Ductile Crack Growth Modelling Using Cohesive Zone Approach

2008 ◽  
pp. 191-207
Author(s):  
Vladislav Kozák
Keyword(s):  
Crack Growth ◽  
Cohesive Zone ◽  
Growth Modelling ◽  
Ductile Crack ◽  
Ductile Crack Growth

Numerical Simulation of Dynamic Ductile Fracture Propagation Using Cohesive Zone Modeling

2008 ◽  
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.

Cohesive Zone Modeling of Ductile Crack Growth in Circumferential Through-Wall-Cracked Pipe Tests

2011 ◽  
Author(s):  
Do-Jun Shim ◽  
Mohammed Uddin ◽  
Frederick Brust ◽  
Gery Wilkowski
Keyword(s):  
Crack Growth ◽  
Cohesive Zone ◽  
Bending Moment ◽  
Growth Behavior ◽  
Cohesive Zone Modeling ◽  
Crack Growth Behavior ◽  
Ductile Crack ◽  
Element Analysis ◽  
Ductile Crack Growth ◽  
Zone Modeling

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. However, the cohesive zone modeling has not been applied to simulate the ductile crack growth behavior of a circumferential through-wall cracked pipe. In this paper, cohesive zone modeling has been applied to simulate the ductile crack growth of a past through-wall-cracked pipe test that was conducted during Degraded Piping Program. The ABAQUS code was used for the three-dimensional finite element analysis. The bending moment at crack initiation, maximum bending moment, crack extension, and J-integral values were calculated from the finite element analysis. These results were compared with the experimental results. In addition, results obtained from an existing J-estimation scheme (LBB.ENG2) were provided for comparison. All results showed reasonable agreement. The results of the present study demonstrate that the cohesive zone modeling can be applied to simulate the ductile crack growth behavior of a through-wall cracked pipe.

Ductile Crack Extension Analysis for X80 Bending Deformation Using Damage-Based Model

2014 ◽  
Author(s):  
Satoshi Igi ◽  
Mitsuru Ohata ◽  
Takahiro Sakimoto ◽  
Kenji Oi ◽  
Joe Kondo
Keyword(s):  
Plastic Strain ◽  
Simulation Model ◽  
Crack Growth ◽  
Crack Extension ◽  
Damage Model ◽  
Stress Triaxiality ◽  
Crack Growth Behavior ◽  
Ductile Crack ◽  
Ductile Crack Growth ◽  
Notch Tip

This paper presents experimental and analytical results focusing on the strain limit of X80 linepipe. Ductile crack growth behavior from a girth weld notch is simulated by FE analysis based on a proposed damage model and is compared with the experimental results. The simulation model for ductile crack growth accompanied by penetration through the wall thickness consists of two criteria. One is a criterion for ductile crack initiation from the notch-tip, which is described by the plastic strain at the notch tip, because the onset of ductile cracking can be expressed by constant plastic strain independent of the shape and size of the components and the loading mode. The other is a damage-based criterion for simulating ductile crack extension associated with damage evolution influenced by plastic strain in accordance with the stress triaxiality ahead of the extending crack tip. The proposed simulation model is applicable to prediction of ductile crack growth behaviors from a circumferentially-notched girth welded pipe with high internal pressure, which is subjected to tensile loading or bending (post-buckling) deformation.

Ductile Damage Model Based On Void Growth Analysis for Application to Ductile Crack Growth Simulation

2021 ◽  
Author(s):  
Takehisa Yamada ◽  
Mitsuru Ohata
Keyword(s):  
Crack Growth ◽  
Void Growth ◽  
Damage Evolution ◽  
Damage Model ◽  
Crack Growth Resistance ◽  
Growth Behavior ◽  
Ductile Crack ◽  
Growth Simulation ◽  
Crack Growth Simulation ◽  
Ductile Crack Growth

Abstract The aim of this study is to propose damage model on the basis of the mechanism for ductile fracture related to void growth and to confirm the applicability of the proposed model to ductile crack growth simulation for steel. To figure out void growth behavior, elasto-plastic finite element analyses using unit cell model with an initial void were methodically performed. From the results of those analyses, it was evident that the relationships between normalized void volume fraction and normalized strain by each critical value corresponding to crack initiation were independent of stress-strain relationship of material and stress triaxiality state. Based on this characteristic associated with void growth, damage evolution law was derived. Then, using the damage evolution law, simple and phenomenological ductile damage model reflecting void growth behavior and ductility of material was proposed. To confirm the validation and application of proposed damage model, the damage model was implemented in finite element models and ductile crack growth resistance was simulated for cracked components were performed. Then, the simulated results were compared with experimental ones and it was found that the proposed damage model could accurately predict ductile crack growth resistance and was applicable to ductile crack growth simulation.

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