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  • Open Access


    Cyclic plasticity and damage of a metal matrix composite by a gradient-enhanced CDM model

    G. Minak1, F. E. G. Chimisso2, H. S. Costa Mattos3

    Structural Durability & Health Monitoring, Vol.1, No.3, pp. 193-202, 2005, DOI:10.3970/sdhm.2005.001.193

    Abstract Cyclic plasticity and damage of a metal matrix composite have been studied in the framework of continuum damage mechanics. The material was considered as macroscopically homogeneous and a model incorporating damage gradient was applied. Strain-controlled fully reversed low-cycle fatigue uniaxial tests were performed to identify material parameters related to yield stress, isotropic and kinematic hardening, fatigue life and damage diffusion. From previous studies it has been found that in the most general case the parameters of the model are constant or depend exponentially on total strain so that only two or three tests are needed for the characterisation. The results… More >

  • Open Access


    Effect of correct statistical description of fatigue crackpropagation data on the time to first inspection

    G. Bertrand1

    Structural Durability & Health Monitoring, Vol.1, No.3, pp. 185-192, 2005, DOI:10.3970/sdhm.2005.001.185

    Abstract Each maintenance strategy demands for the definition of an inspection threshold and further inspection intervals. A general criterion for the calculation of the time to first inspection is high probability of detection of a certain crack size and low failure probability in case a predicted crack size was not detected. The proposed method demonstrates that a top down analysis of crack development from critical sizes to detectable sizes reveals an economic benefit with respect to the frequency of inspections. The dispersion of fatigue stress cycles at rupture obtained from component tests at riveted lap joints is transformed to the distribution… More >

  • Open Access


    Finite Element Modeling of Fatigue Crack Growth in Curved-Welded Joints Using Interface Elements

    M. S. Alam1, M.A. Wahab1,2

    Structural Durability & Health Monitoring, Vol.1, No.3, pp. 171-184, 2005, DOI:10.3970/sdhm.2005.001.171

    Abstract Fatigue life of curved structural joints in ship structures under constant amplitude cyclic loading has been studied in this research. A new approach for the simulation of fatigue crack growth in welded joints has been developed and the concept has been applied to welded curved butt-joints. The phenomena of crack propagation and interface debonding can be regarded as the formation of new surfaces. Thus, it is possible to model these problems by introducing the mechanism of surface formation. In the proposed method, the formation of new surface is represented by interface element based on the interface surface potential energy. The… More >

  • Open Access


    The Theory of Critical Distances Applied to the Prediction of Brittle Fracture in Metallic Materials


    Structural Durability & Health Monitoring, Vol.1, No.2, pp. 145-154, 2005, DOI:10.3970/sdhm.2005.001.145

    Abstract The Theory of Critical Distances (TCD) is a general term for any of those methods of analysis which use continuum mechanics in conjunction with a characteristic material length constant, L. This paper discusses the use of two simple versions of the TCD: a point-stress approach which we call the Point Method (PM) and a line-average approach: the Line Method (LM). It is shown that they are able to predict the onset of unstable, brittle fracture in specimens of metallic materials containing notches of varying root radii. The approach was successful whatever the micromechanism of crack growth (cleavage or ductile tearing);… More >

  • Open Access


    The MLPG Method for Crack Analysis in Anisotropic Functionally Graded Materials

    J. Sladek1, V. Sladek, Ch.Zhang2

    Structural Durability & Health Monitoring, Vol.1, No.2, pp. 131-144, 2005, DOI:10.3970/sdhm.2005.001.131

    Abstract A meshless method based on the local Petrov-Galerkin approach is proposed for crack analysis in two-dimensional (2-d), anisotropic and linear elastic solids with continuously varying material properties. Both quasi-static and transient elastodynamic problems are considered. For time-dependent problems, the Laplace-transform technique is utilized. A unit step function is used as the test function in the local weak-form. It is leading to local boundary integral equations (LBIEs) involving only a domain-integral in the case of transient dynamic problems. The analyzed domain is divided into small subdomains with a circular shape. The moving least-squares (MLS) method is adopted for approximating the physical… More >

  • Open Access


    Vibration Fatigue Analysis of Cylinder Head of a New Two-Stroke Free Poston Engine Using Finite Element Approach

    M. M. Rahman1, A. K. Ariffin1, N. Jamaludin1, C. H. C. Haron1

    Structural Durability & Health Monitoring, Vol.1, No.2, pp. 121-130, 2005, DOI:10.3970/sdhm.2005.001.121

    Abstract The focus of this paper is to design a new two-stroke linear generator engine. This paper describes the finite element based vibration fatigue analysis techniques that can be used to predict fatigue life using total life approach. Fatigue damage in traditionally determined from time signals of loading, usually in the form of stress and strain. However, there are scenarios when a spectral form of loading is more appropriate. In this case the loading is defined in terms of its magnitude at different frequencies in the form of a power spectral density (PSD) plot. A power spectral density function is the… More >

  • Open Access


    Reliable Fracture Analysis of OF 2-D Crack Problems Using NI-MVCCI Technique

    G.S. Palani1, Nagesh R. Iyer1, B. Dattaguru2

    Structural Durability & Health Monitoring, Vol.1, No.2, pp. 107-120, 2005, DOI:10.3970/sdhm.2005.001.107

    Abstract A posteriori error estimation and adaptive refinement technique for 2-D/3-D crack problems is the state-of-the-art. In this paper a new a posteriori error estimator based on strain energy release rate (SERR) or stress intensity factor (SIF) at the crack tip region has been proposed and used along with the stress based error estimator for reliable fracture analysis of 2-D crack problems. The proposed a posteriori error estimator is called the K-S error estimator. Further, h-adaptive mesh refinement strategy which can be used with K-S error estimator has been proposed for fracture analysis of 2-D crack problems. The performance of the… More >

  • Open Access


    Constitutive Equations in Finite Element Codes: The INTERATOM Model in ABAQUS

    D.K. Anding1

    Structural Durability & Health Monitoring, Vol.1, No.2, pp. 95-106, 2005, DOI:10.3970/sdhm.2005.001.095

    Abstract The paper deals with the implementation of constitutive equations for isotropic viscoplastic material behaviour into modern Finite Element codes like ABAQUS. ABAQUS provides an user interface called UMAT (USER MATERIAL) for the definition of quite general material behaviour. The user can take advantage of the complete Finite Element code from ABAQUS and has to focus only on the solution of the constitutive equations. Key problems are accuracy and stability of this local solution procedure, which comes from the numerical stiffness of the governing equations (mostly first order ordinary differential equations). The numerical stiffness does not allow to use explicit integration… More >

  • Open Access


    Probability Methods for Estimation of Cleavage Fracture Toughness from Small Data Sets

    R. Moskovic1, P. E. J. Flewitt1,2

    Structural Durability & Health Monitoring, Vol.1, No.1, pp. 83-94, 2005, DOI:10.3970/sdhm.2005.001.083

    Abstract Consideration of the structural integrity is one of the inputs when evaluating potential solutions to plant problems. Structural integrity assessments of components forming the pressure boundaries of nuclear plant evaluate safety margins against cleavage fracture. These assessments consider the reserve factors between the applied stress and fracture toughness of the material as well as temperature margins between the operating temperature and the temperature at which the steel is ductile as defined by upper shelf behaviour. To carry out these structural integrity assessments, estimates of cleavage fracture toughness are required. The approach presented in this paper allows for differences between cleavage… More >

  • Open Access


    Numerical Analysis of Damage Evolution in Ductile Solids

    M. Mashayekhi1, S. Ziaei-Rad2, J. Parvizian3, K. Nikbin1, H. Hadavinia1

    Structural Durability & Health Monitoring, Vol.1, No.1, pp. 67-82, 2005, DOI:10.3970/sdhm.2005.001.067

    Abstract The continuum mechanical simulation of microstructural damage process is important in the study of ductile fracture mechanics. An essential feature in these analyses, is the strong influence of stress triaxiality ratio, i.e. the ratio of mean stress to equivalent stress, on the rate of damage growth. In this paper, finite element simulation of damage evolution and fracture initiation in ductile solids will be investigated. A fully coupled constitutive elastic-plastic-damage model has been implemented. The stress update algorithm for the constitutive model is presented together with the consistent tangent operator, which is needed for implicit FEA. Simulations are performed and the… More >

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