Browsing by Author "Ergut A."

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    Effect of 3D isotropic resolutions of sequenced images on natural vibration properties of trabecular bone
    (Sharif University of Technology, 2013) Altintas G.; Ergut A.; Goktepe A.B.
    The voxel based finite element (FE) method used to obtain primary data for non-invasive imaging techniques has emerged as a major focus of interest in several disciplines such as medicine, mechanics and material engineering for solving micro and nano-scale problems. Owing to the fact that, voxel based FE models are directly affected by parameters of imaging techniques such as Computed Tomography (CT) and Magnetic Resonance Imaging (MRI), the consequences of these effects on the natural vibration analysis of structures having complex geometry in micro scale, are investigated in this study. In this context, voxel based FE models are obtained using Micro-CT imaging data that has three different resolutions of vertebral trabecular bone tissue. Furthermore, resolutions of image data sets are artificially increased and equalized for evaluating voxel based FE models that are free from FE size effects. Natural vibration characteristics of voxel based FE models are investigated not only numerically but also including associated mode shapes. Unpredictable vibrational behavior for various voxel sizes, is, thus, revealed. Element size effects of voxel based FE models are considerably different from the effects on structural components with regular prismatic shapes. Obtained results show that, investigated parameters have a crucial influence on the natural vibration behavior of trabecular bone tissue which is selected as an example of complex geometries. Modal behaviors that are effective in micro local regions, but less in the whole body, where there are possibilities for working with approximate geometry without considering the micro structure have been observed. Moreover, the results are new from a theoretical point of view, and they also represent the importance of quality in imaging data, which, in practical applications must be taken into consideration. © 2013 Sharif University of Technology. Production and hosting by Elsevier B.V. All rights reserved.
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    Effect of application area distributions of mass, force, and support on free and forced vibration behavior of viscoelastically supported plates
    (2013) Ergut A.; Altintas G.
    In real world systems, implementation areas of mass, force and supports have considerable quantity, unlike homogenized areas in numerical solutions. In this study, the effect of area distributions of non-structural additional mass, external force and supports on linear vibrating plate systems are analyzed. There are two key questions addressed in this study. First, the majority of the previous works cover the range of a fundamental mode, and do not answer the question of how results of the fundamental analyses can be generalized for the higher modes based on investigated parameters, particularly for the case of forced vibration. Second, how structural safety is threatened by focused idealizations has not been adequately studied before. Numerical results of this study are obtained by using the variational difference method (VDM), which is based on a variational procedure in conjunction with traditional finite difference method. VDM is applied for determining free vibration characteristics and steady-state responses to a sinusoidally varying force applied to a viscoelastically supported plate.Because the results of the investigated systems showed that the vibration characteristics had a high sensitivity to analyzed parameters (the amount of area distributions of non-structural additional mass, external force and supports), the idealization process of areas must be attentively employed. The study provides insight not only for a fundamental mode but also for higher modes. Obviously the results of this deterministic study have showed that theoretical importance shall be considered in practical applications. © The Author(s) 2012 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.
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    Major Constructional Dispute Causes in Turkey
    (De Gruyter Open Ltd, 2016) Yildizel S.A.; Dogan E.; Kaplan G.; Ergut A.
    The possibility of construction disputes can be reduced, but they cannot be avoided due to the uncertain and risky nature of the building industry. Conflicts between construction parties often have very unfavourable effects, such as cost increases, poor construction quality and time extension in the schedule. Lots of studies have been carried out in order to try and avoid these disagreements. However, there are no common resolution tools or techniques due to the improving conditions and scope of contracted works. Advanced methods and dispute reasons should be fully monitored and updated for the applicable solutions. This paper discusses the current major constructional dispute reasons in Turkey. The questionnaire method was applied within the scope of this study. The questionnaire documents were randomly distributed to 80 contractors to analyse major dispute reasons in Turkey. Analysis of the questionnaire results indicates that the major current dispute causes are poor quality of performed works, delays in progress payments, inefficient site management, poorly written contracts and design mistakes. © 2016 Polish Academy of Sciences.
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    Dynamics of fluid conveying pipes using Rayleigh theory under non-classical boundary conditions
    (Elsevier Ltd, 2019) Dagli B.Y.; Ergut A.
    The dynamic behavior of fluid conveying pipe has been investigated by using Rayleigh theory to present the effect of non-classical boundary conditions on natural frequencies. The assumption of ideal fluid is used for acquiring the equation of motion for a uniform Rayleigh pipe. The ideal fluid moves in the vertical direction with pipe and the pipe makes small oscillations by Hamilton's variation principle. Euler equation is adopted for the modeling of the flow behavior in the pipe. Accordingly, the dimensionless partial differential equations of motion are converted into matrix equations and solved for two different set of non-classical boundary conditions. The natural frequencies are obtained depending on fluid velocity and stiffnesses of boundary conditions by using Rayleigh Theory. The effect of mass ratio and slenderness ratio on vibration frequency is examined for the first three modes. The one-way FSI (Fluid–Structure Interaction) technique is used by ANSYS software to determine natural frequencies of pipe. The results of first natural frequency based on the numerical solution performed by using ANSYS-FSI are compared with the results of analytical solution for Rayleigh pipe. © 2019
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    Estimation of Natural Frequencies of Pipe–Fluid–Mass System by Using Causal Discovery Algorithm
    (Institute for Ionics, 2023) Dagli B.Y.; Ergut A.; Özyüksel Çiftçioğlu A.
    This paper employs a novel approach to investigating the dynamic behavior of a pipe conveying fluid and the relationship between the variables that influence it, based on causal inference. The pipe is modeled as a beam with Rayleigh beam theory and Hamilton’s variation principle is demonstrated to obtain the equation of motion. Concentrated mass at various locations is introduced using the Dirac delta function. The fluid in the pipe has no compression properties and no viscosity. The non-dimensional equations of motion of the pipe–fluid–mass system are achieved by using the approach of the fluid–structure interaction problem. The non-dimensional partial differential equations of motion are converted into matrix equations and the values of natural frequencies are obtained by using the Finite Differences Method. The relationship between the variables is investigated by causal discovery using the produced natural vibration frequencies dataset. Moreover, the Bayesian Network's probability distribution is fitted to the discretized data using the structural model created through causal discovery, resulting in trustworthy predictions without the need for sophisticated analysis. The findings highlighted that the proposed causal discovery can be an alternative practical way for real-time applications of pipe conveying fluid systems. © 2022, King Fahd University of Petroleum & Minerals.
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    Prediction of natural frequencies of Rayleigh pipe by hybrid meta-heuristic artificial neural network
    (Springer Science and Business Media Deutschland GmbH, 2023) Dagli B.Y.; Ergut A.; Turan M.E.
    This paper focuses on determination of the natural frequencies in slenderness pipe flows by considering fluid–structure interaction approach. Rayleigh beam theory is used to model the pipe. The fluid in the pipe is assumed as ideal, steady and uniform. Hamilton’s variation principle is demonstrated to obtain the equation of motion of pipe–fluid system. The dimensionless partial differential equations of motion are converted into matrix equations, and the values of natural frequencies of first three modes are archived with the analytical method. The results are arranged to be a data set for hybrid meta-heuristic artificial neural network (ANN) method. Three different meta-heuristic algorithms are used to train the ANN: particle swarm optimization (PSO) and artificial bee colony (ABC) and grey wolf optimizer (GWO). The comparison is presented to find a suitable algorithm based on accuracy for determining the natural frequency of the Rayleigh pipe conveying fluid. The results show that the PSO algorithm outperforms the other meta-heuristics in terms of performance indicators in prediction analysis. However, all algorithms and models can predict the natural frequencies with rate with satisfactory accuracy. © 2023, The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering.
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    Analysis of Transverse Vibration in a Concentrated Mass Rayleigh Pipe
    (Multidisciplinary Digital Publishing Institute (MDPI), 2025) Ergut A.
    The dynamic behavior of pipelines subjected to additional masses is crucial for optimizing the design and reliability of engineering systems, particularly in offshore and industrial applications. This study investigates the effect of slenderness on the dynamic response of a pipe with one or more additional masses placed at different positions along its length, considering the symmetry of the system in mass distribution. The aim is to analyze how mass placement influences vibration characteristics under fluid–structure interaction (FSI) conditions. The pipe is modeled as a Rayleigh beam, and the governing equations of motion are derived using Hamilton’s principle while preserving the inherent symmetry of the system. A non-dimensionalized approach is employed to ensure broad applicability across different geometric and material configurations. The vibration frequencies are obtained using the Galerkin method (GM) and validated via a two-way FSI technique, integrating computational fluid dynamics (CFDs) and structural mechanics using ANSYS 2022 software. The results demonstrate the relationship between the concentrated mass ratio and vibration frequency for the first three modes, highlighting the influence of slenderness ratio on system stability. These findings provide valuable insights for the engineering design of pipeline systems subjected to dynamic loading. © 2025 by the author.