Fatigue assessment of cord rubber composite air spring bellows based on specimen testing and numerical analysis

Abstract

Rail vehicle air spring bellows consisting of cord rubber composites are subject to a wide variety of stresses. It is therefore crucial to understand the fatigue behavior of such components, as the development process involves the use of empirical methods, which are both time‐consuming and costly. This paper outlines a methodology for assessing the fatigue strength of air spring bellows through representative specimen testing. Ten component tests and a validated numerical model of the air spring bellows are presented. The primary loading scenario investigated in this study is pure pulsating tensile stress with a strain ratio R in the range of 0–0.25. This scenario is considered to be highly damaging, leading to delamination. Comprehensive damage analysis of the specimen is performed using microcomputed tomography. To ensure the transferability of the results, a failure criterion is defined as 20% elongation of the specimen, based on the defined 10% internal pressure drop for the bellow. After statistical evaluation, the transferability of the specimen tests to the component is validated using a local fatigue approach. The correlation coefficient R2 is 0.84, indicating a sound agreement between model and tests with 7 points out of 10 within a scatter factor of 2.