• 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

Nov 1981

Volume 70, Issue S1, pp. S1-S109

Return to All Sections
back to top
RSS Feeds
back to top Session T. Physical Acoustics III: Ultrasonic Characterization of Materials I
Invited Papers
FREE

Acoustoelastic measurement of stress field variations (A)

G. S. Kino

J. Acoust. Soc. Am. Volume 70, Issue S1, pp. S45-S45 (1981); (1 page)

Online Publication Date: 12 Aug 2005

Full Text: | Download PDF

Show Abstract
New techniques for measuring the stress field variations near a crack or a weld will be described. The basic method makes use of the perturbation in acoustic velocity of a longitudinal wave in the presence of stress by using a small scanned transducer in a computer‐controlled system. It is possible to determine stress field variations over the cross section. Furthermore, if a focused transducer is employed, it is possible to design a phase contrast system which can measure stress field variations in all three directions. A detailed acoustoelastic perturbation theory, based on the change in energy associated with the third‐order elastic effects, has been derived and used to predict our experimental results. A brief description of the theoretical techniques employed will be given.
FREE

Ultrasonic backscattering from random rough solid interfaces (A)

Michel de Billy, Gerard J. Quentin, and Laszlo Adler

J. Acoust. Soc. Am. Volume 70, Issue S1, pp. S45-S45 (1981); (1 page)

Online Publication Date: 12 Aug 2005

Full Text: | Download PDF

Show Abstract
The angular variations of the mean backscattered intensity of ultrasonic waves by randomly rough surfaces of elastic solids are analyzed. The theoretical approach is based on the potential method. The calculations have been done for a normal distribution of heights and a Gaussian autocorrelation function. The experiences have been done at discrete frequencies and the roughness of the samples varied from 8 to 110 μm. (10−2  ⩽  g  =  k12h2γ2  ⩽  90). A good agreement between theoretical and experimental curves is observed for the angles of incidence ⩽ 40°. Another feature of the experimental data is the increase of the backscattered intensity at the Rayleigh angle for k1h ⩽ 1. Results of this study have been applied to surface and bulk defects with rough surfaces.
FREE

Wave propagation for metalography and materials characterization (A)

Emmanuel P. Papadakis

J. Acoust. Soc. Am. Volume 70, Issue S1, pp. S45-S45 (1981); (1 page)

Online Publication Date: 12 Aug 2005

Full Text: | Download PDF

Show Abstract
Ultrasonic wave propagation can be used to substitute for metallography or augment it in certain cases to characterize metals. The two parameters used are attenuation and velocity. Attenuation is related to grain size, grain size distribution, phase transformations, and separate phases within polycrystalline metals through grain scattering, while velocity is related to phase transformations and the continuity of the racial in the presence of other phases of various morphologies through the elastic moduli. Grain scattering will be explained in terms of both diffusion‐controlled and diffusionless transformations. Graphite morphology in cast iron will be used to illustrate the industrial use of velocity measurements. Certain situations will be mentioned in which ultrasonic measurements are superior to metallography in practice. The subject matter will be a review of published material.
FREE

Present status of elastic wave inverse scattering techniques (A)

R. Bruce Thompson

J. Acoust. Soc. Am. Volume 70, Issue S1, pp. S45-S45 (1981); (1 page)

Online Publication Date: 12 Aug 2005

Full Text: | Download PDF

Show Abstract
Recent progress in the development of elastic wave inverse scattering techniques to size flaws in solids is reviewed. A summary of the underlying physical models for forward scattering is first presented. This is followed by a more detailed discussion of development and experimental evaluation of inverse scattering techniques, spanning regimes in which the wavelength is large, comparable, or short, with respect to the flaw size. Included are discussions of the sensitivity of the techniques to such nonideal conditions as irregularly shaped scatterers, material anisotropy, beam focusing, and finite measurement bandwidth and aperture. Throughout the paper, the similarities and differences between the elastic and acoustic wave cases are noted.
Contributed Papers
FREE

Acousto‐optic method to locate surface inhomogeneities on solids (A)

Walter G. Mayer and Tran D. K. Ngoc

J. Acoust. Soc. Am. Volume 70, Issue S1, pp. S46-S46 (1981); (1 page)

Online Publication Date: 12 Aug 2005

Full Text: | Download PDF

Show Abstract
Changes in the profile of a reflected ultrasonic beam incident at the Rayleigh angle are observed and are used to locate small inhomogeneities in the surface of a solid. These beam profile changes are caused by minute changes in the Rayleigh wave velocity. Whether the inhomogeneity is related to variation in the longitudinal wave velocity is determined by observation of longitudinal critical angle reflectivity. [Supported by the Office of Naval Research, U.S. Navy and in part through an award (WGM) by the Alexander von Humboldt Foundation, Bonn.]
FREE

Optical detection of acoustic waves for the characterization of materials with unpolished surfaces (A)

P. Cielo

J. Acoust. Soc. Am. Volume 70, Issue S1, pp. S46-S46 (1981); (1 page)

Online Publication Date: 12 Aug 2005

Full Text: | Download PDF

Show Abstract
An interferometric ultrasound sensor was developed for use in ultrasonic characterization of materials with unpolished surfaces. A systematic investigation was made of the variation of the sensor's performance with the roughness of the surface to be inspected. Results show that even very rough surfaces can be inspected by this method with little decrease in the modulation index, provided that adequate optical components are used. An analysis of the dependence of the modulation index on the optical parameters is presented. Different applications of this sensor to ultrasonic characterization of materials are presented, and calibration problems encountered with samples of varying angular reflectivity are discussed. The variations in angular reflectivity are caused mainly by microstructure‐produced speckle noise and defocussing. A self‐calibrating system is presented, making use of a feedback loop incorporated in the electronic stabilisation system, which continuously compensates for the variations in angular reflectivity.
FREE

A comparison of ray tracing and exact methods for scattering from flaws (A)

C. H. Chou, B. I. Khuri‐Yakub, and G. S. Kino

J. Acoust. Soc. Am. Volume 70, Issue S1, pp. S46-S46 (1981); (1 page)

Online Publication Date: 12 Aug 2005

Full Text: | Download PDF

Show Abstract
The exact theory of Ying and Truell has been evaluated for scattering of waves from voids and inclusions in a surrounding isotropic matrix. The scattering has been determined both in the frequency domain and in the time domain for an incident band‐limited pulse to provide a good comparison with experiment. The theory can be interpreted well by a ray tracing analysis. This ray tracing analysis has been carried out in some detail. We get good quantitative agreement with the exact theory for spherical voids and inclusions if the ratio of diameter to wavelength is sufficiently large. The advantage of the ray tracing theory is that it can also be used for other shapes. Some examples for ellipsoids will be given.
FREE

Effects of closure on the detection probability of fatigue cracks (A)

O. Buck and B. J. Skillings

J. Acoust. Soc. Am. Volume 70, Issue S1, pp. S46-S46 (1981); (1 page)

Full Text: | Download PDF

Show Abstract
Fatigue cracks often can be (more or less) tightly closed. Under such “closure” conditions the crack may be transparent to ultrasound and actually form electrical contact between fracture surfaces, diminishing the eddy current response with respect to the fully open crack. In addition, external environments, which affect the crack propagation rate, also change the state of closure. The present paper reports on a recently developed model which seems to describe this closure phenomenon and aids in the interpretation of NDT data such that the crack size can be determined even for tightly closed cracks.
FREE

Acoustic surface wave studies of interfacial adhesives (A)

G. C. Knollman and J. J. Hartog

J. Acoust. Soc. Am. Volume 70, Issue S1, pp. S46-S46 (1981); (1 page)

Online Publication Date: 12 Aug 2005

Full Text: | Download PDF

Show Abstract
Ultrasonic surface waves have been utilized to study shear modulus gradients near adhesive‐adhered interfaces. For a given adhesive, Rayleigh waves are propagated over surfaces of the material which are sequentially exposed from bulk down toward an interfacial bondline. Measured Rayleigh‐wave velocity over each exposed adhesive surface is used to determine the corresponding shear modulus at that stratum relative to the interface. The experimental acoustic surface‐wave apparatus and its evaluation are described. Also, procedures for adhesive sample preparation and measurement are discussed. Data are presented which display significant gradients in shear modulus through the interfacial region for two different types of adhesive material. [Work supported by the Lockheed Independent Research Program.]
Return to All Sections
Close

Home Publications Meetings Contact ASA Site Map Back to Top

Copyright © Acoustical Society of America

close