Simulation of Fatigue Fracture of a Rubber Rail Support

摘要

Fatigue Crack Growth Characteristics (FCGC), the relationship between the fatiguerncrack growth rate and the strain energy release rate, has been used successfully tornpredict residual strength or the fatigue service life of metallic structures. FCGC hasrnnot been used to the same extent for rubber components, even though rubberrncomponents are often employed in dynamic rather than static applications, for whichrnfatigue mode of failure should be used as the criterion in analysis and design. Thisrnpaper investigates the application of fracture mechanics and FEM in therninvestigation of the propagation of crack in a rubber rail support and the estimationrnof its fatigue service life by using FCGC of a natural rubber. The key technique usedrnin this investigation is to determine the strain energy release rates G of the structurernby using finite element method (FEM) and the virtual crack extension method. ThernG versus crack growth curve is then combined with FCGC to predict the number ofrncycles to failure. For the case of the rubber rail support, because of the high degreernof non-linearity of the problem due to rubber material properties, large deformationrnand great discrepancy between the rigidity of steel and rubber components, thernanalysis is divided into two stages: first a three-dimensional model of the structure isrnanalysed under static loading, the maximum stress thus found and the displacementsrnmeasured in static testing were used to validate an equivalent two-dimensionalrnmodel. Then the two-dimensional model is subjected to the virtual crack extensionrnsimulation, from which the strain energy release rate is found and combined withrnFCGC of rubber to determine the service life. Results compared favourably withrnfatigue test results indicating that FCGC and FEM modelling can be used to predictrnfatigue behaviour of rubber components and provide tools for improvement in theirrndesign.