软铁/锶铁氧体磁流变液的磁动力学特性

前期工作中分别将软磁微米粒和锶铁氧体纳米粒表面改性，通过适当方法在基液中成功形成稳定的磁流变液，具有极好的化学稳定性、极低的零磁场粘度和极强的磁响应，在外磁场作用下表现出特异的结构和性能，其粘度瞬间增大3个数量级，由液态转变成类固态，比磁性流体的磁响应性更强烈、展现出更复杂的多相流和流变特性。本研究以磁流变液中磁性微米粒在磁场和剪切流场中的链状等微观结构作为物理模型，考虑浓度、磁场强度、外力大小、速度梯度和时间，推导本构方程，描述磁流变液的磁增粘、磁凝固、磁动力学的时滞特性、静态结构破坏的Bingham特性和动态流变断裂等失稳现象；将本构方程和磁场力作为源项置入N-S方程，得到描述磁动力学的多尺度模型，模拟磁流变液的动态复杂特性；使用哈克旋转流变仪、Couette(双平板拉伸剪切流场)流变仪和高速摄像的实验方法，验证和完善多尺度模型。研究结果可用于磁流变阻尼、减震、抛光、离合和无极变速等。

The soft magnetic microparticles (carbonyl iron powder) and strontium ferrite magnetic nanoparitcles were surface modified, respectively, and were successfully dispersed in base fluid to form stable magneto-rheological fluid (MRF) in the preparatory work. The as-prepared MRF has superior chemical stabiligy, very low viscosity at zero magnetic field intensity and extraordinary strong magnetic response. Its viscosity increases three-order of magnitude and its form changes from liquid to quasi-solid state, demonstrating special micro-structures and characteristics, and showing much complicated multiphase and rheological properties at external magnetic field. In the present investigation, the constituitive equation (CE), as a function of concentration, magnetic intensity, external force, velocity gradient and time, will be derived based on the chain microstructure of magnetic microparticles in the flow field with shearing force and applied magnetic field. The CE could be used to describe the magnetic viscosity augment, magnetic solidification, hysteresis behavior of magneto dynamics, Bingham characteristics of static-structure breakage, and dynamic rheological rupture at high shearing stress, etc. The multiscle model describing the complicated macro-dynamics of MRF could be obtained by substituting the CE and magnetic force into the N-S equation. The HAAKE rotating rheometer, homemade Couette rheometer, and high-speed photography will be used to validate and consummate the multiscale model. The results could be used in magnetic damping, shock abatement, polishing, clutching, and stepless transmission.