Fatigue Life Prediction And Experimental Study Of Rubber Mounts Based On Road Load Spectrum

Rubber mounts is a kind of the main vibration isolators used in the automotive vibrationisolation systems. Fatigue failures often occur within rubber mounts under alternative loads,which are caused by the engine actuation and road roughness. Therefore, establishing afatigue life prediction method is now becoming one major research area on studying rubbermounts. The main work of this dissertation includes the following aspects:1. Fatigue experiments of the dumbbell rubber specimens are carried out based on localstress/strain method, and fatigue life prediction models of rubber isolators are established bythree different methods. Firstly, mean strain effect on fatigue life under constant strainamplitude is analyzed, and a fatigue life prediction model based on mean strain function isthen established. Secondly, the effect of the strain ratio on fatigue life is analyzed, and afatigue life prediction model based on strain ratio is established. Lastly, a fatigue lifeprediction model is obtained by the biharmonic function interpolation. Fatigue experiments ofrubber mounts are then carried out in order to validate the three prediction model. Theexperimental results show good agreement with the three proposed prediction models.2. Taking a prototypical rubber mount as a study example, the strain spectrum of themount at critical location is obtained through editing. Additionally, a data acquisition systemis designed in order to get the road load spectrum of the rubber mount. The obtained loadspectrums under different roads are counted by the rain-flow counting algorithm. Furthermore,the dynamic and static characteristics tests on rubber specimens are performed, where adatabase of dynamic-static stiffness ratio is therefore established. The conversion relationshipbetween road load and strain of mount at critical location is determined by Finite ElementAnalysis (FEA) and the database of dynamic-static stiffness ratio.3. The block fatigue experiments are carried out with the dumbbell specimen. Based onMiner’s rule, the characteristic of critical damage value is studied. It is found that criticaldamage value is subject to Weilbull distribution with two parameters. The critical damagevalue of rubber material with certain confidence is calculated based on the probabilistic Miner’s rule.4. The fatigue lives of rubber mounts are predicted based on the proposed predictionmodel. And the road simulation experiments for rubber mounts durability are carried outbased on the Remote Parameter Control (RPC) technology. The results show that, the fatiguelife prediction method based on fatigue life database, load road spectrum and fatiguecumulative damage theory showed good agreement with the experimental results.The fatigue life prediction method based on road load spectrum presented in the paper isinstructive to estimate the fatigue life of rubber mounts, which will help engineers savingdevelopment time.