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This study combines the edge-based smoothed finite element method (ES-FEM) and the extended finite element method (XFEM) to develop a new simulation technique (ES-XFEM) for fracture analysis of 2D elasticity. In the XFEM, the need for the mesh alignment with the crack and remeshing, as the crack evolves, is eliminated because of the use of partition of unity. The ES-FEM uses the generalized smoothing operation over smoothing domain associated with edges of simplex meshes, and produces a softening effect leading to a close-to-exact stiffness, "super-convergence" and "ultra-accurate" solutions for the numerical model. Taking advantage of both ES-FEM and XFEM, the present method introduces the edge-based strain smoothing technique into the context of XFEM. Thanks to strain smoothing, the necessity of sub-division in elements cut by discontinuities is suppressed via transforming interior integration into boundary integration. Hence, it simplifies the numerical integration procedure in the XFEM. Numerical examples showed that the proposed method improves significantly the accuracy of stress intensity factors and achieves a quasi optimal convergence rate in the energy norm without geometrical enrichment or blending correction. [ABSTRACT FROM AUTHOR]

An efficient edge-based smoothed finite element method (ES-FEM) has been recently developed for solving solid mechanics problems. The ES-FEM uses triangular elements that can be generated easily for complicated domains. In this paper, the complexity study of the ES-FEM based on triangular elements is conducted in detail, which confirms the ES-FEM produces higher computational efficiency compared to the FEM. Therefore, the ES-FEM offers an excellent platform for adaptive analysis, and this paper presents an efficient adaptive procedure based on the ES-FEM. A smoothing domain based energy (SDE) error estimate is first devised making use of the features of the ES-FEM. The present error estimate differs from the conventional approaches and evaluates error based on smoothing domains used in the ES-FEM. A local refinement technique based on the Delaunay algorithm is then implemented to achieve high efficiency in the mesh refinement. In this refinement technique, each node is assigned a scaling factor to control the local nodal density, and refinement of the neighborhood of a node is accomplished simply by adjusting its scaling factor. Intensive numerical studies, including an actual engineering problem of an automobile part, show that the proposed adaptive procedure is effective and efficient in producing solutions of desired accuracy. [ABSTRACT FROM AUTHOR]

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This paper presents our recent study on determination of interfacial adhesion properties of soft-film-on-hard-substrate (SFHS) systems using finite element simulation (FEM) and wedge indentation experiments. The objectives of this study are: (i) to simulate the interfacial delamination processes during wedge indentation experiments; (ii) to study the effects of interfacial delamination on the characteristics of the indentation load-displacement (P-h) curves, (iii) to determine the interfacial adhesion properties; and (iv) to compare the simulation and experimental results. During the FEM simulation, a traction-separation law is used to describe the interfacial adhesion properties due to the large-scale yielding during indentations. The effects of main parameters in the traction-separation law, i.e. interfacial strength and interfacial energy, to the initiation of interfacial delamination are studied by parametric studies. An interface energy-strength contour, which can be used to determine the interfacial adhesion properties of the thin-film/substrate systems based on a wedge indentation experiment, is developed from the outcomes of the FEM simulation of the indentations using wedge tips with the inclusion angles of 90° and 120°. Using the respective interface energy-strength contours, the interfacial energy and strength of a BlackDiamond® (BD)/Si system and a methylsilsesquioxane (MSQ)/Si system are determined. The simulated results are then compared with the previous experimentally derived interfacial fracture toughness values and some further discussions are given. [ABSTRACT FROM AUTHOR]

A constitutive model for thermoplastic polymeric materials and its finite element implementation are presented. The model was verified by both tensile and indentation experimental results. In addition, a five-step indentation scheme, which is able to separate time-dependent plastic deformation from elastic and visco-elastic–plastic deformations, was formulated to extract the complete list of parameters in the constitutive model. Four types of indentation tests on polymethylmethacrylate (PMMA), following the five-step and other schemes, were performed. Experimental data were used to extract all the parameters in the model and verify the five-step test scheme. Good agreement between the experimental results and model prediction indicate that the five-step indentation scheme is a practical approach to determine the mechanical properties of thermoplastic polymers. [ABSTRACT FROM AUTHOR]