Experiment And Theoretical Study On Constant Amplitude Fatigue Performance Of High-Strength Bolts For End-plate Of Lightning Rod Structure

The structure of the lightning rod structure is an important facility for preventing lightning strikes in substations,and is of great significance to the safe operation of power grid equipment.The structure’s lightning rod structure is a high-rise construction with weak lateral stiffness and belongs to a highly flexible structure.When it is located in a strong wind area,the high-strength bolts at the connection of the end plates of the lightning rod structure of the frame may be fatigue damaged under wind load,which may cause certain hidden dangers to the structural safety.Regarding the high-strength bolts at the end plate connection,domestic and foreign scholars have conducted a lot of experimental and theoretical studies on their static performance and hysteretic behavior,but the research on the fatigue properties of high-strength bolts and its main influencing factors is not yet complete.This article is funded by the National Natural Science Fund Project(No.51708384);Shanxi Province Overseas Researchers’ Science and Technology Activities Funding Project(DC1900000602);Shanxi Basic Research Youth Fund Project(201901D211017).Research background,for its end plate connection with 8.8M24 high-strength bolts as the research object,it is planned to conduct 6groups of fatigue performance tests and theoretical studies under the stress ratio.The main research contents and conclusions are as follows:(1)3 sets of stress ratios(R = 0.3,R = 0.5 and R = 0.8)of A total of 238.8 grade M24 high-strength bolt specimens with constant amplitude and amplitude amplitude fatigue test,and statistical analysis of the obtained constant amplitude fatigue life data,respectively obtained different stress ratio M24 high strength bolt test SN curve,linear regression equation and nominal allowable stress amplitude corresponding to 2 million cycles.(2)A total of 14 high-strength bolt constant-amplitude fatigue specimens with 3 different stress ratios and 6 sets of the same stress amplitude were selected,and their fatigue fractures were analyzed macroscopically and microscopically,reflecting the qualitative and quantitative analysis of the fatigue strength of the high-strength bolts with different amplitudes influences.ABAQUS finite element software was used to establish the finite element model of the high-strength bolt specimen,and based on the static analysisresults,the FE-SAFE software was used to perform the second-order numerical simulation analysis to obtain its corresponding theoretical fatigue life: compare the results obtained from 7 high-strength bolt specimens The theoretical fatigue life obtained from the data(R = 0.5)and the numerical simulation proves that the theoretical simulation method is feasible;based on the above verification simulation method,three sets of ideal stress ratios(R = 0.4,R = 0.6 and R = 0.7)were performed 24 The theoretical fatigue life of a high-strength bolt specimen was calculated and statistically analyzed.The corresponding SN curve,linear regression equation and the nominal allowable stress amplitude corresponding to 2 million cycles were obtained.