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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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Journal ArticleDOI
TL;DR: In this article, a boundary effect detection (BED) method for pinpointing locations of small damages in beams using operational deflection shapes (ODSs) measured by a scanning laser vibrometer is presented.

92 citations

Journal ArticleDOI
Steve Heath1
TL;DR: In this article, the authors presented a new analysis method for identifying synchronous resonance engine order using two tip-timing vibration measurements, made at different locations on the turbomachinery casing using a minimum of two probes.
Abstract: Non-contact measurement of vibration at turbomachinery rotor blade tips using blade tip-timing has become an industry-standard procedure Current research focuses on analysis methods for interpretation of the measured vibration data from a limited number of probes The methods are classified by the form of the vibration they can identify Identification of asynchronous response amplitude and frequency is well documented Whilst a method for identifying maximum synchronous resonance amplitude has existed since the early 1970s, there is no published evidence of a method for directly identifying frequency or engine order using a small number of probes This paper presents a new analysis method for identifying synchronous resonance engine order using two tip-timing vibration measurements The measurements are made at different locations on the turbomachinery casing using a minimum of two probes A detailed description of the method and results from its practical application are given The potential of the method to identify the amplitude and frequency of close modes, not possible with current methods, is demonstrated The effect of blade mistuning on the accuracy of the method is investigated Existing synchronous response analysis methods and the new method presented here give the response amplitude and frequency after the resonance has been traversed Real-time identification of synchronous response amplitude and frequency would allow tip-timing to be used as a safety monitor of all blades Real-time methods, their limitations and practical application are discussed The future use of tip-timing as the dominant vibration measurement system is discussed with reference to experience on measurements made solely with tip-timing on assemblies with undefined vibration characteristics

91 citations

Journal ArticleDOI
TL;DR: A quantitative model is presented for a sphere vibrated by two ultrasound beams of frequency omega1 and omega2 due to the interference of two sound beams, which can be used to estimate the material properties of the medium surrounding the sphere.
Abstract: A quantitative model is presented for a sphere vibrated by two ultrasound beams of frequency ω1 and ω2. Due to the interference of two sound beams, the radiation force has a dynamic component of frequency ω2−ω1. The radiation impedance and mechanical impedance of the sphere are then used to compute the vibration speed of the sphere. Vibration speed versus vibration frequency is measured by laser vibrometer on several spheres, both in water and in gel phantom. These experimental results are used to verify the model. This method can be used to estimate the material properties of the medium (e.g., shear modulus) surrounding the sphere.

91 citations

Journal ArticleDOI
TL;DR: A new method is developed to estimate tissue's elasticity based on surface wave speed measurement, and it shows that the surfaceWave speed can be used for inversely estimating tissue' elastic properties based on tissue's surface measurement.
Abstract: The mechanical response of tissues to external forces has gained considerable interest in medical diagnosis. One approach to imaging tissue elastic properties is to apply an external force on the surface of the body. Another approach is to generate a localized force inside the tissue with the radiation force of ultrasound. In this paper, a new method is developed to estimate tissue’s elasticity based on surface wave speed measurement. The theory of surface wave speed is developed for estimating tissue’s elasticity. Experiments are carried out on a tissue-mimicking ultrasound phantom. An amplitude modulated ultrasound signal of a few hundred hertz is used to generate a localized force in the phantom. The surface wave fields are measured with a laser vibrometer. It shows that the surface wave speed can be used for inversely estimating tissue’s elastic properties based on tissue’s surface measurement.

90 citations

Journal ArticleDOI
TL;DR: It is shown that electronic subtraction is nearly as effective as field superposition in measuring differential vibrations, and is of interest in the study of friction induced vibration damping of gas turbine blades for aircraft applications.
Abstract: An instrument for noncontact measurement of differential vibrations is developed, based on the self-mixing interferometer. As no reference arm is available in the self-mixing configuration, the differential mode is obtained by electronic subtraction of signals from two (nominally equal) vibrometer channels, taking advantage that channels are servo stabilized and thus insensitive to speckle and other sources of amplitude fluctuation. We show that electronic subtraction is nearly as effective as field superposition. Common-mode suppression is 25-30 dB, the dynamic range (amplitude) is in excess of 100 μm, and the minimum measurable (differential) amplitude is 20 nm on a B=10 kHz bandwidth. The instrument has been used to measure vibrations of two metal samples kept in contact, revealing the hysteresis cycle in the microslip and gross-slip regimes, which are of interest in the study of friction induced vibration damping of gas turbine blades for aircraft applications.

90 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202381
2022177
2021122
2020142
2019134
2018174