Experimental study on high-cycle fatigue performance of LQ550 cold-rolled high-strength steel sheet

Due to the advantages of convenient cold working, flexible section and easy connection, the application of cold-formed steel (CFS) structure system becomes more and more extensive. Meanwhile,as one of the important forms of damage, fatigue failure deserves investigation for further promotion of CFS. However, there are no relevant provisions on anti-fatigue design of CFS, even in the GB 50018—202X ‘Standard for cold-formed steel structures’ (revised version for approval). In this paper, tensile high-cycle fatigue tests were carried out on LQ550 cold-rolled high-strength steel sheets with thicknesses of 0. 8 mm and 1. 2 mm and with different rolling directions. The fitted S-N curves were compared with that predicted by the current design standards and previous Q690 high-strength steel fatigue tests. The results show that the fatigue performance of the steel sheet along the rolling direction is better than that cross the rolling direction. With increasing thickness, the fatigue performance of the steel sheet along the rolling direction is reduced, while that cross the rolling direction is increased. For steel sheets with thickness of 0. 8 mm and 1. 2 mm, with merged fitting and 95% survival probability, the fatigue limit stresses along rolling direction are 192%, 172% and 165% higher than calculated values of AISC 360-2016, AISI S100-2016 and GB 50017—2017, respectively. The improvements of fatigue limit stress cross the rolling direction are 103%, 88% and 84%, respectively. The results show that the fatigue performance of steel sheet is much higher than that of common steel due to the rolling effect. The fatigue performance of the steel sheet across the rolling direction is similar to that of high-strength steel. © 2024 Science Press. All rights reserved.