An inverse analysis of cohesive zone model parameter values for ductile crack growth simulations

In the present paper, ductile crack growth in an aluminium alloy is numerically simulated using a cohesive zone model under both plane stress and plane strain conditions for two different fracture types, shear and normal modes. The cohesive law for ductile fracture consists of two parts—a specific material’s separation traction and energy. Both are assumed to be constant during ductile fracture (stable crack growth). In order to verify the assumed cohesive law to be suitable for ductile fracture processes, experimental records are used as control curves for the numerical simulations. For a constant separation traction, determined experimentally from tension test data, the corresponding cohesive energy was determined by finite element calculations. It is confirmed that the cohesive zone model can be used to characterize a single ductile fracture mode and is roughly independent of stable crack extention. Both the cohesive traction and the cohesive fracture energy should be material specific parameters. The extension of the cohesive zone is restricted to a very small region near the crack tip and is in the order of the physical fracture process. Based on the present observations, the cohesive zone model is a promising criterion to characterize ductile fracture.

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Numerical Simulation of Dynamic Ductile Fracture Propagation Using Cohesive Zone Modeling

2008 7th International Pipeline Conference, Volume 3 ◽

10.1115/ipc2008-64049 ◽

2008 ◽

Cited By ~ 6

Author(s):

Do-Jun Shim ◽

Gery Wilkowski ◽

David Rudland ◽

Brian Rothwell ◽

James Merritt

Keyword(s):

Finite Element ◽

Crack Propagation ◽

Crack Growth ◽

Growth Model ◽

Cohesive Zone ◽

Zone Model ◽

Pipe Material ◽

Ductile Crack ◽

Ductile Crack Growth ◽

Crack Growth Model

This paper presents the development of a dynamic ductile crack growth model to simulate an axially running crack in a pipe by finite element analyses. The model was developed using the finite element (FE) program ABAQUS/Explicit. To simulate the ductile crack propagation, a cohesive zone model was employed. Moreover, the interaction between the gas decompression and the structural deformation was simulated by using an approximate three-dimensional pressure decay relationship from experimental results. The dynamic ductile crack growth model was employed to simulate 152.4 mm (6-inch) diameter pipe tests, where the measured fracture speed was used to calibrate the cohesive model parameters. From the simulation, the CTOA values were calculated during the dynamic ductile crack propagation. In order to validate the calculated CTOA value, drop-weight tear test (DWTT) experiments were conducted for the pipe material, where the CTOA was measured with high-speed video during the impact test. The calculated and measured CTOA values showed reasonable agreement. Finally, the developed model was employed to investigate the effect of pipe diameter on fracture speed for small-diameter pipes.

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Comparison of Through-Wall and Complex Crack Behaviors in Dissimilar Metal Weld Pipe Using Cohesive Zone Modeling

Volume 6A: Materials and Fabrication ◽

10.1115/pvp2013-98041 ◽

2013 ◽

Cited By ~ 4

Author(s):

Do-Jun Shim ◽

David Rudland ◽

Frederick Brust

Keyword(s):

Cohesive Zone ◽

Cohesive Zone Model ◽

Cohesive Zone Modeling ◽

Zone Model ◽

Ductile Crack ◽

Dissimilar Metal ◽

Ductile Crack Growth ◽

Zone Modeling ◽

Dissimilar Metal Weld ◽

Metal Weld

Cohesive zone modeling has been shown to be a convenient and effective method to simulate and analyze the ductile crack growth behavior in fracture specimens and structures. Recently, authors have applied the cohesive zone model to simulate the ductile fracture behavior of a through-wall cracked pipe test consisting of a single material. In this paper, cohesive zone modeling has been applied to simulate the ductile crack growth in dissimilar metal weld pipe tests that was recently conducted by the U.S. NRC. Two crack types, i.e. through-wall and complex cracks, were simulated in the work. This paper describes how the cohesive parameters were determined and discusses in detail about the finite element modeling of the cohesive zone model. Various fracture parameters were compared between the finite element analyses and the experiments to validate the model. The results of the cohesive zone models showed good agreement with the pipe test results. Furthermore, the results of the cohesive zone model demonstrate that the fracture toughness (J at crack initiation, Jinit.) of the complex cracked pipe can be significantly lower (factor of 0.41) than that of the through-wall cracked pipe.

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