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About 7,015 papers for “Modal testing”
D. J. Ewins · 2007
This chapter contains sections titled: Introduction Theoreticalbasis Objectives and Applications of Experimental Modal Analysis Planning a Modal Test Measurement Techniques Parameter Extraction Techniques References
Cited by 5
Roy R. Craig · NASA STI Repository (National Aeronautics and Space Administration) · 1986
A component mode synthesis method for damped structures was developed and modal test methods were explored which could be employed to determine the relevant parameters required by the component mode synthesis method. Research was conducted on the following topics: (1) Development of a generalized time-domain component mode synthesis technique for damped systems; (2) Development of a frequency-domain component mode synthesis method for damped systems; and (3) Development of a system identification algorithm applicable to general damped systems. Abstracts are presented of the major publications which have been previously issued on these topics.
Cited by 0Open access
Emiliano Mucchi · Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science · 2015
The conventional modal testing (referred to as displacement modal testing (DMT)) is based on measurement of displacement, velocity or acceleration as well as excitation force. Though there exits an enormous literature with regard to DMT, on the contrary, a few papers address modal testing based on strain gauges or strain sensor (referred to as strain modal testing (SMT)). The main reason for this scenario is due to practical problems in the use of strain gauges as calibration procedure, ground loop sensitivity are not adequate at high frequency, bonding quality. In this work, a novel piezoelectric strain sensor is used for SMT. In this study it is demonstrated that this sensor overcomes the practical drawbacks related to the use of strain gauges. Thus, SMT based on piezoelectric strain sensors can be a valid alternative to DMT which is usually based on accelerometers. Comparisons between the modal testing results concerning brackets with different constraint conditions using both accelerometers and strain sensors are given in terms of modal parameters, highlighting their pros and cons.
Cited by 6Open access
Craig, R. R., Jr., Blair, M. · NASA STI Repository (National Aeronautics and Space Administration)
A review of several modal testing techniques is made, along with brief discussions of their advantages and limitations. A new technique is presented which overcomes many of the previous limitations. Several simulated experiments are included to verify the validity and accuracy of the new method. Conclusions are drawn from the simulation studies and recommendations for further work are presented. The complete computer code configured for the simulation study is presented.
Cited by 0Open access
Aerospace Testing International · 2020
Modal testing is a very useful technique for verifying and understanding the dynamic behavior of complex structures
Cited by 0
Amanda Garner · Zenodo (CERN European Organization for Nuclear Research) · 2024
Cited by 0Open access
D. J. Ewins · 1990
Cited by 1
Tobias Kristensson · Lund University Publications Student Papers (Lund University) · 2014
Bridges have been built around the world for at least 3000 years and have made it possible for man to travel over obstacles like valleys and rivers, which has contributed to the rapidly growing infrastructure we have today. Efforts made to save materials and reduce production costs have led to lighter and slender structures, which in turn can cause dynamic problems where the bridge is sensitive to vibrations. Vibrations from traffic, wind, wave and seismic loads may cause major problems for a lightweight design as the risk of fatigue of structural elements is very large. Therefore, it is important to always study the dynamic parameters: natural frequencies, mode shapes and damping ratios using both measurement techniques and computer models. The classical measuring method is called Experimental Modal Analysis (EMA), where both the applied force on the structure and the structure's response are measured. The force can be generated by either an impact hammer or a shaker and recorded using an attached force sensor. The structure’s response is then measured with accelerometers. Since EMA is difficult to perform on larger structures and is sensitive to disturbing vibrations, it has become more common to use so called Operational Modal Analysis (OMA). The OMA technique is based on measuring only the structure’s response from random unknown vibrations. This is very advantageous when performing measurements on for example a bridge, because it can be fully operational during the measurements without disturbing the traffic. The aim of this thesis is to study and compare different types of measurement methods used to identify structures’ dynamic parameters and to compare them with numerical calculations. To facilitate the comparisons between the methods and to avoid environmental interference, measurements were carried out in a lab on a well-defined steel structure. A computer model of the structure was made by using the finite element software ABAQUS, where both the natural frequencies and the mode shapes were predicted. Measurements were performed by using equipment and software from Brüel & Kjær. Measured and calculated natural frequencies and mode shapes of the steel structure have good compliance for all of the different measurement methods. The modal damping was difficult to estimate since it varied a lot between measurements. The measurement with the impact hammer was quick and flexible to perform since the procedure does not require much equipment. The shaker measurement required more equipment but gave much more accurate and clearer results than the measurement with the impact hammer. The results obtained by the OMA were very similar to the results from the EMA with the shaker. The OMA technique has proven to work well even with poor time signals that are far from ideal white noise. The major drawback with the OMA technique is that the measurements require long time signals, but with today’s low storage costs and powerful CPUs that process large amounts of data, this is no longer an issue. The conclusion is that the OMA technique seems to be the most appropriate method to use for measurements on large structures such as towers and bridges that are difficult to excite artificially. The EMA technique could possibly be used for lighter and smaller structures such as footbridges made of wood or steel.
Cited by 0Open access
Ashory, M.R. · OpenGrey (Institut de l'Information Scientifique et Technique) · 1999
Cited by 6Open access
Amanda Garner · Zenodo (CERN European Organization for Nuclear Research) · 2024
Cited by 0Open access
Ken Shye, Charles VanKarsen, Mark Richardson · 1987
With the increased availability of multi-channel FFT analyzers, more emphasis has been placed in recent years on the development of new methods for modal testing using multiple references. In the case of shaker testing, this means the use of two or more shakers. In the case of hammer (impact) testing, this means the use of two or more reference transducers. This paper presents the results of our recent experiences in both the collection of FRF data, and the curve fitting of it to obtain the modal parameters of a structure. The key difference between these results and those of a more traditional mo dal test is that multiple rows or columns of the structure's FRF matrix are not only collected simultaneously, but are also curve fit in a simultaneous manner. In this paper, the advantages offered by multiple reference modal testing and curve fitting are addressed. The theory and usefulness of a frequency domain curve fitting algorithm are extended to account for the effects of “out-of-band ” modes, which always occur in practical applications. Verifications of the method and its implementation using both analytical and experimental FRF data are also presented in the paper.
Cited by 2
Christian Brecher, Stephan Bäumler, Mark Wissmann et al. · River Publishers eBooks · 2025
Modal testing is performed for the characterization of structure dynamics, diagnostics, and condition monitoring. Modal analysis is also used for the detection of sources of vibrations, design optimizations and as comparison data to improve computation results. For open surfaces in the automotive and aerospace industries, the modal testing is often performed using scanning laser vibrometers. In the case of partially closed structures such as machine tools, vibration measurement is typically conducted using three-axial accelerometers. This paper presents a novel approach to performing modal analyses using a single laser tracking-interferometer. First, tracking-interferometers are introduced - followed by an explanation of the modal testing using this device. A holistic measurement method for modal testing is introduced and the individual functionalities are explained as follows. The principle for three-dimensional dynamic measurement is discussed and the performance of the tracking-interferometer measurements in beam direction and in lateral directions are benchmarked against alternative measurement methods. Three-dimensional measurements are presented, including the coordinate transformation and modal analysis results of a machining center. Dynamic measurements and tracking-interferometer-aided geometric model design are presented along with the multiangulation-based position detection for the interferometer head.
Cited by 0
J.-C. CHEN · 25th Structures, Structural Dynamics and Materials Conference · 1984
Modal tests are playing an increasingly important role in structural dynamics efforts which are in need of analytical model verification or trouble shootings. In the meantime, the existing modal testing methods are undergoing great changes as well as new methods are being created. Although devoted advocates of each method can be found to argue the relative advantages and disadvantages, the general superiority, if any, of one or the other is not yet evident. The Galileo spacecraft, a realistic, complex structural system, will be used as a test article for performing modal tests by various methods. The results will be used to evaluate the relative merits of the various modal testing methods.
Cited by 13
Mohamad Asyraf, Ahmad Bustamang · UMP Institutional Repository (Universiti Malaysia Pahang) · 2013
Low surface finish, low accuracy and reduction in tool life were happening towards the machining product and cutting tools during high speedmachining (HSM) process. The defects were happening because of chatter effect or resonance of the whole machine system. A study was conducted to study and optimizing between tool-life and machining speed operation for controlling these chatter effect by using an electromagnetic actuator (EMA) anon-contacting excitation force. The objective of this project is to determine the modal analysis of electromagnetic actuator for non-contact modal testing. The method use for determining modal analysis of electromagnetic actuator by modal testing was by electromagnetic shaker. The modal analysis of electromagnetic actuator was determined by comparison result of computational and experimental modal analysis methods. The electromagnetic actuator was analysed in two types that were structured with and without electromagnetic core for each of modal analysis methods. ANSYS 14.0 was used as the finite element analysis (FEA) software for generating modal analysis of the structure and ME‟Scope software used for determining the modal analysis based on the experimental method. The result of these modal analyses was supported by result of operational deflection shape (ODS) for each type of assembling the structure. The result of modal analysis of electromagnetic actuator was determined based on the similarity data collected between computational and experimental methods. The operational deflection shape determines the deflection of the structure under certain operation condition. Based on modal analysis and operational deflection shape, the structure of electromagnetic actuator can be used for the experiment with high frequency excitation.
Cited by 0Open access
Brian Schwarz, Mark Richardson, Pete Avitabile · 2014
The Complex Mode Indicator Function (CMIF) was origi-nally proposed as a method for improving modal parameter estimation. CMIF utilizes singular value decomposition (SVD) on a set of FRFs as a mechanism for extracting pa-rameters. The Multivariate Mode Indicator Function (MMIF) was originally proposed as a method for force appropriation to excite normal modes. MMIF utilizes an eigenvalue solution method on a set of FRFs to isolate modes. Both CMIF & MMIF also have the ability to indicate the presence of closely coupled modes or repeated roots in a structure. Both methods can be used as tools for identifying a minimum set of reference DOFs for performing a modal test. Using a small set of potential reference FRFs and their cross measurements, either CMIF or MMIF can be used to deter-mine the minimum number of references required to ade-quately excite all the desired modes in a frequency band. This technique has previously been demonstrated to provide reasonable results on several test structures. In this paper, the previous work is extended to provide a testing strategy for determining the number and locations of optimum refer-ences for modal testing. Examples are provided to demon-strate its use.
Cited by 1
Anders Brandt · 2023
Cited by 0Open access
James Brownjohn, Aleksandar Pavić, E. Peter Carden et al. · Open Research Exeter (University of Exeter) · 2006
As part of a continuing investigation on the Tamar Suspension Bridge, vibration measurements on the Tamar Bridge were conducted on two occasions. Using three sensors, the first measurement (in 2005) identified possible deck vibration modes and characterised the performance of new additional stay cables. The second measurement, in 2006, used 16 accelerometers to characterise the motion of main and side spans as well as the towers, by means of identification of a full set of modal parameters (except modal masses). The procedures for these two brief operational modal tests are described with the significance of some of the findings in relation to the 'structural mechanisms' of the bridge.
Cited by 15Open access
Mark F. Green, David Cebon · Cambridge University Engineering Department Publications Database · 1993
Cited by 6
Sam R. Ibrahim · Journal of Spacecraft and Rockets · 1978
Covers advancements in spacecraft and tactical and strategic missile systems, including subsystem design and application, mission design and analysis, materials and structures, developments in space sciences, space processing and manufacturing, space operations, and applications of space technologies to other fields.
Cited by 88
Janet Wolfson, Jason R. Foley, Lashaun M. Watkins et al. · Conference proceedings of the Society for Experimental Mechanics · 2011
Cited by 2