Observation of fatigue microcracks and estimation of fatigue strength of a thin sheet arc welded part considering micro-ripples

Fatigue tests were conducted on a thin sheet arc welded part using two types of welding wires. Microscopic observations of specimens tested at the fatigue limit stress revealed that microcracks were initiated in the micro-ripples on the weld metal surface. Furthermore, a coarse ferrite structure often contains existing microcracks. A method for quantitatively evaluating the effects of microscopic irregularities on the weld metal surface and macroscopic toe shape on the fatigue strength is proposed. It was found that microscopic irregularities on weld metal have a significant impact on the fatigue limit, depending on their metallurgical structure.