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.

scholarly journals Numerical Simulation of Fatigue Crack Growth Rate and Crack Retardation due to an Overload Using a Cohesive Zone Model

2014 ◽  
Vol 891-892 ◽  
pp. 777-783 ◽  
Author(s):  
Sarmediran Silitonga ◽  
Johan Maljaars ◽  
Frans Soetens ◽  
Hubertus H. Snijder
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Propagation ◽  
Crack Growth ◽  
Cohesive Zone ◽  
Cohesive Zone Model ◽  
Crack Tip ◽  
Zone Model ◽  
Cohesive Elements

In this work, a numerical method is pursued based on a cohesive zone model (CZM). The method is aimed at simulating fatigue crack growth as well as crack growth retardation due to an overload. In this cohesive zone model, the degradation of the material strength is represented by a variation of the cohesive traction with respect to separation of the cohesive surfaces. Simulation of crack propagation under cyclic loads is implemented by introducing a damage mechanism into the cohesive zone. Crack propagation is represented in the process zone (cohesive zone in front of crack-tip) by deterioration of the cohesive strength due to damage development in the cohesive element. Damage accumulation during loading is based on the displacements in the cohesive zone. A finite element model of a compact tension (CT) specimen subjected to a constant amplitude loading with an overload is developed. The cohesive elements are placed in front of the crack-tip along a pre-defined crack path. The simulation is performed in the finite element code Abaqus. The cohesive elements behavior is described using the user element subroutine UEL. The new damage evolution function used in this work provides a good agreement between simulation results and experimental data.

Crack Growth Model under Creep-Fatigue Interaction

2011 ◽  
Vol 243-249 ◽  
pp. 241-244 ◽  
Author(s):  
Rui Zhang ◽  
Hong Liang Li
Keyword(s):  
Growth Rate ◽  
Crack Growth Rate ◽  
Crack Growth ◽  
Growth Model ◽  
Cohesive Zone ◽  
Cohesive Zone Model ◽  
Zone Model ◽  
J Integral ◽  
Creep Fatigue ◽  
Crack Growth Model

In the present paper, a new creep-fatigue crack growth model of J-integral criterion is proposed. The model is built based on the dislocation-free zone (DFZ) theory and cohesive zone model. The process of crack growth is viewed as the intermittent quasi-cleavage fracture of the DFZ. The microscopic void caused by creep will grow and join the dominant crack under creep-fatigue interaction. In this process, material’s plastic deformation induces the change of the dislocation’s density. The redistribution of dislocation will change the value of J-integral within the cohesive zone. When the value of J-integral attains the critical value Jc, crack will grow by the original width of DFZ. Based on it, a simple relation is employed to evaluate crack growth rate under creep-fatigue interaction. The calculated crack growth rate curve exhibits three different regimes, which is in agreement with the general crack propagation pattern under creep-fatigue interaction. The model gives a reasonable explanation for crack growth under creep-fatigue interaction. The calculated value is close to the value obtained by experiment.

Verification of a Cohesive Zone Model for Ductile Fracture

1996 ◽  
Vol 118 (2) ◽  
pp. 192-200 ◽  
Author(s):  
Huang Yuan ◽  
Guoyu Lin ◽  
Alfred Cornec
Keyword(s):  
Ductile Fracture ◽  
Crack Growth ◽  
Cohesive Zone ◽  
Cohesive Zone Model ◽  
Normal Modes ◽  
Stable Crack Growth ◽  
Small Region ◽  
Zone Model ◽  
Cohesive Law ◽  
Ductile Crack Growth

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.

Cohesive Zone Model and GTN Model Collation for Ductile Crack Growth

2007 ◽  
Vol 567-568 ◽  
pp. 145-148
Author(s):  
Vladislav Kozák ◽  
Ivo Dlouhý ◽  
Zdeněk Chlup
Keyword(s):  
Fracture Mechanics ◽  
Crack Propagation ◽  
Cohesive Zone ◽  
Cohesive Zone Model ◽  
Zone Model ◽  
Interface Elements ◽  
Ductile Crack Growth ◽  
Propagation Analysis ◽  
Wide Range ◽  
Finite Element Package

The micromechanical modelling encounters a problem that is different from basic assumptions of continuum mechanics. The material is not uniform on the microscale level and the material within an element has its own complex microstructure. Therefore the concept of a representative volume element (RVE) has been introduced. The general advantage, compared to conventional fracture mechanics, is that, in principle, the parameters of the respective models depend only on the material and not on the geometry. These concepts guarantee transferability from specimen to components over a wide range of dimensions and geometries. The prediction of crack propagation through interface elements based on the fracture mechanics approach (damage) and cohesive zone model is presented. The cohesive model for crack propagation analysis is incorporated into finite element package by interface elements which separations are controlled by the traction-separation law.

Sign in / Sign up

Export Citation Format

Share Document