Effects of Couple Stresses on Pure Squeeze EHL Motion of Circular Contacts

Abstract

A method for investigating the pure squeeze action in an isothermal elastohydrodynamically lubrication (EHL) problem, i.e., circular contacts lubricated with couple stress fluid, was developed. A constant load condition was used in the calculations. The initial conditions such as pressure profiles, normal squeeze velocities, and film shapes were obtained from the classical hydrodynamic lubrication theory at a specified large central film thickness. The coupled transient modified Reynolds, elasticity deformation, and load equilibrium equations are solved simultaneously. The simulation results reveal that the effect of the couple stress is equivalent to enhancing the lubricant viscosity, thus enlarging the film thickness. The effect of couple stress in thin film lubrication varies with film size. That is, the thinner the lubricating film is, the more obvious the effect of couple stress is. For larger characteristic length, materials parameter, and load, the central pressure, central film thickness, and rigid separation are larger than those of smaller characteristic length under the same load. The time needed to achieve maximum central pressure and the Hertzian pressure increases with increasing characteristic length.

Numerical Analysis of Couple Stress Fluid Past an Infinite Vertical Cylinder

“…This iterative procedure is repeated for many time steps until the steady-state solution is reached. The steady-state solution is assumed to have been reached when the absolute difference between the values of velocity as well as temperature at two consecutive time steps is less than 3 …”

“…Other important fields where couple stress fluids have applications are squeezing and lubrication theory, biofluidmechanics, MHD flows and also in synthetic and plastic industries. Chu et al (2006) investigated the pure squeeze action in an isothermal and elastohydrodynamical lubrication problem, in which the circular contacts lubricated with couple stress fluid are developed. Lin (1998) investigated the squeeze film behaviour for a finite journal bearing lubricated with couple stress fluids and compared their results with the case of a Newtonian lubricant.…”

Coupled couple stress and surface roughness effects on elasto-hydrodynamic contact

“…and Λ = 6μU. Equation (7) was obtained, for example, by Elsharkawy and Al-Fadhalah 13 in the case of squeeze film between a sphere and a rough porous flat plate with a micropolar fluid and also by Chu et al 14 in the study on elasto-hydrodynamic lubrication of rough circular contact using the average flow model.…”

“…In what follows, the gradient operator is written as follows 15 : Introducing the equation (10) into (7) and using the gradient operator (11), we obtain an expansion of differential operators with respect to ε j ( j = À1, 0, 1). Equating terms of same powers of ε gives the following:…”

“…Several researchers have used the Stokes couple stress theory to analyse the performance characteristics of various bearing systems, such as Lin 4 for finite journal bearing in squeeze situation, Wang et al 5 for journal bearing, Elsharkawy and Guedouar 6 for finite journal bearing using a simple elastic model to determine the elastic deformation and Chu et al 7 for pure squeeze elasto-hydrodynamic lubrication motion of circular contacts. It is noteworthy to recall that all these studies assume that the contact surfaces of lubricated mechanisms are completely smooth.…”