Stochastic analysis on tribological behavior of radial shaft seals with focus on lubricants

This study deals with a methodical interpretation into the complex landscape of the tribological behavior of Radial Shaft Seals (RSS) using dynamic investigations focusing on the influence factor lubricant. The RSS forms a tribological system with the shaft surface as counterpart and the applied lubricant as medium. The lubricant has been identified as one of the main drivers for the tribological behavior of RSS especially due to its chemical structure and physical viscosity. Previous research has shown that the tribological behavior of RSS, such as leakage or wear, can be observed during and after testing with different lubricants, especially with different viscosities. This study evaluates the impact of lubricants with different chemical structure but similar viscosity, which allows to gain a deeper understanding of the further properties of lubricants. More specifically, different kinds of lubricants have been analyzed on RSS with different materials and diameters. Thereby, the rotational speed has been varied in relevant ranges. Using stochastic calculus analysis, the tribological behavior of RSS with lubricants can be evaluated in more detail. Especially, the variance of the frictional moment of the seal can be analyzed and interpreted depending on the test conditions. Secondly the potential damage and the wear formation can be evaluated optically with a microscopy. These results not only contribute to the academic discourse on RSS and lubricants as well as the tribological system, but also classify the different operating combinations for real applications. A specially designed RSS test rig at the Institute for Machine Elements, Design and Manufacturing is available for the experimental investigations. The aim of the extensive investigations is to create a basis for future, more in-depth research into understanding on the tribological behavior of the RSS as well as predictions for specific classified working environment for the different RSS systems.