Ductile tearing analysis of TC128 tank car steel under mode I loading condition

The objective of the present work is to incorporate the effect of post-failure softening on fracture initiation modeling of steel alloy TC128 commonly used in railroad tank car manufacturing. The fracture initiation process is determined through a comprehensive mechanical tests, which includes tensile tests on standard dog-bone specimens, flat specimens with circular cutouts and central hole, notched round bars, punch indentation tests on circular blanks and special flat shear specimens. Ductile fracture toughness usually referred to as resistance curve is measured from two types of typical fracture mechanics specimen geometries: the compact tension C(T) and the three-point bending SE(B). Post-failure softening is then coupled with the constitutive model to describe ductile fracture propagation. It turns out that in the absence of softening in fracture, the crack growth rate increases with little resistance opposite of what has been observed in fracture response of typical steels. On the other hand, the post-failure softening algorithm increases the ductile resistance behavior of the material more realistically, compared to experiments and provides additional information regarding the state of stress governing the fracture process.