Numerical Simulation of Dynamic Ductile Fracture Propagation Using Cohesive Zone Modeling

Abstract

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.

Simulation of ductile crack propagation and determination of CTOAs in pipeline steels using cohesive zone modelling

“…The steady‐state CTOAs of the TH materials during the DWTT simulations were in the range of 2–4.5°, which is in close agreement to the steady‐state CTOAs measured from the SSY simulations. The estimated steady‐state CTOAs of the C2 materials during the DWTT simulations were in the range of 14–26°; the experiment yielded a value of 18.5° on the surface (measured optically) and 12.4° from load–displacement data (using the S‐SSM), which should give a value representative of the CTOA averaged through the thickness . The DWTT simulations reach lower values than those measured from the SSY simulations because the SSY simulations did not propagate far enough to reach steady‐state conditions.…”

“…It has been observed in the literature that the size of the cohesive element affects simulation results. 10 In the present work, the mesh designs of the cohesive elements have been implemented following Ref. [20] with 3 1/3 cohesive elements per adjacent elastic-plastic element, as described earlier.…”

“…Several researchers have simulated ductile crack growth with CZM and extracted CTOA for pipeline steels. For example, the group of researchers in Engineering Mechanics Corporation of Columbus used the classical cohesive zone (CZ) model discussed by Tvergaard and Hutchinson . CSM also uses a one‐dimensional CZ model of crack propagation, with a modified traction–separation (TS) law .…”

State-of-the-art review of fracture control technology for modern and vintage gas transmission pipelines

“…Nevertheless, the recent studies [86,87,90,91] using the cohesive zone model to simulate the ductile fracture propagation in modern gas pipelines is encouraging.…”

“…It seems for the first time that Shim [90] performed the numerical simulation of dynamic ductile fracture propagation in a gas pipeline using a cohesive zone model and ABAQUS/Explicit. The cohesive parameters were calibrated using the measured fracture velocity from a full-scale pipe test.…”