EXPERIMENTAL STUDY ON FATIGUE STRENGTH OF WELDED JOINTS OF HIGH STRENGTH STEEL Q550D

The basic mechanical property of domestic Q550D high-strength structural steel and its weld, as well as the fatigue behavior of transverse butt weld and non-load carrying transverse fillet-weld attachment were investigated experimentally. The fabrication and welding procedure of test specimens, as well as the methods of fatigue tests and data processing were described. The fatigue test results were analyzed and compared with the domestic and international design standards of steel structures and other research results. It is concluded that both the Q550D steel and its weld had fine elongation and low-temperature impact toughness. The fatigue strength of the Q550D steel butt weldment ground flush to plate surface and transverse fillet-weld attachment was much higher than that of relevant welded joints of normal-strength steel given in the design standards of steel structures, increased by 72%~125% and 27%~68% respectively. Grinding butt weld surface could improve stress concentration due to weld geometry and defects, so as to have better fatigue behavior than the butt weldment as a welded condition. The butt weldment regardless grinding weld surface or not, and the transverse fillet-weld attachment showed a growing trend in fatigue strength as their yield strength increased. Both the S-N curves for the Q550 high-strength steel butt weldment with grinding surface and the transverse fillet-weld attachment were proposed for the application of pertinent fatigue design.