State of the Art Review on Theoretical Tribology of Fluid Power Displacement Machines

Over the past 20 years an increasing focus on efficiency and reliability in fluid power displacement machines has provided an incentive to study loss and wear mechanisms. One example is the hydrostatic fluid power transmission systems for wind and wave energy applications. The loss and wear mechanisms are mainly attributed to the tribological interfaces in fluid power machines. Consequently, optimization of efficiency and reliability of fluid power machines imply consideration of tribological interface design. The majority of the work done by researchers and engineers on the study of loss and wear mechanisms in the lubricating gaps in fluid power machines is confined to simulation models, as experimental treatments of these mechanisms are very difficult. This means, that a complete verification of the theoretical work is difficult. The aim of this paper is a state of the art review on the theoretical work for the design and optimization of fluid power displacement machines, and also the work done to validate the theoretical models. This review is not a complete historical account, but aim to describe current trends in fluid power displacement machine tribology. The review considers the rheological models used in the theoretical approaches, the modeling of elastohydrodynamic effects, the modeling of thermal effects, and finally the experimental validation of the theoretical models.