Fatigue Crack Propagation And Life Prediction Of High Strength Wires Of Bridge Hangers

With the increase of service life,the corrosion,aging and damage of the bridge under the influence of vehicle load and adverse environment will gradually emerge.Sling as the main force of the bridge,because the sling in a long time under high stress state work,easily lead to fatigue fracture occurred.In recent years,many domestic and international bridge accident frequency caused by slings fatigue fracture occurred during service,causing great economic losses.Therefore,it is an important engineering significance to evaluate the residual life of the slings accurately by studying the fatigue behavior of the fatigue crack by means of the steel wire fatigue test.In this paper,the study of fatigue crack propagation and the finite element simulation based on Abaqus software are carried out,to study the high strength galvanized steel wire used in the sling.The main work is as follows:(1)The finite element software Abaqus is used to calculate the stress intensity factor of fatigue crack propagation.The variation law of the stress intensity factor correction coefficient of radial point and surface point under different crack shapes is analyzed and the stress intensity factor correction is given Coefficient of expression,and finally the radial point of the correction factor expression and test results for comparative analysis,the accuracy is better.(2)Fatigue crack growth tests of 12 high strength galvanized steel wires were carried out,and the fatigue crack growth rate and life curve under different stress amplitude and stress ratio were obtained.By analyzing the da/dN-?K curve,it is found that the linearity of the curve is better,and the curve increases with the increase of the stress amplitude.The parameters under the same stress ratio are analyzed and the variation of the parameters is obtained.(3)The advantages of extended finite element method in simulating fatigue crack propagation are described.Based on the finite element software Abaqus combined with the specific loading process of the fatigue crack propagation test,the finite element model of the fatigue crack growth of the steel wire was established.The stress cloud with the crack propagation depth changed with the load step,and the stress of the crack tip was the largest,Finally,the calculated results are compared with the experimental results.The results are in good agreement with each other,indicating that the extended finite element model is reliable.(4)The method of updating the maximum relative entropy principle can be used to consider the principle of instability and uncertainty,and the stochastic process of fatigue crack propagation is predicted by continuous updating using the maximum relative entropy principle.Using this method,the fatigue life of fatigue crack can be predicted more accurately.