42525 Michel, J. Apparatus for detecting defects, particularly in castings U.S. Patent No. 4,829,823 (16 May 1989)

Sound resonance frequencies of a work piece are measured in order to evaluate its quality and detect defects. Items, such as castings, can be tested by this method. Vibrations in the work piece arc sensed, filtered, phase shifted, amplified so as to sustain its oscillation so that its frequency response can be recorded.

42364 Drouillard, T.F.; Ikle, D.N.; Gustaveson, D.K. Structural verification using modal frequency testing: a nondestructive evaluation Lawrence Livermore National Lab, (United States). DE89-004163, CONF- 881076-11, 24 pp. (Nov. 1988)

An investigation was carried out to study the application of modal frequency testing as a nondestructive method for structural v~rification and bond characterization of a dissimilar-metal structure ioined by solid-state bonding. Important to the success of this investigation were the contributions from three disciplines: nondestructive evaluation, experimental modal analysis, and statistical analysis. This interdisciplinary effort resulted in a unique concept of structural verification - the use of modal frequency testing to determine the geometrical consistency of precision parts and to characterize the condition of the silver solid-state bonds in a beryllium/stainless steel structure during its manufacture.

42211 Wallo, M.J.; Stott, H.R, Monitoring and diagnostic program for major rotating machinery of an electric utility Materials Evaluation, Vol. 47, No. 6, pp. 604-608, 610, 612 (Jun. 1989)

Rotating machinery used from electricity generation can now be inspected by a monitoring and diagnostic programme which combines computerized information for vibration analysis, multiplane dynamic balancing and ultrasonic inspection. The design of the system is described, together with its operating procedures. The vibration monitoring and balancing program has proved successful and savings in personnel time have been realized. Rotor evaluation can now be performed more expediently.

42124 Siemens AG Inspection of mechanical integrity of components - vibration signals are detected by sensors and processed to denote whether fault in component has occurred and then produce alarm signal European Patent No. 309,829 (5 Apr. 1989)

42098 Newman, J. W. Non-destructive testing by laser scanning U.S. Patent No. 4,824,250 (25 Apr. 1989)

An object, vibrated with a coherent light beam, can be examined nondestructively with this laser scanning method. A reflection pattern of a point on the object is formed and detected. Control system cause each point on the object to be scanned during energizing and de- energizing of the vibration means. A display shows the difference between the reflection patterns of the stationary and vibrating object.

41977 Lang, J.F. Applying Machinery Vibration Monitoring Electric Power Research Industries, Paio Alto, California (United States), EPRI NP 6340, 55 pp. (Apr. 1989)

Monitoring the vibration of rotating machinery helps utilities detect failures and plan maintenance. Experiences at five utilities provide practical guidance for maximizing the benefits of vibration monitoring by integrating it into a total preventive maintenance program.

41937 Webster, J.R. Vibro-acoustic emission rubbing sources Journal of Acoustic Emission, Vol. 8, Nos. 1-2, pp. 5197-5200 (Jan, - Jun. 1989). Special Supplement - Extended Summaries of Papers to be presented at the World Meeting on Acoustic Emission, Charlotte, North Carolina, USA, 20-23 Mar. 1989

Vibro-Acoustic Emission (VAE) was developed to use the acoustic emission (AE) generated within a vibrating structure or component. Two main sources of AE of interest in these applications are rubbing and impacts, VAE generation is shown to depend on certain physical parameters and vibration conditions and can be successfully modelled. Signal detection and analysis methods used are described. Applications of VAE in the aerospace industries are noted. Relative levels of energy dissipation at a rubbing source are demonstrated, offering the possibility of evaluating or predicting wear. VAE is also successful in defect detection, failure analysis and mechanism investigations.

41869 Ginnis, A.F.; Larkin, W.F. Transient holographic indication analysis U.S. Patent No. 4,807,996 (28 Feb. 1989)

This new characterization method is conducted by comparing two time- averaged holograms of the article, one at a higher vibration amplitude than the other, with two reference time-averaged holograms. The reference holograms arc produced at the same two vibration amplitudes using a reference article containing a known anomaly.

41828 Srivatsan, T.S.; Mantena, R.; Gibson, R.I,.: Place, T.A.: Sudarshan, T.S. Electromagnetic measurement of damping capacity to detect damage in adhesively bonded material Materials Evaluation, Vol. 47, No. 5, pp. 564-570 (May 1989)

In this study, contributions from intrinsic defects caused by improper curing, induced porosity, and improper surface preparation on the performance of double-lap adhesive joints bonded with a structural epoxy adhesive have been nondcstructively evaluated through damping- capacity measurements. The damping measurements were made using the novel impulse-frequency response technique. The double-lap adhesively joined specimens were excited in flexural vibration by an electromagnetic hammer with a force transducer at its tip. The specimen response was measured with an eddy current probe. A fast- Fourier transform analyzer was used for rapid acquisition of data and the computation of the loss factor (a measure of damping) by curve- fitting to the frequency response function. Strength of the adhesive joints was determined for different types and levels (size and volume) of defects. The loss factor was found to correlate well with strength, with strength decreasing and damping increasingly with increasing severity (size and/or volume) of the defect. The potential uses of the impulse technique are highlighted.

41769 Allen, J.; Oesterling, L.M. Loose part monitor sensor validation, impact detection, and charac- terization Nuclear Plant Journal, Vol. 7, No. 3, pp. 80,82,84,91 (May Jun. 1989)

A new approach, based on statistical signal analysis, is presented for monitoring the impacts of free-moving objects or loose parts in the reactor coolant systems (RCS) of nuclear power plants with important safety implications. The methodology used to analyze the signals generated is explained. The new system for loose part monitoring (LPM) is described and details of operation in various nuclear power plants are presented.

41754 Barna, B.A.; Allemeier, R.T.; Carlson, N.M.; Johnson, J.A.; Rodriguez, J.G.; Shull, C.L.; Tow, D.M. NDE methods for high-temperature materials and environments EG and G. Idaho, Inc., Idaho (United States), DE89 005195, EGG-M-26287, 5pp. (1989)

The application of acousto-optic or optic sensing techniques to three high-temperature materials or processes is described. Noncontacting, laser- based sensors are used to image high-luminosity processes, generate ultrasound in molten weld pools, and detect surface dynamics for vibrational analysis. The description of these distinct research efforts gives an overview of one potential approach for developing new capabilities for high-temperature environments.

41593 Southwest Research Institute Combustion turbine vibration monitoring Electric Power Research Industries, Polo Alto, California (United States), EPRI AP 6119, 144 pp. (Dec. 1988)

This report describes the use of vibration monitoring for large U.S. industrial gas turbines that generate electric power. By surveying monitoring practices, it offers many examples of how this technique has uncovered defective turbine equipment and avoided costly damage, especially in axially migrated compressor blades, bearing and tie-bolt failures, blade tip loss, and blade damage.

41590 Bedewi, N.E.; Kung, D-N.; Qi, G-Z.; Jackson, C.S.Y. Use of the random decrement technique for detecting flaws and monitoring the initiation and propagation of fatigue cracks in high- performance materials Nondestructive Testing of High-Performance Ceramics, Conference Proceedings, Boston, Massachusetts, (United States), 25-27 Aug. 1987, pp. 424-44l Edited by A. Vary and J. Snyder. The American Ceramic Society (1987)

The vibration response of high-performance materials depends to a great extent on the structural characteristics of the material. These characteristics, often represented by the model frequencies and damping ratios, are very sensitive to the presence of flaws or singularities in the material. An experimental approach is presented based on the Random Decrement (Randomdec) signal processing technique. The random response of the system, when analyzed using the Randomdec technique, results in a signature unique to the system. Comparison of this signature to that of a "flawless" system yields meaningful information regarding the presence and size of flaws. The purpose of this paper is to evaluate the sensitivity of the proposed technique to the size and severity of the flaws by means of a controlled experiment. Initial studies performed using graphite-epoxy plates resulted in successful flaw detection.

41589 Warren, C.H.; Barbin, A.R. Vibration of Pressurized Cylinders Army Missile Command, Redstone Arsenal, Alabama (United States), AD- A199 191/8/GAR, 20 pp. (Jan. 1988)

A study was conducted of the effects of internal pressure and media on the vibration of small cylindrical pressure vessels. Utilizing approximate expressions for elastic potential and kinetic energies of the cylinder-fluid system, LaGrangc's equation was applied and an expression developed for predicting the frequency of vibration as a function of the pressure and density of the fluid for axial wave factors. End conditions are empirically included in the measured zero- pressure frequency. A series of cxperiments on a small cylinder of the type used a pneumatic power sources on missiles confirmed the predictions over a range of

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