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This work concerns the steady-state and dynamic analysis of misaligned compliant journal bearings considering the effects of couple stresses arising from the lubricant blended with polymer additives. Based on the Stokes micro-continuum theory, a modifi ed form of the Reynolds equation is derived. The displacement fi eld at the fl uid fi lm-bearing liner interface due to pressure forces is determined using the elastic thin liner model. The effects of the misalignment and the couple stress parameters on static and dynamic performances such as pressure distribution, load-carrying capacity, power loss, side leakage fl ow, misalignment moment, critical mass and whirl frequency are presented and discussed.

Elastohydrodynamic (EHD) analysis of a journal bearing with a realistic model for the bearing made of two distinct layers is extended to include couple-stress effects in lubricants blended with polymer additives. Based on the Stokes microcontinuum theory, a transient pressure differential equation (modified Reynolds' equation) is derived from the fluid motion equations and solved numerically. The elegant and powerful semi-analytical approach based on the complex variable theory developed in an earlier work is extended to solve linear elastostatics problems for a double-layered journal bearing. The EHD solution in isothermal conditions is obtained numerically by means of an iterative procedure. By the finite perturbation technique, the eight fluid-film stiffness and damping coefficients are determined. At the threshold of instability, the dynamic coefficients are used as input data for studying the linear stability of the rotor-bearing system. According to the results obtained, the influence of couple-stress parameter on the static and dynamic performance characteristics of the compliant journal-bearing system is physically apparent and not negligible. Compared with the Newtonian lubricants case, lubricants with couple-stresses provide an increase in the load-carrying capacity and stability, a reduction in the attitude angle and the friction factor. It is also found that the fluid -solid interaction effect on the performance characteristics is more important, especially for high values of couple-stress parameter and relative rigidity of liner-bush assembly.

In this article, the effect of both static and dynamic deformations of the bearing liner on the dynamic performance characteristics and stability of a water-lubricated, rubber-lined journal bearing operating under small harmonic vibrations is theoretically investigated. To take into account the dynamic deformations of the bearing liner, the first-order perturbation technique is used to determine the eight dynamic coefficients for a given excitation frequency value. The static and dynamic deformation of the fluid/bearing-liner interface is assumed to be proportional to the steady-state and dynamic fluid-film pressures. It was found that the dynamic properties and stability of the compliant finite-length journal bearing are affected by surface coatings from soft materials. It was also shown that when dynamic deformations are considered in the calculations, the dynamic coefficients depend on the excitation frequency, especially for higher values of this parameter. Moreover, the two cross-damping coefficients differ from each other, while the classical elastohydrodynamic (EHD) theory predicts them to be equal, when the dynamic deformations are ignored.

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An isothermal hydrodynamic analysis of big end connecting rod bearings for both diesel and gasoline engines lubricated with couple stress fluids is undertaken. Based on the V. K. Stokes micro-continuum theory, an incompressible modified Reynolds equation is derived from the fluid motion and mass conservation equations using the assumptions of thin-film theory. The hydrodynamic performance and the crank pin center trajectories are determined numerically by means of the Booker mobility technique. Compared with the Newtonian lubricant case, the lubricants with couple stresses provide an increase of the minimum film thickness, and a drastic decrease of the power loss, peak pressure, and flow rate over one engine cycle for both engines.

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