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  • Open Access

    ARTICLE

    Extraction of Fatigue Damaging Events from Road Spectrum Loadings Using the Wavelet-Based Fatigue Data Editing Algorithm

    S. Abdullah1

    Structural Durability & Health Monitoring, Vol.4, No.4, pp. 181-198, 2008, DOI:10.3970/sdhm.2008.004.181

    Abstract This paper describes a technique to identify the important features in fatigue road spectrum loading, for which these features cause the majority of the total damage. Fatigue damaging events, called bump segments, are extracted from the spectrum loading using a wavelet-based algorithm, called Wavelet Bump Extraction (WBE). This algorithm is also used to produce a shortened mission signal that retains most of the fatigue damage whilst preserving the cycle sequences. The bump identification process has been evaluated by analysing two road spectrum loadings having a variable amplitude pattern. These data sets were obtained from the… More >

  • Open Access

    ARTICLE

    Fatigue Analysis of Spot-Welded Joint for Automative Structures

    M. M. Rahman1, A. K. Arrifin2, M. J. M. Nor2, S. Abdullah2

    Structural Durability & Health Monitoring, Vol.4, No.3, pp. 173-180, 2008, DOI:10.3970/sdhm.2008.004.173

    Abstract This paper presents the fatigue analysis of spot-weld joints for automative structures to predict the lifetime and location of the weakest spot-welds due to the imposed loading conditions. A simple model was used to illustrate the technique of spot-weld fatigue analysis. Finite element model and analysis were carried out utilizing the finite element analysis commercial codes. Linear elastic finite element analysis was carried out to predict the stress state along the weld direction. It can be seen from the results that the predicted life greatly influence the sheet thickness, spot diameter and loading conditions of More >

  • Open Access

    ARTICLE

    Sample Size Determination for Development of S-N Curve of A356.2-T6 Aluminum Alloy

    P. Ramamurty Raju1, B. Satyanarayana2, K. Ramji3

    Structural Durability & Health Monitoring, Vol.4, No.3, pp. 161-172, 2008, DOI:10.3970/sdhm.2008.004.161

    Abstract This paper presents the details of method of sample size determination to estimate the characteristic fatigue life of aluminum alloy. The characteristic fatigue life of Aluminum alloy A356.2-T6 has been estimated by assuming a two parameter Weibull distribution model. A stepwise procedure is outlined to determine the number of specimens required at a predetermined stress amplitude to estimate the fatigue life within an acceptable error at a given probability and confidence level. The percentage of error is calculated at various probabilities and confidence levels (C.L). The probabilities considered are 50%, 90% and 95% whereas C.Ls More >

  • Open Access

    ARTICLE

    FE Analysis of a Notched Cylinder under Multiaxial Cyclic Loading Using the Multilayer Model of Besseling

    G. Savaidis1, N. Pitatzis1, A. Savaidis1, Ch. Zhang2

    Structural Durability & Health Monitoring, Vol.4, No.3, pp. 145-160, 2008, DOI:10.3970/sdhm.2008.004.145

    Abstract This paper presents an elastic-plastic finite element analysis of a circumferentially notched cylinder subjected to multiaxial non-proportional fatigue loading. Two different load combinations are investigated: (1) constant tension with cyclic torsion and (2) constant torsion with cyclic tension. The multilayer plasticity model of Besseling in conjunction with the von Mises yield criterion is applied to describe the elastic-plastic material behaviour. The parametrical study contains a coarse and a fine finite element mesh with and without mid-nodes as well as three different types of multilinear approximations of the material law, namely, a twenty-segments, a five-segments and More >

  • Open Access

    ARTICLE

    Sensitivity of Eigen Value to Damage and Its Identification

    B.K.Raghuprasad1, N.Lakshmanan2, N.Gopalakrishnan2, K.Muthumani2

    Structural Durability & Health Monitoring, Vol.4, No.3, pp. 117-144, 2008, DOI:10.3970/sdhm.2008.004.117

    Abstract The reduction in natural frequencies, however small, of a civil engineering structure, is the first and the easiest method of estimating its impending damage. As a first level screening for health-monitoring, information on the frequency reduction of a few fundamental modes can be used to estimate the positions and the magnitude of damage in a smeared fashion. The paper presents the Eigen value sensitivity equations, derived from first-order perturbation technique, for typical infra-structural systems like a simply supported bridge girder, modelled as a beam, an end-bearing pile, modelled as an axial rod and a simply… More >

  • Open Access

    ARTICLE

    Boundary Element Analysis of Cracked Thick Plates Repaired with Adhesively Bonded Composite Patches

    J. Useche, P. Sollero, E.L. Albuquerque1, L. Palermo2

    Structural Durability & Health Monitoring, Vol.4, No.2, pp. 107-116, 2008, DOI:10.3970/sdhm.2008.004.107

    Abstract The fracture analysis of cracked thick plates repaired with adhesively bonded composite patches using a boundary element formulation is presented. The shear deformable cracked isotropic plate was modeled using the dual boundary method. In order to model the repair, a three parameter boundary element formulation was established. This formulation is based on Kirchhoff's theory for symmetric layer composite plates and considers the transversal deflection and two in-plane rotations. Interaction forces and moments between the cracked plate and the composite repair were modeled as distributed loading, and discretized using continuous and semi-discontinuous domain cells. Coupling equations, More >

  • Open Access

    ARTICLE

    Electroelastic Problem of Two Anti-Plane Collinear Cracks at the Interface of Two Bonded Dissimilar Piezoelectric Layers

    B. M. Singh, J. Rokne, R. S. Dhaliwal1

    Structural Durability & Health Monitoring, Vol.4, No.2, pp. 95-106, 2008, DOI:10.3970/sdhm.2008.004.095

    Abstract Under the permeable electric boundary condition the problem of two collinear anti-plane shear cracks situated at the interface of two bonded dissimilar piezoelectric layers is considered. It is assumed that applied longitudinal shear stress and electric loading at the layer surfaces are prescribed. By the use of Fourier transforms we reduce the problem to solving a set of triple integral equations with a cosine kernel. The triple integral equations are further reduced to a Fredholm integral equation of the second kind whose iterative solution has been obtained. Analytical expressions for the stress intensity factors are More >

  • Open Access

    ARTICLE

    A Generalized Technique for Fracture Analysis of 2-D Crack Problems Employing Singular Finite Elements

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

    Structural Durability & Health Monitoring, Vol.4, No.2, pp. 77-94, 2008, DOI:10.3970/sdhm.2008.004.077

    Abstract The objective of this paper is to present a generalized technique called as, numerically integrated Modified Virtual Crack Closure Integral (NI-MVCCI) technique for computation of strain energy release rate (SERR) for 2-D crack problems employing singular finite elements. NI-MVCCI technique is generalized one and the expressions for computing SERR are independent of the finite element employed. Stress intensity factor (SIF) can be computed using the relations between SERR and SIF depending on the assumption of plane stress/strain conditions. NI-MVCCI technique has been demonstrated for 8-noded Serendipity (regular & quarter-point) and 9-noded Lagrangian (regular & quarter-point) More >

  • Open Access

    ARTICLE

    Experimental Assessment of Stress Intensity Factors in Internal Cracks under Mixed-mode Loading

    C. Colombo1, M. Guagliano1,2, L. Vergani1

    Structural Durability & Health Monitoring, Vol.4, No.2, pp. 67-76, 2008, DOI:10.3970/sdhm.2008.004.067

    Abstract With the aim of experimentally assessing the stress intensity factors under mixed-mode loading along a crack front, the case of an internal elliptical crack is analyzed. An experimental test is performed on a three-dimensional photoelastic model made in epoxy resin. This model contains an inner natural crack, created by thermal shock. The crack is inclined in the cylindrical model, loaded with a tensile stress field.
    Exploiting the characteristics of the epoxy resin, and using the stress freezing technique, it is possible to keep memory of the stresses near to the crack tip, once the specimen is unloaded. More >

  • Open Access

    ARTICLE

    A Study of Damage Identification and Crack Propagation in Concrete Beams

    A. Brasiliano1, W.R. Souza2, G.N. Doz3, J.L.V. Brito4

    Structural Durability & Health Monitoring, Vol.4, No.2, pp. 53-66, 2008, DOI:10.3970/sdhm.2008.004.053

    Abstract It can be observed that usually, during structures useful life they are submitted to deterioration processes that, depending on the intensity, may affect their performance and load capacity and, as a result, their safety. In this case, it is necessary to accomplish an inspection in order to evaluate the conditions of the structure and to locate and quantify the intensity of the damage. Another important point is to study the behavior of brittle material beams with cracks, as an attempt of understanding the rupture mechanism and crack propagation phenomenon. In this paper, the Residual Error More >

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