A digital twin approach toward unlocking elasto-plastic fatigue crack growth rates under negative load ratios

This paper introduces a novel digital twin solution for unlocking the elasto-plastic fatigue crack growth within an S550 steel under negative load ratios. The digital twin transforms solely strain data from a strain-interfaced welded plate joint specimen to the load-displacement curve to compute cyclic J-integral values using the eta approach, eliminating the need for load and displacement measurements. The accurate computation of the elasto-plastic Delta J effectively extends the fatigue crack growth relationship derived from standard fracture specimens. The extended fatigue crack growth relationship accurately predicts the fatigue life of specimens under separate step-up and step-down variable amplitude loading regimes.