Full Field Response Prediction Technique in Dynamic Design

2010 ◽  
Vol 34-35 ◽  
pp. 1635-1639
Author(s):  
Qian Jin Wang ◽  
Wen Zhong Qu ◽  
Li Xiao
Keyword(s):  
Response Prediction ◽  
Mode Shapes ◽  
Vibration Test ◽  
Limited Data ◽  
Dynamic Design ◽  
Full Field ◽  
Field Response ◽  
Prediction Technique ◽  
Sufficient Set ◽  
Equivalent Reduction

Structure vibration test plays an important role in dynamic design, but in most cases the experimental data we get is always limited and insufficient for succeeding upgrade and optimization. The response prediction technique presented in this paper is the corresponding technique to deduce the full field response from the limited data obtained by simple vibration test instead of conducting the full-size test. SEREP (System Equivalent Reduction-Expansion Process) method was used to conduct the prediction research and the procedure was elaborated in detail theoretically first, then several simulations were carried on to demonstrate the prediction procedure, inspect the accuracy under various loads and investigate the factors which may influence the accuracy including the number of modes used in the prediction, the noise, and the measured points. Results show that this method has excellent accuracy and good adaptability to various loads as long as a sufficient set of orthogonal mode shapes participate in the prediction procedure.

An Approach to Approximate the Full Strain Field of Turbofan Blades During Operation

2018 ◽  
Author(s):  
Gen Fu ◽  
Alexandrina Untaroiu ◽  
Walter O’Brien
Keyword(s):  
Numerical Model ◽  
Cantilever Beam ◽  
Strain Field ◽  
Measured Data ◽  
Mode Shapes ◽  
Beam Model ◽  
Reference Solution ◽  
Full Field ◽  
Field Response ◽  
Critical Locations

The measurement of the aeromechanical response of the fan blades is important to quantifying their integrity. The accurate knowledge of the response at critical locations of the structure is crucial when assessing the structural condition. A reliable and low cost measuring technique is necessary. Currently, sensors can only provide the measured data at several discrete points. A significant number of sensors may be required to fully characterize the aeromechanical response of the blades. However, the amount of instrumentation that can be placed on the structure is limited due to data acquisition system limitations, instrumentation accessibility, and the effect of the instrumentation on the measured response. From a practical stand point, it is not possible to place sensors at all the critical locations for different excitations. Therefore, development of an approach that derives the full strain field response based on a limited set of measured data is required. In this study, the traditional model reduction method is used to expand the full strain field response of the structure by using a set of discrete measured data. Two computational models are developed and used to verify the expansion approach. The solution of the numerical model is chosen as the reference solution. In addition, the numerical model also provides the mode shapes of the structure. In the expansion approach, this information is used to develop the algorithm. First, a cantilever beam model is created. The influences of the sensor location, number of sensors and the number of modes included are analyzed using this cantilever beam model. The expanded full field response data is compared with the reference solution to evaluate the expansion procedure. The rotor 67 blade model is then used to test the expansion method. The results show that the expanded full field data is in good agreement with the calculated data. The expansion algorithm can be used for the full field strain by using the limited sets of strain data.

Straked Riser Design With VIVA

2010 ◽  
Author(s):  
Dhyanjyoti Deka ◽  
Paul R. Hays ◽  
Kamaldev Raghavan ◽  
Mike Campbell
Keyword(s):  
Traveling Waves ◽  
Oil And Gas ◽  
Cross Flow ◽  
Oil And Gas Industry ◽  
Response Prediction ◽  
Design Tool ◽  
Mode Shapes ◽  
Fe Model ◽  
Viv Suppression ◽  
Modal Solution

VIVA is a vortex induced vibration (VIV) analysis software that to date has not been widely used as a design tool in the offshore oil and gas industry. VIVA employs a hydrodynamic database that has been benchmarked and calibrated against test data [1]. It offers relatively few input variables reducing the risk of user induced variability of results [2]. In addition to cross flow current induced standing wave vibration, VIVA has the capability of predicting traveling waves on a subsea riser, or a combination of standing and traveling waves. Riser boundary conditions including fixed, pinned, flex joint or SCR seabed interaction can be modeled using springs and dashpots. VIVA calculates riser natural frequencies and mode shapes and also has the flexibility to import external modal solutions. In this paper, the applicability of VIVA for the design of straked steel catenary risers (SCR) and top tensioned risers (TTR) is explored. The use of linear and rotational springs provided by VIVA to model SCR soil interaction and flex joint articulation is evaluated. Comparisons of the VIV fatigue damage output with internal and external modal solution is presented in this paper. This paper includes validation of the VIVA generated modal solution by comparing the modal frequencies and curvatures against a finite element (FE) model of the risers. Fatigue life is calculated using long term Gulf of Mexico (GoM) currents and is compared against the industry standard software SHEAR7. Three different lift curve selections in SHEAR7 are used for this comparison. The differences in riser response prediction by the two software tools are discussed in detail. The sensitivity of the VIVA predicted riser response to the absence of VIV suppression devices is presented in this paper. The riser VIV response with and without external FE generated modal input is compared and the relative merits of the two modeling approaches are discussed. Finally, the recommended approach for VIVA usage for SCR and TTR design is given.

Free Vibration Test for Damping Characteristics of Hybrid Polyester Matrix Composite with Carbon Particles

2016 ◽  
Vol 11 ◽  
pp. 1-6
Author(s):  
K. Karthik ◽  
R. Rohith Renish ◽  
I. Irfan Ahmed ◽  
T. Niruban Projoth
Keyword(s):  
Free Vibration ◽  
Hybrid Composites ◽  
Glass Fibers ◽  
Damping Ratio ◽  
Mode Shapes ◽  
Vibration Test ◽  
Engineering Structures ◽  
Carbon Filler ◽  
Damping Characteristics ◽  
Free Vibration Test

In this research aims to study the damping characteristics of hybrid polymer composite, which can be used in engineering structures and in many other applications. Hybrid composites are namely Glass fiber and carbon filler reinforced with polyester and epoxy matrix have been prepared by vacuum bag molding fabrication technique. Then the free vibration test were conducted using FFT analyzer with Lab VIEW software. The damping ratio and natural frequency were investigated for fabricated composites. Then through ANSYS, the mode shapes and natural frequencies were determined and the results were compared with experimental results. The damping ratio increases with increased volume fractions of E-glass fibers for both the types of polymer composites. Vibrations are concerned to large structures such as aircraft, as well as small structures such as electronic equipments.

Vibration Modal Analysis of Involve Gear with Asymmetric Tooth Profile and Double Pressure Angles

2011 ◽  
Vol 418-420 ◽  
pp. 1748-1751
Author(s):  
Wei Li ◽  
Ning Liu ◽  
Ning Li ◽  
Yan Jun Liu ◽  
Liang Ma
Keyword(s):  
Modal Analysis ◽  
3D Model ◽  
Natural Frequencies ◽  
Reference Value ◽  
Tooth Profile ◽  
Mode Shapes ◽  
Ansys Software ◽  
Dynamic Design ◽  
Dynamic Performances ◽  
Vibration Modal

The 3D model of gear with asymmetric profile and double pressure angles is built by the autodesk inventor software. It is imported and analyzed by the ANSYS software. Then each order natural frequencies and mode shapes are obtained. So resonance and harmful mode shapes can be avoided, and dynamic performances of gear with asymmetric profile and double pressure angles is improved. This paper has a certain reference value for the dynamic design of other types of gears.

scholarly journals Experimental Measurement of Mode Shapes and Frequencies for Vibration of Plates by Optical Interferometry Method

2000 ◽  
Vol 123 (2) ◽  
pp. 276-280 ◽  
Author(s):  
Chi-Hung Huang ◽  
Chien-Ching Ma
Keyword(s):  
Video Recording ◽  
Field Configuration ◽  
Mode Shapes ◽  
Resonant Frequencies ◽  
Full Field ◽  
Out Of Plane ◽  
Vibrating Plates ◽  
Optical Reconstruction ◽  
Fringe Patterns ◽  
Plane Displacement

Most of the published literature for vibration mode shapes of plates is concerned with analytical and numerical results. There are only very few experimental results available for the full field configuration of mode shapes for vibrating plates. In this study, an optical system called the AF-ESPI method with the out-of-plane displacement measurement is employed to investigate experimentally the vibration behavior of square isotropic plates with different boundary conditions. The edges of the plates may either be clamped or free. As compared with the film recording and optical reconstruction procedures used for holographic interferometry, the interferometric fringes of AF-ESPI are produced instantly by a video recording system. Based on the fact that clear fringe patterns will appear only at resonant frequencies, both resonant frequencies and corresponding mode shapes can be obtained experimentally at the same time by the proposed AF-ESPI method. Excellent quality of the interferometric fringe patterns for the mode shapes is demonstrated.

Image Analysis for Full-Field Displacement/Strain Data: Method and Applications

2011 ◽  
Vol 70 ◽  
pp. 39-44 ◽  
Author(s):  
Wei Zhuo Wang ◽  
John E. Mottershead ◽  
Christopher M Sebastian ◽  
Eann A Patterson ◽  
Thorsten Siebert ◽  
...  
Keyword(s):  
Image Analysis ◽  
Image Features ◽  
Kernel Functions ◽  
Orthogonal Basis ◽  
Image Correlation ◽  
Mode Shapes ◽  
Essential Information ◽  
Full Field ◽  
Field Displacement ◽  
Strain Data

Recent advances in measurement techniques, including digital image correlation, automated photoelasticity, electronic speckle pattern interferometry and thermoelastic stress analysis, permit full-field maps of displacement or strain to be obtained easily. They provide large volumes of mostly redundant data, which should be condensed to the essential information to permit straightforward processes such as validations of computational models or damage assessments. A way to do this is by image processing, an important aspect of which is the definition of an orthogonal basis (orthogonal kernel functions). Generally, this is problem dependent and requires some skill from the analyst if the number of image features (the coefficients of the orthogonal basis) is to be restricted to a suitably small number. Advantage may be taken of patterns of symmetry, for example cyclically symmetric patterns are well-suited to treatment by Zernike polynomials and rectangular patterns are well-suited to treatment by Fourier series. The Zernike and Fourier kernels are continuous polynomials with orthogonality properties that require integration and must be discretised. The discrete Tchebichef polynomials are ideal for the treatment of full-field information at multiple discrete data points. In many cases the data field is localised around a particular feature, such as local strain around a hole in a tension-test specimen. In this case, the polynomial basis should similarly be localised by various forms of scaling – this requires the application of the Gram-Schmidt procedure to maintain orthogonality. The image features (sometimes called shape features) are meaningful and may be used to identify particular patterns in the data – e.g. for detecting cracks or other forms of damage. When assembled in a feature vector, the distance between feature vectors from measured and numerical results are useful for refining numerical models. In this paper the principles of image analysis, as applied to full-field displacement/strain data are explained and experimental examples are used to illustrate the practical usefulness of the method. The applications include (i) vibration mode shapes of laminated honeycomb structures and, (ii) strain in an aluminium plate with a central hole in tension.

Efficiency of grey wolf optimization algorithm for damage detection of skeletal structures via expanded mode shapes

2020 ◽  
Vol 23 (13) ◽  
pp. 2850-2865 ◽  
Author(s):  
Parsa Ghannadi ◽  
Seyed Sina Kourehli ◽  
Mohammad Noori ◽  
Wael A Altabey
Keyword(s):  
Objective Function ◽  
Damage Identification ◽  
Optimization Techniques ◽  
Mode Shapes ◽  
Grey Wolf ◽  
Objective Functions ◽  
Expansion Process ◽  
Grey Wolf Optimization ◽  
Skeletal Structures ◽  
Equivalent Reduction

Vibration-based structural damage identification through optimization techniques has become an interesting research topic in recent years. Dynamic characteristics such as frequencies and mode shapes are used to construct the objective function. The objective functions based on only frequencies are not very sensitive to damage in large structures. However, objective functions based on both mode shapes and frequencies are very effective. In real measurement condition, the number of installed sensors is limited, and there are no economic reasons for measuring the mode shapes at all degrees of freedom. In this kind of circumstances, mode expansion methods are used to address the incompleteness of mode shapes. In this article, the system equivalent reduction and expansion process is applied to determine the unmeasured mode shapes. Two experimental examples including a cantilever beam and a truss tower are investigated to show system equivalent reduction and expansion process’ efficiency in estimating unmeasured mode shapes. The results show that the technique used for expansion is influential. Damage identification is formulated as an optimization problem, and the residual force vector based on expanded mode shapes is considered as an objective function. In order to minimize the objective function, grey wolf optimization and Harris hawks optimization are used. Numerical studies on a 56-bar dome space truss and experimental validation on a steel frame are performed to demonstrate the efficiency of the developed approach. Both numerical and experimental results indicate that the combination of the grey wolf optimization and expanded mode shapes with system equivalent reduction and expansion process can provide a reliable approach for determining the severities and locations of damage of skeletal structures when it compares with those obtained by Harris hawks optimization.

Dynamic characteristics evaluation of Masjed Soleiman Dam using in situ dynamic tests

2006 ◽  
Vol 43 (10) ◽  
pp. 997-1014 ◽  
Author(s):  
Mohammad Kazem Jafari ◽  
Mohammad Davoodi
Keyword(s):  
Dynamic Characteristics ◽  
Ambient Vibration ◽  
Mode Shapes ◽  
Vibration Test ◽  
Embankment Dam ◽  
Reservoir Water ◽  
Ambient Vibration Test ◽  
Reservoir Water Level ◽  
Foundation Model ◽  
Comparison Of The Results

The responses to forced vibrations, ambient vibrations, and large explosives were measured for Masjed Soleiman Dam, the highest embankment dam in Iran. Based on the results of these tests, the first 23 modal frequencies of the dam were measured and the related mode shapes for the first 16 modes were identified. A modal analysis of the dam body was also performed. The effects of reservoir water level variation, the rigidity and flexibility of the foundation and abutments and their depths and inertial properties, and the effect of material properties on the dynamic characteristics of the dam body were investigated, and the first eight modes of the dam body were identified. A comparison of the results of the numerical analysis with those from the tests indicates the best fit in lower modes occurs when the complete mass foundation is considered, whereas in higher modes the massless foundation model is a better fit.Key words: embankment dam, forced vibration test, ambient vibration test, explosion, modal properties.

scholarly journals Identification, Model Updating, and Response Prediction of an Instrumented 15-Story Steel-Frame Building

2006 ◽  
Vol 22 (3) ◽  
pp. 781-802 ◽  
Author(s):  
Derek Skolnik ◽  
Ying Lei ◽  
Eunjong Yu ◽  
John W. Wallace
Keyword(s):  
Structural Damage ◽  
Model Updating ◽  
Three Dimensional ◽  
Response Prediction ◽  
Element Model ◽  
Ambient Vibration ◽  
Mode Shapes ◽  
Northridge Earthquake ◽  
Vibration Data ◽  
Modal Properties

Identification of the modal properties of the UCLA Factor Building, a 15-story steel moment-resisting frame, is performed using low-amplitude earthquake and ambient vibration data. The numerical algorithm for subspace state-space system identification is employed to identify the structural frequencies, damping ratios, and mode shapes corresponding to the first nine modes. The frequencies and mode shapes identified based on the data recorded during the 2004 Parkfield earthquake ( Mw=6.0) are used to update a three-dimensional finite element model of the building to improve correlation between analytical and identified modal properties and responses. A linear dynamic analysis of the updated model excited by the 1994 Northridge earthquake is performed to assess the likelihood of structural damage.

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