磁流变液的屈服应力与温度效应

Yield Stress and Temperature Effect of Magneto rheological Fluids

通常磁流变液的屈服应力大约比电流变液大一个数量级，磁流变液由于其具有较强的屈服应力而受到广泛的重视。我们用多畴的软磁材料同连续相一起充分混合获得的磁流变液，在３×１０５Ａ／ｍ的场强下静态屈服应力达到６０ｋＰａ以上，而其零场时的粘度仅为１５ｍＰａ．ｓ。本文报道了我们研制的拖板式磁流变仪的性能。同时，我们比较了几种磁流变液在零场下的沉淀性、以及外加磁场、屈服应力、温度、永磁材料、表面处理剂、添加剂和磁流变效应的关系。我们发现，磁流变效应主要由固相材料决定；表面处理剂可以改善固液界面的性质，并增强磁流变效应；不同的载液需不同的添加剂与其匹配；磁流变液的屈服应力对温度具有很好的稳定性。

Extensive attention has been paid to magneto rheological(MR) fluids because of their high yield stress.The yield stress of MR fluids is generally one order of magnitude larger than that of electrorheological(ER) fluids in equivalent conditions.In this paper,a new type of MR fluid consisting of multi domain magnetic materials is reported.The yield stress of the MR fluid is more than 60kPa under a magnetic field of 3×10 5A/m,while its dynamic viscosity at zero external magnetic field is only 15mPa.s.Also,a device for measuring the yield stress of MR fluids designed by our own is reported.At the same time,sedimentation of several MR fluids is compared under no magnetic field applied.The dependence of MR effect with magnetic field,temperature,types of magneto solid materials,types of surfactants and additives is studied.We find out that the MR effect is mainly due to ferromagnetic material.Suitable surfactants can improve affinity between solid and liquid and furthermore improve sedimentation and strengthen MR effect.The yield stress of our MR fluid is of good thermal stability.