Abstract
Experiments and theoretical analysis are performed to characterize the ductile crack growth and crack tunneling of 25mm thick carbon-manganese steel bar. The ductile crack growth of the cracked bars is determined by a developed procedure. This procedure depends on the material fracture toughness and the applied crack driving force (J-Integral), as well as the crack tip stress triaxiality determined numerically using finite element analysis. Fracture mechanics testing is also conducted in order to determine the plane strain fracture toughness of the material through fracture resistance curves in terms of J-Δa curve. It is shown that the variation of the stress triaxiality and J-integral are consistent across the thickness, and both control the crack instability. A good agreement is obtained between the experiments and the developed mathematical expression.