Techno Press
Techno Press

Steel and Composite Structures
  Volume 33, Number 3, November10 2019 , pages 433-444
DOI: https://doi.org/10.12989/scs.2019.33.3.433
 


Variable amplitude fatigue test of M30 high-strength bolt in bolt-sphere joint grid structures
Bin Qiu, Honggang Lei, Xu Yang, Zichun Zhou and Guoqing Wang

 
Abstract
    Fatigue failure of a grid structure using bolt-sphere joints is liable to occur in a high-strength bolt due to the alternating and reciprocal actions of a suspension crane. In this study, variable amplitude fatigue tests were carried out on 20 40 Cr steel alloy M30 high-strength bolts using an MTS fatigue testing machine, and four cyclic stress amplitude loading patterns, Low-High, High- Low, Low-High-Low, and High-Low-High, were tested. The scanning electron microscope images of bolt fatigue failure due to variable amplitude stress were obtained, and the fractographic analysis of fatigue fractures was performed to investigate the fatigue failure mechanisms. Based on the available data from the constant amplitude fatigue tests, the variable amplitude fatigue life of an M30 high-strength bolt in a bolt-sphere joint was estimated using both Miner's rule and the Corten-Dolan model. Since both cumulative damage models gave similar predictions, Miner's rule is suggested for estimating the variable-amplitude fatigue life of M30 high-strength bolts in a grid structure with bolt-sphere joints; the S-N fatigue curve of the M30 high-strength bolts under variable amplitude loading was derived using equivalent stress amplitude as a design parameter.
 
Key Words
    grid structure; bolt-sphere joint; M30 high-strength bolt; variable amplitude fatigue; cumulative fatigue damage; S-N curve
 
Address
College of Civil Engineering, Taiyuan University of Technology, 79 West Yingze Street, Taiyuan, Shanxi, People's Repulic of China.
 

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