[10] conducted 40 axial tensile tests on bolted ball joints with five different bolt types and eight different screw in depths, and obtained a reliable numerical simulation method to estimate the ultimate strength, failure mode, detailed stress distribution and failure development process.

Before the test, the appearance of each bolt shall be surveyed to ensure that there are no apparent defects affecting the test results such as thread damage.

In order to further determine the material properties and select a more reasonable test loading scheme, three high-strength bolts are randomly selected from the test materials to make standard specimens for static tensile test according to the tensile test of metallic materials Part 1: room temperature test method (GB / t228.1-2010) [12].

Yan Yajie et al.

[5], Zhang Jian et al.

PVC Chamfer

With the more and more extensive application of high-strength bolts, the high-strength bolts in practical engineering are complicated due to the pre tension testing process It takes a long time and the phenomenon of under pretension is common, which makes the engineering safety problems have great hidden dangers.

The above research on the fatigue performance of high-strength bolts mainly focuses on the evaluation and updating of high-strength bolts for space truss and foreign design standards.

[7] conducted the false tightening constant amplitude fatigue test of seven groups of M30 high-strength bolts, established its S-N curve and calculated that the false tightening fatigue strength of M30 high-strength bolts is only 1 / 4 of that of full tightening when three threads are screwed in.

[9] obtained the effects of end plate thickness, bolt diameter and weld form on the fatigue life of high-strength bolt suspension end plate connection through the test and numerical study of three different connection forms of bolt and end plate.

The S-N curve of constant amplitude fatigue failure is drawn and the fatigue life calculation method is established.

The static test results are shown in Table 1, and all mechanical performance indexes meet the standard requirements.

Lead authors: Shen Yu, Lei Honggang, Feng xuze (School of civil engineering, Taiyuan University of technology, Taiyuan 030024, Shanxi) source: Journal of Taiyuan University of technology, December 2021 Abstract: high strength bolts in cast steel structure buildings are more and more widely used because of their advantages of convenient construction, superior mechanical performance, detachable replacement and strong fatigue resistance, However, the relaxation of pretension caused by the immature pretension detection technology of high-strength bolts has laid a major hidden danger for the safety of the project.

The clamping position of extensometer and standard specimens are shown in Figure 1.

Johan maljaars et al.

Ding Beidou et al.

Feng Xiujuan et al.

Lei Honggang [3] obtained 18 M20 and 14 M30 constant amplitude fatigue test data through bilateral and unilateral loading tests respectively, which provides a basis for the follow-up study of establishing fatigue design method with hot spot stress amplitude as a parameter.

The stress-strain curve of M20 high-strength bolt under static load is shown in Figure 2..

Test overview # 1.1 mechanical properties # 1.1.1 material property test # the bolts used in this test are ML20MnTiB, grade 10.9 and M20 high-strength bolt connection pairs of the same batch, with the specification of M20 × 100.

[6] respectively conducted constant amplitude fatigue tests on M20, M22, M24 and M30 high-strength bolts, supplemented a large number of valuable fatigue data, established a more general S-N curve, analyzed the fatigue failure fracture, and revealed the fatigue failure mechanism.

Qiu bin et al.

In this paper, MTS servo hydraulic fatigue testing machine is used to carry out 3 groups of static tensile tests and 10 groups of constant amplitude fatigue tests of under pretension on ML20MnTiB, grade 10.9 and M20 high-strength bolts commonly used in engineering.

In this paper, through the experimental research on the constant amplitude fatigue performance of M20 high-strength bolt under under pretension, the S-N curve is obtained, the fatigue life design method is established, and the fatigue fracture is analyzed macroscopically and microscopically, in order to provide design basis and theoretical help for the prosperity and development of cast steel structure buildings.

There is still a lack of research and test data on the fatigue performance of high-strength bolts used in domestic cast steel structure buildings.

With the in-depth and steady development of cast steel structure buildings in China, high-strength bolt connection, as one of the main connection forms, is more and more favored by people because of its reliable strength, simple construction, convenient assembly and mature technology.

For a long time, the fatigue failure of high-strength bolts has been widely concerned by scholars at home and abroad because of its unpredictable and sudden characteristics, which often leads to catastrophic accidents and huge economic losses [1].

[4], Yang Xu et al.

[8] studied and discussed the fatigue properties of Q460 and Q690 high-strength steels and bolted connections, carried out fatigue tests on base materials, perforated plates and bolted connections, and proposed that aisc360 and bs7608 design curves are suitable for the fatigue life analysis of Q460 bolted connections, while EC3 curve is relatively conservative.

[11] updated the relevant stress parameters and the shape and position of S-N curve in the revised version of European standard en1993-1-9 by conducting a large number of fatigue tests on bolts and their connections of different grades and sizes.

Guo Hongchao et al.

[2] designed loading devices for the members, hanging point specimens and joint truss specimens of bolted spherical joint space truss, completed the constant amplitude fatigue performance test research, and obtained the S-N curve and fatigue checking formula of bolted spherical joint space truss.

Helen Bartsch et al.

The fatigue fracture of bolts is analyzed macroscopically and microscopically by phenomprox electron microscope energy spectrum integrated machine, The typical characteristics of the morphology of fatigue source area, propagation area and instantaneous fracture area are displayed, and the failure mechanism and failure process of high-strength bolt are revealed, which provides a scientific basis for its fatigue safety design and fracture analysis.

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