Tuesday  |  Salon 11  |  04:00 PM–04:20 PM

#15665, A Full Experimental Characterization of Aged Nitrile Butadiene Rubbers (NBR)

Part of the sealing function in the pneumatic system of the French high-speed train (TGV) is provided by elastomeric components, such as nitrile butadiene rubber (NBR) O-rings. Like most elastomers, NBR is sensitive to thermo-oxidative aging. In the current application, aging results in a strong hardening of the O-rings that alters the sealing function and impacts the lifetime of the mechanical pneumatic system. This places severe demands on maintenance operations. Therefore, understanding the origin of this aging, studying its effects on the material properties and modeling it is significant in limiting train maintenance operations.
In the present study, accelerated aging tests have been carried out with different NBR formulations at different temperatures. These tests enabled us to reproduce ex-situ the hardening observed on the O-rings. Aging mechanisms have been identified and related to the aging conditions of the NBR formulations through different characterization techniques: infrared spectroscopy, swelling tests, X-ray fluorescence spectrometry, differential scanning calorimetry, thermogravimetric analysis and micro-hardness.
To consider the effects of the mechanical loading on the aging process and the mechanical behavior of the tested NBRs, mechanical spectroscopy (DMA) analyses have been carried out. The results obtained highlight how mechanical loadings impact the aging of these NBRs and quantify the effects of aging on their viscoelasticity. From the collected data, a hyperelastic model has finally been identified to simulate the behavior of O-rings by the finite element method. These first results lay the foundations of a selection methodology for O-rings used in a train’s pneumatic system.

Adrien Redon   University of Rennes
Mathieu Miroir   University of Rennes
Eric Robin   University of Rennes
Jean-Charles Fralin   SNCF
Jean-Benoît Le Cam   University of Rennes