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  • Open Access

    ARTICLE

    Strength Failure Conditions of the Various Structural Materials: Is there some Common Basis existing?

    Ralf G. Cuntze1

    Structural Durability & Health Monitoring, Vol.3, No.2, pp. 87-106, 2007, DOI:10.3970/sdhm.2007.003.087

    Abstract The paper deals with the application of phenomenological, invariant-based strength conditions (fracture failure) and their interrelationships. The conditions have been generated and are just applied here for a variety of materials. These might possess a dense or a porous consistency, and belong to brittle and ductile behaving isotropic materials, brittle unidirectional laminae and brittle woven fabrics. The derivation of the conditions was based on the author's so-called Failure Mode Concept (FMC) which basically builds up on the hypotheses of Beltrami and Mohr-Coulomb.
    Essential topics of the paper are: 'global fitting' versus 'failure mode fitting', a short derivation of the FMC,… 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 using contact angle measurements.… More >

  • Open Access

    ARTICLE

    Prediction of Crack Path Bifurcation under Quasi-Static Loading by the Cohesive Model

    W. Brocks1, I. Scheider1

    Structural Durability & Health Monitoring, Vol.3, No.2, pp. 69-80, 2007, DOI:10.3970/sdhm.2007.003.069

    Abstract Cohesive models are used for numerical crack extension analyses in order to predict the mechanical behavior of structures in cases of crack path bifurcation. Possible applications range from the macroscopic to the microscopic scale. As an example of applications to macroscopic engineering structures, simulations of a stiffened cylindrical shell under internal pressure are presented, where a skin crack may penetrate the rib or deviate. On the micro-scale, unit-cell calculation for a fiber-reinforced material is performed, where the fiber may debond or break. More >

  • Open Access

    ARTICLE

    Role of Residual Stress in Structural Integrity Assessment of Cracked Components at Elevated Temperatures

    Kamran Nikbin1

    Structural Durability & Health Monitoring, Vol.3, No.1, pp. 51-68, 2007, DOI:10.3970/sdhm.2007.003.051

    Abstract Weldments and welded regions of components are likely to see failure at elevated temperatures earlier than homogenous parent material. In some cases variable loading could also introduce creep/fatigue crack growth. These weld regions not only contain variable creep properties but are likely to contain residual stresses which could relax in time. There are three key factors which may determine a successful outcome for remaining life assessment of engineering components containing residual stresses in the vicinity of welds. The first is standardized testing and measurement procedures. The second is the development of appropriate and accurate correlating parameters to treat the results… More >

  • Open Access

    ARTICLE

    Structural Integrity and Durability of High Voltage Composite (Non-Ceramic) Insulators

    M. Kumosa1

    Structural Durability & Health Monitoring, Vol.3, No.1, pp. 35-50, 2007, DOI:10.3970/sdhm.2007.003.035

    Abstract This paper deals with the structural integrity and durability of suspension composite (non-ceramic, polymer) insulators widely used in power transmission systems around the world. Under certain conditions, the insulators can fail in-service both electrically and mechanically resulting in the drop of energized transmission lines and power outages. In this work, predominantly mechanical failures of the insulators are discussed. In particular, the most important characteristics of a catastrophic failure process called brittle fracture are described. Subsequently, two examples of insulator failures by brittle fracture are shown and their causes explained. Finally, several recommendations on how to avoid brittle fracture as well… 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 topic of interest on… More >

  • Open Access

    ARTICLE

    Two-dimensional Numerical Estimation of Stress Intensity Factors and Crack Propagation in Linear Elastic Analysis

    Abdulnaser M. Alshoaibi1,2, M. S. A. Hadi2, A. K. Ariffin2

    Structural Durability & Health Monitoring, Vol.3, No.1, pp. 15-28, 2007, DOI:10.3970/sdhm.2007.003.015

    Abstract An adaptive finite element method is employed to analyze two-dimensional linear elastic fracture problems. The mesh is generated by the advancing front method and the norm stress error is taken as a posteriori error estimator for the h-type adaptive refinement. The stress intensity factors are estimated by a displacement extrapolation technique. The near crack tip displacements used are obtained from specific nodes of natural six-noded quarter-point elements which are generated around the crack tip defined by the user. The crack growth and its direction are determined by the calculated stress intensity factors as the maximum circumference theory is also been… More >

  • Open Access

    ARTICLE

    Finite Element Based Durability Assessment of a Free Piston Linear Engine Component

    M. M. Rahman1, A. K. Ariffin1, S. Abdullah1, N. Jamaludin1

    Structural Durability & Health Monitoring, Vol.3, No.1, pp. 1-14, 2007, DOI:10.3970/sdhm.2007.003.001

    Abstract A modern computational approach based on finite element analysis for durability assessment in a two-stroke free piston linear engine component using the variable amplitude loadings is presented. This paper describes the finite element analysis techniques to predict the fatigue life and identify the critical locations of the component. The effect of mean stress on the fatigue life is also investigated. The finite element modeling and analysis has been performed using a computer-aided design and a finite element analysis software package, and the fatigue life prediction was carried out using finite element based fatigue life prediction codes. The fatigue crack initiation… 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 tension which is subjected to… More >

  • Open Access

    ARTICLE

    Cold Drawn Eutectoid Pearlitic Steel Wires as High Performance Materials in Structural Engineering

    J. Toribio 1

    Structural Durability & Health Monitoring, Vol.2, No.4, pp. 239-248, 2006, DOI:10.3970/sdhm.2006.002.239

    Abstract This paper reviews the fracture performance in air and aggressive environment (stress corrosion cracking) of eutectoid prestressing steel wires with different levels of cold drawing. In air environment, a micromechanical model of fracture is proposed to rationalize the results on the basis of the microstructure of the steels after drawing and the model of Miller & Smith of fracture of pearlitic microstructure by shear cracking of the cementite lamellae. In hydrogen assisted cracking (HAC), a microstructure-based model is proposed on the basis of the Miller & Smith model and the mechanism of hydrogen enhanced decohesion or, more properly, hydrogen enhanced… More >

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