Ductile crack growth simulation from near crack tip dissipated energy

A method to calculate ductile tearing in both small scale fracture mechanic s specimens and cracked components is presented. This method is based on an estimation of the dissipated energy calculated near the crack tip. Firstly , the method is presented. It is shown that a characteristic parameter G(fr ) can be obtained, relevant to the dissipated energy in the fracture proces s. The application of the method to the calculation of side grooved crack t ip (CT) specimens of different sizes is examined. The value of G(fr) is ide ntified by comparing the calculated and experimental load line displacement versus crack extension curve for the smallest CT specimen. With this ident ified value, it is possible to calculate the global behaviour of the larges t specimen. The method is then applied to the calculation of a pipe contain ing a through-wall thickness crack subjected to a bending moment. This pipe is made of the same material as the CT specimens. It is shown that it is p ossible to simulate the global behaviour of the structure including the pre diction of up to 90-mm crack extension. Local terms such as the equivalent stress or the crack tip opening angle are found to be constant during the c rack extension process. This supports the view that G(fr) controls the fiel ds in the vicinity near the crack tip. (C) 2000 Elsevier Science S.A. All r ights reserved.