• Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Journal of the Acoustical Society of America

SECTION LISTING

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue Next Issue

Apr 1982

Volume 71, Issue S1, pp. S1-S113

Return to All Sections
back to top
RSS Feeds
back to top Session CC. Engineering Acoustics II: Acoustic Signatures
Invited Papers
FREE

The detection and diagnosis of faults in sophisticated machinery systems (A)

R. M. Stewart

J. Acoust. Soc. Am. Volume 71, Issue S1, pp. S61-S61 (1982); (1 page)

Online Publication Date: 12 Aug 2005

Full Text: | Download PDF

Show Abstract
The detection and diagnosis of faults in sophisticated machinery systems presents the monitoring engineer with some of his most challenging problems. One of these is inter‐fault definition, first of all between the various components of the machine and then down at component level. For example, the intermediate casing of an aeroengine gas turbine is literally packed solid with shafts, bearings large and small, gears, splines, seals, etc., each with its own particular set of failure modes. In particular, the gears and bearings can fail in a large variety of ways, some more disastrously than others. For reasons connected with the statistical validity of his result, which is essentially to give the machine a “bill of health,” the engineer must seek ways of identifying the faulty state of each component as though it were an isolated unit running on a test stand. The author will describe what progress is being made in the U.K. to achieve this aim, emphasizing primarily the role of vibration analysis, but touching briefly on other important techniques such as debris, performance, temperature and electrostatic signature analysis.
FREE

Target information obtained from resonant acoustic echoes (A)

H. Überall and G. C. Gaunaurd

J. Acoust. Soc. Am. Volume 71, Issue S1, pp. S61-S61 (1982); (1 page)

Online Publication Date: 12 Aug 2005

Full Text: | Download PDF

Show Abstract
Submerged targets may be detected by the echoes they generate in response to an incident acoustic signal; similarly, material inhomogeneities in solids may be detected by ultrasonic echoes. Target identification, i.e., the determination of the scattering object's shape, composition, and orientation, represents a problem of a different order of magnitude. In many cases, the incident signal causes the target to resonate at its eigenfrequencies, and the resonance information is contained in the echo from which it may be extracted. Examples will be shown to demonstrate that the resonance spacings and resonance widths determine the composition of a target of known shape; or that the resonance positions determine the size and shape of a target of known composition. In addition, the relative excitation strengths of the resonances depend on the target orientation so that the latter may be determined. The corresponding method of “acoustic spectroscopy” may thus be used for solving the inverse scattering problem of identifying a target from an analysis of its echo. Relevant experiments (e.g., Maze, Taconet, and Ripoche) will be discussed.
FREE

Vibration monitoring for damage in offshore platforms (A)

Sheldon Rubin

J. Acoust. Soc. Am. Volume 71, Issue S1, pp. S62-S62 (1982); (1 page)

Online Publication Date: 12 Aug 2005

Full Text: | Download PDF

Show Abstract
A number of vibration‐based techniques have been considered for the detection of underwater structural damage in fixed offshore platforms for oil and gas production. Most platforms are primarily composed of welded steel pipes, and are pile anchored to the sea floor in depths of up to 320 m (1050 ft). The standard inspection technique employs divers to visually survey for severance or cracking of members. This is costly, can be hazardous, and is subject to environment constraints. Various vibration instrumentation approaches are described. All employ accelerometers to measure ambient excited or forced vibration. The crucial issues are (1) the ability to reliably detect damage before there is a significant loss of structural integrity, (2) the avoidance of false alarms due to nondamage changes, and (3) the masking of the desired information by machinery and other noise. A highly promising new technique, soon to be field tested, employs accelerometer placements down special chutes to reach various underwater positions for detection of overall shear stiffness of the individual platform bays. Results are described for a USGS/ONR sponsored blind laboratory test program in which several techniques were evaluated.
FREE

Acoustic monitoring and signature analysis in nuclear and fossil energy generation (A)

Henry B. Karplus

J. Acoust. Soc. Am. Volume 71, Issue S1, pp. S62-S62 (1982); (1 page)

Online Publication Date: 12 Aug 2005

Full Text: | Download PDF

Show Abstract
Acoustic monitoring and analysis in nuclear and fossil energy plants has been accompanied by transducer development for the hot environment. The Nuclear Regulatory Commission requires acoustic monitoring systems on nuclear reactors for detecting potential failures. Accelerometers are attached at critical points and their output is automatically analyzed to give warnings of loose parts or excessive vibration. In addition to providing a warning, the system can monitor arrival time to be used for fault location. For use as a potential boiling detector of breeder reactors, the acoustic signature of the sodium coolant boiling has been compared with background noise level. High temperature sodium‐immersible microphones and waveguides for smooth energy transfer were developed for this investigation. High‐temperature acoustic sensors have been used in a coal gasification plant. The presence of solids in a steam‐char line has been automatically determined using passive monitoring of relative sound intensities of different frequency bands.
FREE

Computer‐aided acoustical pattern recognition of pathological knee joints (A)

M. L. Chu

J. Acoust. Soc. Am. Volume 71, Issue S1, pp. S62-S62 (1982); (1 page)

Online Publication Date: 12 Aug 2005

Full Text: | Download PDF

Show Abstract
Degenerative joint disorders are, today, the most common nonfatal crippling diseases. In every case these diseases involve progressive destruction of the articular cartilage. At present, there is no available noninvasive clinical tool which will permit on‐going objective evaluation of the relative degree of damage to the articular cartilage. Recently a computer‐aided, electroacoustical technique was developed to enhance diagnosis of the disease more objectively. The procedure involved the recording of the acoustic energy emitted by the joint during active articulation, as picked up by a dual 1‐in. B & K condenser microphones using the principle of “noise cancellation” to minimize high‐frequency background noise. The recorded data are then digitized and statistically analyzed both in the time and frequency domain using an IBM computer to extract unique statistical properties which characterize specific pathological disorder and/or cartilage deterioration. Also a three‐dimensional spectral history plot was developed to present the extent and relative location of cartilage damage. The respective statistical features of recordings covering normal, rheumatoid arthritic, and degenerative knees apear to be unique and prove to be a promising noninvasive diagnostic tool for early detection of the type and extent of joint damage.
FREE

Acoustic signatures of railroad wheels (A)

R. D. Finch

J. Acoust. Soc. Am. Volume 71, Issue S1, pp. S62-S63 (1982); (2 pages)

Online Publication Date: 12 Aug 2005

Full Text: | Download PDF

Show Abstract
When a railroad wheel is impacted with a hammer blow it emits a characteristic sound. By comparing sounds from the two members of a wheelset a measure of the difference of their mechanical properties is obtained. Both frequency and time domain processing is found to be useful. Reference will be made to both laboratory and field tests and results will be summarized. Considerations in the design of automatic hammers, wheel sensors, and all weather microphones will be discussed. The influence of train speed on the required performance of hardware will be discussed, and parameters in the selection of signal processing hardware will be defined. The principal objective of the work is to recognize the presence of cracks. The main difficulty with meeting this objective is avoiding false alarms due to differential wheel wear, etc. Progress in developing algorithms to reduce this false alarm rate will be described. [Work supported by the Association of American Railroads.]
Contributed Papers
FREE

Ring model of railroad wheel vibrations (A)

S. Haran

J. Acoust. Soc. Am. Volume 71, Issue S1, pp. S63-S63 (1982); (1 page)

Online Publication Date: 12 Aug 2005

Full Text: | Download PDF

Show Abstract
A ring model for prediction of the vibration characteristics of railroad wheels is presented. Earlier workers showed that ring theory gave a good explanation of the ratio of resonant frequencies in the railroad wheel, assuming flexural modes are excited in the rim. It was assumed that the massive rim drove the plate of the wheel in forced vibration. In this paper the wheel is modeled by taking the flange, the rim, and the plate as a series of elastically connected concentric rings. The differential equations governing normal mode flexural vibrations are developed for such a system of n elastically connected rings, based on the general equations developed by Love. The free vibration of the system, with displacements both in the plane and out of the plane of the wheel was studied. Modifications were made to include wear on the flange and tread. The effect of hoop stresses in the rim was also modeled. The results agree well with those from other theoretical models and also with experimental values. [Work supported by Association of American Railroads.]
FREE

Recognition of defects from impact generated surface waves on the rim of a railroad wheel (A)

M. Fahmy

J. Acoust. Soc. Am. Volume 71, Issue S1, pp. S63-S63 (1982); (1 page)

Online Publication Date: 12 Aug 2005

Full Text: | Download PDF

Show Abstract
Ultrasonic surface waves have been used to detect thermal cracks on the rim of a railroad wheel. In this paper it is pointed out that surface waves may alternatively be generated by an impact on the rim of the wheel. Several circuits of such waves around the rim can be recognized in the first few milliseconds, after impact, of the signal from a microphone in proximity to the rim or an accelerometer in contact with the wheel. Reflections from cracks can also be recognized. Experimental results were obtained using a ball bearing impact and various types of transducers as receivers. Time domain signals resemble seismograms from which the wave velocity can be calculated. This velocity is in approximate agreement with the theory of surface wave propagation on the edge of a plate. Some developments in this theory will also be presented. The significance of the work lies in the potential for adding surface wave recognition algorithms to an Acoustic Signature Inspection System. [Work supported by Association of American Railroads.]
Return to All Sections
Close

Home Publications Meetings Contact ASA Site Map Back to Top

Copyright © Acoustical Society of America

close