Experimental Modal Testing of the Elastic Tube Bundle

2013 ◽  
Vol 718-720 ◽  
pp. 1816-1819
Author(s):  
Ji Zhou Zheng ◽  
Jia Lin Hou ◽  
Yan Zhang
Keyword(s):  
Complex Shape ◽  
Tube Bundle ◽  
Dynamic Properties ◽  
Elastic Tube ◽  
Modal Testing ◽  
Mode Shapes ◽  
Constraint Condition ◽  
Heat Transfer Efficiency ◽  
Reduce Energy Consumption ◽  
Experimental Modal Testing

The elastic tube bundle is a new-style heat exchange element that can enhance heat transfer efficiency and reduce energy consumption. It is difficult to obtain exact analytical solutions because of the complex shape and constraint condition. An experimental modal testing technique is applied to get the dynamic properties. Some issues to which one should pay attention during the experiment are emphasized. Natural frequencies and mode shapes are identified from the test and compared to numerical results. Agreement is found for most frequencies of interest. But, some discrepancies exist for the vibration in-plane due to the inevitable operation error.

Modal Modeling of Micro-Machining Center

2012 ◽  
Author(s):  
Marcin Chodźko ◽  
Krzysztof Marchelek
Keyword(s):  
Machine Tool ◽  
Model Updating ◽  
Dynamic Properties ◽  
Modal Testing ◽  
Mode Shapes ◽  
Experimental Investigations ◽  
Micro Machining ◽  
Machining Center ◽  
Modal Model ◽  
The Impact

Modeling of dynamic properties of machine tools has a significant influence on improvement of its construction. This process is extremely important when a new construction of machine tool is under development. Experimental modal analysis provides information about frequency bandwidths with significant amplitudes of resonances, damping values and mode shapes. This information can be used in FEM model updating, stability prediction or finding weak elements of the machine tool structure as well. In the paper the modal model of prototype of the micro machining center is presented. Polymax algorithm was used to estimate the poles (frequency, damping) of modal model and modal shapes. Modal model was built on the basis of the impact test results. Methodology of conducted experimental test is presented. Tested machine tool was made of different materials (steel, aluminum, stone and others) which causes difficulties during experimental investigations. In the construction different types of guideways were implemented — rolling, slide and pneumatic ones. Maximum rotational speed of the tool is about 100 000 rev/min, so the frequency range where poles of modal model are estimated is wide (high frequencies of excitation during machining). Weight of sensors used during testing is an important issue due to a low mass of the structure. Also the excitation of the structure is troublesome because of vulnerability of precise guideways and forces sensors used in machine tool construction. Validation of the modal model is also presented in the paper and practical problems of modal testing are discussed.

Verification of a Finite Element Model of an Unmanned Aerial Vehicle Wing Torque Box via Experimental Modal Testing

2012 ◽  
Author(s):  
Levent Unlusoy ◽  
Melin Sahin ◽  
Yavuz Yaman
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Unmanned Aerial Vehicle ◽  
Natural Frequencies ◽  
Element Model ◽  
Modal Testing ◽  
Mode Shapes ◽  
Resonance Frequencies ◽  
Aerial Vehicle ◽  
Experimental Modal Testing

In this study, the detailed finite element model (FEM) of an unmanned aerial vehicle wing torque box was verified by the experimental modal testing. During the computational studies the free-free boundary conditions were used and the natural frequencies and mode-shapes of the structure were obtained by using the MSC® Software. The results were then compared with the experimentally obtained resonance frequencies and mode-shapes. It was observed that the frequencies were in close agreement having an error within the range of 1.5–3.6%.

Finite volume free vibration analysis of a new aerodynamic styling wind turbine

2018 ◽  
Vol 42 (5) ◽  
pp. 397-410 ◽  
Author(s):  
Takwa Sellami ◽  
Sana Jelassi ◽  
Hanen Berriri ◽  
Abdel Moumen Darcherif ◽  
Med Faouzi Mimouni
Keyword(s):  
Numerical Model ◽  
Free Vibration ◽  
Wind Turbine ◽  
Finite Volume ◽  
Dynamic Properties ◽  
Life Cycles ◽  
Modal Testing ◽  
Mode Shapes ◽  
Sustainable Solutions ◽  
Tower Foundation

Due to the short life cycles of large-scale wind turbines and difficulties in getting permission for farms installations, micro-scale turbines have become interesting sustainable solutions to product energy. However, micro-size turbines have to be able to generate balanced powers while ensuring maximum life services under unpredictable environment conditions. Hence, designers must mainly investigate the dynamic characteristics of turbine tower–foundation systems in order to protect the structural security and stability of the system under vibration constraints. In this framework, this article aims to analyze the vibration behavior of modern micro-turbines. A new aerodynamic styling wind turbine, which is Rutland 504 six-bladed commercial turbine, is selected in this study in order to highlight the impacts of extra components like ring, nose, and tail on the vibrational properties. Accordingly, a three-dimensional model of the turbine tower–foundation system was created basing on finite volume method. The newest version of ANSYS academic software is used. Dynamic properties of the numerical model were determined by solving equations of motion. After identifying mode shapes and natural frequencies, experimental modal testing was applied to validate the numerical model. Then, deformations and vibrations of different components of the system were studied under free vibration conditions. The components of the system most sensitive to vibrate were determined. Moreover, the stress distributions were discussed in order to identify the components most exposed to fatigue fractures.

Measured natural periods of concrete shear wall buildings: insights for the design of Canadian buildings

2012 ◽  
Vol 39 (8) ◽  
pp. 867-877 ◽  
Author(s):  
Damien Gilles ◽  
Ghyslaine McClure
Keyword(s):  
Seismic Analysis ◽  
Dynamic Properties ◽  
Response Spectrum ◽  
Shear Wall ◽  
Mode Shapes ◽  
Design Stage ◽  
Base Shear ◽  
Period Equation ◽  
Input Load ◽  
Structural Engineers

Structural engineers routinely use rational dynamic analysis methods for the seismic analysis of buildings. In linear analysis based on modal superposition or response spectrum approaches, the overall response of a structure (for instance, base shear or inter-storey drift) is obtained by combining the responses in several vibration modes. These modal responses depend on the input load, but also on the dynamic characteristics of the building, such as its natural periods, mode shapes, and damping. At the design stage, engineers can only predict the natural periods using eigenvalue analysis of structural models or empirical equations provided in building codes. However, once a building is constructed, it is possible to measure more precisely its dynamic properties using a variety of in situ dynamic tests. In this paper, we use ambient motions recorded in 27 reinforced concrete shear wall (RCSW) buildings in Montréal to examine how various empirical models to predict the natural periods of RCSW buildings compare to the periods measured in actual buildings under ambient loading conditions. We show that a model in which the fundamental period of RCSW buildings varies linearly with building height would be a significant improvement over the period equation proposed in the 2010 National Building Code of Canada. Models to predict the natural periods of the first two torsion modes and second sway modes are also presented, along with their uncertainty.

scholarly journals Evaluation of Stiffness and Dynamic Properties of a Mine Shaft Steelwork Structure through In Situ Tests and Numerical Simulations

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 664
Author(s):  
Jacek Jakubowski ◽  
Przemysław Fiołek
Keyword(s):  
Numerical Simulations ◽  
Dynamic Properties ◽  
Vertical Motion ◽  
Load Test ◽  
Mode Shapes ◽  
Dynamic Amplification Factor ◽  
In Situ Tests ◽  
Mine Shaft ◽  
Numerical Investigations

A mine shaft steelwork is a three-dimensional frame that directs the vertical motion of conveyances in mine shafts. Here, we conduct field and numerical investigations on the stiffness and dynamic properties of these structures. Based on the design documentation of the shaft, materials data, and site inspection, the steelwork’s finite element model, featuring material and geometric non-linearities, was developed in Abaqus. Static load tests of steelwork were carried out in an underground mine shaft. Numerical simulations reflecting the load test conditions showed strong agreement with the in situ measurements. The validated numerical model was used to assess the dynamic characteristics of the structure. Dynamic linear and non-linear analyses delivered the natural frequencies, mode shapes, and structural response to dynamic loads. The current practices and regulations regarding shaft steelwork design and maintenance do not account for the stiffness of guide-to-bunton connections and disregard dynamic factors. Our experimental and numerical investigations show that these connections provide considerable stiffness, which leads to the redistribution and reduction in bending moments and increased stiffness of the construction. The results also show a high dynamic amplification factor. The omission of these features implicates an incorrect assessment of the design loads and can lead to over- or under-sized structures and ultimately to shortened design working life or failure.

Experimental Study of Blade Vibration in Centrifugal Compressors

2011 ◽  
Author(s):  
Andrew H. Lerche ◽  
J. Jeffrey Moore ◽  
Timothy C. Allison
Keyword(s):  
High Cycle Fatigue ◽  
Axial Flow ◽  
Modal Testing ◽  
Mode Shapes ◽  
Cyclic Symmetry ◽  
Centrifugal Compressors ◽  
Compressor Blades ◽  
Blade Vibration ◽  
Phase Cancellation ◽  
Blade Failure

Blade vibration in turbomachinery is a common problem that can lead to blade failure by high cycle fatigue. Although much research has been performed on axial flow turbomachinery, little has been published for radial flow machines such as centrifugal compressors and radial inflow turbines. This work develops a test rig that measures the resonant vibration of centrifugal compressor blades. The blade vibrations are caused by the wakes coming from the inlet guide vanes. These vibrations are measured using blade mounted strain gauges during a rotating test. The total damping of the blade response from the rotating test is compared to the damping from the modal testing performed on the impeller. The mode shapes of the response and possible effects of mistuning are also discussed. The results show that mistuning can affect the phase cancellation which one would expect to see on a system with perfect cyclic symmetry.

Fast Characterization of Silicon Membrane Structures by Laser-Doppler Vibrometry

2007 ◽  
Vol 1052 ◽  
Author(s):  
Ronny Gerbach ◽  
Matthias Ebert ◽  
Joerg Bagdahn
Keyword(s):  
Dynamic Properties ◽  
Laser Doppler ◽  
Mode Shapes ◽  
Defect Structures ◽  
Silicon Membrane ◽  
Membrane Structures ◽  
Unknown Parameters ◽  
Laser Doppler Vibrometry ◽  
Resonant Frequencies ◽  
Micromechanical Structures

AbstractMicromechanical structures were investigated nondestructively via laser-Doppler-vibrometry to determine defect structures. Therefore, silicon membrane structures were characterized by their measured resonant frequencies and mode shapes. The influence of defects on the micromechanical structures is shown on the measured dynamic properties. Defect samples were indentified on the basis of the ratios of measured resonant frequencies and the quantified comparison of mode shapes without an identification of unknown parameters. The investigations showed that a fast determination of defect structures is possible by measured dynamic properties.

Seismic response for self-strained structures

1974 ◽  
Vol 64 (6) ◽  
pp. 1809-1824
Author(s):  
Mario Paz ◽  
Michael A. Cassaro ◽  
Steven N. Stewart
Keyword(s):  
Seismic Response ◽  
Ground Motion ◽  
Dynamic Properties ◽  
Equations Of Motion ◽  
The Self ◽  
Mode Shapes ◽  
Strain Effect ◽  
Structure Changes ◽  
Superposition Technique ◽  
Initial Strains

abstract The seismic response of multistory building and other structural systems is affected by the existence of self strains which may be induced by temperature gradients, mechanical actions, or prestraining. The fundamental dynamic properties such as natural frequencies and mode shapes are influenced by the presence of these strains. As a consequence, the response of the structure changes to the extent that the self strains change its dynamic characteristics and to the extent that these characteristics are relevant in the interaction of a particular structure with a given ground motion. This paper presents a detailed study of some simple structures such as beams and frames whose members are subjected to initial strains. The homogeneous differential equations of motion are expressed in terms of the stiffness, mass, and geometry matrices and a parameter accounting for the self-strain effect. The solution of the resulting eigenvalue problem is used to write the modal equations into which the desired ground motion is applied. The final response is obtained from the appropriate shock spectrum and the application of root-mean-square superposition technique. The disturbing action produced by the ground motion of the well known El Centro earthquake of 1940 is applied to several structures in which the amount of self-strain is varied as a parameter.

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