Investigation on fatigue crack resistance of Q370qE bridge steel at a low ambient temperature

Abstract

The Q370qE steel has a wide application in the medium and long span railway steel bridges in China, due to its excellent material characteristics including high strength, high toughness and good weldability at room temperature. Nevertheless, the limited research work on the fatigue properties of the Q370qE steel challenges the safety of steel bridges in cold and severe cold regions under the cyclic actions. This study first conducts a series of strain-controlled fatigue tests of coupon specimens at room temperature and −60 °C to characterize the cyclic stress-strain curve, hysteresis loops, Masing behavior and fatigue crack initiation resistance by Coffin-Manson relationship. Thereafter, the fatigue crack propagation tests of the compact tension specimens under different stress ratios and different temperatures reveal the effect due to stress ratios and temperatures on the fatigue crack propagation resistance of the Q370qE steel through the Paris formula. Results demonstrate that the low temperatures enhance the resistance to the fatigue crack initiation and propagation of the Q370qE steel. Finally, to better quantify the performance of the Q370qE steel, this paper collects different bridge steels and compares the fatigue crack initiation resistance and fatigue crack propagation between the Q370qE steel and other bridge steels. The results quantify the excellent higher fatigue resistance of Q370qE steel in comparison with other bridge steels.