Abstract: Under various strain ratios R loads, a uniaxial fatigue experiment is carried out for a dumbbell cylindrical specimen of filled natural rubbers used in automotive rubber isolators. Based on the measured fatigue data, the effect of R on fatigue life is discussed and two fatigue prediction models are established. The model I is based on the damage parameter of strain peak, and the model II is based on the damage parameter of strain amplitude. It is concluded that both the two models are appropriate for predicting fatigue life under R0 loading conditions, while under R<0 loading conditions the model II can’t be used for predicting fatigue life of filled natural rubbers. An equivalent strain amplitude is proposed as a damage parameter for predicting fatigue life under R<0 loading conditions. The predicted fatigue life using the proposed equivalent strain amplitude as the damage parameter is in a good agreement with the experimental fatigue life within a factor of two, and with an improved correlation coefficient of 0.923 1. The proposed model for fatigue life prediction with the equivalent strain amplitude can be used to estimate the fatigue life for a rubber component with filled natural rubbers for any strain ratio.

Key words: Fatigue testing, Life cycle, Prediction, Rubber, Strain ratio