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Title: Cohesive Zone Model User Element

Abstract

Cohesive Zone Model User Element (CZM UEL) is an implementation of a Cohesive Zone Model as an element for use in finite element simulations. CZM UEL computes a nodal force vector and stiffness matrix from a vector of nodal displacements. It is designed for structural analysts using finite element software to predict crack initiation, crack propagation, and the effect of a crack on the rest of a structure.

Authors:
Publication Date:
Research Org.:
Los Alamos National Laboratory
Sponsoring Org.:
USDOE
OSTI Identifier:
1231009
Report Number(s):
CZM UEL; 002107MLTPL00
C-07, 013
DOE Contract Number:
DE-AC52-06NA25396
Resource Type:
Software
Software Revision:
00
Software Package Number:
002107
Software Package Contents:
Media Directory; Software Abstract; Media includes Source Code; Object Library and User Manual;/ 1 CD ROM
Software CPU:
MLTPL
Open Source:
No
Source Code Available:
Yes
Related Software:
ABAQUS
Country of Publication:
United States

Citation Formats

Tippetts, Trevor. Cohesive Zone Model User Element. Computer software. Vers. 00. USDOE. 17 Apr. 2007. Web.
Tippetts, Trevor. (2007, April 17). Cohesive Zone Model User Element (Version 00) [Computer software].
Tippetts, Trevor. Cohesive Zone Model User Element. Computer software. Version 00. April 17, 2007.
@misc{osti_1231009,
title = {Cohesive Zone Model User Element, Version 00},
author = {Tippetts, Trevor},
abstractNote = {Cohesive Zone Model User Element (CZM UEL) is an implementation of a Cohesive Zone Model as an element for use in finite element simulations. CZM UEL computes a nodal force vector and stiffness matrix from a vector of nodal displacements. It is designed for structural analysts using finite element software to predict crack initiation, crack propagation, and the effect of a crack on the rest of a structure.},
doi = {},
year = {Tue Apr 17 00:00:00 EDT 2007},
month = {Tue Apr 17 00:00:00 EDT 2007},
note =
}

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  • The Cohesive zone (CZ) fracture analysis techniques are used to predict the initiation of crack growth from the interface corner of an adhesively bonded butt joint. In this plane strain analysis, a thin linear elastic adhesive layer is sandwiched between rigid adherends. There is no preexisting crack in the problem analyzed, and the focus is on how the shape of the traction–separation (T–U) relationship affects the predicted joint strength. Unlike the case of a preexisting interfacial crack, the calculated results clearly indicate that the predicted joint strength depends on the shape of the T–U relationship. Most of the calculations usedmore » a rectangular T–U relationship whose shape (aspect ratio) is defined by two parameters: the interfacial strength σ* and the work of separation/unit area Γ. The principal finding of this study is that for a specified adhesive layer thickness, there is any number of σ*, Γ combinations that generate the same predicted joint strength. For each combination there is a corresponding CZ length. We developed an approximate CZ-like elasticity solution to show how such combinations arise and their connection with the CZ length.« less
  • The Cohesive zone (CZ) fracture analysis techniques are used to predict the initiation of crack growth from the interface corner of an adhesively bonded butt joint. In this plane strain analysis, a thin linear elastic adhesive layer is sandwiched between rigid adherends. There is no preexisting crack in the problem analyzed, and the focus is on how the shape of the traction–separation (T–U) relationship affects the predicted joint strength. Unlike the case of a preexisting interfacial crack, the calculated results clearly indicate that the predicted joint strength depends on the shape of the T–U relationship. Most of the calculations usedmore » a rectangular T–U relationship whose shape (aspect ratio) is defined by two parameters: the interfacial strength σ* and the work of separation/unit area Γ. The principal finding of this study is that for a specified adhesive layer thickness, there is any number of σ*, Γ combinations that generate the same predicted joint strength. For each combination there is a corresponding CZ length. We developed an approximate CZ-like elasticity solution to show how such combinations arise and their connection with the CZ length.« less
  • In the present paper, ductile crack growth in an aluminum 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 materials` 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 testmore » 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 extension. 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.« less
  • A time-dependent cohesive zone model is employed to model adhesive failure and grain-boundary cracking. Through the incorporation of viscoelasticity and evolving damage, the viscoelastic cohesive zone model (VCZM) yields a time-dependent critical energy release rate. A double-cantilever beam configuration is investigated. Crack growth curves are presented for the Xu-Needleman and VCZM model. In addition, a fifty-five grain polycrystal is simulated in compression. Time-dependent grain boundary prying and sliding result in inter-granular separation parallel to the major axis of loading.
  • Interface damage mechanics, or cohesive zone models, have been developed over the last decade as a method of modeling crack growth in a material or debonding between two different materials. These methods have alleviated many of the numerical problems inherent in crack modeling, including the large length scale difference between crack fronts and crack areas, strem singularities, and the adaptation of crack propagation criteria to non-linear materials. Cohesive zone models can also predict crack initiation at any number of predetermined possible crack locations. However, researchers have also found that numerical instabilities in the solutions emerge if the finite element meshmore » is too coarse relative to the crack process radius. Consequently, these have been practical only for very small structures, on the order of tens of millimeters, without the use of supercomputers. We will show that changing the order of numerical integration of the interface properties independently from their spatial discretization solves this convergence problem and in most cases decreases the total computation time, allowing for simulations of much larger structures. We will also show how these results are incorporated into our multilength scale model for predicting impact damage in laminated composite plates.« less

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