Fatigue and fracture behaviour of high-strength lath martensitic steel

The paper addresses the fatigue and fracture behaviour of a low-alloy lath martensitic steel that conform a new class of high-strength tendon-bars for structural engineering. In order to assess the damage tolerance of such bars, a failure assessment diagram (FAD) is constructed from experimental results by plotting the failure loads of fatigue-cracked cylindrical notched specimens against the cracked area, as respective fractions of the bearing load capacity and the cross section of the uncracked specimen. The FAD includes the theoretical regions where failure is respectively controlled by the steel yielding capacity and toughness. The positions occupied in the FAD by the experimentally obtained failure data indicate that toughness is sufficient to prevent the brittle failure. Thus, it can be concluded that the toughness and ductility of the lath martensitic steel provide the bars with a substantial level of crack resistance.