Numerical Simulation Analysis Of Fatigue Life Of Non-pneumatic New Structure Tires

As the dominant design of the tire market,pneumatic tires have certain potential safety hazards due to their puncture-prone defects.As a result,non-pneumatic tires,which have the advantages of pneumatic tires and are resistant to punctures,came into being.Non-pneumatic tires use spokes to replace the traditional inflation structures.Fatigue life becomes a critical issue in the design of this new structure.The material fatigue test faces the defects of high cost,long time and difficult to establish quantitative relationship within complex thermomechanical coupling conditions.The finite element analysis method can effectively solve the shortcomings of the test and is an effective means to study the thermo-mechanical coupling fatigue of materials.This work adopts the viscoelastic mechanism and fatigue failure mechanism,based on the joint simulation of Abaqus software and Endurica software,to develop a thermo-mechanical coupling analysis methodology that can realize the fatigue life of the critical rubber component for non-pneumatic tires-spokes.Finally,the influence of the partial geometric structure of the spokes on their fatigue life was explored.This can provide upfront guidance for the design of non-pneumatic tires with high fatigue life.The main research work is divided into the following three parts:(1)Taking the fatigue life of dumbbell-shaped uniaxial tensile rubber specimens as benchmark data,the predicted fatigue life and the experimental fatigue life was compared to establishing an accurate and effective simulation methodology.Firstly,the hyperelastic constitutive model and its parameters were determined from uniaxial,planar and biaxial cyclic tensile test data.Secondly,the relationship between hysteresis energy,temperature,strain and frequency was established through test,and the parameters of Kraus self-heating model for calculation of temperature field were obtained by fitting.Finally,through the fatigue crack growth rate(FCGR)test,the parameters of the Thomas fatigue model were obtained by fitting.These parameters were iteratively analyzed in combination with the calculated values of the crack precursor and the results of the temperature field.The fatigue life of the specimen within the thermo-mechanical coupling effect was obtained.The comparison of the experiment shows that the simulation error of average temperature is 3.3%.The error of the average fatigue life simulation result with the thermo-mechanical coupling effect is only 2.0%.This reduces the error by 82.2% compared with the simulation results without considering the thermo-mechanical coupling effect.The effectiveness of this thermomechanical coupled fatigue simulation analysis method is verified.(2)The spokes of the non-pneumatic tires were simulated and analyzed by the thermo-mechanical coupling fatigue analysis method in(1).Firstly,the Tweel non-pneumatic tire was modeled so that its radial stiffness was close to that of the benchmark 305/80R18 pneumatic tire.Secondly,the ideal material test conditions and simulation conditions should be similar to the service conditions of the product.The traditional FCGR test mostly adopts the sine waveform mode.But when the tire is rolling,the load on and off the ground during the cycle is more similar to the pulse waveform mode.From the FCGR test results,we found that the pulse waveform mode corresponds to a faster fatigue crack growth rate and a higher dynamic temperature rise compared to the sine waveform mode.Therefore,in the FCGR test and fatigue life simulation prediction,the loading conditions conforming to the tire product should be paid attention to.Finally,the temperature analysis of the spokes of the Tweel nonpneumatic tire shows that when the initial temperature is 25.0℃,the maximum temperature is about 67.4℃ when the temperature field reaches a steady state.The maximum temperature is distributed at the middle bend of the spoke.The thermo-mechanical coupling fatigue life analysis shows that the minimum fatigue life of the spoke is distributed in the middle bending region and its connecting region,and the value is equivalent to6348 kilometers.(3)Taking the thermo-mechanical coupling fatigue life of the spokes of the Tweel non-pneumatic tire as the experimental purpose,and taking the structural parameters and loading conditions of the spokes as the experimental factors,a six-factor two-level orthogonal test was established.The results show that the importance of the geometric structure of the spokes of the Tweel non-pneumatic tire on its fatigue life is as follows:Outer De Rad,length,radius of curvature and Inner De Rad.When the static load increases by 13%,its fatigue life decreases by about 21.6%;when the tire rotation speed increases by 13%,its fatigue life decreases by about27.8%.Meanwhile,compared with the static load,the tire rotation speed has a greater influence on the fatigue life of the spokes of the Tweel nonpneumatic tire.