Studies On Stiffness And Fatigue Life Of Rubber Bushing

Rubber material comprises natural rubber and synthetic rubber. Due to its mechanical properties such as hyper-elasticity, large strain, etc., the rubber material has been widely used in many engineering structures. The rubber bushing studied in this paper consists of a metal sleeve, a metal core and a rubber cylinder, and has been widely applied to the fields such as mechanics, vehicles, automobiles and the like. It can transfer loads in axial, radial, torsional and deflection directions, and plays an important role of eliminating impact and vibration in the load transferring process. Owning to requirement of load transfer, the rubber bushing must own suitable stiffness. Furthermore, the rubber bushing is generally used under the periodical load and may fail to work due to fatigue. Therefore, it is also extremely necessary to investigate the fatigue performance of the rubber bushing. In order to improve the fatigue strength and prolong the service life, the metal sleeve is extruded during the fabricating process of the bushing so that the rubber part is at a radial pre-compression state. However, the influence of the pre-compression on stiffness and fatigue life of the rubber bushing is seldom reported in the literature.This paper takes the rubber bushing used in modern rail transportation as a research object and researches the constitutive behavior of the rubber material and the stiffness and failure life of the rubber bushing. Some preliminary conclusions are drawn as follows:1. Some advances in the studies of the hyperelastic constitutive models of rubber material were briefly summarized. Uniaxial tension, equa-biaxial tension and planar tension tests were performed on standard specimens of the rubber material used for rubber bushing. Furthermore, the analysis was carried out by several frequently-used rubber hyperelastic constitutive models, thus discussing the adaptability of each model on the rubber constitutive behavior of the bushing. The results indicate that the four-order Ogden model can well describe all test phenomena.2. Tests and finite element analysis were carried out respectively to the static stiffness of the rubber bushing, such as axial stiffness, radial stiffness, deflection stiffness and distortion stiffness. The results of the tests and the finite element analysis match with each other basically. The influence of the pre-compression amount on the static stiffness is taken into account in the finite element analysis. The results show that all stiffness increases with the increment of the pre-compression amount.3. Fatigue tests were carried out on rubber hourglass specimens. The test results indicate that there exists a negative exponent relationship between the fatigue life and the maximum principal logarithmic strain. This fatigue life equation of the material was then applied to the fatigue life analysis of the rubber bushing. The influence of radial pre-compression on the maximum principal logarithmic strain, and thus on the fatigue life of the rubber bushing was discussed. The results show that the fatigue life of the rubber bushing increases firstly and decreases subsequently with the increment of the radial pre-compression amount. Therefore, the optimum scheme of the pre-compression amount of the rubber bushing can be determined.