| Considering the hyperelasticity and viscoelasticity of the carbin-black(CB)filled rubber,the thermal rheological properties,temperature dependent hysteresis loss and fatigue crack propagation kinetics of the material were studied based on the time-temperature equivalence principle.The dissertation focuses on the theoretical analysis and experimental investigations in the following aspects:(1)Selection of hyperelastic constitutive model of the CB filled rubber.The theory of rubber hyperelasticity was reviewed and divided into two categories:the statistical models based on the molecular chain network and the phenomenological models based on continuum mechanics.The relationships between the nominal stress and the stretch ratio for several commonly used models under the uniaxial tension,plane tension and euqi-biaxial tension were derived,and the corresponding basic tests were carried out.The experimental data were fitted with those models,thus their applicability of each model was assessed.The results show that the third-order Ogden model is the best choice for the hyperelastic constitutive model of rubber material if the stress-stretch data for three kinds of basic tests are available.(2)Study on the thermorheological properties of the CB filled rubber.Frequency sweep DMA tests were carried out at different temperatures,and the master curves of dynamic viscoelastic properties,the Cole-Cole diagram and the van Gurp-Palmen diagram were constructed respectively.The results show that the CB filled rubber is a thermorheologically simple material,and that the material meets the time-temperature superposition principle.Meanwhile,the temperature shift factors of the dynamic viscoelastic properties at different temperatures are determined.(3)Study on the hysteresis dissipation of the CB filled rubber.Dynamic tension and compression tests were performed on CB filled rubber with DMA to analyze the effects of load frequency and strain amplitude on the hysteresis loss.The results show that the hysteresis loss is linearly related to the load frequency,and varies nonlinearly with the dynamic strain amplitude by a power law,which can be predicted by the Kraus model.Besides,a predictive model for temperature rise due to cyclic deformation was developed.The model predictions are in good agreement with the experimental results,which shows that the model can well characterize the heat generation in CB filled rubber.(4)Study on fatigue crack growth and fatigue life of the CB filled rubber.The static tearing tests at different temperatures and fatigue crack growth tests at room temperature were carried on the plane tension specimens of CB filled rubber.The results show that the critical tear energy decreases exponentially with the increase of temperature,and the relationship between fatigue crack growth rate and tear energy satisfies the power law.Considering the variations of the tear energy with the maximum strain and temperature,the temperature dependent fatigue crack growth kinetics is established,which can be used to predict the fatigue life and S-N curve at specific high temperature.(5)Development of a fatigue life evaluation scheme of the CB filled rubber.The fatigue failure tests of the hourglass shaped CB filled rubber specimens were carried out,during which the surface temperature changes of the specimens were recorded by the infrared thermograph,and a model for calculating the self-heating equilibrium temperature was established.The model predictions are in good agreement with the experimental results.Based on the fact that there is an equilibrium self-heating temperature during fatigue followed by a sharp temperature rise right before the fatigue failure,a fatigue life evaluation scheme is developed based on criterion of the self-heating equilibrium temperature rise. |
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