Papers by Keyword: Extended Finite Element Method (XFEM)

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Authors: Yi Tang Zhou, Luo Ke Li, Peng Cao, Yi Na Wang
Abstract: The degradation of concrete structures due to steel reinforcement corrosion is a serious problem for durability and serviceability. Cracking behavior due to reinforcement corrosion is evaluated experimentally and analytically in this paper. In the experiments, in which corrosion was induced electronically, the structure proportion of corrosion product was analyzed. In the analysis, a micromechanical cracking mechanical analytic model, which considered the coupling effects of corrosion product and concrete protective layer was established. The initial cracks and crack growth process of smeared cracks in cover concrete were simulated and explored for the deterioration process of concrete structures due to corrosion expansion. It is indicated that the numerically predicted crack mode agrees well with the experimental results.
Authors: Jie Jia, Yuan Yuan Chen, Ling Yu, Ming Bao Li
Abstract: A new interaction integral technique is derived for computation of mixed-mode stress intensity factors (SIFs) in nonhomogeneous materials with continuous or discontinuous properties. This method is based on a conservation integral that relies on two admissible mechanical states (actual and auxiliary fields). In the equivalent domain formulation, the integrand does not involve any derivatives of material properties. Moreover, the formulation is proved to be still valid when the integral domain contains material interfaces. Therefore, its applicable range is greatly enlarged. The method is combined with the extended finite element method (XFEM) to calculate the SIFs for different integral domains. Numerical results show that the interaction integral has excellent convergence for material nonhomogeneity and discontinuity.
Authors: Liang Wu, Li Xing Zhang, Ya Kun Guo
Abstract: A new energy approach is proposed by coupling the virtual crack extension with the extended finite element method (X-FEM) to extract the Strain Energy Release Rates and then convert it to stress intensity factors. By means of meshes independence of the location and geometry of the crack, the proposed approach avoids the mesh perturbation around the crack tip to compute the stiffness derivatives with respect to a virtual extension of the crack. In comparison to the interaction integral, this combined method is implemented more easily without the post-processing of the numerical results. The effect of different enriched region around the crack tip on the accuracy of results is discussed. Numerical results presented are in excellent agreement with the available analytical and those obtained using the interaction integral.
Authors: Omar Bacarreza, M.H. Aliabadi
Abstract: A novel methodology for analysis of fatigue delamination growth, capable of dealing with complex delamination shapes and mixed-modes in a computationally efficient way, is proposed. It combines the VCCT to find the energy release rates and the XFEM to update the geometry during the progressive failure, thus making it very robust and computationally efficient. The methodology is demonstrated at coupon level.
Authors: Liang Wu, Li Xing Zhang, Ya Kun Guo
Abstract: The extended finite element method (X-FEM) is reviewed and some new developments for fracture analysis of structures is presented. The X-FEM is an extension to the classical finite element method (FEM), using the concepts of partition of unity and meshless approaches. It is specifically designed to improve the performance of the conventional finite element method, while keeping the computational costs at an acceptable level, and avoiding the cumbersome remeshing of FEM in crack propagation problems. The simplicity, flexibility in handling several cracks and crack propagation patterns on a fixed mesh, and the level of accuracy with minimum additional degrees of freedom have transformed X-FEM into the most efficient numerical procedure in the arena of computational fracture mechanics.
Authors: Lin Sheng Li, Chang Jun Qiu, Lan Li
Abstract: A simple integration scheme is presented for numerical integration in the extended finite element method(XFEM). In this scheme, the integral domain of common triangular mesh is converted to that of standard triangular mesh and the integral domain of standard triangular mesh is converted to that of quadrilateral mesh. By this transformation of integral domain, the strength intensity factors for straight crack are worked out. Finally, the accuracy of this method is analyzed by a typical example. It is concluded that the results obtained by new integral scheme are more accurate and simple than common Gaussian integration scheme.
Authors: Yu Zhou Sima, Fu Zhou Wang
Abstract: An extended finite element method (XFEM) for multiple crack growth in asphalt pavement is described. A discontinuous function and the two-dimensional asymptotic crack-tip displacement fields are added to the finite element approximation to account for the crack using the notion of partition of unity. This enables the domain to be modeled by finite element with no explicit meshing of the crack surfaces. Computational geometry issues associated with the representation of the crack and the enrichment of the finite element approximation are discussed. Finally, the propagation path of the cracks in asphalt pavement under different load conditions is presented.
Authors: Feng Wang, Hui Xu, Jing Yu, Xi Quan Jiang, Long Yu
Abstract: The XFEM makes research within a standard finite element framework and needs not mesh repartition to geometric and physical interface, and it reserves all merits of the CFEM, therefore it is the most effective numerical method to solve discontinuous dynamic problems so far. The crack growth problem was studied in the XFEM computation, and the displacement mode of elements with cracks and fracture criterion were presented. The numerical examples for steel rod penetrating in the aluminum target concluded that the method and program were reasonable and effective. The crack growth discipline of penetration process for metal material was summarized, and it would establish theoretic base for the further application of the XFEM.
Authors: Jia Min Zhang, Bo Zhang, Jin Chang Wang
Abstract: Firstly, the parameters of cohesive zone model in ABAQUS software are calibrated through the cohesive constitutive model determined by cohesive potential energy, which is provided by Oriz and Pandofi(1999). Then, the validity and liability are verified by the single element example which compares extended finite element simulation with experimental results. Lastly, it puts forward the model of FEM based on the highway pre-sawed cracks. The curve of CMOD with changing temperature is obtained, and the curve can be divided into three stage segments. The middle stage segment changes dramatically for the local cracking in the crack tip field between asphalt surface and base. The research results illustrate the cracking mechanisms of asphalt pavement under changing temperature.
Authors: Wei Li, Chaiy Rungsiyakull, Zhong Pu Zhang, Shi Wei Zhou, Michael V. Swain, Ionut Ichim, Qing Li
Abstract: Bioceramics have rapidly emerged as one of major biomaterials in modern biomedical applications because of its outstanding biocompatibility. However, one drawback is its low tensile strength and fracture toughness due to brittleness and inherent microstructural defects, which to a certain extent prevents the ceramics from fully replacing metals used as load-bearing prostheses. This paper aims to model the crack initiation and propagation in ceramic fixed partial denture, namely dental bridge, by using two recently developed methods namely continuum-to-discrete element method (CDEM) in ELFEN and extended finite element methods (XFEM) in ABAQUS. Unlike most existing studies that typically required prescriptions of initial cracks, these two new approaches will model crack initiation and propagation automatically. They are applied to a typical prosthodontic example, thereby demonstrating their applicability and effectiveness in biomedical applications.
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