Abstract
Fatigue tests were conducted on arc welded lap joints made of 440MPa grade high-strength hot-rolled steel sheets under a repeated two-step variable amplitude loading condition. The cumulative damage (D) decreased when increasing the difference in the loading amplitude between the high- and the low-level loadings. Moreover, D increased with the increase of the number of cycles at the low-level loading amplitude, under the condition that the low-level loading was below the fatigue limit. Furthermore, the EBSD observation nearby cracks was conducted and revealed that D might be in correlation with the amount of concentrated strain at the crack tip.
