| Rubber isolator is a key element of automotive isolation system.And the fatigue performance of isolator has an important impact on vehicle's safety,comfort,handling and stability.Especially,it's high engineering and academic value for rubber material and rubber isolator fatigue test and life prediction under high temperatures and variable amplitude loading conditions.The main research works of this thesis are summarized as follow:(1)Rubber material hyper-elastic constitutive characteristics and Mullins effect under high temperature are studied.Firstly,uniaxial tension,biaxial tension and planar tension tests are conducted for filled natural rubber under high temperature to obtain stress-strain data.Secondly,the above stress-strain data is fitted for hyper-elastic constitutive model,and the constitutive model parameters are obtained for the rubber material.Finally,rubber Mullins effect parameters are accurately characterized,which can describe the stress softening effect of rubber material.(2)Uniaxial fatigue characteristics of rubber material under high temperature are studied.According to the research results,the relationship of damage parameters and fatigue life is obtained based on fatigue crack initiation method,and the correlation coefficient can meet the requirements of engineering application.High temperature has impact on fatigue life characteristics of rubber material.Rubber fatigue life is decreased rapidly with increased environmental temperatures under large strain loading,while rubber fatigue life is changed slightly due to high temperature softening effect under small strain loading.A fatigue life model considered loading strain peak and mean value is established based on equivalent strain amplitude,and the fatigue life prediction model correlation coefficient is very high.(3)A fatigue prediction model is established for rubber material under uniaxial variable amplitude loading and high temperature condition.The fatigue influence of loading strain ratio,load level and load sequence are studied based on rubber variable amplitude loading fatigue life test.The Miner linear cumulative damage rule is verified in filled natural rubber under variable amplitude loading fatigue prediction,(4)Isolator natural rubber material fatigue crack growth(FCG)is studied under high temperature.Rubber fatigue crack growth is tested under crack energy ratio R=0 and R>0 conditions.The relationship of crack length and loading cycles is fitted with power law,and the crack growth rate is calculated.A unified fatigue crack growth model is built for natural rubber under high temperature.(5)Fatigue life is predicted for a typical rubber isolator based on crack initiation method under high temperature.The predicted life is within 1.5 times dispersion line of measured life.And the fatigue life is predicted based on FCG method,the ratio of prediction and experimental results are range from 0.87 to 1.31,which show high accuracy of the fatigue life prediction model for filled natural rubber. |
PDF Full Text Request