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1983

Optics

Articles 1 - 7 of 7

Full-Text Articles in Mechanical Engineering

Fiber Optics For A Damage Assessment System For Fiber Reinforced Plastic Composite Structures, Roger M. Crane, Aleksander B. Macander, James Gagorik Jan 1983

Fiber Optics For A Damage Assessment System For Fiber Reinforced Plastic Composite Structures, Roger M. Crane, Aleksander B. Macander, James Gagorik

Review of Progress in Quantitative Nondestructive Evaluation

There are a limited number of nondestructive evaluation techniques available for field inspection of large composite structures and practically no viable techniques for in-service inspection. With this in mind, an innovative Damage Assessment System is proposed which is based on a concept of using an optical fiber mesh, implanted into the body of a fiber reinforced composite structure. Such a mesh would become an integral part of the structure during the course of its fabrication. The selection of the mesh fibers would be predicated on their strain to failure characteristics and strain compatibility with the base, composite reinforcing fibers. This ...


Noncontacting Measurement Of Surface Acoustic Waves, R. L. Jungerman, J. E. Bowers, B. T. Khuri-Yakub, G. S. Kino Jan 1983

Noncontacting Measurement Of Surface Acoustic Waves, R. L. Jungerman, J. E. Bowers, B. T. Khuri-Yakub, G. S. Kino

Review of Progress in Quantitative Nondestructive Evaluation

A new sensor is presented for detecting surface acoustic waves. The sensor constructed, using single mode fiber components, is small and rugged and has better sensitivity (.0003 Å) than has been reported for other SAW sensors. Optical reflection changes encountered while scanning surfaces can be divided out, making the probe applicable to rough samples of practical interest. Normal surface displacements near a defect (100 μm deep crack) have been measured in both long and short wavelength acoustic regimes.


Ultrasonic Nondestructive Evaluation Using Laser Transducers, Michael J. Rudd Jan 1983

Ultrasonic Nondestructive Evaluation Using Laser Transducers, Michael J. Rudd

Review of Progress in Quantitative Nondestructive Evaluation

A program is described which employs lasers for ultrasonic NDE. A high-power laser is used to generate a brief sound pulse in the test specimen. A second low-power laser then measures the response of the specimen to that sound pulse.

The response of the specimen is measured by a “Laser Vibrometer.” This is a novel type of heterodyne interferometer which focuses a Helium-Neon laser beam onto the surface of the specimen and measures its displacement. Displacements as small as 2×10-12 meters on a 0.15 sec averaging time can be detected and also displacements of 1.5×l0-9 meters ...


Nondestructive Evaluation With Beamforming Transducer Arrays, M. Simaan Jan 1983

Nondestructive Evaluation With Beamforming Transducer Arrays, M. Simaan

Review of Progress in Quantitative Nondestructive Evaluation

If a nondestructive evaluation system is designed to detect the presence or absence of a flaw in a material, typically one transducer may be sufficient. If, however, a characterization of the flaw is desired, then an array of transducers is in most cases required. Besides the capability of two and three dimensional imaging, array data has the advantages of increased resolution, improved signal-to-noise ratio after preprocessing and sharper focusing.

In any NDE system, the acquisition of data is only one step towards the final objective of flaw characterization. The other step is that of processing the data in order to ...


Thermoelastic Structures For High Density Ultrasonic Energy, R. J. Von Gutfeld, D. R. Vigliotti, C. S. Oh, W. R. Scott Jan 1983

Thermoelastic Structures For High Density Ultrasonic Energy, R. J. Von Gutfeld, D. R. Vigliotti, C. S. Oh, W. R. Scott

Review of Progress in Quantitative Nondestructive Evaluation

The use of lasers to generate thermoelastic waves has received considerable attention since the publication of the theoretical work of White.1 The author derives equations for the propagation of longitudinal elastic waves produced by surface heating of a semi-infinite medium with harmonic thermal (laser) excitation. The importance of the boundary conditions in determining the magnitude of the resulting elastic waves is described. Two conditions are imposed and the resulting amplitudes derived: (1) Laser absorption at x = 0 with elastic amplitude u=0 at x = 0 for all times t ≥ 0 (perfectly clamped or constrained surface) and (2) for the ...


Ultrasonic Transducer Standards, N. Jayasundere, Leonard J. Bond Jan 1983

Ultrasonic Transducer Standards, N. Jayasundere, Leonard J. Bond

Review of Progress in Quantitative Nondestructive Evaluation

The piezoelectric transducer is the electromechanical conversion element in NDE. Existing transducers of this type are found to impose limits on the improvement in system performance and, at present, there is a lack of standards as required for calibration procedures. Physical “standards” based on equivalent circuits have been produced which model individual transducers, single transducers in pulse-echo mode and two-transducer configurations. The performance of these “standards” is shown to be in good agreement with that given by real transducers, and subject to less variability.


A Miniature Optical Acoustic Emission Transducer, D. C. Emmony, M. W. Godfrey, R. G. White Jan 1983

A Miniature Optical Acoustic Emission Transducer, D. C. Emmony, M. W. Godfrey, R. G. White

Review of Progress in Quantitative Nondestructive Evaluation

The optical transduction of acoustic emission signals offers many advantages over piezoelectric devices. These include high bandwidth, no modification to the signal as well as providing contactless measurement. The major difficulties associated with optical devices are stability against low frequency vibrations and the generally complex nature of an optical interferometer. This paper describes the attempts to miniaturize a Michelson interferometer while at the same time overcoming some of the stability problems associated with these devices.

Active stability of an interferometric transducer with dimensions of ∿ 5cm (2″) cube has been achieved over 8 fringes of red light at 100Hz and 4 ...