Rheological Characterization and EHL Simulation of a Grease in a Lubricated Sealing Contact

Abstract

This contribution provides an insight into the tribological behavior of grease-lubricated contacts in pneumatic spool valves. As the properties of the grease are strongly non-Newtonian, multiple measurements were performed to parameterize two viscosity models, the Herschel-Bulkley and the Palacios-Palacios model. These models are integrated into an EHL simulation of the sealing contact and qualitatively compared for two temperatures. For that system, the total friction force is rather unaffected by the choice of the viscosity model. In addition, qualitatively similar results with about 10 % deviation from the non-Newtonian behavior could be obtained using a Newtonian approximation of the lubricant.

Extrapolation of Hydrodynamic Pressure in Lubricated Contacts: A Novel Multi-Case Physics-Informed Neural Network Framework

“…The ifas-DDS model is an advanced simulation framework, validated with experimental measurements for different operation points [1], specifically designed to elucidate the complex interactions between a seal and its mating counterface. Central to this model is the consideration of a lubricating film that separates the seal and counterface.…”

“…The ifas-DDS calculates the friction of reciprocating seals by analyzing the hydrodynamics within the sealing contact according to the Reynolds equation, the contact mechanics, and the seal's deformation. In prior work, a thorough investigation of the agreement of the EHL simulation model with a test rig across various operating conditions, offering validation through experimental measurements has been conducted [1]. However, a notable limitation is the extensive computation time required for simulating short-term physical processes, attributed to the complexity of the underlying partial differential equations and their computationally intensive numerical solutions.…”

Elastohydrodynamic Simulation of Pneumatic Sealing Friction Considering 3D Surface Topography

“…The presented mesh, boundary conditions, and material properties have been used in an earlier publication [14] to determine the influence of different non-Newtonian viscosity models. The following description of these parameters has been taken from the aforementioned publication.…”

“…For the fluid, a dynamic viscosity of 87.2 mPa s was chosen. This corresponds to a Newtonian approximation of the shear viscosity of the grease at 50 °C for the chosen operating condition [14]. The pressure and shear flow factors used are given in Sect.…”

Experimental determination and EHL simulation of transient friction of pneumatic seals in spool valves

“…The inner seals (1) make or lose contact to the housing depending on the position of the spool and are used in the switching operations to open or close the respective air ports. The two outer seals (2) are always in contact with their counterfaces and seal the pressurized air against the environment. During operation, the relative movement of the seals on their respective counterfaces causes friction.…”