The authors propose the use of generic elements as a viable tool for parametric model based damage detection. The subject is divided into two related papers, and this paper is concerned with the ...requirements of the baseline model for damage detection, and the use of model updating to produce a validated finite element model of the undamaged structure. Two parameterisations are considered, based on the need to use the same parameterisation for subsequent damage detection. The novel aspect of this approach is the use of generic elements in damage detection where a preliminary updating exercise is required. The result is an updated model with physical meaning that may be used to detect and locate damage in a symmetric structure.
The Use of Modan 3D in Experimental Modal Analysis Schrötter, Martin; Huňady, Róbert; Trebuňa, František ...
Applied Mechanics and Materials,
12/2013, Volume:
486, Issue:
Experimental Stress Analysis 51
Journal Article
Peer reviewed
Experimental modal analysis is a relatively young part of dynamics, which deals with the vibration modes identification of machines or their parts. Its development has started since the beginning of ...the eighties, when the computers hardware equipment has improved and the fast Fourier transform (FFT) could be used for the results determination. Nowadays it provides an uncountable set of vibration analysis possibilities starting with conventional contact transducers of acceleration and ending with modern noncontact optical methods. In this contribution we mention the use of high-speed digital image correlation by experimental determination of mode shapes and modal frequencies. The aim of our work is to create a program application called Modan 3D enabling the performing of experimental modal analysis and operational modal analysis. In this paper the experimental modal analysis of a thin steel sample performed with Q-450 Dantec Dynamics is described. In Modan 3D the experiment data were processed and the vibration modes were determined. The reached results were verified by PULSE modulus specialized for mechanical vibration analysis.
In this paper, mechanical characteristics (Young’s modulus and shear modulus) of an adhesive are identified using modal based direct model updating method and experimental modal data. The results ...show that both Young’s and shear moduli of adhesive are frequency dependent. Also, it is demonstrated that the thickness and length of the adhesive-line have influence on these properties. All experiments and subsequent identifications are conducted both in bending and shear modes, and it has been shown that the shear modulus of adhesive is more sensitive to length and thickness variations. The repeatability and consistency of method is proved through repeating the process several times and with different adherends.
Modal analysis of plates has been an active research subject of engineering field. The plates are used for manufacturing many engineering structures such as in aerospace, mechanical, civil structures ...etc. This work attempts to present comprehensive comparison of modal analysis of square plate with free-free boundary condition. The first six natural frequencies of square plate with free-free boundary condition is first determined by analytical method. The modal analysis of plate is than solved by FEM using ANSYS 14.5 simulation. In this method, the first six natural frequencies of plate are determined. Then the experimental setup is developed to identify the first six natural frequencies of plate. All the methods of finding the first six fundamental frequencies are compared. During comparison it is observed that all the six fundamental frequencies obtained by different methods are close to each other. Hence, from this it is clear that the results of analytical, FEM (simulation) and experimental methods are in agreement with each other.
The design of civil engineering floors is increasingly being governed by their vibration serviceability performance. This trend is the result of advancements in design technologies offering designers ...greater flexibilities in realising more lightweight, longer span and more open-plan layouts. These floors are prone to excitation from human activities. The present research work looks at analytical studies of active vibration control on a case study floor prototype that has been specifically designed to be representative of a real office floor structure. Specifically, it looks at tuning fuzzy control gains with the aim of adapting them to measured structural responses under human excitation. Vibration mitigation performances are compared with those of a general velocity feedback controller, and these are found to be identical in these sets of studies. It is also found that slightly less control force is required for the fuzzy controller scheme at moderate to low response levels and as a result of the adaptive gain, at very low responses the control force is close to zero, which is a desirable control feature. There is also saturation in the peak gain with the fuzzy controller scheme, with this gain tending towards the optimal feedback gain of the direct velocity feedback (DVF) at high response levels for this fuzzy design.
Vibration techniques have been employed for detecting the presence and monitoring the progression of damage in structures. Pinpointing the location of damage is a more complicated and elaborate task. ...This paper presents modal analysis techniques for locating damage in a wooden wall structure by evaluating damage-sensitive parameters such as resonant pole shifts and mode shapes, residue and stiffness changes. Artificial damage (simulating termite degradation) was created in one of the walls of a specially constructed room. The wall was excited using an impact hammer and its frequency response measured using a laser vibrometer. Resonant poles (plotted in the s-plane) were used for identifying modes that are sensitive to damage, since not all modes are equally affected by the presence of damage. The damaged region was identified by visual comparison of the deformation mode shapes before and after damage. The modal residue and stiffness changes were also quantified for a better representation of the damage location.
Generally, agricultural tires have high and large cross-switch lugs to achieve optimal motion without slipping in a rice field. Therefore, when the agricultural machines run on normal roads, the ...vibration and noise caused by interaction between the tire lugs and the road surface are inevitable. In this study, a test equipment is manufactured to determine the motion of a rolling agricultural tire with ground contact and the characteristics of motion for rotational speed are investigated. Next, natural frequencies and natural modes of the tire are obtained by carrying out experimental modal analysis. By using the obtained results, the influence of vibration characteristics on the dynamic behavior of rolling tires are investigated.
A modal parameter identification software named as N-Broband is developed in VC++ platform. The software is suitable for EMA and OMA with broband identification feature. Meanwhile it also includes ...narrow band and selected band modal parameter identification methods. Correlation analysis between experiment and FEA can be performed in N-Broband. The validation of N-Broband is carried out by Test.Lab modal analysis software. The result coincides with Test.Lab very well, which indicates that the developed software can be used in modal analysis of real structure.
The singular value decomposition of the measured frequency response function matrix, as a very effective tool of experimental modal analysis is used over the last twenty-five years. The complex mode ...indication function has become a common numerical tool in processing experimental data. There are many references on the development of complex mode indication function including the enhanced mode indication function and its use together with the enhanced frequency response function to form spatial domain modal parameter estimation methods. Another amendment of the enhanced mode indicator function method is the extension of the single degree-of-freedom aspects of the complex mode indication function method to include a limited number of modes. In the paper, methods for estimation of damped eigen frequencies, modal damping and mode shapes are presented that are based on singular value decomposition of frequency response function matrix. It is shown how to obtain phase information for the complex mode indication function, in order to use the standard single degree-of-freedom modal parameter estimation methods. New aggregated frequency response function is introduced. A leastsquares approximation will be presented for eliminating the error caused by frequency discretization. Analytical models and examples taken from vehicle industry are also used to demonstrate applications of the aggregated frequency response function method and estimation of modal damping. Keywords: complex mode indication function; damping estimate; experimental modal analysis; frequency response function matrix; singular values decomposition Dekompozicija singularnih vrijednosti izmjerene matrice funkcije frekventnog odziva se, kao vrlo ucinkovit alat eksperimentalne modalne analize, koristi zadnjih dvadeset i pet godina. Funkcija indikacije kompleksnog moda postala je uobicajeni numericki alat u obradi eksperimentalnih podataka. Veliki je broj referenci o razvoju funkcije indikacije kompleksnog moda ukljucujuci poboljsanu funkciju indikacije moda i njenu primjenu skupa s poboljsanom funkcijom frekventnog odgovora u razvoju metoda procjene modalnog parametra prostornog podrucja. Jos jednu nadopunu poboljsanoj metodi funkcije indikatora moda predstavlja prosirenje aspekata jednog stupnja slobode metode indikacije funkcije kompleksnog moda na ograniceni broj modova. U radu su predstavljene metode za procjenu prigusenih eigen frekvencija, modalnog prigusenja i oblika modova, zasnovane na dekompoziciji singularne vrijednosti matrice funkcije frekventnog odgovora. Pokazano je kako dobiti faznu informaciju za funkciju indikacije kompleksnog moda u svrhu primjene standardnih metoda procjene modalnim parametrom s jednim stupnjem slobode. Uvedena je novo dobivena funkcija frekventnog odziva. Pokazat ce se aproksimacija najmanjih kvadrata za eliminiranje greske izazvane diskretizacijom frekvencije. Koristeni su tako?er analiticki modeli i primjeri iz industrije vozila u svrhu demonstracije primjene dobivene metode funkcije frekventnog odziva i procjene modalnog prigusenja. Kljucne rijeci: dekompozicija singularnih vrijednosti; eksperimentalna modalna analiza; funkcija indikacije kompleksnog moda; matrica funkcije frekventnog odziva; procjena prigusenja
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