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A three-phase composite cylinder model is utilized to study the interaction between screw dislocations and nanoscale inclusions. The stress boundary condition at the interface between nanoscale inclusion and the matrix is modified by incorporating surface/ interface stress. The explicit solution to this problem is derived by means of the complex variable method. The explicit expressions of image forces exerted on screw dislocations are obtained. The mobility and the equilibrium positions of the dislocation near one of the inclusions are discussed. The results show that, compared to the classical solution (without interface stress), more equilibrium positions of the screw dislocation may be available when the dislocation is close to the nanoscale inclusion due to consider interface stress. Also, the mobility of the dislocation in the matrix will become more complex than the classical case.

Web-based process planning is an internet application for distributed and knowledge-sharing process planning providing important support for virtual enterprises. Route sheet documents are widely adopted as user interfaces for information input, output, browsing, sharing and integration. In traditional applications, data and their presentation in specially formatted route sheet documents are implemented together. Separation of data and their presentation is emphasized in this paper because not only can it provide multi-level and multi-orientation views of the same data, but it can also improve context-sensitivity in process planning by better information sharing. An eXtensible Markup Language (XML)-based method for route sheet presentation and implementation is proposed to support context-sensitive and web-based process planning. The route sheet document includes a declarative user interface, a tree-style data structure, and processing rules embedded in documents to support context-sensitive information processing. An XML application named Manufacturing Process XML (MPXML) was developed as a meta-language for description of manufacturing process information. [ABSTRACT FROM AUTHOR]

• Erdogan fundamental solutions are employed in the method of fundamental solution for cracked body in functionally graded materials. • The accuracy and convergence of MFS have been observed; • Dynamic problem is solved without dynamic fundamental solutions; • Mapping method is applied in the domain integral. In this paper the Method of Fundamental Solutions (MFS) incorporating Erdogan's solutions for Functionally Graded Materials (FGM) is presented for analysis of 2D fracture problems subjected to static and dynamics loads. Erdogan derived analytical solutions for a pair of static concentrated force in an infinite isotropic plate with a straight cut. Based on homogenous isotropic analysis, the contribution from non-homogeneity in equilibrium equations is treated as body forces and domain integrals based on the Erdogan's fundamental solutions are required. In the domain integrals, all singularities are cancelled by introduction of a polar coordinate system at collocation points and crack tips. In the dynamic cases, the Laplace transformation with the Durbin inversion technique is adopted to determine the time-dependent variables such as the stress intensity factors at crack tips. The domain integrals are obtained numerically with the sub-region technique. The accuracy of the MFS is demonstrated with four numerical examples and comparisons are implemented with different numerical approaches. [ABSTRACT FROM AUTHOR]

Axisymmetric cracked solid structures in functionally graded materials (FGMs) under static and dynamic loading are analysed by using the Finite Block Method (FBM). Based on the axisymmetric elasticity theory, the equilibrium equations inside the rotating section of FGMs in the cylinder coordinate system are formulated in strong form. The shape functions in the FBM are constructed by Lagrange polynomial interpolation with mapping techniques for the irregular finite or semi-infinite physical domains. A special approximation technique is proposed to avoid singularities in the traction boundary conditions on the axis of symmetry. The stress intensity factor is obtained by the crack opening displacement. The time-dependent problems are addressed using the Laplace transform and Durbin's inverse approach. Several numerical examples are investigated in order to illustrate the accuracy and convergence of the proposed method, and the numerical solutions are compared with analytical solutions, the finite element method and other methods. • Algorithm for layered 3D structure in semi-infinite space. • Infinite element in the finite block method. • Static/Dynamic load for fracture problems. • Functionally graded material. [ABSTRACT FROM AUTHOR]

• Boundary integral equation method for 3D fracture static mechanics. • Stress intensity factors and T-stresses with curved surface crack. • High accurate/convergent solutions with Chebyshev polynomials. • Solutions can be used as benchmarks. This paper presents the boundary integral equation method (BIEM) for the stress intensity factors and elasticity T-stresses evaluation in 3D problems. Flat rectangular, elliptic, penny-shaped cracks and rectangular crack on a cylindrical surface have been investigated. The hyper-singular integrals are treated with the Taylor's series expansion of the kernel, and the Chebyshev polynomials of the second kind are used to solve the integral equations numerically. The stress intensity factors (SIFs) on the crack front are obtained by the coefficients of the Chebyshev polynomials. In order to verify the solutions by BIEM, the finite element method (FEM) with ABAQUS is conducted. The efficiency and convergence of the BIEM are observed in three examples. Comparisons are made with the analytical solutions in the stress intensity factor handbook and numerical solutions using the displacement discontinuity method (DDM). [ABSTRACT FROM AUTHOR]

The recent progress in the development and research of functionally graded materials (FGMs) has prompted the development of numerical methods in engineering analysis for continuously non-homogeneous media. This paper presents the hybrid Meshless Displacement Discontinuity Method (MDDM) for a cracked structure with functionally graded materials. The fundamental solutions of displacement discontinuity for an isotropic homogenous body form a part of the general solutions for non-homogenous materials, in order to create the gap on the crack surface. The governing equations are satisfied by using the Meshless Local Petrov-Galerkin method (MLPG) at the scattered nodes in the domain. The stress intensity factors (SIFs) are evaluated by either crack opening displacement (COD) method or equivalent stress technique. The crack growth paths with different FGMs gradient parameters are investigated and compared with the solutions given by the finite element method (FEM). The efficiency and accuracy of hybrid MDDM are demonstrated by four examples and comparisons have been e with other analytical and numerical methods. [ABSTRACT FROM AUTHOR]

• There is an optimal position of nanotwin to make the dislocations most susceptible to emit from crack tips. • There is a critical inclination of nanotwin oriental making dislocations hardest to launch. • The increase of crack length and grain size will make the dislocation emission of crack tip difficult. • The dislocation pileup makes the dislocation emission from crack tips difficult. A theoretical model describing edge dislocation emission from an elliptical blunt crack tip in nanocrystalline solid is established to consider the effect of the nanotwin and dislocation pileup at twin boundary. The nanotwin is represented by a wedge disclination quadrupole and some dislocations are deposited on one of twin boundaries. The complex variable function method is used to calculate the force acting on the first dislocation emitted from the tip of blunt crack, and expressions of critical stress intensity factors corresponding to dislocation emission are obtained. Then the influence of the dislocation emission angle, the position and orientation of the twin, the strength of nanotwin, the shape and the surface effects of the elliptical blunt crack on the critical stress intensity factor for dislocation emission is analyze in detail. The results shows that the effect of nanotwin on dislocations emitting from crack tip depends on its position and azimuth. There is an optimal position that dislocations are most easily emitted from the crack tip. The dislocation pileup at the twin boundary will increase the critical stress intensity factors for dislocation emission, making the dislocation emission from crack tip difficult, thus reducing the toughness of the material contributed by dislocation emission. In addition, the surface stress has a significant effect on the critical stress intensity factor. [ABSTRACT FROM AUTHOR]

Due to the differences in Young's moduli under the tensile and compressive loadings for a rock-like and asphalt-mixture materials, the analysis becomes difficult as all coefficients in Hook's law are dependent on the stress state in the field. In this paper, the meshless method is formulated for the first time to evaluate a cracked structure made of bimodular materials. In general, there are four stress zones in the field determined by the principal stresses. It is known that for classical elasticity (single modulus material), the stresses are singular at the crack tip described by William's series. For the pure mode I fracture, it is proved that the solutions for the stress and displacement by William's series are still valid for bimodular materials as there is only first kind zone in the vicinity of the crack tip. With the utilization of the Lagrange series, the meshless Finite Block Method (FBM) is demonstrated to deal with cracked structures with bimodular materials. The numerical solutions of the partial differential equations with variable coefficients are solved in a strong form by using the iterative technique. Numerical examples are demonstrated to verify the degree of accuracy and convergence with Finite Element Method (FEM) with very fine mesh. • Cracked structures made of bimodular materials are analyzed first time. • Singular stress at crack tip for bimodular materials is analyzed first time. • Singular stress field of Mode I is the same as classical singular stress field. • Meshless FBM and FEM are utilized to study bimodules materials. • The iterative algorithm is applied to solve nonlinear system. [ABSTRACT FROM AUTHOR]