Topic
Laser Doppler vibrometer
About: Laser Doppler vibrometer is a research topic. Over the lifetime, 6319 publications have been published within this topic receiving 76068 citations.
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TL;DR: The study shows that the presence of simulated damage in a steel connection can be detected by tracking the modal phase difference and by quantify- ing the additional stiffness and damping.
Abstract: A system that uses ambient vibration and two laser Doppler vibrometer (LDV) is developed for noncontact operational modal analysis of structural members. The system employs natural excitation tech- nique (NExT) to generate the cross-correlation functions from laser signals, and the eigensystem realization al- gorithm (ERA) to identify modal parameters of struc- tural members. To facilitate simultaneous modal identifi- cation, time-synchronization technique and construction of cross-correlation functions from ambient response of laser signals are proposed. Performance of the proposed system is verified experimentally by evaluating the con- sistency and accuracy of identification results in differ- ent measurement conditions. The work presented here is an extension of the previous study, where a modal-based damage detection method using LDV was formulated. In the present study, application of LDV for structural parameters identification of a combined dynamical sys- tem is proposed. A model that represents the connection properties in terms of additional stiffness and damping is developed, and its importance for structural damage de- tection is discussed. The study shows that the presence of simulated damage in a steel connection can be detected by tracking the modal phase difference and by quantify- ing the additional stiffness and damping.
55 citations
TL;DR: An innovative method is presented to measure the mechanical driving point impedance of biological structures up to at least 40 kHz, using an atomic force cantilever with a ferromagnetic coating and an external magnetic field to apply a calibrated force to the cantilevers.
55 citations
TL;DR: In this article, the authors presented the application of the laser Doppler Vibrometer as a nonintrusive measurement instrument to detect shape and location of damage in fresco paintings.
54 citations
Patent•
27 Feb 1974
TL;DR: In this article, a laser Doppler velocimeter is described which is capable of effectively measuring two different velocity components of a fluid simultaneously, including a pair of coherent beams of laser light which are focused to an intersection point through which flow particles within the fluid whose velocity is to be measured.
Abstract: A laser Doppler velocimeter is described which is capable of effectively measuring two different velocity components of a fluid simultaneously. Such a velocimeter includes a pair of coherent beams of laser light which are focused to an intersection point through which flow particles within the fluid whose velocity is to be measured. Both beams are plane polarized with the plane of polarization of one being rotated normally with respect to the other, with the result that the scattered radiation is separable into two different beams respectively corresponding to the two incident beams. Such scattered radiation is Doppler shifted by the moving particles and is collected for conventionally providing a measurement of the velocity of any particle flowing through the intersection point on a path which is generally transverse thereto. Moreover, the wavelength of the light scattered by the particles from one of the beams is compared to the wavelength of such beam prior to it being Doppler shifted by the moving particles. This comparison provides a measurement of another component of the particle velocity, which measurement can be combined with the first measurement to provide a resultant velocity in a two-dimensional reference frame.
54 citations
TL;DR: In this paper, a single co-planar electrode is placed symmetrically around the actuated grounded cantilever to increase the stiffness of the structure in its elastic regime.
Abstract: Large amplitude flexural vibrations have been excited in single layer silicon-on-insulator micromechanical cantilever beams in ambient air environment. Our driving approach relies on a single co-planar electrode located symmetrically around the actuated grounded cantilever. Electrostatic forces are created via tailored asymmetries in the fringing fields of deformed mechanical states during their electric actuation, with strong restoring forces acting in a direction opposite to the deflection. This results in an effective increase in the structure stiffness in its elastic regime. The devices had been fabricated using deep reactive ion etching based process and their responses were characterized in a laser Doppler vibrometer under ambient conditions. Harmonic voltages applied to the electrode result in the periodic modulation of the effective stiffness and lead to strong parametric excitation of the structure. As opposed to close gap actuators, where high-amplitude drives are severely limited by pull-in instabilities, squeezed gas damping, and stiction, our resonators exhibit very large vibration amplitudes (up to 8 in terms of the amplitude to thickness ratio in the strong parametric regime), with no apparent damage, via the application of highly tunable distributed forces. A reduced order model, based on the Galerkin decomposition, captures the main dynamical features of the system, and is consistent with the observed beam characteristics.
54 citations