A study on the decrease of fracture resistance curve under reversed cyclicloading

Fracture resistance (J-R) curves, which are used for elastic-plastic fractu re mechanics analyses, decrease under reversed cyclic loading condition. Se veral former researchers reported this phenomenon, but the causes have not been clear. The objective of this paper has been to investigate the causes of this phenomenon. Hen, we attempt to provide an explanation for the decre ase in J-R curve based on an increase in strain-hardening, the correspondin g stress redistribution during cyclic loading and crack opening phenomenon. Hardness tests, automated ball indentation tests, and theoretical stress f ield analyses were performed on SA516 steel to prove the hypotheses. The re sults revealed that the decrease in the J-R curve is related to the increas ed strain-hardening and generation of tensile residual stress at the crack tip during cyclic loading. (C) 2000 Published by Elsevier Science Ltd.