【作者】 侯鹏；

【导师】 程海斌；

【作者基本信息】 武汉理工大学 ， 材料学， 2008， 硕士

【摘要】 磁流变液(Magnetorheological fluid,MRF)是一种由软磁性颗粒、基液以及添加剂组成的悬浮液,由于磁流变液中铁磁性颗粒在外加磁场作用下形成有序结构,且该结构随外加磁场的变化而变化,因此它的力学性能可由外加磁场来控制,并且这种控制是极速、可逆的。磁流变液的这一可控特性可以在许多领域得到广泛应用,正是由于磁流变液具有如此广阔的工程应用前景,因而成为近年来最具应用潜力的智能材料之一。目前,磁流变液的稳定性能的研究主要集中在沉降稳定性的研究,以及如何改善磁流变液的沉降稳定性。本文基于磁流变液长期稳定性随结构变化而改变,而结构变化引起其零场粘度变化的特点,根据时温等效原理提出了一种新的思路,研究长期静置的磁流变液稳定性的分析模型,即用粘度变化评价磁流变液长期稳定性分析模型。总结文献中所报道的磁流变液沉降稳定性的表征方法。到目前为止,国内外文献所报道的表征方法包括:静置观察法、沉降电势法、电感法、透光率脉动检测法、定时定量采样化学分析法。这些方法在一定程度上都无法快速、简捷的表征磁流变液的长期稳定性。研究发现,磁流变液的结构变化直接影响磁流变液的粘度。所以本文拟通过研究磁流变液零场粘度变化建立评价MR液稳定性的分析模型。首先,制备一批磁性颗粒体积分数为40%的油基磁流变液。通过升高温度加速磁性颗粒的沉降,来模拟磁流变液在室温下的沉降。通过研究发现:室温下长期静置的磁流变液的零场粘度总是与经过90℃条件静置的磁流变液的零场粘度相近。在此基础上,建立表征磁流变液沉降稳定性的分析模型。通过模拟在磁流变液服役期间温度的变化,研究了温度对磁流变液沉降稳定性的影响。结果表明:温度可以加速磁流变液中分散颗粒的布朗运动,随着温度的升高,磁流变液的零场粘度、剪切应力都有下降的趋势,作为结果之一,磁流变液的沉降也会加剧。更多还原

【Abstract】 Magnetorheological (MR) fluids are dispersions of fine (～0.05-10μm) magnetically soft, multidomain particles. The apparent yield strength of these fluids can be changed significantly within milliseconds by the application of an external magnetic field. MR fluid devices are being used and developed for shock absorbers, clutches, brakes, and seismic dampers. The major goals of this research were to advance the science of MR fluids.The stability of magnetorheological (MR) fluids used in magnetorheological application remain is a main of factors to hold back the development of magnetorheological technology. And how to character the sedimentation stability of MR fluids is also a key technology. The stability of MR fluids in long time will change with the structure, which can bring the chang of the viscosity. In this article, a new method is discussed: the viscosities were measured by the Rheometric Scientific Advanced Rheometric Expansion System (ARES) dynamic strain rheometer. And a modle was established to predict the stability of the MR fluids.At present, Some methods for characterization of the stability fasten on the sedimentation stability of the MR fluids. The current techniques of improving the subsidence stability in magnetorheological fluids are reviewed in detail. But, there is not a viable method to character the sedimentation stability of the MR fluids, which is expedite and save sample. In this article, a modle. which will save time, was established to predict the stability of the MR fluids.At first, MR fluids were prepared with volume function of 40%. Some samples of MR fluids were transferred to 10 ml graduated test tubes and placed in still storage,at a room temperature. And another were placed at 90℃. The sedimentation ratio can be obtained by observing the phase boundary between the supernatant liquid and the concentrated suspension, until reaching an asymptotic value. Secondly, the rheology properties of the MR sample were tested. The relationship of the viscosity between room temperature and 90℃was discussed.The effection of temperature on the sedimentation stability of MR fluids was discussed. We found that the viscosity and shear stress of MR fluids without magnetic fields was decreased with the increasing of the temperature. As a result, the sedimentation of MR fluids became quickly.更多还原