scholarly journals Simulation of Stress-Corrosion Cracking by the Cohesive Model

2009 ◽  
Vol 417-418 ◽  
pp. 329-332 ◽  
Author(s):  
Rainer Falkenberg ◽  
Wolfgang Brocks ◽  
Wolfgang Dietzel ◽  
Ingo Schneider
Keyword(s):  
Crack Extension ◽  
Cohesive Zone Model ◽  
Hydrostatic Stress ◽  
Deformation Behaviour ◽  
Coupled Model ◽  
Isotropic Hardening ◽  
Zone Model ◽  
Coupled Diffusion ◽  
Von Mises ◽  
Von Mises Plasticity

The effect of hydrogen on the mechanical behaviour is twofold: It affects the local yield stress and it accelerates material damage. On the other hand, the diffusion behaviour is influenced by the hydrostatic stress, the plastic deformation and the strain rate. This requires a coupled model of deformation, damage and diffusion. The deformation behaviour is described by von Mises plasticity with pure isotropic hardening, and crack extension is simulated by a cohesive zone model. The local hydrogen concentration, which is obtained from the diffusion analysis, causes a reduction of the cohesive strength. Crack extension in a C(T) specimen of a ferritic steel under hydrogen charging is simulated by fully coupled diffusion and mechanical finite element analyses with ABAQUS and the results are compared with test results.

Asymmetric Shielding Mechanisms in the Mixed-Mode Fracture of a Glass/Epoxy Interface

1998 ◽  
Vol 65 (1) ◽  
pp. 25-29 ◽  
Author(s):  
J. G. Swadener ◽  
K. M. Liechti
Keyword(s):  
Cohesive Zone Model ◽  
Hydrostatic Stress ◽  
Crack Opening ◽  
Shielding Effect ◽  
Mixed Mode Fracture ◽  
Zone Model ◽  
Element Analysis ◽  
Rate Dependent ◽  
Numerical Predictions ◽  
Wide Range

An asymmetric increase in the apparent values of the interfacial fracture toughness with increasing mode II component of loading has been observed by several investigators. In this study, cracks were grown in a steady-state manner along the glass/epoxy interface in sandwich specimens in order to determine the mechanisms responsible for the shielding effect. Finite element analysis using a hydrostatic stress and strain rate dependent plasticity model for the epoxy and a cohesive zone model for the interface shows that plastic dissipation in the epoxy accounts for the asymmetric shielding seen in these experiments which cover a wide range of mode mix. Numerical predictions of normal crack-opening displacements yielded results that were consistent with measured values which were made as close as 0.3 μm from the crack tip.

Study on 3D Edge Crack Extension Simulation in Cold Rolling with the Cohesive Zone Model

2016 ◽  
Vol 853 ◽  
pp. 101-105
Author(s):  
Da Qian Zan ◽  
Quan Sun ◽  
Hong Liang Pan ◽  
Jian Jun Chen ◽  
Zheng Dong Wang
Keyword(s):  
Cold Rolling ◽  
Cohesive Energy ◽  
Cohesive Zone ◽  
Edge Crack ◽  
Crack Extension ◽  
Cohesive Zone Model ◽  
Rolling Process ◽  
Zone Model ◽  
Hybrid Technique ◽  
Cohesive Stress

In the cold rolling process, the edge crack extension can cause the strip rupture completely due to the micro manufacturing defects in the edge. It can greatly impact on the production efficiency and cause the huge economic loss. Thus predicting the edge crack extension behavior becomes important to cold rolling industry. In this paper, a 3D extended finite element method (XFEM) based on the cohesive zone model (CZM) was used to study the edge crack extension under the non-reversing two-high mill cold rolling experiment condition. A bi-linear traction-separation law was utilized which is primarily given by the CZM parameters including the cohesive stress, T0 and the cohesive energy, Γ0. The cohesive stress was determined by hybrid technique of the thin-plate tension test and FEM simulation. The cohesive energy was obtained by the In-Situ SEM three points bending experiment. Different reductions were the mainly analysis factor which can study the extent of the edge crack extension by presetting the edge notch. By comparing the experimental and simulation results, they agreed well with each other. It illustrated that the CZM can provide accurate predictions for the edge crack extension in the cold rolling process. Parametric analysis was carried out and showed that the extent of the crack extension increases with the increasing of the reduction ratio.

Numerical Test Method for Random Chopped Fiber Composites

2010 ◽  
Author(s):  
Yi Pan ◽  
Assimina A. Pelegri
Keyword(s):  
Composite Material ◽  
Cohesive Zone Model ◽  
Hydrostatic Stress ◽  
Numerical Test ◽  
Test Method ◽  
Zone Model ◽  
Matrix Interface ◽  
Material Constants ◽  
Fiber Matrix Interface ◽  
Fiber Matrix

A two-scale approach for numerical determination of composite material constants using a finite element model is developed. A representative volume element is numerically generated using a modified sequential adsorption algorithm. To determine the strength of the composite material, progressive material degradation models are adopted for the matrix, fiber and the fiber/matrix interface. The epoxy resin is modeled with a modified von Mises criterion in which the effect of hydrostatic stress on yield is accounted for. The resin’s elastic constants degrade with increasing loading application. The glass fiber is modeled as an isotropic material whose failure is governed by the maximum strain criterion. A traction-separation type cohesive zone model is applied at the fiber/matrix interface. Validation of the presented model is achieved by comparing numerical simulations with experimental data. The effective material constants that have been homogenized by the numerical test approach can be applied for future structural analysis.

Constitutive Modeling of Creep and Damage Behaviors of the Non-Mises Type for a Class of Polycrystalline Metals

2002 ◽  
Vol 11 (3) ◽  
pp. 223-245 ◽  
Author(s):  
M. Kawai
Keyword(s):  
Hydrostatic Stress ◽  
Kinematic Hardening ◽  
Constitutive Models ◽  
Irreversible Thermodynamics ◽  
Polycrystalline Materials ◽  
Isotropic Hardening ◽  
Stress Deviator ◽  
Third Invariant ◽  
Scaling Parameters ◽  
Von Mises

Phenomenological constitutive models to describe the creep and damage behaviors that deviate from the von Mises type for a class of polycrystalline materials are developed. Theoretical and empirical approaches are taken to the formulation. The effective stresses that govern the rates of creep and damage are scaled to describe any deviation from the response of the von Mises type. A general form of scaling parameter is proposed which can consider the hydrostatic stress and/or the third invariant of the stress deviator. A kinematic hardening model is first formulated on the basis of irreversible thermodynamics using the scaling parameters for creep and damage. Then, two kinds of empirical basis models are presented for cases of kinematic hardening and isotropic hardening, respectively. The proposed models can describe the primary, secondary and tertiary creep behaviors and distinguish between the creep and damage behaviors under different modes of loading. To illustrate the features of the proposed models, numerical simulations of the unequal creep behaviors under tension, compression, and torsion are carried out and compared with experimental results.

Crack Extensions in Compact Tension Specimens of Hydrided Irradiated Zr-2.5Nb Materials Using Cohesive Zone Model

2017 ◽  
Author(s):  
Shengjia Wu ◽  
Shin-Jang Sung ◽  
Jwo Pan ◽  
Poh-Sang Lam ◽  
Douglas A. Scarth
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Cohesive Zone ◽  
Crack Extension ◽  
Cohesive Zone Model ◽  
Compact Tension ◽  
Compact Tension Specimen ◽  
Zone Model ◽  
Element Analysis ◽  
The Finite Element Analysis

The crack extension in a compact tension specimen of hydrided irradiated Zr-2.5Nb material is investigated by a two-dimensional plane stress finite element analysis. The stress-strain relation of the Zr-2.5Nb material for the finite element analysis is obtained from fitting the experimental tensile stress-strain curve of the irradiated Zr-2.5Nb material without hydrides by a three-dimensional finite element analysis. The calibration of the cohesive zone model with a trapezoidal traction-separation law is based on fitting the load-displacement-crack extension experimental data of a compact tension specimen of hydrided irradiated Zr-2.5Nb material. The general trends of the load-displacement, crack extension-displacement, and load-crack extension curves obtained from the finite element analysis based on the calibrated cohesive zone model are in agreement with the experimental data.

Modelling void nucleation and growth in axisymmetric extrusion

1997 ◽  
Vol 211 (4) ◽  
pp. 285-297 ◽  
Author(s):  
L G Lim ◽  
F P E Dunne
Keyword(s):  
Residual Stress ◽  
Void Growth ◽  
Constitutive Equations ◽  
Defect Formation ◽  
Void Nucleation ◽  
Hydrostatic Stress ◽  
Deformation Behaviour ◽  
Nucleation And Growth ◽  
Isotropic Hardening ◽  
Void Nucleation And Growth

Elastic-viscoplastic constitutive equations, with kinematic and isotropic hardening, are employed to model the deformation behaviour of an aluminium alloy in extrusion. Constitutive equations are also employed for void nucleation and growth, which are fully coupled with the deformation behaviour. The material model is employed to investigate the roles of void nucleation and growth in extrusion defect formation. It has been shown that central bursting is a void growth controlled process. The existence of nucleated voids only leads to central burst formation with the existence of appropriate stress states which lead to void growth. The results obtained show excellent agreement with well-established limit diagrams, obtained analytically and experimentally. The results also show that for a given combination of area reduction and semi-cone die angle, the introduction of friction tends to inhibit the formation of central bursting, but increases the likelihood of surface tearing/cracking. The tendency to inhibit central burst formation with increasing friction results from the reduction in the levels of tensile hydrostatic stress, which therefore reduce the rate of void growth. A comparison of the results obtained using kinematic and isotropic hardening in the extrusion process showed that significantly different residual stress fields are obtained for the two cases. This is of importance, for example, in the case of multipass extrusion or where the residual stress field is to be used subsequently in design analysis.

Modeling and Experimental Validation of Superconductor Tape Rolling

2000 ◽  
Vol 123 (4) ◽  
pp. 665-673 ◽  
Author(s):  
M. Pandheeradi ◽  
S. P. Vaze ◽  
D.-W. Yuan ◽  
H. A. Kuhn
Keyword(s):  
Electrical Power ◽  
Three Dimensional ◽  
Element Model ◽  
Rolling Process ◽  
Isotropic Hardening ◽  
Plasticity Model ◽  
Cross Sectional ◽  
Manufacturing Operations ◽  
Von Mises ◽  
Von Mises Plasticity

Efficient, defect-free manufacturing of high-temperature superconducting (HTS) wires and tapes is critical to a variety of defense and electrical power applications. To contribute to the improvement of these manufacturing operations, an analytical and experimental study of the early stages of the multipass rolling process for transforming HTS wires into tapes was conducted. The rolling process was simulated by a three-dimensional (3D) finite element model that uses the Drucker-Prager Cap plasticity model to represent the powder core and a Von-Mises plasticity model with isotropic hardening to represent the silver sheath. The predicted cross-sectional geometry of the tapes is compared with experiments. The results show that the tape cross-sectional geometry and powder core sizes can be predicted accurately. Further, alternate boundary conditions were found to have minimal effect on the predicted cross-sectional geometry for the range of reductions considered, even though the frictional shear stress distributions were significantly different.

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