磁流变液力学性能及其应用研究

发布时间：2018-03-26 18:26

本文选题：空心结构纳米颗粒　切入点：磁-力-电耦合响应　出处：《中国科学技术大学》2017年博士论文

【摘要】：作为一种磁敏智能材料,磁流变液(Magnetorheological Fluid,MRF)主要由磁性颗粒和液态的基体共同组成,通常还会添加一些其它的添加剂来增加其稳定性。对磁流变液施加外部磁场,它能够在几毫秒的时间内从液态转变成为类固态,而当外部磁场撤去时,它又能够迅速地从类固态转变为液态。磁流变液因其优良的性能迅速地引起了大家的关注,越来越多的学者从性能优化、机理和应用等方面对其展开研究;虽然关于磁流变液的研究很多,但是依然有很多问题亟待解决,例如磁流变液的沉降问题依然困扰着磁流变液的应用、关于磁流变液导电机理的研究还不透彻、磁流变器械性能有待提高等。因此,本文中首先研究了具有空心结构的磁性颗粒对磁性液体的流变性能和沉降性能的影响,并用数值模拟的方法对其进行了分析;其次研究了磁场、振荡剪切、挤压等外界因素对磁流变液电学性能的影响,并探究了磁流变液的法向力与电学性能之间的联系;最后设计开发了两种基于磁流变液法向力的挤压式阻尼器,并对它们的动态力学性能进行了测试和分析。具体工作内容如下:1.空心结构的颗粒对磁性液体性能的影响制备了一种具有空心结构的四氧化三铁纳米颗粒,用于研究空心结构对磁性液体性能的影响。表征结果显示得到的产物是纯度很高,并且具有空心结构的颗粒,具有超顺磁性和较高的饱和磁化强度。用四氧化三铁空心球颗粒制备了磁性液体,并测试了其流变性能和抗沉降性能,结果表明所得的磁性液体具有较高的剪切屈服应力,抗沉降性也很好。利用颗粒动力学方法对磁性液体进行了数值模拟,得到了磁性液体在不同条件下的剪切应力,以及磁性液体内部的颗粒链在外界磁场和剪切的作用下结构演化情况;数值模拟和试验测试的结果吻合得很好。从试验和数值模拟两个方面对具有空心结构的四氧化三铁纳米颗粒进行了研究,结果表明空心球结构的四氧化三铁性能更加优良,为磁流变液的优化设计提供了另一种思路。2.磁流变液的磁-力-电耦合响应利用自建的测试系统分别研究了振荡剪切和挤压条件下,磁流变液的磁-力-电耦合响应。首先研究了外界磁场对磁流变液电学性能的影响,对磁流变液施加外界磁场,可以使其导电性增加数千倍。振荡剪切也可以显著地改善磁流变液的导电性,并且会导致样品电阻随着外界的振荡剪切一起振荡变化。提出了一种颗粒导电模型,对磁流变液在不同条件下的导电性进行了理论分析。对磁流变液施加挤压时,样品的导电性随着挤压速度、挤压应变和基体粘度等外界条件的改变而改变。研究了在磁场的作用下,样品法向力与电阻之间的关系,发现样品法向力和电阻的变化都依赖于磁流变液内部颗粒链结构的演变。上述研究为磁流变液在传感器、非接触式检测与控制等领域的应用提供了必要的理论依据。3.挤压式磁流变阻尼器基于磁流变液的法向力,设计了一种纯挤压式的磁流变阻尼器,并对其动态力学性能进行了测试与分析。测试结果表明纯挤压式磁流变阻尼器的动态力学性能良好,输出的最大阻尼力可以达到6 kN,高于相同尺寸的传统阻尼器输出的阻尼力,并对阻尼器的工作原理进行了详细的分析;研究了纯挤压式阻尼器在工作时,阻尼力的组成与来源。对纯挤压式阻尼器进行改进,设计了挤压-阀混合式磁流变阻尼器。混合式阻尼器最大的亮点是在运动的活塞中加入了一个供磁流变液流通的通道,可以极大地促进混合式阻尼器中磁流变液的流动,从而抑制磁流变液在混合式阻尼器中的沉积。混合式阻尼器的动态力学性能测试结果表明,混合式阻尼器输出的最大阻尼力大约为6.5 kN,并且力-位移曲线很饱满;这表明我们的改进不仅能够提高阻尼器输出的阻尼力,还能有效地抑制阻尼器中磁流变液的沉积,提高阻尼器的性能。最后用Back Propagation神经网络对混合式阻尼器输出的阻尼力进行了分析,不同条件下阻尼力的神经网络预测值与试验测试值很接近,说明我们的阻尼器在半主动控制方面有着很广阔的应用前景。
[Abstract]:As a kind of magnetic sensitive smart material, magneto rheological fluid (Magnetorheological Fluid MRF) is mainly composed of a matrix of magnetic particles and liquid together, usually add some other additives to increase its stability. The external magnetic field is applied on the magnetic rheological fluid, it can in a few milli seconds from the liquid into a solid. When the external magnetic field is removed, it can quickly from solid into liquid. Magnetorheological fluid because of its good performance quickly attracted everyone's attention, more and more scholars from the performance optimization, mechanism and applications of the research; although a lot of research about the magnetorheological fluid, but still there are a lot of problems to be solved, such as the settlement of MRF are still plagued by the application of magnetorheological fluid, a magnetorheological fluid guide mechanism research is not thorough, magneto rheological instrument performance needs to be improved Therefore, this paper firstly studied the influence of rheological properties of magnetic particles with hollow structure of the magnetic fluid and settling properties, and by numerical simulation method to analyze the magnetic field; secondly, oscillatory shear, extrusion and other external factors affect the performance of magnetorheological fluid electric, magnetic and explore the normal force between rheological and electrical properties of the contact; finally, designed and developed two kinds of MRF method based on force to squeeze damper, and dynamic mechanical properties of them were tested and analyzed. The specific contents are as follows: 1. hollow structure of the particles impact on the property of magnetic liquid was prepared. With the hollow structure of the Fe3O4 nanoparticles, and used to study the effects of hollow structure on the performance of magnetic fluid. The characterization results showed that the product obtained is very high purity, and has a hollow structure with granules. Superparamagnetic and high saturation magnetization. Using Fe3O4 hollow sphere particles prepared by magnetic fluid, and the rheological properties and anti settling performance, results show that the shear magnetic liquid with high yield stress, anti settling is also very good. The particle dynamics method for numerical simulation of magnetic fluid to obtain the shear magnetic fluid under different conditions of stress, and the magnetic fluid inside the particle chain in external magnetic field and shear under the action of structure evolution; numerical simulation and test results are in good agreement. The two aspects of the study of magnetite nanoparticles with hollow structure from test and numerical the simulation results show that, the performance of Fe3O4 hollow ball structure is more excellent, provides another way.2. MRF magnetic force for the optimization design of magnetorheological fluid electric coupling Response were studied by oscillatory shear and extrusion conditions using the self built test system, magnetorheological fluid magnetic force electric coupling response. First studied the influence of external magnetic field on the electrical properties of magnetorheological fluid, applying external magnetic field on the magnetic rheological fluid, can make the conductivity increase the number of thousands of times. The conductivity oscillation shearing can significantly improve the MRF, and will cause the sample resistance with the outside world with oscillatory shear oscillations is presented. A model of conductive particles, the conductivity of magnetorheological fluid under different conditions were analyzed. The fluid applied extrusion on the magnetic current, the conductivity of the samples with extrusion the speed of extrusion, strain and viscosity of the matrix and other external conditions change. In the study of the magnetic field, the sample method to the relationship between force and resistance of the samples to found changes in force and resistance are dependent on the magnetic flow The evolution of liquid variable particles inside the chain structure. The research of magnetorheological fluid in the sensor,.3. provides a necessary theoretical basis for the extrusion of magnetorheological damper force based on MRF method application of non-contact detection and control field, design a kind of pure squeeze type magnetic damper, and the the dynamic mechanical properties were tested and analyzed. The test results show that the dynamic mechanical properties of pure squeeze type MR damper, the maximum damping force output can reach 6 kN, the output is higher than the traditional damping force damper of the same size, and the working principle of the damper are analyzed in detail; the pure squeeze the work type damper, composition and source of damping force. The pure squeeze damper was improved, the design of extrusion - valve hybrid magneto rheological damper. The hybrid damper is the biggest bright spot in the sports activity Plug added for a magneto rheological fluid circulation, can greatly promote the magnetorheological fluid damper in mixed flow, thereby inhibiting the deposition of magnetorheological fluid damper. In the hybrid test results of dynamic mechanical properties of hybrid damper showed that the maximum damping force of hybrid damper output is about 6.5 kN, and the force displacement curve is full; this shows that our improvement can not only improve the damper force output, can effectively inhibit the deposition of magnetorheological fluid damper in improving damper performance. Finally, analyzed the damping force of the hybrid damper output using Back Propagation neural network, the prediction value is close to the the test value of neural network damping force under different conditions, we show the damper has a broad prospect in semi-active control.

【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TB381

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