Experimental analysis of air bearings dynamic characteristics using an impact hammer

摘要

The problem of viscoelastic lubrication theory mainly reduces to the determination of a realistic state constitutive equation connecting stress and rate of deformation. Most investigations to date, while using mathematically simple models, have used either physically unrealistic or mathematically inadmissible equations of state. It thus appears that a re-appraisal would be useful. Most previous investigations have concentrated on steady-flow problems. In such situations the flow of viscoelastic liquids is indistinguishable from the flow of fluids showing non-Newtonian viscosity characteristics. The presence of nonlinearities during the simple shear flow of such a lubricant is considered to increase the load carrying capacity of the lubricant film whereas the reduction in the viscosity of the lubricant with shear rate contributes to the reduction in friction. The formulation of a single generalized constitutive equation for the investigation of different types of flow situations is almost impossible. An adequate form of the constitutive equation which can satisfactorily predict the interested aspect of the flow situation to the required accuracy is the actual requirement for an investigation.