For most engineering materials are influenced by the dominant mechanism resisting crack extention under large scale yielding conditions. Continuum mechanics analysis shows that fracture toughness, in addition to depending on young`s modulus, flow stress strain hardening exponent, and yield strain, should be nearly proportoinal to the effective fracture ductility obtained for the stress state characteristic for region ahead of the crack; plane stress or plane strain. It`s known that, in most ductile materials, crack propagation of the material strongly governed by the J_(IC) value, which is still difficult to determine for it`s complicate and troble-some determinative process. This paper, on the assumption that, initiation of crack tip strain field reaches on the relationships between the critical value of J-integral (J_(IC)) and the local fracture strain(ε_c) in uniaxial tensile test in the region of maximun reduction areas was described.