In terms of experimental research on weld performance of cast steel joints, Zou Hui of Southeast University conducted fatigue tests on two gs-20mn5 cast steel welded structures and obtained the S-N curves of the two welded structures; The fatigue checking calculation of the cast steel joint and weld of a sightseeing tower is carried out. The numerical analysis results show that the fatigue strength of the cast steel part is much higher than that of the weld part, and the weld is the fatigue weak link of the whole joint. Guo Qi of Tianjin University carried out fatigue tests on standard welded specimens of cast steel hot rolled steel and circular butt welds of cast steel hot rolled steel to study the fatigue failure mechanism of butt welds of cast steel joints;
Through the fatigue test of welded standard specimens of cast steel g20mnqt and hot rolled steel Q345B, it is found that the fatigue performance is slightly lower than that of cast steel g20mn5qt; The fatigue failure of welded standard specimens is basically in the heat affected zone on the side of cast steel, not at the weld. Its fatigue source is mainly casting defects, so its fatigue performance is close to that of cast steel, but the uneven grain size in the welding heat affected zone makes its fatigue performance slightly lower than that of cast steel.
In terms of fatigue calculation method, Li Jing of Southeast University studied the design of different annular butt welds of cast steel joints of a sightseeing tower, including four weld details: bilateral welding, unilateral welding with sleeve, unilateral welding with cushion block and unilateral welding without cushion block. The fatigue life of various welds under constant amplitude wave load was analyzed by hot spot stress method.
Lin Yunchang of Tianjin University used the hot spot stress method to analyze the fatigue problem of circular butt weld of cast steel joint, and compared four hot spot stress extrapolation methods. The research results show that the results obtained by using the method recommended by the international welding society are slightly greater than those obtained by using the method recommended by det Norske Veritas, and the results obtained by using the three-point quadratic extrapolation method are slightly greater than those obtained by the corresponding two-point linear extrapolation method. Chen Da of Southeast University carried out finite element modeling and Analysis on the weld details of five kinds of cast steel joints, calculated the hot spot stress value and nominal stress value at the weld root under the given load, obtained the hot spot stress concentration factor of weld root with different details, and deduced the surface extrapolation method and direct calculation method suitable for calculating the hot spot stress value of weld root; It is found that the extrapolation method of weld toe can not be used to calculate the hot spot stress of weld root, and the surface extrapolation method and the direct calculation method have their own advantages and disadvantages. The former result is more real and the latter result is more stable.