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RISS 인기검색어
- 검색키워드
- 저자 : Honggang Lei (검색결과 4 건)
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Constant amplitude fatigue test of high strength bolts in grid structures with bolt-sphere joints
Xu Yang,Honggang Lei 국제구조공학회 2017 Steel and Composite Structures, An International J Vol.25 No.5
The grid structure with bolt-sphere joints is widely adopted by industrial plants with suspending crane. The alternating reciprocating action of the suspending crane will cause fatigue problems of the grid structure with bolt-sphere joints with respect to the rod, the cone, the sealing plate, the bolt ball and the high strength bolt; while the fatigue of the high strength bolt is the key issue of fatigue failure. Based on efficient and smooth loading equipment with the AMSLER fatigue testing machine, this paper conducted a constant amplitude fatigue test on 18 M20 and 14 M30 high strength bolts with 40Cr material, and obtained 19 valid failure points, 9 unspoiled points with more than 2 million cycles, and 4 abnormal failure points. In addition, it established the constant amplitude fatigue design method, [Δσ]2×10 6 =58.91MPa, and analyzed the stress concentration and the fatigue fracture of high strength bolts. It can be explained that the geometrical stress concentration of high-strength bolt caused by spiral burr is severe.
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Variable amplitude fatigue test of M30 high-strength bolt in bolt-sphere joint grid structures
Bin Qiu,Honggang Lei,Xu Yang,Zichun Zhou,Guoqing Wang 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.33 No.3
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.
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Fatigue performance and life prediction methods research on steel tube-welded hollow spherical joint
Qi Guo,Ying Xing,Honggang Lei,Jingfeng Jiao,Qingwei Chen 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.36 No.1
The grid structures with welded hollow spherical joint (WHSJ) have gained increasing popularity for use in industrial buildings with suspended cranes, and usually welded with steel tube (ST). The fatigue performance of steel tube-welded hollow spherical joint (ST-WHSJ) is however not yet well characterized, and there is little research on fatigue life prediction methods of ST-WHSJ. In this study, based on previous fatigue tests, three series of specimen fatigue data with different design parameters and stress ratios were compared, and two fatigue failure modes were revealed: failure at the weld toe of the ST and the WHSJ respectively. Then, S–N curves of nominal stress were uniformed. Furthermore, a finite element model (FEM) was validated by static test, and was introduced to assess fatigue behavior with the hot spot stress method (HSSM) and the effective notch stress method (ENSM). Both methods could provide conservative predictions, and these two methods had similar results. However, ENSM, especially when using von Mises stress, had a better fit for the series with a non- positive stress ratio. After including the welding residual stress and mean stress, analyses with the local stress method (LSM) and the critical distance method (CDM, including point method and line method) were carried out. It could be seen that the point method of CDM led to more accurate predictions than LSM, and was recommended for series with positive stress ratios.
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Jinfeng Jiao,Xiao Ma,Honggang Lei,Y. Frank Chen 한국강구조학회 2018 International Journal of Steel Structures Vol.18 No.5
A test rig with multi-functional purposes was specifi cally designed and manufactured to study the behavior of multi-planar welded tubular joints subjected to multi-planar concurrent axial loading. An experimental investigation was conducted on full-scale welded tubular joints with each consisting of one chord and eight braces under monotonic loading conditions. Two pairs or four representative specimens (two specimens for each joint type) were tested, in which each pair was reinforced with two kinds of diff erent internal stiff eners at the intersections between the chords using welded rectangular hollow steel sections (RHSSs) and the braces using rolled circular hollow steel sections (CHSSs) and welded RHSSs. The eff ects of different internal stiff eners at the chord–brace intersection on the load capacity of joints under concurrent multi-planar axial compression/tension are discussed. The test results of joint strengths, failure modes, and load–stress curves are presented. Finite element analyses were performed to verify the experimental results. The study results show that the two diff erent joint types with the internal stiff eners at the chord–brace intersection under axial compression/tension signifi cantly increase the corresponding ultimate strength to far exceed the usual design strength. The load carrying capacity of welded tubular joints decreases with a higher degree of the manufacturing imperfection in individual braces at the tubular joints. Furthermore, the interaction eff ect of the concurrent axial loading applied at the welded tubular joint on member stress is apparent.
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