Abstract
There is very limited fatigue data over 10 million cycles for structural steel welds. Unalloyed low-carbon steels according to EN 10025 are dominant structural materials of the heavy machinery for minerals and mining applications. The main purpose of this research is a fatigue performance comparison of the welds made of currently preferred steel S355JR and the candidate steel S275JR. Welded machinery assemblies are designed to work for several years at typically 16-20 Hz frequencies of loading under low stress amplitudes. In order to reach a few billion cycles within a practically sustainable testing time, an accelerated fatigue testing is required. The goal of reaching gigacycle fatigue domain is achieved using the ultrasonic fatigue testing approach with Shimadzu USF-2000A system. The fatigue samples for S275JR and S355JR steels have a standard tapered shape are cut out of the welded plates to have a HAZ in the middle. The fatigue samples are prepared to investigate the influence of two surface conditions – polished and pre-corroded. In the polished samples, fatigue failures are driven primarily by the welding porosity with the fatigue life duration dependent on the size and location of pores. In the pre-corroded samples, fatigue failures are driven primarily by the corrosion pitting with the fatigue life duration dependent on the amount of corrosion damage to the surface. Visual comparison of fatigue data for S275JR and S355JR steels poses a challenge, because of the massive scatter of experimental data points making the determination of SN curves impossible. Therefore, statistical approach is used. Session
