Crack closure concept is often used to explain the crack propagation behavior in cracked components. Cellbased smoothed finite element methodvirtual crack. In this technique, twodimensional elasticperfectly plastic finite element analyses of middlecrack tension mt geometry is conducted to study fatigue crack. In particular, attempts are made to study the effects of overload spacing on closure levels and the underlying physical mechanisms involved. The significance and even the existence of crack closure is being questioned by several researchers. Since analytical determination of the fatigue crack propagation life in real geometries is rarely viable, crack propagation problems are normally solved using some computational method. On the finite element analysis of fatigue crack closure2. The crackclosure phenomenon is caused by residual plastic deformations remaining in the wake of an advancing crack tip. Crack deflection along the fibermatrix interface for fiberreinforced composites is an important condition upon which the toughening mechanisms depend. These crack tip plastic zones have been used to characterize the degree of finite element mesh refinement required when modeling plasticityinduced closure 8. Use of finite element analysis to create robust composite. A modified elasticplastic finite element program was used to simulate fatigue crack growth and closure. Free mesh method fmm is one of useful methods for fracture mechanics analysis. Acluri school of engineering science and mechanics georgia institute of technology atlanta, georgia 30332.
This technique has not yet been implemented in large commercial finite element codes. Virtual crack closure technique vcct for stress intensity factor sif calculations was proposed 30 years ago. Fatigue crack closure determination by means of finite. The finite element model was created with the feacrack software 3, a commercial pre and postprocessor developed by quest integrity for 3d crack analysis. A virtual crack closureintegral method for generalized. This study is focused on the consequences of the bauschinger effect on. Numerical modeling issues in finite element simulation of. With the detailed stress and strain response taken from the finite element fe simulation, the whole process of crack closure was described by the load curve. In the transition regime, the crack closure load decreases and can decrease into the compression regime of the load amplitude for high and low cyclic fatigue loadings. Finite element analysis of plasticity induced fatigue. Finite element modeling of plasticityinduced crack. Finite elementbased model for crack propagation in.
Abaqus implementation of extended finite element method. Finite element visualization of fatigue crack closure in plane stress. Elasticplastic finite element simulations of growing fatigue cracks in both plane stress and plane strain are used as an aid to visualization and analysis. Most work has been performed considering bidimensional models where the numerical methodology has been.
A threedimensional extended finite element method xfem coupled with a narrow band fast marching method fmm is developed and implemented in the abaqus finite element package for curvilinear fatigue crack growth and life prediction analysis of metallic structures. Review on fatiguecrack growth and finite element method. The intended aim of the paper is to show general conditions of applying the vcct in conjunction with commercial programs. Summarization on crack propagation that the crack closure is affected by the material properties like yield stress y, fracture stress f, maximum intensity factor k. In the example of a central crack in a bimaterial block under the plane strain condition, comparisons are made with the exact solution to determine the accuracy and efficiency of the numerical method.
Finite element analysis of the competition between crack. A twodimensional finiteelement computer program, which. The objective of this study was to determine if crack closure occurs and to quantify its significance. In this paper, a 2d finite element model for the fatigue crack closure is. A finiteelement analysis of fatigue crack closure by j. Department of automation and design engineering, korea advanced institute of science and technology, seoul. A finite element calculation of stress intensity factors. Finite element analysis of plasticityinduced fatigue.
Christensen discovered the crack closure in 1963, which was later defined by elber in 1968. Most work has been performed considering bidimensional models where the numerical methodology has. The finite element method fem has been the principal numerical tool employed. It has been approached by means of experimental and numerical methods. Influence of minimum element size to determine crack. Twodimensional, elasticperfectly plastic finite element analyses of middlecrack tension mt and compact tension ct geometries were conducted to study fatigue crack closure and to calculate the crackopening values under planestrain and planestress conditions. Modelling of crack closure for finiteelement analysis of. Crack closure concept was often used to explain the crack propagation behavior in cracked components. Endofem nodereleased strategy in the simulations of. The present paper is concerned with the application of a twodimensional, nonlinear, finiteelement analysis using an incremental theory of plasticity to predict crackclosure and crackopening stresses during the crack.
Endofem nodereleased strategy in the simulations of fatigue crack closure phenomena volume 14 issue 2 l. Abstract in this paper, an efficient elasticplastic finite element procedure to analyze crackclosure. Numerical modeling issues in finite element simulation of plasticity induced crack closure with an emphasis on material model effects welcome to the ideals repository. It provides a comprehensive overview on numerical techniques to assist in crack modelling such as continuum damage mechanics, special crack tip elements, cohesive zone modelling, the virtual crack closure technique and the extended finite element method. Finite element simulations of fatigue crack growth and closure. Bilinear elasticplastic material behaviour with linear kinematic hardening was considered in the finite element analyses. The opening and closing behavior of fatigue cracks is studied with an elasticplastic finite element model which has been described and evaluated in part i. An approach combining experimental measurement techniques with. Combined with the virtual crack closure technique, a finite element model of composites is proposed to predict the competition between the matrix crack deflection along the interface and the matrix crack penetration into the fibers under the thermomechanical coupling fields. Elastic crack growth in finite elements with minimal. It was found that the virtual crack closure integral method does lead to very accurate results with a relatively coarse finite element mesh. It has provided an evaluation of stress, strain and displacement fields near crack tips and their contribution to crack closure. Combined with the virtual crack closure technique, a finite element model of composites is proposed to predict the. The study has identified some of the factors that contribute to crack closure.
Experiments have shown that fatigue cracks close at positive loads during constantamplitude load cycling. On the finite element analysis of fatigue crack closure1. Fatigue crack closure has been studied by means of the finite element method for a long time. Pdf finite element analysis of plasticity induced fatigue crack. The different approaches to predict crack closure can be divided into. Starting with a finite element model of cracked beam element, the equation of strain energy of a cracked beam element is formed by the displacement method combined with the linear fracture mechanics. The method, based on the crack closure integral, can be used with a constant strain finite element stress analysis and a coarse grid. Its use for composites gives us a tool for predicting crack. On mixed mode crack propagation analysis based on vccm. Results show that careful attention must be given to a series of critical decisions about mesh and model design if the analysis is to be reliable. Nasa langley research center hampton, virginia abstract experiments have shown that fatigue cracks close at positive loads during.
The model is used to study the behaviour of structural concrete members under various types of loading, encompassing both proportional and sequential loadings. Buchholz fg 1994, finite element analysis of a 3d mixedmode fracture problem by virtual crack closure integral method, proceedings of the indogerman workshop, avk murthy and fg buchholz eds, indian institute of science, interline publications, bangalore, 712. In this paper, investigations of crack closure due to repeated overloads are presented using finite element fe and simplified analytical modelling approaches. Using finite element software to simulation fracture. A minimal remeshing finite element method for crack growth is presented. Influence of finite element software on energy release rates computed using the virtual crack closure technique. A combined experimental and finite element study of crack. Virtual crack closure is a method that was originally developed for crack growth analysis in metal structures in 1977 ref 3. In this case, depending on the thicknesses ratio of the two sublaminates, the out of plane displacement of. Finite element analysis of plasticityinduced fatigue crack closure.
Implementation of the virtual crack closure technique in. The authors have been developing a crack propagation analysis system that can model arbitrary shaped cracks in threedimensional solids. Finite element analysis is perhaps the most commonly used numerical method to model plasticityinduced fatigue crack closure. Virtual crack closure technique and finite element method. Modelling a cracked beam structure using the finite. The effective stress intensity factor range is considered as. An elasticplastic analysis of fatigue crack closure in. Sound control for the interface debonding of composites contributes to improving the fracture toughness of composites. Finite element crack closure analysis of a compact tension. Special attention is given to the effects of maximum stress, strain hardening and yield stress. Discontinuous enrichment functions are added to the finite element approximation to account for the presence of the crack. However, accurate determination of fatigue crack closure has been a complex task for years. This method allows the crack to be arbitrarily aligned within the mesh.
The technique also permits evaluation of both mode i and mode ii stress intensity factors from the results of a single analysis. In order to improve the accuracy and efficiency of solving fracture parameters of piezoelectric materials, a piezoelectric element, tailored for the virtual crack closure technique vcct, was used to study piezoelectric materials containing a crack. The virtual crack closure technique vcct is widely 14, 15 used for computing energy release rates based on results from continuum 2d and solid 3d finite element analyses to supply the mode separation required when using the mixedmode fracture criterion. A twodimensional finite element fe model has been developed for determining crack opening and closure stresses, with the eventual aim of investigating plasticity induced closure effects on. Finite element analysis of plasticity induced fatigue crack closure. These include mesh refinement level, crack advancement schemes, crack shape evolution, geometry effects. Measuring opening or closure stress is a complex process that influences the low accuracy of obtained data.
A model for the elasticplastic finite element simulation of fatigue crack growth and crack closure is presented and evaluated. Nasa langley research center hampton, virginia abstract experiments have shown that fatigue cracks close at positive loads during constantamplitude load cycling. Influence of finite element software on energy release. The effective stress intensity factor range was considered as a driving force of fatigue crack propagation based on the traditional crack closure concept. Finite element and analytical modelling of crack closure. Plasticityinduced crack closure is an observed phenomenon during fatigue crack growth.
Fatigue, crack closure, plasticity, stripyield models, fem. The load corresponding to maximum crack closure length is firstly proposed to describe the effect of fatigue damage. An existing finite element fe model of structural concrete is extended so as to also allow for crack closure in localized regions of a structure. Finite element study on the closure of thermal microcracks. The model is used to study the behaviour of structural concrete members under various types of loading, encompassing both proportional and. Crackclosure modelled by repressurizing the rock is substantially different for an aggregate with parallel oriented cracks gbc i than for a composite where most of the grain boundaries are broken matrix containing totally separated grains, gbc ii. Finite element analysis of slant edge crack by abaqus.
Then, based on the finite element method, the dynamic model of the cracked beam structure is obtained. A virtual crack closureintegral method vccm for the generalized finite element with drilling and strain degrees of freedoms dofs is presented in this paper. Recently, the cellbased smoothed finite element method csfem and vcct have been used to simulate the fracture mechanics of piezoelectric. We use cookies to distinguish you from other users and to provide you with a better experience on our websites. Modeling of fatigue crack closure by finite element method. A finite element analysis of fatigue crack closure. Crack closure behaviour of a compact tension specimen subjected to a constant amplitude cyclic mechanical load, with the maximum load approaching and exceeding the yield strength based limit load of the specimen and a load ratio r. Finite element models have been one of the available ways to deal with this problem. The first analytical crack closure model was developed by newman in 1974, based on the dugdale crack model. How to model crack propagation using finite element analysis. Virtual crack closure technique and finite element method for predicting the delamination growth initiation in composite structures 467 sublaminate is induced.
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