An investigation into isolator fatigue design on crack evaluation

Abstract

Fracture mechanics has long dominated the study of rubber crack propagation. Despite the successful achievement of the fracture mechanics approach in laboratory settings under plane-loading conditions using pre-cut specimens, its progress in antivibration isolators under multiaxial loading remains limited. Conversely, the ETS (effective tensile stress) has been effectively verified across both positive and negative R ratios (the ratio of the minimum to the maximum) without fitting functions and has been employed to predict crack initiation in industrial products. Therefore, in this study, ETS was utilised not only for crack initiation but also for crack propagation. No pre-cut crack was necessary to simulate crack growth using this approach. A type of traction rod bushing used in a rail vehicle was selected to validate the methodology. The comparison of the load-deflection data acquired from simulation and test ensured the accuracy of the material model. The prediction indicates that a fatigue crack initiated at the centre of the bushing groove at 140k and propagated to the groove edge by 800k cycles. Observations in the operating environment confirmed the final position, and the simulation result was approved by the customer. Compared to the fracture mechanics approach, this method does not require a pre-cut crack or a predefined crack-growth path to simulate crack growth in antivibration components. This study provides an alternative approach to fracture mechanics and demonstrates more realistic results. It could be beneficial in the fatigue design of industrial isolators. Further validation with more cases of actual antivibration components would still be required.