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  • Open Access

    ARTICLE

    Unsupervised Time-series Fatigue Damage State Estimation of Complex Structure Using Ultrasound Based Narrowband and Broadband Active Sensing

    S.Mohanty1, A. Chattopadhyay2, J. Wei3, P. Peralta4

    Structural Durability & Health Monitoring, Vol.5, No.3, pp. 227-250, 2009, DOI:10.3970/sdhm.2009.005.227

    Abstract This paper proposes unsupervised system identification based methods to estimate time-series fatigue damage states in real-time. Ultrasound broadband input is used for active damage interrogation. Novel damage index estimation techniques based on dual sensor signals are proposed. The dual sensor configuration is used to remove electrical noise, as well as to improve spatial resolution in damage state estimation. The scalar damage index at any particular damage condition is evaluated using nonparametric system identification techniques, which includes an empirical transfer function estimation approach and a correlation analysis approach. In addition, the effectiveness of two sensor configurations More >

  • Open Access

    ARTICLE

    Studies on Methodological Developments in Structural Damage Identification

    V. Srinivas1, Saptarshi Sasmal1, K. Ramanjaneyulu2

    Structural Durability & Health Monitoring, Vol.5, No.2, pp. 133-160, 2009, DOI:10.3970/sdhm.2009.005.133

    Abstract Many advances have taken place in the area of structural damage detection and localization using several approaches. Availability of cost-effective computing memory and speed, improvement in sensor technology including remotely monitored sensors, advancements in the finite element method, adaptation of modal testing and development of non-linear system identification methods bring out immense technical advancements that have contributed to the advancement of modal-based damage detection methods. Advances in modal-based damage detection methods over the last 20-30 years have produced new techniques for examining vibration data for identification of structural damage. In this paper, studies carried out… More >

  • Open Access

    ARTICLE

    Temperature Sensitivity Assessment of Vibration-based Damage Identification Techniques

    N.H.M. Kamrujjaman Serker1, Zhishen Wu

    Structural Durability & Health Monitoring, Vol.5, No.2, pp. 87-108, 2009, DOI:10.3970/sdhm.2009.005.087

    Abstract This paper presents the study on the temperature sensitivity of some vibration-based damage identification techniques. With the help of a simple supported beam with different damage levels, reliability of these techniques for damage identification in a changing environmental temperature condition was investigated. The temperature effect was considered as the change in modulus of elasticity of the material. The techniques evaluated herein are based on measured modal parameters which use only few mode shapes and/or modal frequencies of the structure that can easily be obtained by dynamic tests. The effect of temperature on identification of different More >

  • Open Access

    ABSTRACT

    Modal identification of structure under varying environmental conditions

    Deyi Zhang1, Yuequan Bao, Feng Zhou, Hui Li

    The International Conference on Computational & Experimental Engineering and Sciences, Vol.12, No.2, pp. 65-72, 2009, DOI:10.3970/icces.2009.012.065

    Abstract Modal identification is essential in structural health monitoring (SHM) because that the modal parameters are often used for model updating and damage detection. However, in practical situations, the variation of environmental conditions (e.g. temperature, temperature gradients, humidity, etc.) will impede the reliability of modal identification. In this paper, firstly, the relation of frequency change and variation of environment temperature of space structure is investigated. Then, a structural state assessment method by combing autoregressive moving average (ARMA) and PCA is proposed. The acceleration data from China National Aquatics Center is employed as an example. The results More >

  • Open Access

    ARTICLE

    Numerical Inversion of Multi-Parameters in Multi-Components Reactive Solutes Transportation in an Undisturbed Soil-Column Experiment

    G.S. Li1, D. Yao2, Y.Z. Wang3, H.Y. Jiang2

    CMES-Computer Modeling in Engineering & Sciences, Vol.51, No.1, pp. 53-72, 2009, DOI:10.3970/cmes.2009.051.053

    Abstract In this paper, an undisturbed soil-column infiltrating experiment is investigated, and a mathematical model describing multi-components solutes transport behaviors in the column is put forward by combing hydro-chemical analysis with advection dispersion mechanisms, which is a group of advection-dispersion-reaction partial differential equations. Since the model involving six reaction coefficients which can not be obtained directly, an optimal perturbation regularization algorithm of determining these parameters is performed, and numerical simulations under different conditions are carried out. Furthermore, the inversion algorithm is applied to solve the real inverse problem by utilizing the measured breakthrough data. The reconstruction More >

  • Open Access

    ARTICLE

    Fast Identification of Poroelastic Parameters from Indentation Tests

    M.Galli , M.L.Oyen1

    CMES-Computer Modeling in Engineering & Sciences, Vol.48, No.3, pp. 241-270, 2009, DOI:10.3970/cmes.2009.048.241

    Abstract A novel approach is presented for the identification of constitutive parameters of linear poroelastic materials from indentation tests. Load-controlled spherical indentation with a ramp-hold creep profile is considered. The identification approach is based on the normalization of the time-displacement indentation response, in analogy to the well-known one-dimensional consolidation problem. The identification algorithm consists of two nested optimization routines, one in the time-displacement domain and the other in a normalized domain. The procedure is validated by identifying poroelastic parameters from the displacement-time outputs of finite element simulations; the new identification scheme proves both quantitatively reliable and More >

  • Open Access

    ARTICLE

    A Numerical Method for Estimating the Maximal Temperature Gradients Reached in Fire-Damaged Concrete Structures Based on the Parameter Identification

    Dong Wei1, Yinghua Liu1,2, Zhihai Xiang1

    CMES-Computer Modeling in Engineering & Sciences, Vol.46, No.1, pp. 77-106, 2009, DOI:10.3970/cmes.2009.046.077

    Abstract Taking advantage of the parameter identification, a new numerical method is developed in this paper to estimate the maximal temperature gradients reached in fire-damaged concrete structures. This method can avoid the hypotheses of temperature-time curve and fire duration usually made in conventional numerical methods, availably evaluate the depth and degree of fire damage of concrete structures and consider the effects of localized fire. A material model taking into account the properties of fire-damaged concrete is firstly proposed in the present research. The least-squares estimation and the Gauss-Newton method are used to identify the material parameters… More >

  • Open Access

    ARTICLE

    Parameter identification of beam-column structures on two-parameter elastic foundation

    F. Daghia1, W. Hasan1, L. Nobile1, E. Viola1,2

    CMES-Computer Modeling in Engineering & Sciences, Vol.39, No.1, pp. 1-28, 2009, DOI:10.3970/cmes.2009.039.001

    Abstract In this paper, a finite element model has been developed for analysing the flexural vibrations of a uniform Timoshenko beam-column on a two-parameter elastic foundation. The beam was discretized into a number of finite elements having four degrees of freedom each. The effect of end springs was incorporated in order to identify the end constraints. \newline The procedure for identifying geometric and mechanical parameters as well as the end restraints of a beam on two-parameter elastic foundation is based on experimentally measured natural frequencies from dynamic tests on the structure itself. \newline An iterative statistical More >

  • Open Access

    ARTICLE

    Identification of dynamical systems with fractional derivative damping models using inverse sensitivity analysis

    R Sivaprasad1,2, S Venkatesha1, C S Manohar1,3

    CMC-Computers, Materials & Continua, Vol.9, No.3, pp. 179-208, 2009, DOI:10.3970/cmc.2009.009.179

    Abstract The problem of identifying parameters of time invariant linear dynamical systems with fractional derivative damping models, based on a spatially incomplete set of measured frequency response functions and experimentally determined eigensolutions, is considered. Methods based on inverse sensitivity analysis of damped eigensolutions and frequency response functions are developed. It is shown that the eigensensitivity method requires the development of derivatives of solutions of an asymmetric generalized eigenvalue problem. Both the first and second order inverse sensitivity analyses are considered. The study demonstrates the successful performance of the identification algorithms developed based on synthetic data on More >

  • Open Access

    ARTICLE

    Identification of Particle Stimulated Nucleation during Recrystallization of AA 7050

    D.P. Field1, L. Behrens2, J.M. Root1

    CMC-Computers, Materials & Continua, Vol.14, No.3, pp. 171-184, 2009, DOI:10.3970/cmc.2009.014.171

    Abstract Mechanical properties of polycrystalline metals are dependent upon the arrangement of microstructural features in the metal. Recrystallization is an important phenomenon that often occurs during thermo-mechanical processing of metals. This work focuses upon aluminum alloy 7050 and uses crystallographic texture and pair correlation functions of recrystallized grains to characterize the dominance of particle stimulated nucleation in the recrystallization process. The randomization of the recrystallization texture and similar pair correlation functions for the particle distribution and the recrystallization nuclei distribution indicate that particle stimulated nucleation controls the recrystallization behavior in this alloy. More >

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