Frequency-domain analysis of non-Newtonian fluid behavior in head-disk interface lubrication

A lubricant in a head-disk interface is considered as a non-Newtonian fluid. Properties of non-Newtonian lubricants are specified by three nonlinear functions and a modified Reynolds equation is derived for the varied film thickness in the interface. The shear dependent viscosity is the principal factor and it is expressed by a first order transfer function. Its amplitude frequency response describes the process of the viscosity variation and indicates that the shear dependent viscosity is affected not only by the lubricant material parameters, but also by the shear frequency. Based on the modified Reynolds equation, the numerical result of lubrication is given. The load capacity is not always higher or always lower than that of the Newtonian fluid. The effect of the first normal stress difference is enlarged with the slider flying height varies.