Laser Doppler Vibrometer: Application of DOE/Taguchi Methodologies to Pyroshock Response Spectra

Statistical methodologies were employed for measuring and analyzing the explosively induced transient responses of a flat steel plate excited with shock. The application of design of experiment methodology was made to structure and test a Taguchi L9(32) full factorial experimental matrix (which uses nine tests to study two factors, with each factor examined at three levels) in which a helium-neon laser Doppler vibrometer and two piezocrystal accelerometers were used to monitor explosively induced vibrations ranging from 10 to 105Hz on a 96 × 48 × 0.25 in. flat steel plate. Resulting conclusions were drawn indicating how these techniques aid in understanding the pyroshock phenomenon with respect to the effects and interrelationships of explosive-charge weight and location on the laser Doppler and contract accelerometer recording systems.

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Measurement of defects in a plate using dry-coupled interdigital transducer–based scanning laser Doppler vibrometer

Structural Health Monitoring ◽

10.1177/1475921720960240 ◽

2020 ◽

pp. 147592172096024

Author(s):

To Kang ◽

Seong-Jin Han ◽

Seongin Moon ◽

Soonwoo Han ◽

Jun Young Jeon ◽

...

Keyword(s):

Steel Plate ◽

Excitation Frequency ◽

Laser Doppler Vibrometer ◽

Laser Doppler ◽

Scanning Laser ◽

Lead Zirconium Titanate ◽

Thick Plates ◽

Scanning Laser Doppler Vibrometer ◽

Degree Of Separation ◽

Interdigital Transducer

The interdigital transducer–based scanning laser Doppler vibrometer has recently been introduced to efficiently generate the symmetric mode for damage detection of shallow defects in thick plates. To measure shallow defects in a carbon steel plate, the excitation frequency is optimized based on the analysis of wavenumber sensitivity and degree of separation between modes. Even though the interdigital transducer–based scanning laser Doppler vibrometer method using continuous excitation is a promising method for visualizing defects in plate-like structures, the interdigital transducer has to be coupled to media, such as oil or water, to minimize the variation in acoustic impedance between the lead zirconium titanate and the plate-like structures. In this study, we develop a dry-coupled interdigital transducer–based scanning laser Doppler vibrometer system for the detection of shallow defects in a plate to facilitate easy mounting and demounting from the plate. To verify the proposed dry-coupled interdigital transducer–based scanning laser Doppler vibrometer, plates with four and eight different depth defects are introduced, and it is demonstrated that the defects in thick plates measured by dry-coupled interdigital transducer–based scanning laser Doppler vibrometer are visualized compared to those measured by interdigital transducer–based scanning laser Doppler vibrometer.

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Blood flow measurement by laser Doppler method in orofacial region

Stomatoloski glasnik Srbije ◽

10.2298/sgs1003141g ◽

2010 ◽

Vol 57 (3) ◽

pp. 141-148 ◽

Cited By ~ 2

Author(s):

Djurica Grga ◽

Bojan Dzeletovic ◽

Slavoljub Zivkovic ◽

Elena Krsljak

Keyword(s):

Blood Flow ◽

Blood Vessels ◽

Optical Fibers ◽

Laser Doppler ◽

Ambient Conditions ◽

Doppler Method ◽

Reflected Light ◽

Helium Neon Laser ◽

Orofacial Region ◽

Helium Neon

Laser Doppler is a noninvasive, objective, reproducible and painless method for measuring blood flow in tissue microcirculation. This method is based on the Doppler effect, the change in frequency of light reflecting from blood cells in motion. Light from helium-neon laser through optical fibers and probes is directed to the surface of the tissue in which the flow is measured. Light portion is reflected from the cells in motion and changes the frequency while another portion is reflected from the static tissue maintaining the same frequency as the initial light. The total reflected light, with changed and original frequency, reaches photo detector in the same probe where the emitter is and it is transformed into electrical impulse. In the orofacial region the laser Doppler method is used to examine blood flow in the mandible, teeth pulp and masticator muscles. A significant drawback of the laser Doppler method is its sensitivity to the ambient conditions during measuring and the fact that blood flow is measured in all blood vessels of examined microregion. Therefore, the circulation of isolated individual blood vessels can not be monitored. Laser Doppler method can give reliable indicators of blood flow in mouth tissue and method is acceptable for the patients.

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