切间隙、外加电流(磁场)以及多孔泡沫金属的材料等参数对动态响应性能的影响,同时分析了响应时间的其它影响因素,建立了多孔泡沫金属磁流变液阻尼材料的响应时间计算模型,利用建立的响应时间计算模型,对多孔泡沫金属磁流变液阻尼材料剪切转矩和响应时间的变化进行了分析。更多还原

【Abstract】 Magnetorheological fluid (MR fluid) damper, as a kind of the semiactive and controllable dampers, has been focused for the academia and engineering region since the MR effect was discovered. MR fluid, as the damping medium of the damper, is a stable disperse system composed of two phases, such as micro sized magnetic particles, carrier oil and stabilizer. Although fully commercial, mass-produced MR fluids and devices have been available via the retail market and applied, the high cost of MR fluid damper is still a barrier to widespread commercial acceptance in many areas. The typical MRF dampers need large volume of MR fluid and specific sealing component to restrict MRF leakage make them very expensive. Beside this, the wear produced by the magnetic particles will also shorten the life of the damper.The motivation of the work is to overcome the large volume of MRF and costly seal needed by conventional MRF dampers. Referring to the porous sponge MR fluid damper, this dissertation presents an original idea to use porous foam metal to hold magneto-rheological fluid (MRF) when unexcited and the MR fluid can be propelled when excited with external magnetic field. The feasibility and theory on the porous foam metal used to store MR fluid and produce the damping effect is studied.The main research works of this dissertation are as followings:1) The principles for selection of the porous materials are put forward. The relationship between the MR fluid capillary force and the pore size, the change of MR fluid characteristics in the micro tube such as density are investigated. The MRF storing ability and the penetrability of different porous materials have been evaluated. These experimental works are much useful for the selection of the suitable materials to store MRF.2) The performance of porous foam metals is studied and tested. The porosity of porous foam metal (Fe, Ni and Cu) is measured using fusible paraffin. The relationship between the penetrability of porous foam metal and the change of characteristics of MR fluid is obtained by measuring of MR fluid after flowing through the porous foam metal. The relative permeability of three porous foam metals are measured by vibrating sample magnetometer. The effect of the different materials and thickness of porous foam metals on the distribution of magnetic field is studied.3) The mechanism of the rising phenomenon of MR fluid under magnetic field is investigated. The computing model of the rising height of MR fluid is built up. A test rig is developed to evaluate the rising height under the different magnetic field; the experimental results validate the computing model of the rising height. These works provide the theoretic and experimental basis for the damping effect of MRF soaked porous metal foam (also named porous foam metal MRF damping materials).4) A shearing plate-on-plate test-rig is developed so as to investigate the performance of MRF soaked metal foam. The effect, shearing gap, current and different metal foams on the shearing performance, are investigated experimentally. The porous foam metal Cu, which could provide the maximal shear torque, is found out. At the same condition of magnetic field and shear gap, the shearing performance is sensitive to the volume of the propelled MRF.5) The performance of dynamic response of the MRF soaked porous metal foam is investigated. The three time parameters are defined to describe the dynamic response. The effect, shearing gap, current (or magnetic field) and different metal foams on the dynamic response, are investigated experimentally. The computing model on the response time is built up to explain the shear performance and dynamic response.更多还原