Abstract: The definition accuracy of hyperelastic constitutive model material parameters of tyre rubber is significant for vehicle tire design. Current theory and test methods for the material definition are studied, and several popular stress-strain curves for determining the material parameters are reviewed. Through the research of the influence of some factors, such as rubber cure state, fatigue cycle numbers, and load & unloading sequence, on the rubber properties, the material definition method is discussed. It is found that the mechanical properties of rubber are not only related to the withstand peak load, but also to a large extend related to the load applied sequence. Based on the rubber elasticity theory and through comparison and investigation, the principle of selecting the experimental curves used for the fitting of constitutive model parameters in the mechanical analysis of tire is determined. Firstly, the actual cure state of test tire rubber should be evaluated. Secondly, based on the actual running condition of tire, through test or numerical simulation technique, the max peak load experienced by the material in the loading sequence is determined. At last, rubber cycle curves at the peak load are .adopted as the constitutive relation curves of material to fit the corresponding material parameters. 30 000 cycle numbers in the test can meet the accuracy requirement. is proved valid, although 7 cycle numbers can be optional if test effeciency is highlighted.

Key words: Cure state, Cycle, Fatigue, Hyperelastic constitutive model