A Study On The Tensile Fatigue Properties Of High-Strength Bolts

As the main conjunctive mode of the steel structure, high-strength bolt has got widely used in steel structure fasteners of domestic and foreign constructions 、 bridges and machineries. During use of high-strength bolt, the study of tensile fatigue properties of high-strength bolts are not mature enough to rely upon. Selecting bolt sphere joint as the research object, this paper conducted research on the stress concentration and fatigue life of high-strength bolt by using ABAQUS and fe-safe respectively and analyzing constant amplitude fatigue test data of high strength bolt. Results are shown below:(1) The fatigue of high strength is the main cause of the fatigue of bolt sphere joint. Constant amplitude fatigue test data of high strength bolt made 40 Cr has been collected and analyzed in this paper. Regression analysis was conducted on the whole valid data and different specifications of high strength bolt test data. Different correlation of regression curves and fatigue safe lives of three stress level test data are put forward. If N=2×106 are used as the reference period, 62 10[ ?]?? from the regression curves are not the same. More fatigue tests are suggested to be done.(2)Stress concentration coefficients of different specifications of high-strength bolt were obtained. Based on the analysis results, fatigue notch factors were calculated with experience formula. The calculation shows that as the ratio of diameter of the bottom of thread to the nominal diameter of high strength bolt grows, so did the fatigue notch factors.(3)The paper has gained fatigue life of three specifications of high-strength bolt. These results show that the minimum of fatigue life inosculates with experimental results well. As the ratio of diameter of the bottom of thread to the nominal diameter of high strength bolt grows, fatigue performance decreases.(4)Fatigue life of high-strength bolt is related to the stress ratio and the stress ratio should be considered in fatigue design properly. As the surface roughness increases, the fatigue performance of high-strength bolt slides down.This paper has studied the fatigue properties of high-strength bolt. It conducted finite element analysis using full-size model(high-strength bolt and bolt sphere joint). This work has a reference value to fatigue design of tensile high-strength bolt.