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  • Open Access


    Cost Optimized Non-Contacting Experimental Modal Analysis Using a Smartphone

    Jaafar Hallal1,2,3,*, Mohammad Hammoud2,3, Mahmoud Fakih2,3,4, Ali Hallal2,3

    Sound & Vibration, Vol.54, No.4, pp. 225-236, 2020, DOI:10.32604/sv.2020.011513

    Abstract The vibrations behavior analysis is an essential step in the mechanical design process. Several methods such as analytical modelling, numerical analysis and experimental measurements can be used for this purpose. However, the numerical or analytical models should be validated through experimental measurements, usually expensive. This paper introduces an inexpensive smartphone as an accurate, non-intrusive vibrations’ behavior measurement device. An experimental measurement procedure based on the video processing method is presented. This procedure allows the measurement of the natural frequencies and the mode shapes of a vibrating structure, simply by using a smartphone built-in camera. The experimental results are compared to… More >

  • Open Access


    Finite Element Analysis on Vibration Characteristics of an Offshore Floating Breakwater

    Hongyi Yan1, Dingguo Zhang1, Liang Li1,*, Xiaoyu Luo2

    Structural Durability & Health Monitoring, Vol.14, No.1, pp. 19-36, 2020, DOI:10.32604/sdhm.2020.07457

    Abstract The construction of seaside facilities is a hot topic in the field of ocean engineering. In this paper, a new type of floating breakwater is designed by 3DCAD geometric modeling. Based on the vibration theory and finite element technology, the floating breakwater model is optimized, and the modal analysis of the structure with the bracket as main body and blades as functional attachments is carried out. Natural frequencies and mode shapes of the blades are first calculated, and the effects of the natural frequencies in both dry and wet conditions are taken into account. Modal analysis and harmonic response analysis… More >

  • Open Access


    Overview of the New OMAH Technique for Scaling OMA Mode Shapes

    Anders Brandt1, Marta Berardengo2, Stefano Manzoni3, Marcello Vanali2, Alfredo Cigada3

    Sound & Vibration, Vol.52, No.3, pp. 18-22, 2018, DOI:10.32604/sv.2018.03872

    Abstract Methods for scaling mode shapes determined by operational modal analysis (OMA) have been extensively investigated in the last years. A recent addition to the range of methods for scaling OMA mode shapes is the so-called OMAH technique, which is based on exciting the structure by harmonic forces applied by an actuator. By applying harmonic forces in at least one degree-of-freedom (DOF), and measuring the response in at least one response DOF, while using at least as many frequencies as the number of mode shapes to be scaled, the mode shape scaling (modal mass) of all modes of interest may be… More >

  • Open Access


    Complex Modal Analysis for the Time-Variant Dynamical Problem of Rotating Pipe Conveying Fluid

    Lihua Wang1,*, Zheng Zhong1

    CMES-Computer Modeling in Engineering & Sciences, Vol.114, No.1, pp. 1-18, 2018, DOI:10.3970/cmes.2018.114.001

    Abstract A semi-analytical form of complex modal analysis is proposed for the time-variant dynamical problem of rotating pipe conveying fluid system. The complex mode superposition method is introduced for the dynamic analysis in the time and frequency domains, in which appropriate orthogonality conditions are constructed to decouple the time-variant equation of motion. Consequently, complex frequencies and modes of vibration are analytically formulated and the variations of frequencies and damping of the system are evaluated. Numerical time-variant example of rotating pipe conveying fluid illustrates the effectiveness and accuracy of this method. Furthermore, the proposed solution scheme is also applicable to other similar… More >

  • Open Access


    Modal Analysis Technique for Anisotropic Composite Laminates

    G.M. Mota1, P. Sollero1, F.B. Batista1, E.L. Albuquerque1

    The International Conference on Computational & Experimental Engineering and Sciences, Vol.7, No.2, pp. 95-100, 2008, DOI:10.3970/icces.2008.007.095

    Abstract Nowadays, the experimental modal analysis in composite materials is an important tool in the structural analysis of new designs in aircraft structures. It supplies data on the behavior of these materials and, when associated with numerical methods, it can also be used to identify elastic properties. However, lightweight composite materials demand the use of appropriate techniques and devices. This paper describes an experimental modal analysis technique where the response is measured without physical contact in a large number of points using a Laser Doopler Vibrometer (LDV), and the excitation is carried out on a single point by an electromechanical shaker. More >

  • Open Access


    Multi-Component Modal Analysis of Protein Structure

    G. Yoon1, K. Bong2, J. Kim3, I.H. Ahn4, K. Eom5, S. Na6

    The International Conference on Computational & Experimental Engineering and Sciences, Vol.2, No.2, pp. 53-60, 2007, DOI:10.3970/icces.2007.002.053

    Abstract This paper presents multi-component mode methodology applicable to biomolecular structures for understanding the dynamics of proteins. Even though the conventional normal mode analysis has been contributed for analyzing the dynamics and thermal fluctuations of proteins, it frequently encounters with the computational prohibition for large proteins due to memory requirement. To overcome the conventional computational limitations, the drawback motivates one to develop various model reduction methods, which reduces the degrees of freedom of the full model so as to decrease the computational expense, while the computational accuracy is maintained. Our results demonstrate that the multi-component modal analysis applied to the biomolecular… More >

  • Open Access


    System Identification of Heritage Structures Through AVT and OMA: A Review

    Vinay Shimpi1, Madappa V. R. Sivasubramanian1,*, S. B. Singh2

    Structural Durability & Health Monitoring, Vol.13, No.1, pp. 1-40, 2019, DOI:10.32604/sdhm.2019.05951

    Abstract In this review article, the past investigations carried out on heritage structures using Ambient Vibration Test (AVT) and Operational Modal Analysis (OMA) for system identification (determination of dynamic properties like frequency, mode shape and damping ratios) and associated applications are summarized. A total of 68 major research studies on heritage structures around the world that are available in literature are surveyed for this purpose. At first, field investigations carried out on heritage structures prior to conducting AVT are explained in detail. Next, specifications of accelerometers, location of accelerometers and optimization of accelerometer networks have been elaborated with respect to the… More >

  • Open Access


    Compact Modelling of Electric Arc Furnace Electrodes for Vibration Analysis, Detection and Suppression

    E. Brusa1, E. Franceschinis2, S. Morsut2

    CMES-Computer Modeling in Engineering & Sciences, Vol.42, No.2, pp. 75-106, 2009, DOI:10.3970/cmes.2009.042.075

    Abstract Electrodes motion and positioning are critical issues of the Electric Arc Furnace (EAF) operation in steelmaking process. During the melting process electrode is exposed to some impulsive and harmonic forces, superimposing to the structure's static loading. Unfortunately, structural vibration may interact with the electric arc regulation, because of the dynamic resonance. Instability in the furnace power supplying and dangerous electrode breakage may occur as a consequence of those dynamic effects. In this paper the dynamic behaviour of a real EAF structure is discussed and some numerical models are proposed. Available experimental data, collected by a monitoring system on a real… More >

  • Open Access


    Estimation and Validation of Elastic Modulus of Carbon Nanotubes Using Nano-Scale Tensile and Vibrational Analysis

    C. J. Wu1, C. Y. Chou1, C. N. Han1, K. N. Chiang2

    CMES-Computer Modeling in Engineering & Sciences, Vol.41, No.1, pp. 49-68, 2009, DOI:10.3970/cmes.2009.041.049

    Abstract In this paper, the atomistic-continuum mechanics method (ACM) is applied for carbon nanotube modeling. The atomistic-continuum mechanics is based on the transformation of chemical bonds between atoms in molecular mechanics into appropriate elements in finite element method and continuum mechanics. Spring elements are treated as chemical bonds between carbon atoms in carbon nanotube, whose force-displacement function is determined by the Reactive Empirical Bond Order (REBO) potential model. The advantages and unique feature of ACM method is same analytical model can be used for both tensile and vibration analyses, and most importantly, there are no prior inputs such as Young's Modulus,… More >

  • Open Access


    Segmentation and Simulation of Objects Represented in Images using Physical Principles

    Patrícia C.T. Gonçalves1,2, João Manuel R.S. Tavares1,2, R.M. Natal Jorge1,3

    CMES-Computer Modeling in Engineering & Sciences, Vol.32, No.1, pp. 45-56, 2008, DOI:10.3970/cmes.2008.032.045

    Abstract The main goals of the present work are to automatically extract the contour of an object and to simulate its deformation using a physical approach. In this work, to segment an object represented in an image, an initial contour is manually defined for it that will then automatically evolve until it reaches the border of the desired object. In this approach, the contour is modelled by a physical formulation using the finite element method, and its temporal evolution to the desired final contour is driven by internal and external forces. The internal forces are defined by the intrinsic characteristics of… More >

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