Development of an online-wear-measurement for elastomer materials in a tribologically equivalent system for radial shaft seals

Abstract

In a dynamic radial shaft sealing (RSS) system good wear resistance is crucial for proper functionality. This contribution is dedicated to the analysis of wear in radial shaft seal applications in a sealing system itself and on a tribologically equivalent system. To make elastomers more wear resistant, new and innovative material concepts and compounds have to be evaluated. To do so a simple tribologically equivalent system, the ring-cone-tribometer (RFT), consisting of an elastomer ring and a coned shaft, was used.Two different radial shaft seal types were compared under identical test conditions on a multi-shaft test bench, to the results generated on the RFT. This was done to evaluate and compare the tribological properties of the RFT towards RSS. To avoid ageing or batch-to-batch influences the slabs for the production of the ring samples were molded from the same elastomer material batch as the radial shaft seals. Initial differences in terms of wear, friction, contact width and hardness between RSS and RFT were reduced step by step using an optimized, stiffer test setup on the RFT and a FE-simulation model to optimize the contact geometry. Data scattering on the RFT was reduced to a minimum so that the higher scatter within the results of the RSS test population was in a similar dimension as the deviation in both systems.To determine the wear during a test run, an online-wear measurement system, based on eddy current sensors, was developed that allows for the online estimation of seal wear progress on the RFT at any time. This process is based on a geometrical approach using the initial contact width and the axial displacement during the operation. The online-wear measurement correlates very well with the post-mortem wear measurement. All results form a set of tools which constitutes a solid foundation for online evaluation of rubber and seals in the future.