Mass normalized mode shapes using impact excitation and continuous-scan laser Doppler vibrometry

2008 ◽  
Author(s):  
Matthew S. Allen ◽  
Michael W. Sracic
Keyword(s):  
Laser Doppler ◽  
Impact Excitation ◽  
Mode Shapes ◽  
Laser Doppler Vibrometry

Two Algorithms for Mass Normalizing Mode Shapes From Impact Excited Continuous-Scan Laser Doppler Vibrometry

2012 ◽  
Vol 134 (2) ◽  
Author(s):  
Shifei Yang ◽  
Michael W. Sracic ◽  
Matthew S. Allen
Keyword(s):  
Time Synchronization ◽  
Small Mass ◽  
Laser Doppler ◽  
Impact Excitation ◽  
Mode Shapes ◽  
Laser Doppler Vibrometry ◽  
Structural Modifications ◽  
Synchronization Errors ◽  
Modal Model ◽  
Free Beam

Continuous-scan laser Doppler vibrometry (CSLDV), a concept where a vibrometer measures the motion of a structure as the laser measurement point sweeps over the structure, has proven to be an effective method for rapidly obtaining mode shape measurements with very high spatial detail using a completely non-contact approach. Existing CSLDV methods obtain only the operating shapes or arbitrarily scaled modes of a structure, but the mass-normalized modes are sought in many applications; for example, when the experimental modal model is to be used for substructuring predictions or to predict the effect of structural modifications. This paper extends an approach based on impact excitation and CSLDV, presenting a new least squares algorithm that can be used to estimate the mass-normalized modes of a structure from CSLDV measurements. Two formulations are derived: one based on real-modes that is appropriate when the structure is proportionally damped and a second that accommodates a complex-mode description. The latter approach also gives the algorithm further latitude to accommodate time-synchronization errors in the data acquisition system. The method is demonstrated on a free-free beam, where both CSLDV and a conventional test using an accelerometer and a roving-hammer are used to find its first seven mass normalized modes. The scale factors produced by both methods are found to agree with a tuned analytical model for the beam to within about ten percent. The results are further verified by attaching a small mass to the beam and using the model to predict the change in the structure’s natural frequencies and mode shapes due to the added mass.

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.

scholarly journals Correction of Oblique-Angle Oscillation for Laser Doppler Vibrometry

2019 ◽  
Vol 21 (4) ◽  
pp. 75-80
Author(s):  
Vladimir Kindl ◽  
Tomas Kavalir ◽  
Jiri Sika ◽  
Michal Krizek
Keyword(s):  
Natural Frequencies ◽  
Correction Method ◽  
Laser Doppler ◽  
Mode Shapes ◽  
Reference Plane ◽  
Oblique Angle ◽  
Voltage Transformer ◽  
Laser Doppler Vibrometry ◽  
High Voltage Transformer ◽  
Accelerometer Measurement

The paper proposes a correction method of the oblique-angle vibration for laser doppler vibrometry. It briefly discusses the key mathematical approach considering the surface of the analysed object to be a reference plane and gives a practical example of the method proper application. The proposed correction method is practically verified by laboratory measurement of natural frequencies and mode shapes for vibrations of high voltage transformer housing. The results are further compared to equivalent accelerometer measurement.

Facial Muscle Activity: High-Sensitivity Noncontact Measurement Using Laser Doppler Vibrometry

2021 ◽  
Vol 70 ◽  
pp. 1-10
Author(s):  
Sara Casaccia ◽  
Erik J. Sirevaag ◽  
Mark G. Frank ◽  
Joseph A. O'Sullivan ◽  
Lorenzo Scalise ◽  
...  
Keyword(s):  
Muscle Activity ◽  
High Sensitivity ◽  
Laser Doppler ◽  
Facial Muscle ◽  
Laser Doppler Vibrometry ◽  
Noncontact Measurement

Two-Photon Polymerization Lithography and Laser Doppler Vibrometry of a SU-8-Based Suspended Microchannel Resonator

2015 ◽  
Vol 24 (4) ◽  
pp. 1038-1042 ◽  
Author(s):  
Celso Accoto ◽  
Antonio Qualtieri ◽  
Ferruccio Pisanello ◽  
Carlo Ricciardi ◽  
Candido Fabrizio Pirri ◽  
...  
Keyword(s):  
Laser Doppler ◽  
Laser Doppler Vibrometry ◽  
Two Photon ◽  
Two Photon Polymerization

Use of Laser Doppler Vibrometry for Measuring Flow-Induced Vibration of a Thermowell in a Pipe Flow

2021 ◽  
Author(s):  
Sejong Chun ◽  
Sibok Lee ◽  
Hyewon Yoon
Keyword(s):  
Strain Rate ◽  
Laser Doppler ◽  
Vortex Street ◽  
Rate Measurement ◽  
Flow Induced Vibration ◽  
Laser Doppler Vibrometry ◽  
Karman Vortex Street ◽  
Kármán Vortex Street ◽  
Karman Vortex ◽  
Strain Rate Measurement

Abstract Thermowells with helical strakes are becoming promising to prevent them from fatigue fracture by Kármán vortex street. Many studies suggest various kinds of measurement techniques, including strain rate measurement, acceleration measurement, and high-speed visualization to evaluate the role of Kármán vortex street to the flow-induced vibration. Nevertheless, use of laser Doppler vibrometry has not yet been reported in the literature. This study compared the tip deflection of a thermowell due to the flow-induced vibration by using the laser Doppler vibrometry and the strain rate measurement. The laser Doppler vibrometry could measure the tip deflection directly. On the other hand, the strain rate measurement had to convert the strain rate into the tip deflection through the Euler-Bernoulli beam theory. Measurement equivalence between the laser Doppler vibrometry and the strain rate measurement was discussed with the results of tip deflections of the thermowell.

Application of laser Doppler vibrometry for ultrasonic velocity assessment in a composite panel with defect

2018 ◽  
Vol 184 ◽  
pp. 1030-1039 ◽  
Author(s):  
L. Maio ◽  
F. Ricci ◽  
V. Memmolo ◽  
E. Monaco ◽  
N.D. Boffa
Keyword(s):  
Ultrasonic Velocity ◽  
Laser Doppler ◽  
Composite Panel ◽  
Laser Doppler Vibrometry

scholarly journals Chemical expansion of praseodymium-cerium oxide films at high temperatures by laser doppler vibrometry

2018 ◽  
Vol 319 ◽  
pp. 61-67 ◽  
Author(s):  
Silja Schmidtchen ◽  
Holger Fritze ◽  
Sean Bishop ◽  
Di Chen ◽  
Harry L. Tuller
Keyword(s):  
Cerium Oxide ◽  
High Temperatures ◽  
Oxide Films ◽  
Laser Doppler ◽  
Laser Doppler Vibrometry ◽  
Chemical Expansion
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