Introduction
Bimonthly, started in 1957
Administrator
Shanxi Provincial Education Department
Sponsor
Taiyuan University of Technology
Publisher
Ed. Office of Journal of TYUT
Editor-in-Chief
SUN Hongbin
ISSN: 1007-9432
CN: 14-1220/N
Administrator
Shanxi Provincial Education Department
Sponsor
Taiyuan University of Technology
Publisher
Ed. Office of Journal of TYUT
Editor-in-Chief
SUN Hongbin
ISSN: 1007-9432
CN: 14-1220/N
location: home > paper >
Experimental Study on Constant Amplitude Fatigue of M24 High-strength Bolts under Critical Stress Ra
DOI:
10.16355/j.cnki.issn1007-9432tyut.2019.06.007
Received:
Accepted:
| Corresponding author | Institute | |
| JIAO Jinfeng | College of Civil Engineering, Taiyuan University of Technology; |
abstract:
In this paper, 3 static tensile tests and 15 axial ‘tension-tension’ constant-amplitude fatigue tests under the critical stress ratio(R=0.8) for the 8.8 grade M24 bolts with the material of 35 K were carried out. S-N curves were fitted, macroscopic and microscopic analyses were conducted for fatigue fracture of typical specimens and all the test results were compared with the calculation results based on relevant formulas given in Chinese national standard GB 50017-2017. The conclusions are as follows: the fatigue test data were highly discrete, and the corresponding cycle number of failure was generally low, but all of them were within the confidence interval of 95%. The fitted S-N curves could basically reflect the fatigue life of specimens under different stress amplitudes. Furthermore, the constant-amplitude fatigue failure of bolt specimens all started at the root of the screw thread, the fatigue failure was caused by the extension of punctiform fatigue source into linear fatigue source, and the characteristics of fracture dimples were obvious. By comparing the test results with the recommended values of allowable fatigue strength stipulated in the national standards, the corresponding fatigue strength of 2×10~6 times was 1.35 times that of the recommended value.
Keywords:
critical stress ratio;high-strength bolts;constant-amplitude fatigue;fatigue surface;Stress-Number curve