The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Zhenjun Yang - One of the best experts on this subject based on the ideXlab platform.
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three dimensional heterogeneous fracture simulation of asphalt mixture under uniaxial tension with Cohesive Crack model
Construction and Building Materials, 2015Co-Authors: Anyi Yin, Xinhua Yang, Chuanchuan Zhang, Guowei Zeng, Zhenjun YangAbstract:Abstract A three-dimensional (3D) heterogeneous fracture modeling technology is presented to simulate complex Crack evolution in quasi-brittle asphalt mixture. In this technology, the random aggregate generation and packing algorithm is employed to create 3D heterogeneous numerical model of asphalt mixture, and the Cohesive elements with the tension/shear softening laws are inserted into both the mastic matrix and the aggregate–mastic interfaces as potential Cracks. The nucleation and coalescence of microCracks, and inception and propagation of main macroCracks are carefully studied under uniaxial tension and temperature of −10 °C. The effects of the averaged coarse aggregate size and the Cohesive fracture parameters on performance of asphalt mixture are also evaluated.
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automatic modelling of Cohesive Crack propagation in concrete using polygon scaled boundary finite elements
Engineering Fracture Mechanics, 2012Co-Authors: Ean Tat Ooi, Chongmin Song, F Tinloi, Zhenjun YangAbstract:An automatic Cohesive Crack propagation modelling methodology for quasi-brittle materials using polygon elements is presented. Each polygon is treated as a subdomain that is modelled by the scaled boundary finite element method (SBFEM). Generalised stress intensity factors (SIFs) based on matrix power function solutions of singular stress fields obtained from the SBFEM following standard finite element stress recovery procedures is used to evaluate the Crack propagation criterion and determine the Crack propagation direction. Interface elements model the fracture process zones and are automatically inserted into the polygon mesh as the Crack propagates. A shadow domain procedure couples the polygons and interface elements. It computes the load–displacement response and Crack propagation criterion, taking into account the Cohesive tractions on the Crack edges that are modelled as side-face tractions in the SBFEM. Cracks are propagated using a simple, yet flexible local remeshing procedure that can remesh any arbitrary polygon. Only minimal changes are made to the global mesh structure each time the remeshing algorithm is called. Five Cohesive Crack propagation benchmarks are modelled to validate the developed method and demonstrate its salient features.
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modelling multiple Cohesive Crack propagation using a finite element scaled boundary finite element coupled method
Engineering Analysis With Boundary Elements, 2009Co-Authors: Zhenjun YangAbstract:Abstract This paper presents an extension of the recently-developed finite element–scaled boundary finite element (FEM–SBFEM) coupled method to model multiple Crack propagation in concrete. The concrete bulk and fracture process zones are modelled using SBFEM and nonlinear Cohesive interface finite elements (CIEs), respectively. The CIEs are automatically inserted into the SBFEM mesh as the Cracks propagate. The algorithm previously devised for single Crack propagation is augmented to model problems with multiple Cracks and to allow Cracks to initiate in an un-Cracked SBFEM mesh. It also addresses Crack propagation from one subdomain into another, as a result of partitioning a coarse SBFEM mesh, required for some mixed–mode problems. Each Crack in the SBFEM mesh propagates when the sign of the Mode-I stress intensity factor at the Crack tip turns positive from negative. Its propagation angle is determined using linear elastic fracture mechanics criteria. Three concrete beams involving multiple Crack propagation are modelled. The predicted Crack propagation patterns and load–displacement curves are in good agreement with data reported in literature.
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fully automatic modelling of Cohesive Crack growth using a finite element scaled boundary finite element coupled method
Engineering Fracture Mechanics, 2007Co-Authors: Zhenjun Yang, Andrew DeeksAbstract:Abstract This study develops a method coupling the finite element method (FEM) and the scaled boundary finite element method (SBFEM) for fully-automatic modelling of Cohesive Crack growth in quasi-brittle materials. The simple linear elastic fracture mechanics (LEFM)-based remeshing procedure developed previously is augmented by inserting nonlinear interface finite elements automatically. The constitutive law of these elements is modelled by the Cohesive/fictitious Crack model to simulate the fracture process zone, while the elastic bulk material is modelled by the SBFEM. The resultant nonlinear equation system is solved by a local arc-length controlled solver. The Crack is assumed to grow when the mode-I stress intensity factor KI vanishes in the direction determined by LEFM criteria. Other salient algorithms associated with the SBFEM, such as mapping state variables after remeshing and calculating KI using a “shadow subdomain”, are also described. Two concrete beams subjected to mode-I and mixed-mode fracture respectively are modelled to validate the new method. The results show that this SBFEM–FEM coupled method is capable of fully-automatically predicting both satisfactory Crack trajectories and accurate load–displacement relations with a small number of degrees of freedom, even for problems with strong snap-back. Parametric studies were carried out on the Crack incremental length, the concrete tensile strength, and the mode-I and mode-II fracture energies. It is found that the KI ⩾ 0 criterion is objective with respect to the Crack incremental length.
Somnath Ghosh - One of the best experts on this subject based on the ideXlab platform.
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multiple Cohesive Crack growth in brittle materials by the extended voronoi cell finite element model
International Journal of Fracture, 2006Co-Authors: Shanhu Li, Somnath GhoshAbstract:This paper is aimed at modeling the propagation of multiple Cohesive Cracks by the extended Voronoi cell finite element model or X-VCFEM. In addition to polynomial terms, the stress functions in X-VCFEM include branch functions in conjunction with level set methods and multi-resolution wavelet functions in the vicinity of Crack tips. The wavelet basis functions are adaptively enriched to accurately capture Crack-tip stress concentrations. Cracks are modeled by an extrinsic Cohesive zone model in this paper. The incremental Crack propagation direction and length are adaptively determined by a Cohesive fracture energy based criterion. Numerical examples are solved and compared with existing solutions in the literature to validate the effectiveness of X-VCFEM. The effect of Cohesive zone parameters on Crack propagation is studied. Additionally, the effects of morphological distributions such as length, orientation and dispersion on Crack propagation are studied.
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extended voronoi cell finite element model for multiple Cohesive Crack propagation in brittle materials
International Journal for Numerical Methods in Engineering, 2006Co-Authors: Shanhu Li, Somnath GhoshAbstract:This paper introduces an extended Voronoi cell finite-element model (X-VCFEM) for modelling Cohesive Crack propagation in brittle materials with multiple Cracks. The Cracks are modelled by a Cohesive zone model and their incremental directions and growth lengths are determined in terms of the Cohesive energy near the Crack tip. Extension to VCFEM is achieved through enhancements in stress functions in the assumed stress hybrid formulation. In addition to polynomial terms, the stress functions include branch functions in conjunction with level set methods, and multi-resolution wavelet functions in the vicinity of Crack tips. The wavelet basis functions are adaptively enriched to accurately capture Crack-tip stress concentrations. Conditions and methods of stability are enforced in X-VCFEM for improved convergence with propagating Cracks. Two classes of problems are solved and compared with existing solutions in the literature for validation of the X-VCFEM algorithms. The first set corresponds to results for static Cracks, while in the latter set, the propagation of Cohesive Cracks are considered. Comparison of X-VCFEM simulation results with results in literature for several fracture mechanics problems validates the effectiveness of X-VCFEM. Copyright © 2005 John Wiley & Sons, Ltd.
J C Galvez - One of the best experts on this subject based on the ideXlab platform.
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modelling of concrete cover Cracking due to non uniform corrosion of reinforcing steel
Construction and Building Materials, 2017Co-Authors: Santiago Guzman, J C GalvezAbstract:Abstract This paper addresses the modelling of non-uniform corrosion in reinforced concrete. An uneven distribution of rust around the perimeter of the rebar is considered which represents the most common situation in real concrete structures and, especially, when they are exposed to a chloride environment. A comparison with the conventional approach based on a uniform corrosion and expansion pressure around the rebar is performed in both Cracking pressure and Cracking radial displacement terms. As a result, surface Cracking appears much earlier in the case of non-uniform corrosion with corresponding vertical surface displacements being rather higher, with such an effect becoming more evident as cover increases. Finally, distinct Cracking patterns are derived through the proposed embedded Cohesive Crack model by means of a practical example.
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an embedded Cohesive Crack model for finite element analysis of quasi brittle materials
Engineering Fracture Mechanics, 2013Co-Authors: J C Galvez, J M Sancho, J Planas, D A Cendon, E Reyes, M J CasatiAbstract:Abstract This paper presents a numerical implementation of the Cohesive Crack model for the analysis of quasibrittle materials based on the strong discontinuity approach in the framework of the finite element method. A simple central force model is used for the stress versus Crack opening curve. The additional degrees of freedom defining the Crack opening are determined at the Crack level, thus avoiding the need for performing a static condensation at the element level. The need for a tracking algorithm is avoided by using a consistent procedure for the selection of the separated nodes. Such a model is then implemented into a commercial program by means of a user subroutine, consequently being contrasted with the experimental results. The model takes into account the anisotropy of the material. Numerical simulations of well-known experiments are presented to show the ability of the proposed model to simulate the fracture of quasibrittle materials such as mortar, concrete and masonry.
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modelling of corrosion induced cover Cracking in reinforced concrete by an embedded Cohesive Crack finite element
Engineering Fracture Mechanics, 2012Co-Authors: Santiago Guzman, J C Galvez, J M SanchoAbstract:Abstract Corrosion of a reinforcement bar leads to expansive pressure on the surrounding concrete that provokes internal Cracking and, eventually, spalling and delamination. Here, an embedded Cohesive Crack 2D finite element is applied for simulating the Cracking process. In addition, four simplified analytical models are introduced for comparative purposes. Under some assumptions about rust properties, corrosion rate, and particularly, the accommodation of oxide products within the open Cracks generated in the process, the proposed FE model is able to estimate time to surface Cracking quite accurately. Moreover, emerging Cracking patterns are in reasonably good agreement with expectations. As a practical case, a prototype application of the model to an actual bridge deck is reported.
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modelling of corrosion induced cover Cracking in reinforced concrete by an embedded Cohesive Crack finite element
Engineering Fracture Mechanics, 2012Co-Authors: Santiago Guzman, J C Galvez, J M SanchoAbstract:Abstract Corrosion of a reinforcement bar leads to expansive pressure on the surrounding concrete that provokes internal Cracking and, eventually, spalling and delamination. Here, an embedded Cohesive Crack 2D finite element is applied for simulating the Cracking process. In addition, four simplified analytical models are introduced for comparative purposes. Under some assumptions about rust properties, corrosion rate, and particularly, the accommodation of oxide products within the open Cracks generated in the process, the proposed FE model is able to estimate time to surface Cracking quite accurately. Moreover, emerging Cracking patterns are in reasonably good agreement with expectations. As a practical case, a prototype application of the model to an actual bridge deck is reported.
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an embedded Cohesive Crack model for finite element analysis of brickwork masonry fracture
Engineering Fracture Mechanics, 2009Co-Authors: E Reyes, J C Galvez, J M Sancho, D A Cendon, M J Casati, J PlanasAbstract:This paper presents a numerical procedure for fracture of brickwork masonry based on the strong discontinuity approach. The model is an extension of the Cohesive model prepared by the authors for concrete, and takes into account the anisotropy of the material. A simple central-force model is used for the stress versus Crack opening curve. The additional degrees of freedom defining the Crack opening are determined at the Crack level, thus avoiding the need of performing a static condensation at the element level. The need for a tracking algorithm is avoided by using a consistent procedure for the selection of the separated nodes. Such a model is then implemented into a commercial code by means of a user subroutine, consequently being contrasted with experimental results. Fracture properties of masonry are independently measured for two directions on the composed masonry, and then input in the numerical model. This numerical procedure accurately predicts the experimental mixed-mode fracture records for different orientations of the brick layers on masonry panels.
Shanhu Li - One of the best experts on this subject based on the ideXlab platform.
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multiple Cohesive Crack growth in brittle materials by the extended voronoi cell finite element model
International Journal of Fracture, 2006Co-Authors: Shanhu Li, Somnath GhoshAbstract:This paper is aimed at modeling the propagation of multiple Cohesive Cracks by the extended Voronoi cell finite element model or X-VCFEM. In addition to polynomial terms, the stress functions in X-VCFEM include branch functions in conjunction with level set methods and multi-resolution wavelet functions in the vicinity of Crack tips. The wavelet basis functions are adaptively enriched to accurately capture Crack-tip stress concentrations. Cracks are modeled by an extrinsic Cohesive zone model in this paper. The incremental Crack propagation direction and length are adaptively determined by a Cohesive fracture energy based criterion. Numerical examples are solved and compared with existing solutions in the literature to validate the effectiveness of X-VCFEM. The effect of Cohesive zone parameters on Crack propagation is studied. Additionally, the effects of morphological distributions such as length, orientation and dispersion on Crack propagation are studied.
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extended voronoi cell finite element model for multiple Cohesive Crack propagation in brittle materials
International Journal for Numerical Methods in Engineering, 2006Co-Authors: Shanhu Li, Somnath GhoshAbstract:This paper introduces an extended Voronoi cell finite-element model (X-VCFEM) for modelling Cohesive Crack propagation in brittle materials with multiple Cracks. The Cracks are modelled by a Cohesive zone model and their incremental directions and growth lengths are determined in terms of the Cohesive energy near the Crack tip. Extension to VCFEM is achieved through enhancements in stress functions in the assumed stress hybrid formulation. In addition to polynomial terms, the stress functions include branch functions in conjunction with level set methods, and multi-resolution wavelet functions in the vicinity of Crack tips. The wavelet basis functions are adaptively enriched to accurately capture Crack-tip stress concentrations. Conditions and methods of stability are enforced in X-VCFEM for improved convergence with propagating Cracks. Two classes of problems are solved and compared with existing solutions in the literature for validation of the X-VCFEM algorithms. The first set corresponds to results for static Cracks, while in the latter set, the propagation of Cohesive Cracks are considered. Comparison of X-VCFEM simulation results with results in literature for several fracture mechanics problems validates the effectiveness of X-VCFEM. Copyright © 2005 John Wiley & Sons, Ltd.
U Perego - One of the best experts on this subject based on the ideXlab platform.
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an extended fe strategy for transition from continuum damage to mode i Cohesive Crack propagation
International Journal for Numerical and Analytical Methods in Geomechanics, 2007Co-Authors: Claudia Comi, Stefano Mariani, U PeregoAbstract:An integrated strategy is proposed for the simulation of damage development and Crack propagation in concrete structures. In the initial stage of damage growth, concrete is considered to be macroscopically integer and is modeled by a non-symmetric isotropic non-local damage model. The transition to the discrete Cohesive Crack model depends on the local mesh size and is driven by an analytical estimate of the current bandwidth. When a Crack is introduced in the model an extended finite element approach is used to follow the propagation path, independent of the background mesh. The proposed methodology is tested on a notched tension specimen and then applied to the analysis of a wedge splitting test. Copyright © 2006 John Wiley & Sons, Ltd.
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extended finite element method for quasi brittle fracture
International Journal for Numerical Methods in Engineering, 2003Co-Authors: Stefano Mariani, U PeregoAbstract:A methodology for the simulation of quasi-static Cohesive Crack propagation in quasi-brittle materials is presented. In the framework of the recently proposed extended finite element method, the partition of unity property of nodal shape functions has been exploited to introduce a higher-order displacement discontinuity in a standard finite element model. In this way, a cubic displacement discontinuity, able to reproduce the typical cusp-like shape of the process zone at the tip of a Cohesive Crack, is allowed to propagate without any need to modify the background finite element mesh. The effectiveness of the proposed method has been assessed by simulating mode-I and mixed-mode experimental tests. Copyright © 2003 John Wiley & Sons, Ltd.