铁磁流体润滑中的非牛顿流影响

利用外加磁场可以直接调节铁磁流体润滑膜的承载能力,因为在外磁场中铁磁流体的粘度增大. 实验研究表明,铁磁流体是一种非牛顿流体,它同时表现出Bingham塑性体和拟塑性体的特性. 铁磁流体的非牛顿流体行为受外磁场强度和方向的影响. 铁磁流体的本构方程可以表示为 τ(H,D)=τ_s(H)+η₁(H)D+η₂(H)D².由于铁磁流体具有屈服剪应力τ_s(H),而可能出现"固态"核粘附于轴承表面上.铁磁流体的拟塑性体行为对核的生成条件有影响.在铁磁流体润滑的轴承中,纯剪切流截面C₀不同于普通Bingham塑性体润滑的轴承.作为一个实际的例子而给出铁磁流体润滑平板滑块的承载能力和摩擦力的解.

Non-Newtonian Effects on Ferrofluid Lubrication

The load carrying capacity of the ferrofluid lubricating films can be controlled directly by means of the applied magnetic field, since the viscosity of the ferrofluid increases in the case of magnetic field. The experimental investigations showed that the ferrofluid is an non-Newtonian fluid: it behaves simultaneously as a Binghamoplastic and as a pseudoplastic. The non-Newtonian behavior of the ferrofluid is dependent both on oreintation and on intensity of the applied magnetic field. The constitutive equation of the ferrofluid can be expressed as τ(H,D)=τs(H)+η1(H)D+η2(H)D2. It is possible that the “solid” cores appear and adhere to the surfaces of bearing, since the ferrofluid has a yield shear stress τs(H). The pseudoplastic behaviors of the ferrofluid have an effect on the condition for core occurrence. The cross section C0 of a pure Couette flow in the ferrofluid lubricated bearing is different from that in the ordinary Binghamoplastic lubricated bearing. The solutions of load carrying capacity and friction force of plane slider lubricated with ferrofluid are given as an actual example.