Study On Fatigue Life Prediction Of Rubber Elastic Absorber

With the rapid development of rail transit, the higher safety, comfort and reliability of vehicles are demanded by people. Rubber elastic absorbers are used in vehicle damping system more and more extensively because of the good property on damping and isolation. Rubber elastic absorbers play the role of traction, suspension, buffering and vibration isolation in vehicle system. As applying working condition of absorbers is complicated and absorbers are subjected to alternating stress, the service life of absorbers is directly related to vehicle safety and reliability. For the sake of providing theoretical guidance for optimization design of absorber structure, the author studies absorbers'behaves of fatigue and fracture under long-term mechanical loads then makes comparatively accurate intensity analysis and life prediction. It has great use value and practical significance.In this thesis, fracture mechanics method is used to study fracture and fatigue properties of rubber material. The fatigue life prediction model of absorber's material is established by tearing energy as the main parameter. By the nonlinear finite element analysis of conical spring, which is one of the typical rubber elastic absorbers, the equivalent stress calculation methods are studied for rubber material under complex stress state. By researching, the author translates the fatigue life of rubber elastic absorber under complex stress into the fatigue life of rubber material under uniaxial stress. So the fatigue life of rubber elastic absorbers can be predicted and the fatigue life prediction model is verified by the result of conical spring fatigue test.The thesis consists of two parts. In the first part, existing rubber material constitutive models were analyzed and studied. For the sake of conical spring nonlinear finite element analysis, the parameters of 3 order, 4 order and 5 order hyperelastic Ogden constitutive model were fitted by the experimental data of rubber mechanical property tests. Secondly, based on fracture mechanics theory, the author studied the relationship between strain energy, tearing energy and crack length, elongation rate of single-edge notched tension (SENT) specimens. Through finite element simulation of SENT specimens, the quantitative relationship between J-integral and tearing energy was established. Thirdly, based on power-law relationship between tearing energy and crack growth rate of rubber material, crack growth rate experiments were conducted using pure shear specimens of NR68 to establish fatigue life prediction model of rubber material, which was the basis of predicting fatigue life of rubber elastic absorbers. The tearing energy range was used as the damage parameter of rubber life prediction mode.In the second part, the nonlinear finite element simulation was conducted to analyse static strength and stiffness characteristics of conical spring and calculate equivalent stress distribution of conical spring according to the mechanical properties of rubber material. The tearing energy range of dangerous place was calculated and the fatigue life of conical spring was predicted by the fatigue life prediction model of rubber material. The prediction life of conical spring was compared with fatigue life of conical spring fatigue bench test and the cause and effect of factors of error were analysed.Finally, the author concludes the main work and results in the thesis and outlooks the research work in future.