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Simulation of concrete using the extended finite element method
Published in Günther Meschke, René de Borst, Herbert Mang, Nenad Bićanić, Computational Modelling of Concrete Structures, 2020
The extended finite element method (XFEM) is often used to model cracks and crack growth, since a crack can be decsribed independently of the background mesh (Moes et al. 1999). That allows the usage of regular meshes, which facilitates the mesh generation. Another interesting feature of the XFEM is, that material discontinuities can be represented without the requirement, that element edges coincide with the material discontinuity (Sukumar et al. 2001). In this paper a combined approach is investigated, where a crack and a material interface at the same position should be modeled. This occurs e.g. in the case of a concrete model on the mesoscale with explicit represention of matrix and aggregates having different material properties and the interfacial transition zone (ITZ) in between. The ITZ is also assumed to have different material properties than the bulk material. In a numerical model the length scale of this zone is often so small compared to the model dimensions, that this zone can not be resolved explicitly. By introducing an interface formulation within the XFEM approach, that couples crack opening displacements with stresses transferred through the interface, this weak transition zone can be considered. In a second example the XFEM is used for a macroscopic crack growth simulation and numerical results are compared with experimental data.
Prediction of crack growth of an aged coast guard patrol ship based on various approaches
Published in C. Guedes Soares, Y. Garbatov, Progress in the Analysis and Design of Marine Structures, 2017
C.S. Kim, C.B. Li, J. Choung, Y.H. Kim
ABSTRACT: Newman-Raju formula is known to be less accurate for complicated weld details and J-integral based on Finite Element Analyses (FEAs) need concentrated efforts to construct FEA models. Recently, an Extended Finite Element Method (XFEM) has been thought to reduce those modeling efforts with reliable accuracy. Assuming prescribed cracks on the front of two bracket toes attached to longitudinal stiffeners in way of deck and bottom for a 25 year-aged coast guard patrol ship, Stress Intensity Factors (SIFs) were derived based on the Newman-Raju formula and the XFEM. To obtain axial tension loads acting on the longitudinal stiffeners, long term hull girder bending stresses were assumed to obey Weibull distribution from a reference (DNV, 2014). Weld-induced residual SIFs and Paris law constants were taken from a reference (BS, 2015). For the complicated weld details and loading patterns, it was concluded that the XFEM could cost-effectively and accurately estimate crack growth rates and residual lives.
Fracture Performance Evaluation of Additively Manufactured Titanium Alloy
Published in Ashwani Kumar, Mangey Ram, Yogesh Kumar Singla, Advanced Materials for Biomechanical Applications, 2022
Tiwari Manvendra, Pankaj Kumar
Extended finite element method (XFEM) is an advanced form of FEM having distinct advantages because of ease in the modeling of any crack or discontinuous domain [5]. In XFEM, the approximation of FEM is enriched with additional functions to capture the discontinuities present in the displacement field. These enrichment functions in the FE solution are added by a partition of unity (PU) property [6,7]. In XFEM, modeling of cracks is independent of mesh as shown in Figure 12.3. In the provided figure, the crack tip and crack surface have been taken care by enriched nodes through Heaviside and asymptotic crack tip enrichment functions. The mathematical derivations are also explained in detail.
Modelling of the fatigue cracking resistance of grid reinforced asphalt concrete by coupling fast BEM and FEM
Published in Road Materials and Pavement Design, 2023
A. Dansou, S. Mouhoubi, C. Chazallon, M. Bonnet
However, the finite element method requires a high degree of refinement around the crack front for stress and displacement fields to be computed accurately, which hampers its efficiency for the study of fatigue cracking in 3D configurations. Moreover, each stage of simulated propagation entails local re-meshing near the new crack front, which is quite cumbersome. The eXtended Finite Element Method (XFEM), developed by Belytschko and Black (1999), Moës et al. (1999), Fries and Belytschko (2010) and Belytschko et al. (2014), is more efficient than the classical FEM for fracture problems, see Sukumar et al. (2008) and Oliver et al. (2006), due to its ability to model the crack and its evolution without remeshing. Alternatively, the boundary element method constitutes a powerful alternative to FEM, particularly in cases where better accuracy is required due to stress concentration in problems such as crack propagation simulation. The most important feature of BEMs is that the solution is approximated on the boundaries, while equilibrium and compatibility are exactly satisfied in the domain. Hence, for 3D problems, only the boundary surface needs meshing, see Figure 1, which greatly facilitates remeshings associated with crack advancement. Equipping BEMs with advanced acceleration techniques, such as the Fast Multipole Method (FMM), for faster computation greatly enhances the performance of large-scale BEM analyses, see e.g. Greengard and Rokhlin (1987), Yoshida (2001), Trinh et al. (2015), and many other references therein.
Microcrack propagation induced by dynamic infiltration of calcium-magnesium-alumino-silicate in columnar structures for thermal barrier coatings
Published in Journal of the Chinese Institute of Engineers, 2021
Shaochen Tseng, Chingkong Chao, Weixu Zhang, Xueling Fan
Understanding the influence of dynamic CMAS infiltration on crack propagation can predict failure mechanism and service life, thereby providing the optimum design of the columnar-structured coating. Using finite element method, two major techniques are applied to simulate the interfacial crack dynamic behavior including the virtual crack closed technique (VCCT) (Sun and Liu 2015) based upon energy release rates (J-integral) and the cohesive zone model (CZM) (Van den Bosch, Schreurs, and Geers 2007) based upon the traction-separation law. The path of crack propagation should be predefined in both of VCCT and CZM. This limitation is suitable for an interfacial crack or a simple model. However, it is difficult to determine the propagation path in complicated structures. The extended finite element method (XFEM) (Guo et al. 2015) is a useful technique which can simulate the dynamic crack behavior. The propagation path is not necessary to define in simulation and a complicated environment can be considered such as pores and inclusions. Recently, based on XFEM, Cai et al. (2019) investigated the crack propagation induced by CMAS penetration during cooling. Nevertheless, the failure mechanism of the columnar-structured coating induced by CMAS has not yet been investigated owing to the complexities of dynamic CMAS infiltration and microstructure in the columnar-structured coating.
Numerical simulation of distortion-induced fatigue crack growth using extended finite element method
Published in Structure and Infrastructure Engineering, 2020
Chun-sheng Wang, Yu-zhu Wang, Bing Cui, Lan Duan, Nai-xuan Ma, Jin-qiang Feng
However, in the extended finite element method (XFEM), the mesh generation is independent of the discontinuous interfaces such as cracks and holes inside the structures (Belytschko & Black, 1999). It avoids the mesh regeneration required during the crack behaviour simulation, greatly improving the solution efficiency and providing a new technological approach to simulate the fatigue crack propagation path efficiently (Stolarska, Chopp, Moes, & Belytschko, 2001). Furthermore, the XFEM can simulate coupled propagation of multi cracks and mixed-mode cracks, which can be used in for welded steel bridges having cracks.