On the determination of the cohesive zone parameters for the modeling of micro-ductile crack growth in thick specimens^*

Authors: Chen C.R.¹; Kolednik O.²; Scheider I.³; Siegmund T.⁴; Tatschl A.⁵; Fischer F.D.⁶

Source: International Journal of Fracture, Volume 120, Number 3, April 2003 , pp. 517-536(20)

Publisher: Springer

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Abstract:

The paper deals with the determination of the cohesive zone parameters (separation energy, Ggr , and cohesive strength, T_max) for the 3D finite element modeling of the micro-ductile crack growth in thick, smooth-sided compact tension specimens made of a low-strength steel. Since the cohesive zone parameters depend, in general, on the local constraint conditions around the crack tip, their values will vary along the crack front and with crack extension. The experimental determination of the separation energy via automated fracture surface analysis is not accurate enough. The basic idea is, therefore, to estimate the cohesive zone parameters, Ggr and T_max, by fitting the simulated distribution of the local crack extension values along the crack front to the experimental data of a multi-specimen J_IC-test. Furthermore, the influence of the cohesive zone parameters on the crack growth behavior is investigated. The point of crack growth initiation is determined only by the magnitude of Ggr . Both Ggr and T_max affect the crack growth rate (or the crack growth resistance), but the influence of the cohesive strength is much stronger than that of the separation energy. It turns out that T_max as well as Ggr vary along the crack front. In the center of the specimen, where plane strain conditions prevail, the separation energy is lower and the cohesive strength is higher than at the side-surface.

Keywords: cohesive zone modeling; micro-ductile fracture; cr

Language: English

Document Type: Research article

Affiliations: 1: Materials Center Leoben, A-8700 Leoben, Austria, and Shenyang National Laboratory for Materials Science, Shenyang 110016, China 2: Erich Schmid Institute of Materials Science, Austrian Academy of Sciences, A-8700 Leoben, Austria (e-mail: kolednik@unileoben.ac.at 3: GKSS Forschungszentrum Geesthacht GmbH, D-21502 Geesthacht, Germany 4: School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907-1288, U.S.A. 5: Erich Schmid Institute of Materials Science, Austrian Academy of Sciences, A-8700 Leoben, Austria (e-mail: kolednik@unileoben.ac.at) 6: Institute of Mechanics, Montanuniversität Leoben, and Erich Schmid Institute of Materials Science, Austrian Academy of Sciences, A-8700 Leoben, Austria

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