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  • Open Access

    ARTICLE

    Meshless Method with Enriched Radial Basis Functions for Fracture Mechanics

    P.H. Wen1, M.H. Aliabadi2

    Structural Durability & Health Monitoring, Vol.3, No.2, pp. 107-120, 2007, DOI:10.3970/sdhm.2007.003.107

    Abstract In the last decade, meshless methods for solving differential equations have become a promising alternative to the finite element and boundary element methods. Based on the variation of potential energy, the element-free Galerkin method is developed on the basis of finite element method by the use of radial basis function interpolation. An enriched radial basis function is formulated to capture the stress singularity at the crack tip. The usual advantages of finite element method are retained in this method but now significant improvement of accuracy. Neither the connectivity of mesh in the domain by the More >

  • Open Access

    ARTICLE

    Influence of an Atmospheric Pressure Plasma Surface Treatment on the Interfacial Fracture Toughness on Bonded Composite Joints

    J. Mohan1, D. Carolan1, N. Murphy1, A. Ivankovic1, D. Dowling1

    Structural Durability & Health Monitoring, Vol.3, No.2, pp. 81-86, 2007, DOI:10.3970/sdhm.2007.003.081

    Abstract The aim of this work is to investigate the influence of a variety of plasma treatments on the surface properties of an epoxy-based composite material and to establish a relationship between these properties and the subsequent mechanical behaviour of adhesively bonded joints. To this end, specimens were subjected to three different types of plasma treatment: two short treatments (2min) of He and He plus O2, and one long treatment (15min) of He plus O2. The variation in surface energy of the composite specimens was examined in each case over a period of up to 3 days… More >

  • Open Access

    ARTICLE

    Integrity of Thermal Actuators using the Concept of Energy Density

    C.P. Providakis1

    Structural Durability & Health Monitoring, Vol.3, No.1, pp. 29-34, 2007, DOI:10.3970/sdhm.2007.003.029

    Abstract Actuators are structures that give micro-electro-mechanical systems (MEMS) the ability to interact with their environment rather than just passively sensing it. Recent studies of MEMS thermal micro-actuators have shown that simple in design and production devices can provide deflection of the order of 10 μm at low voltages. Recently, metals and single-crystal silicon materials were included in the range of materials used for thermal actuators since they operate at lower temperatures than the commonly used (poly)silicon devices. These actuators are liable to meet the loads in service, so the corresponding integrity and stability analysis constitutes a… More >

  • Open Access

    ABSTRACT

    Higher-Order Stress and Size Effects Due to Self Energy of Geometrically Necessary Dislocations

    N. Ohno1, D. Okumura1

    The International Conference on Computational & Experimental Engineering and Sciences, Vol.4, No.4, pp. 207-214, 2007, DOI:10.3970/icces.2007.004.207

    Abstract The self energy of geometrically necessary dislocations (GNDs) is considered to inevitably introduce the higher-order stress work-conjugate to slip gradient in single crystals. It is pointed out that this higher-order stress stepwise changes in response to in-plane slip gradient and thus directly influences the onset of initial yielding in polycrystals. The self energy of GNDs is then incorporated into the strain gradient theory of Gurtin (2002). The resulting theory is applied to model crystal grains of size D, leading to a D-1-dependent term with a coefficient determined by grain shape and orientation. It is thus More >

  • Open Access

    ABSTRACT

    Calculation of Energy Release Rate in Mode I Delamination of Angle Ply Laminated Composites

    K. Gordnian1, H. Hadavinia1, G. Simpson1, A. Aboutorabi1

    The International Conference on Computational & Experimental Engineering and Sciences, Vol.1, No.2, pp. 61-68, 2007, DOI:10.3970/icces.2007.001.061

    Abstract The compliance equation is used to calculate the energy release rate for angle ply laminated double cantilever composite beam specimen. Instead of the traditional approach of a beam on an elastic foundation, a second order shear thickness deformation beam theory (SSTDBT) has been considered. More >

  • Open Access

    ARTICLE

    Symmetric Variational Formulation of BIE for Domain Decomposition Problems in Elasticity -- An SGBEM Approach for Nonconforming Discretizations of Curved Interfaces

    R. Vodička1, V. Mantič2, F. París2

    CMES-Computer Modeling in Engineering & Sciences, Vol.17, No.3, pp. 173-204, 2007, DOI:10.3970/cmes.2007.017.173

    Abstract An original approach to solve domain decomposition problems by the symmetric Galerkin boundary element method is developed. The approach, based on a new variational principle for such problems, yields a fully symmetric system of equations. A natural property of the proposed approach is its capability to deal with nonconforming discretizations along straight and curved interfaces, allowing in this way an independent meshing of non-overlapping subdomains to be performed. Weak coupling conditions of equilibrium and compatibility at an interface are obtained from the critical point conditions of the energy functional. Equilibrium is imposed through local traction… More >

  • Open Access

    ARTICLE

    Evaluations of the BGA Solder Ball Shape by Using Energy Method

    Heng Cheng Lin1,2, Chieh Kung3, Rong Sheng Chen2

    CMC-Computers, Materials & Continua, Vol.6, No.1, pp. 43-50, 2007, DOI:10.3970/cmc.2007.006.043

    Abstract Presented herein are the evaluation results of the BGA solder ball shape using energy method, two types of solder, viz. Sn37Pb and Sn80Pb, are selected .The geometry of the solder bump is firstly estimated using free computer software, the Surface Evolver, an interactive program which is an energy-based approach for the study of liquid droplet surfaces shaped by surface tension and other energies. The solder bump is then numerically constructed in a finite element model that simulates a BGA package. The influences of both upper and bottom solder pad radii, the surface tension on the… More >

  • Open Access

    ARTICLE

    A Strain Energy Density Rate Approach to the BEM Analysis of Creep Fracture Problems

    C.P. Providakis1

    Structural Durability & Health Monitoring, Vol.2, No.4, pp. 249-254, 2006, DOI:10.3970/sdhm.2006.002.249

    Abstract This paper explores the concept of strain energy density rate in relation to the crack initiation in fracture analysis problems arising in creeping cracked structural components. The analysis of the components is performed by using the boundary element methodology in association with the employment of singular boundary elements for the modeling of the crack tip region. The deformation of the material is assumed to be described by an elastic power law creep model. The strain energy density rate theory is applied to determine the direction of the crack initiation for a center cracked plate in More >

  • Open Access

    ARTICLE

    Deriving Shear Correction Factor for Thick Laminated Plates Using the Energy Equivalence Method

    H. Hadavinia1, K. Gordnian1, J. Karwatzki1, A. Aboutorabi1

    Structural Durability & Health Monitoring, Vol.2, No.4, pp. 197-206, 2006, DOI:10.3970/sdhm.2006.002.197

    Abstract The cylindrical bending of thick laminated sandwich plates under static loading is studied based on the first order shear deformation theory (FSDT). FSDT generally requires a shear correction factor (SCF) to account for the deflection owing to the transverse shear. In this paper the SCF is derived using energy equivalence method. It is shown that depending on the mechanical and geometrical properties of the layers, the contribution of the transverse shear stress to the maximum deflection of the plate is variable and in some cases account for up to around 88% of the total deflection. More >

  • Open Access

    ARTICLE

    Cohesive Strength and Separation Energy as Characteristic Parameters of Fracture Toughness and Their Relation to Micromechanics

    W. Brocks1

    Structural Durability & Health Monitoring, Vol.1, No.4, pp. 233-244, 2005, DOI:10.3970/sdhm.2005.001.233

    Abstract A review on phenomenological fracture criteria is given, based on the energy balance for cracked bodies, and the respective toughness parameters are related to micromechanical processes. Griffith's idea of introducing a "surface energy" and Barenblatt's concept of a "process zone" ahead of the crack tip build the foundation of modern cohesive models, which have become versatile tools for numerical simulations of crack extension. The cohesive strength and the separation energy used as phenomenological material parameters in these models appear to represent a physically significant characterisation of "fracture toughness". Micromechanical interpretations of these parameters can be More >

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