Trans-scale Method Of Fatigue Life Analysis For Steel Wires In Arch Bridge Suspenders

As an important part of the middle and lower arch bridge,suspender is prone to fatigue fracture under the coupling of load,temperature and corrosion.In addition,the fatigue failure is a long-term effect,and the microstructure of the material has a significant impact on the fatigue failure.Therefore,the fatigue fracture of the steel wire of the arch bridge suspender attracts wide attention.The fatigue failure process of a component is a cross scale behavior from micro defect to macro fracture.In this paper,based on the macro and micro scale crack propagation model,an effective method for analyzing the fatigue process is developed.The main research work of this paper includes:In the macro micro scale crack propagation model,the micro scale behavior and the micro effect of material failure process from micro to macro are described by 3 scale effect functions.According to the physical mechanism of fatigue failure,3 scale effect functions are reasonably assumed.On the basis,a new method of fatigue analysis is developed,which is used to simulate the fatigue fracture process of low alloy ultra-high strength steel 40CrNi2Si2MoVA.Based on the experimental S-N curve of smooth round bar specimen(Kr=1)the fatigue parameters of 2 materials in the model are fitted.Then,the S-N curves of notched specimens(stress concentration factor Kr=2,3)are calculated respectively,and the theoretical results are in good agreement with the experimental results.The influence of micro factors on the fatigue failure behavior of the material was studied by numerical simulation.In this paper,the macro and micro scale crack propagation model is used to analyze the static strength of materials.The failure process of specimen under static load is also a kind of cross scale process from micro defect to macro fracture.In this paper,the uniaxial tensile failure tests of cast iron specimens were carried out,and the 3 scale effect functions of the model were analyzed.According to the test data of cast iron specimen ultimate strength,using the shooting method fitted 2 material parameters in the model,the cast iron specimen failure process under static load and ultimate strength were calculated.The theoretical results are in good agreement with the experimental results.Based on the numerical simulation,the influence of micro factors on the ultimate strength of cast iron is discussed.It pointed out that the micro factors are the main reasons for the static strength of cast iron.The finite element analysis model of Yibin South Gate Bridge is established,and the finite element analysis of the bridge is carried out.The multiscaling crack growth model to describe the fatigue failure of the steel wire,the fatigue developed multi-scale analysis method,the fatigue of Yibin South Gate Bridge suspender steel wire failure behavior is simulated.According to the results of numerical calculation,the macro and micro factors affecting the fatigue life of the suspender steel wire are analyzed and discussed.Based on the analysis results,some reasonable suggestions are put forward to improve the fatigue resistance of the bridge.