The Fatigue Life Evaluation Method Comparative Research Of Notched Specimens Based On Fatigue Experiment

Fatigue life prediction of engineering components and structures is of great significance.Numerous engineers and scientists set up different fatigue life prediction method based on the various fatigue failure and assumptions.We investigate feasibility and accuracy of four fatigue life evaluation methods combining with fatigue test using 45 # steel notch specimen as the research object.The specific work is as follows:According to the relevant national and international standards of fatigue test,the size of smooth specimen,U shape notch specimen,semicircle notch specimen has been determined.The fatigue life of two notch samples has been predicted by using the nominal stress method,local stress-strain method,point method(TCD),line method(TCD)and the ABAQUS finite element analysis result.The fatigue test of two notch samples has been made on the fatigue test machine in four stress level.The experimental fatigue life data has been obtained by using extrapolation method.Compared to other fatigue life evaluation methods and experimental fatigue life data,we find that standard TCD is not suitable under the condition of this study.Then,the standard TCD algorithm has been modified by 1 KT? parameter.The specific conclusions we get are as follows:1.Compared to look-up table method,Finite element method(FEM)is more suitable for engineering practice when we calculate the theoretical stress concentration factor of notch specimen;2.Compared with the other three methods,the calculation of the nominal stress method is the simplest.Due to its only considers the effect of stress concentration,predicted results is dangerous;3.The low cycle fatigue prediction results of local stress-strain method are more conservative,high cycle fatigue prediction accuracy compared with nominal stress method has greatly improved;4.Using modified TCD which combined linear elastic fracture mechanics(LEFM),stress concentration effect and the stress field near the notch root which is obtained by using finite element analysis software,we get the results are more close to the test results.Compared to the point method,line method gets more accurate predictions of the fatigue life results.Compared to traditional method,the modified TCD has better feasibility and accuracy.It provided a new theoretical calculation method for engineering fatigue life estimates.It has great significance practical engineering.