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1975
Wednesday, January 1st
12:00 AM

Acoustic Emission from Plastic Deformation

Steve H. Carpenter, University of Denver

Thousand Oaks, CA

12:00 AM

I would like to discuss some recent work at the University of Denver concerning acoustic emission generated during plastic deformation. I must emphasize that this is a preliminary progress report and that the investigation is still in its early stages. I would like to acknowledge two people who have been working with me on this investigation, Robert Wittman of the Denver Research Institute and Frank Higgins, a graduate student of mine at the University of Denver.

Acoustic Surface Wave Generation with Electromagnetic Transducers

Robert Thomas, Wayne State University

Thousand Oaks, CA

12:00 AM

In the program description Don Thompson mentioned that one of the overall objectives was to try to increase the communication between the basic research community and the NDE user, and I'd like to mention that my own involvement in NDE did not come from a specific problem oriented research project in NDE. In fact , my interest in electromagnetic generation began from some physics problems, particularly with studies of the electronic properties of potassium single crystals at liquid helium temperature where the contactless feature of electromagnetic transducers was a useful advantage.

Adaptive Learning Network Approach to Defect Characterization

Anthony N. Mucciardi, Adaptronics, Inc.

Thousand Oaks, CA

12:00 AM

The overall objective of this work was to demonstrate feasibility of adaptive nonlinear signal processing techniques applied to characterization of ultrasonic nondestructive testing (UNDT) waveforms for accurate inferences of flat -bottom hole sizes. The classified waveforms were ultrasonic pulse echoes obtained from two different sets of 7075-T6 aluminum area-amplitude test blocks and three different transducers. The eight flat- bottom hole defect sizes ranged from 1/64 to 8/64 inch in steps of l/64 inch

Analysis of Ultrasonic Scattering from Simply Shaped Objects

E Richard Cohen, Rockwell International

Thousand Oaks, CA

12:00 AM

The simple shapes referred to in my title are actually restricted to spheres and spheroids , that is ellipsoids of revolution. Actually , I will not even say too much about the spheroids except to t he extent that I will concentrate on the sphere as the limiting case and as the jumping-off point for the complete analysis of the spheroid.

Angular Dependence of Ultrasonic Waves Scattered from Flat Bottom Holes

Laszlo Adler, University of Tennessee - Knoxville

Thousand Oaks, CA

12:00 AM

I would like to present some of our results on angular and frequency dependence of sound scattering from flaws which are two-dimensional and have sharp edges, and specifically on our study of the end of the flat bottom hole, which may be considered as a circular aperture or disk in an infinite medium.

Applications of Electronically Scanned Acoustic Imaging Techniques to NDE

Gordon S. Kino, Stanford University

Thousand Oaks, CA

12:00 AM

Bob already talked about C-scan systems and I'd like to refresh your memory a little here. In particular, I want to talk about a C-scan system which has been used by Caustin on the B-1 project, in which we had considerable interest because we have been taking some of his samples and measuring them, he having measured them earlier.

Attendees

ARPA/AFML

Thousand Oaks, CA

12:00 AM

Attenuation Influences in Adhesive Bond Modeling

Joe Rose, Drexel University

Thousand Oaks, CA

12:00 AM

The goal of this work is to examine attenuation effects so that suitable procedures, signal processing techniques, etc., can be used in considering attenuation influences in the adhesive bonding inspection problem. I might point out that we've performed some work under sponsorship of AFOSR, and to date have been reasonably successful in performing ultrasonic inspection of aluminum FM-47 aluminum-type bonds. We' ve also developed some of the physical modelling and computer programming tools that were used in the work being presented. The work associated with the attenuation is sponsored by Roc well under the ARPA/AFML program.

Basic Theory of Ultrasonic Scattering by Defects: Numerical Studies and Features for Experimental Application

J A. Krumhansl, Cornell University

Thousand Oaks, CA

12:00 AM

Well, the theory of scattering of elastic waves is difficult. I don't want to minimize that, but I thought I might make a few diversionary introductory remarks. My first reference will be the Los Angeles Times of today, the astrology column. It advises those born under the sign of Leo to choose their words carefully to avoid trouble. That happens to be applicable to yours truly. I hope I do it.

Comparison of Theory and Experiment for Ultrasonic Scattering from Spherical and Flat Bottom Cavities

Bernard R. Tittmann, Rockwell International

Thousand Oaks, CA

12:00 AM

Earlier in the day you heard several talks on the analytical techniques to treat defect scattering. I would like to try to discuss what amounts to two procedures which should hopefully help in not only testing some of these results but also to reduce these techniques to practice, that is to say, with a view toward obtaining defect signatures in the field. The thread that should hopefully be running through my talk is how to develop procedures for applying present scattering results to laboratory field practice.

Concluding Remarks

Donald O. Thompson, Rockwell International

Thousand Oaks, CA

12:00 AM

Deducing Subsurface Property Gradients from Surface Wave Dispersion Data

John Richardson, Rockwell International

Thousand Oaks, CA

12:00 AM

My talk deals with the same subject as that of the previous speaker, Dr. Szabo, except I am not going to assert that it involves residual stresses necessarily. I consider some kind of a perturbation of the elastic properties and/or density due to some kind of surface treatment. As in all problems of this kind I assume, at least for the time being, some kind of an ansatz about mutual proportionality between the various kinds of perturbed physical properties as they vary with depth.

There are, perhaps, four ways of classifying approaches to this kind of problem. One is a parametric approach where one assumes that the candidate profile is defined by a finite set of parameters which are adjusted to give the best fit to the experimental data. Another is a nonparametric approach in which one does not have a finite set of parameters but an essentially infinite set of parameters. Another dimension of classification is whether one is using a probabilistic or a nonprobabilistic approach. In the nonparametric case one is forced to use a probabilistic approach. Here one treats every conceivable profile as being present in a statistical ensemble but with probability weightings reflecting one's a priori knowledge of what is more or less reasonable.

Defect Characterization by Spatial Distribution of Ultrasonic Scattered Energy

Paul F. Packman, Vanderbilt University
E J. Coyne, Vanderbilt University

Thousand Oaks, CA

12:00 AM

The ultrasonic pulse echo technique is a highly sensitive nondestructive method for detecting small defects within the bulk of a structure. The technique is capable of reliably finding small volumetric defects when the defect size is approximately 0.030 inches in diameter and the specimen thicknesses are not too great. If the distance between the transducer and the defect is large, greater than 2 near field distances, the minimum value of volumetric flaw sizes that can be reliably detected rises considerably. For 6-8 inch thick plates, it is not too surprising to occasionally miss volumetric defects such as slag inclusions of considerable length.

Detection of Hydrothermal Aging in Composite Materials

David H. Kaelble, Rockwell International

Thousand Oaks, CA

12:00 AM

In the title of this paper the term "hydrothermal", meaning separate or combined conditions of high moisture and temperature, is introduced to describe the complex property degradation processes in two graphite-epoxy composites. It became evident in the course of this study that important hydroelastic stresses degrade composite strength in much the same fashion that thermoelastic stresses do. In fact, the study shows that there are complex internal stress effects within the composite, probably concentrated at the fiber-matrix interface, which depend upon the detailed prior history of moisture-temperature exposure .

Development of a Field Inspection System for Detection of Cracks Under Installed Fasteners

W Woodmansee, Boeing

Thousand Oaks, CA

12:00 AM

The work that I'm going to describe was funded by the Air Force Materials Lab from February 1972 to February 1974. It is described in an AFML report, TR- 74-80, available from the Air Force. This report describes a more practical type of problem than has been discussed so far. Our work was directed towards building an ultrasonic system to be used on aircraft in the field to detect cracks around fastener holes with the fastener in place. With this system we are able to detect cracks and locate them relative to the depth of the hole. Estimates of crack size by this method are not very accurate.

Diagnostic Aids for Military Systems

William Whelan, The Rand Corporation

Thousand Oaks, CA

12:00 AM

I'm Bill Whelan from the Rand Corporation. I'd like to present a brief and somewhat general set of comments on diagnostic aid systems. The comrnents are general because I am summarizing previous and ongoing Rand study efforts.

As you may be aware, Rand has done considerable work for t he Air Force in several areas related to diagnostic aid systems, such as investigations of engine health monitoring systems and studies of aircraft maintenance policies and programs. Recently, Rand has undertaken, under ARPA sponsor ship, a project to assess the utility and cost-effectiveness of diagnostic aid systems for U.S. Army ground vehicles. My examples will be drawn from the findings of this study. The relationship between diagnostic aid systems and NO[ is left as an exercise for the reader.

Digital Measurements of Scattering from Spheroids and Flat Bottom Holes

Jim Couchman, General Dynamics

Thousand Oaks, CA

12:00 AM

I would like to discuss some of the problems and successes related to using computerized signal processing to characterize internal flaws in materials. The work reported on will be limited to the flawed specimens provided by Rockwell International which ·consist of flat bottom holes and spheroidal voids.

In this presentation I will first discuss the signal processing system that was prepared to perform this study and will identify some of the measurements that can be rather routinely made with the system. Al so, I will describe our attempts to obtain rf and frequency spectral signatures of the various flaws that we have analyzed, and finally, I will discuss a data format that is more convenient for comparison with theoretical calculations.

Energy Dependence of Fatigue-Enhanced Photoemission

Otto Buck, Rockwell International

Thousand Oaks, CA

12:00 AM

This is a progress report on the subject of fatigue-enhanced photoemission. In our studies on fatigue-enhanced photoemission, the ultimate goal is to see whether or not the photoyield can be used as a tool to uniquely define the early and later stages of fatigue on structural materials. This yield results in an electron current off the specimen.

Fracture Mechanics of Bonded Structures

Nate Tupper, United States Air Force

Thousand Oaks, CA

12:00 AM

I want to talk a little bit this morning about the damage tolerance philosophy of the Air Force as applied to new systems. I'm going to talk particularly about metals and try to indicate those areas where the philosophy that we're applying in our metal structure is equally applicable to both adhesive bonded joints and composite materials, the idea being that the techniques to satisfy the requirements will change and some of the requirements will change, but the philosophy will be the same. The philosophy has to do with beginning to recognize, and I think we now all do, that structure that is manufactured, rolled out the door and put into service is defective at the time it rolls out the door.

Guided and Leaking Interface Waves for NDI/NDE

David A. Lee, Air Force Institute of Technology
Dennis M. Corbly, United States Air Force

Thousand Oaks, CA

12:00 AM

Last year at this review one of us pointed out that it was theoretically possible to propagate guided elastic waves along the interface between an installed interference-fit fastener and the parts that it joins, and that these waves might be useful for nondestructive inspection and evaluationl. During discussion of that paper, the speaker was asked if experiments were planned, and another questioner wanted to know what would happen if elastic parameters of fastener and part didn't fall in the comparatively narrow ranges for which unattenuated guided waves can propagate.

The speaker replied that experiments were indeed planned, and that, hopefully, even when material parameters did not allow guided waves, attenuated interface waves might still propagate and be useful for inspection and evaluation.

This report can be viewed as an amplified answer to the two questions. We have carried out experiments. They confirm the existence of both true guided waves, and of "leaking" or attenuated waves, on interfaces between materials of engineering interest. The theory presented last year, with some extensions, is a useful guide to excitation and reception methods, propagation speeds, and for leaking modes, attenuation factors. Preliminary pulse-echo observations indicate that these waves can be used for indications of flaws in awkward places, such as on a fastener hole in an inner plate.

How do you foresee the requirements for ultrasonic standards changing as NDE evolves from a defect detection mode to a quantitative defect characterization mode?

Tom Cooper, United States Air Force
Edward L. Caustin, Rockwell International
Jerry Gardner, Southwest Research Institute
Donald G. Eitzen, National Bureau of Standards
R Bruce Thompson, Rockwell International
William G.W Yee, Convair Aerospace
Harold Berger, National Bureau of Standards
Jerry Posakony, Battelle Northwest
Anthony N. Mucciardi, Adaptronics, Inc.
Bill Andre, National Aeronautics and Space Administration
Steve Hart, United States Navy
Ron Nokes, United States Air Force

Thousand Oaks, CA

12:00 AM

The topic of our panel discussion is: "How do you foresee the requirements for ultrasonic standards changing as NDE evolves from a defect detection mode to a defect characterization mode?"

We've heard a number of comments yesterday and today about the problem of standards. Our plan for the balance of the day in the panel session is to hear from a group of experts who have had considerable experience, and therefore, have developed varied opinions on the problem of standards. We'll hear briefly from each of them, and then have an open discussion where those in the audience are invited to participate.

Inspection Requirements for Adhesive Bonded Primary Structures

William J. Shelton, United States Air Force

Thousand Oaks, CA

12:00 AM

This paper is concerned with a program that's being sponsored by the Air Force for the purpose of building an adhesive bonded structure. A discussion will be given on some of the problems that we are currently trying to address; what we are doing to solve these problems; and some of the road map programs that will support the Primary Adhesive Bonded Structure Techno logy (PABST) program. This program is under contract with t he McDonald-Douglas Corp., Long Beach.

The objective of this program is to demonstrate and validate t hat by the use of adhesive bonding as the primary joining method that a structure can be fabricated that will be cheaper, lighter i n weight, and reliable. The approach is to review and analyze several design configurations and select a single design for fabrication. To support this decision testing will be accomplished on actual test components representative of the design selected, in addition to extensive coupon testing . After fabrication the structure will be subjected to several life cycle test s at the Air Force Flight Dynamics Laboratory, Wright-Patterson Air Force Base, Ohio

Interactive Pattern Analysis and Recognition

George Forsen, Pattern Analysis and Recognition Corporation

Thousand Oaks, CA

12:00 AM

I want to stress the procedural aspects of solving pattern recognition problems. What are the tools, what are the thought processes, and what are the algorithms that you may need to do an efficient job of creating your pattern recognition design? I hope after this presentation you'll appreciate why we have spent many years in developing tools for creating pattern recognition and their designs. These are mainly computer-based, display oriented, large systems that have a comprehensive assortment of algorithms that can be easily accessed by experimenters.

Interfacial Structure and Strength of Adhesive Bonds

Tennyson Smith, Rockwell International

Thousand Oaks, CA

12:00 AM

An adhesive bond is a sandwich structure that has various zones within it as shown in Fig. 1. The physical and chemical properties of these various zones determine the bond strength and the durability of the bond. I hope that I'll be able to shed some light on the real properties of the interface rather than schematic properties as shown in Fig. 1 and relate the physical and chemical properties to the resultant bond strength. I will, therefore, discuss something about the oxide, the topography of the surface after it's been prepared for bonding , the thickness of the oxide, the interface , the primer and the adhesive in an actual fracture surface. The dotted line in Fig. 1 represents a hypothetical fracture line and, in fact, we find that failure does occur in all of these regions designated by the dashed line. The bond fails as the weakest regions fail.

Measurement of Flow Stress Related Phenomena by Nonlinear Acoustics

Otto Buck, Rockwell International

Thousand Oaks, CA

12:00 AM

Before going into acoustic harmonic generation, I should bring to your attention the definition of internal stresses which was made about 40 years ago. Basically, we have to distinguish between two kinds of internal stresses. Internal stresses of the first kind are those which spread out over macroscopic distances of the order of millimeters. Applying x-rays, one obtains a line shift in the Bragg reflection due to a lattice parameter change. A simple example of internal stresses of the first kind is shown in Fig. 1, top: in bending a piece of material elastically, a line shift in the Bragg reflection will be found on the upper and lower surface. Internal stresses of the second kind are restricted to much, much smaller dimensions, say of the order of 1 um or below. Bragg reflection does not show a line shift, but merely a line broadeninq. A typical example is shown in Fig. 1, bottom. Assume dislocations are distributed in a material. The· variation of the elastic stress field surrounding the dislocations is assumed to be sinusoidal and of the periodicity of the dislocation arrangement. If another dislocation is pushed against this chain of dislocations, it will see the stress field of the dislocation arrangement. In work hardening theories, this model is used to calculate the work hardening coefficient. The present paper will be concerned mainly with the internal stresses of the second kind.

Measurement of Residual Stress Using Magnetic Barkhausen Noise Analysis

G A. Matzkanin, Southwest Research Institute
C G. Gardner, Southwest Research Institute

Thousand Oaks, CA

12:00 AM

In this presentation we very briefly review the concepts involved in stress measurement by means of the Barkhausen effect, and cite the major instances of its practical application; the major part of the paper is devoted to a presentation of some recently obtained results regarding the effects of plastic deformation, and of biaxial stress fields.

Measurement of Surface Strain by Surface Reflection Raman Scattering

Susan Ushioda, University of California - Irvine

Thousand Oaks, CA

12:00 AM

My talk today sort of comes from the unreal side of the world in the sense that this method of nondestructive testing is quite new and nobody has used it, and I am presenting this method as a possible method for the future. Of course, the unreal world today often becomes the real world tomorrow, so there is a good possibility that the method that I present here will become a useful one. At the moment, of course, the equipment that I use for these measurements can't be hung on the airplane wing or anything of that sort.

Methods Development for Non-Destructive Measurement of Bond Strength in Adhesively Bonded Structures

James A. Seydel, University of Michigan - Ann Arbor

Thousand Oaks, CA

12:00 AM

While reasonably satisfactory methods exist for nondestructively determining t he presence or absence of an adhesive bond, no method exists for nondestructively determining the strength of what appears to be a good bond. Bonds that do not attain their full strength can be caused by a thin layer of contaminant , improper surface roughness, and a variety of other surface phenomena that are difficult to detect by conventional methods.l,2,3 One technique is to use an ultrasonic pulse to investigate the bond interface. Since the amplitude of the pulse reflected by t he bond interface is a f unction of the elastic properties of the bond, i t should be possible to correlate t he absolute ultrasonic reflectivity with t he bond strength.

Narrow Band Gap Semiconductors as Acoustic Phonon Transducers

A H. Francis, University of Illinois at Chicago

Thousand Oaks, CA

12:00 AM

It 's actually with some considerable apprehension that I address this audience. I will try to alleviate my apprehension somewhat by telling you right at the outset that I do not have a single data slide showing a detected flaw. What's more I have to confess, I have never detected a flaw. I sincerely hope you'll forgive me for this. My apprehension is heightened by my observation over the last several days that there is very little interest in ultrasonic work at the frequencies that are of interest to me, the range of about 1 to 10 GHz. I don't think I've heard anything over 1 GHz mentioned. Perhaps it's becoming apparent to most of you that I am not principally in nondestructive evaluation. What I am interested in is lattice dynamics; more specifically relaxation effects in dielectric solids.

Optimization and Application of Electrodynamic Ultrasonic Wave Transducers

Bruce Maxfield, Cornell University

Thousand Oaks, CA

12:00 AM

First, let me describe briefly what I have in mind when I talk about electrodynamic ultrasonic wave transducers. There are a number of transducers which I would put in this class including the capacitive microphonetype transducers, which are based on an electrodynamic phenomenon as opposed to piezoelectric phenomena. However, I am going to focus my attention on a particular type of electrodynamic device, the electromagnetic acoustic wave transducer or EMAT for short. I will describe electromagnetic acoustic wave generation and, hopefully, will show you how transducers based on this phenomenon have been understood in rather great detail. It is then up to all of us to try and apply this information to solve NDE problems. With this background information, I hope that you will feed back to me ideas so that we can work together on applications.

Overview

R Reynolds, Advanced Research Projects Agency

Thousand Oaks, CA

12:00 AM

I'm very happy to have the opportunity to be here to express ARPA's interest and enthusiasm in the work in this area. I'm glad to see that enthusiasm certainly is reflected by the fine attendance from a wide range of places. Further, I'd like to apologize for Ed's absence; however, a schedule conflict has prevented his arriving before tomorrow .

Piezoelectric Transducers for Quantitative NDE

Ken Lakin, University of Southern California

Thousand Oaks, CA

12:00 AM

Piezoelectric transducers are undoubtedly one of the major elements for use in ultrasonic NDE. and our program essentially was involved for the last nine months in what you might call the NDE of NDE transducers, sort of NDE. Hopefully, we're not multiplying two small numbers together here. So, what I'd like to do is just give a summary of what we have been doing and tell you how far up on the learning curve we are.

Potential Cost Savings Through Advanced NDE

Michael Buckley

Thousand Oaks, CA

12:00 AM

I would like to point out that, although the title of this talk is "Potential Cost Savings Through Advanced NDE," it doesn't mean that we're ignoring the area of structural safety, but rather we 're trying to add to it. In addition, we're not ignoring the role of NDE in the utilization of new cost effective material s and structures, but this area has been discussed previously and I believe is fairly well established.

Program Description and Purpose

Donald O. Thompson, Rockwell International

Thousand Oaks, CA

12:00 AM

I'd like to spend a few minutes to give a brief overview of the ARPA/AFML research program in NDE. The objectives of the program are as follows:

  • To pursue advanced research in quantitati ve techniques for NDE
  • To establish a focal point for NDE research
  • To establish communication between the research community and the NOE user
  • To promote the image of NDE

Quantitative Ultrasonics—Overview

R Bruce Thompson, Rockwell International

Thousand Oaks, CA

12:00 AM

I would like to give an overview of our work in quantitative ultrasonics in the ARPA/AFML program. The goal is to use ultrasonics to determine failure related or fracture critical properties of a flaw. In practice , this implies the use of ultrasonics to determine the geometric shape of the flaw: its size, its shape and its orientation with respect to a stress field.

Random Noise Signal Processing

V L. Newhouse, Purdue University
N M. Bilgutay, Purdue University
E S. Furgason, Purdue University

Thousand Oaks, CA

12:00 AM

Pulse echo flaw detection systems have found extensive use in industry for quality control of many types of metal and ceramic components. The random signal flaw detection system described in this paper provides an increase in sensitivity of several orders of magnitude compared to conventional pulse echo systems.

Following a review of the theory of system operation, we present some recently obtained results of our system on materials which are strongly sound absorbing, including ceramics, plastics and metals as well as material s which have large grains. In addition to detecting flaws in strongly absorbing materials we feel that this system might also be utilized as a way of estimating grain size, inclusion size or porosity.

Recent Advances in Ultrasonic Imaging

Robert C. Addison, American Optical Corporation

Thousand Oaks, CA

12:00 AM

Ultrasonics has been used for many years to detect flaws in materials by means of a pulse echo or A-scan technique. Ultrasonic images are formed by displaying the echoes in a two dimensional pattern so that t he spatial relationships between the interfaces and acoustic impedance discontinuities t hat give rise to the echoes are maintained. When the echo data is arranged in this way, it is possible for one's eye and brain to serve as a very sophisticated pattern recognition system to detect flaws or defects within an object. This capability is particularly important when one is examining an object that normally has a considerable amount of internal structure. Since most of my experience is with medical applications, I will take the human abdominal region as an example. An ultrasonic image will be able to delineate the more or less known outlines of these normal internal structures. Frequently, however, the purpose of such an examination is to look for some abnormality such as a tumor or cyst and using an ultrasonic image these structures can be differentiated from the normal structures by those who have been trained in this sort of procedure. This can be done because the operator has learned to recognize certain patterns and he is able to employ his eye-brain pattern recognition system when the echo data is presented in the form of an image.

Residual Stress Detection by Measurement of Efficiency of Electromagnetic Generation of Ultrasound

R Bruce Thompson, Rockwell International

Thousand Oaks, CA

12:00 AM

I think I should thank George Matzkanin for starting everyone thinking in terms of magnetic phenomena. Yesterday we heard three papers describing the performance of electromagnetic transducers on nonmagnetic materials. The question was asked at the close of one, "Do these transducers work on ferrous materials?" The answer that I will give you is, "Yes, they do, and furthermore, the efficiency of the operation is directly related to the stress within the material." The mechanism of this relationship is very similar to the mechanism of the stress dependence of the Barkhausen effect. However, the information gained is distinct and complimentary.

Residual Stress Measurements from Surface Wave Velocity Dispersion

Thomas L. Sazbo, United States Air Force

Thousand Oaks, CA

12:00 AM

I'm going to try to keep you awake and I hope to tie some of the subjects that were discussed earlier today in with this paper. You may be asking, "What do I mean by velocity dispersion?" and even more, "What do I mean by residual stress?"

Review of Theories of Scattering of Elastic Waves by Cracks

Edgar A. Kraut, Rockwell International

Thousand Oaks, CA

12:00 AM

The ultrasonic detection of cracks in the interior of an elastic solid by the use of surface transducers is a fundamental NDE problem. The presence of cracks may be detected either by observing the back scattered elastic waves using the launching transducer as a receiver or by observing obliquely scattered waves with a separate receiving transducer located elsewhere on the surface. Unfortunately, most of the theoretical work on the scattering of elastic waves from cracks has been confined to the case of a crack in an unbounded elastic solid, a situation far different from the experimental one. Even in that case, exact results are available only for the crack occupying a half plane. Exact results for cracks having finite surface area, such as a penny shaped cracks, are not available in detail, although many approximate calculations have been published, particularly in the low frequency limit.

Scattering of Ultrasonic Pulses from Cylindrical Inclusions in Elastic Solids

Wolfgang Sachse, Cornell University

Thousand Oaks, CA

12:00 AM

I would like to review today the work that we have been doing in the Mechanics Department at Cornell in studying the scattering of ultrasonic pulses by a cylindrical inclusion. A large portion of this work has been supported by the National Science Foundation through a grant to the Materials Science Center at Cornell. This work is the result of a very close interaction between the theoretical studies that have been made by Professor Pao, his students and his associates, and the experimental work that has been done by my students and myself. The first results I will describe have previously been reported in several publications while the later work is taken from the dissertation of Bifulco and a forthcoming publication.

Sources of Acoustic Emission in Aluminum Alloys

Lloyd J. Graham, Rockwell International

Thousand Oaks, CA

12:00 AM

I'd like to start the talk with a brief description of this task on acoustic emission (AE) source identification in terms of its immediate aims and ultimate goals. The _immediate aims were to, first, identify the sources of AE in a variety of materials, making a survey of just where they originate, and their dependence on changes in microstructure. The second aim was to identify characteristics of the AE signals which might be related to these sources and, therefore, indirectly to the microstructural effects. These aims were realized for the materials studied. The ultimate goals of such a study would be the extrapolation of AE data from one test situation or from one material to another, and, ideally, to relate the emissions to a determination of flaw criticality.

Surface Acoustic Wave Filters for Real Time Processing of Ultrasonic Signals

Richard White, University of California - Berkeley

Thousand Oaks, CA

12:00 AM

We shall discuss using surface elastic wave device to do analog signal processing that is applicable to NOE problems . I'm going to talk today about one specific device which we have looked at which can be used with a conventional NOE system to improve resolution.

It's really brave to remain analog in an increasingly digital world, but I think there are some advantages that analog devices can have. The advantages I am referring to are speed of operation (real time operation), and the simplicity of the device, which translates, in part, into low cost.

The Current Status of Nondestructive Testing with Positron Annihilation

J G. Byrne, University of Utah

Thousand Oaks, CA

12:00 AM

The existence of the positron was verified more than 40 years ago by Anderson but only in the 1950's was much attention given to its usefulness in terms of understanding the electronic structure of solids. As more workers became involved in the 1950's and 1960's work began to appear on metals, gasses and insulators and it was realized that positrons were sensitive to lattice defects. This realization has caused a new burst of interest in experimental and theoretical work using the positron as a probe for defects. Advantages of the positron technique are that it is nondestructive, very fast (106 counts in about 10 minutes), and highly sensitive to very low defect concentrations.

Theoretical Analysis of Acoustic Emission Spectra

William J. Pardee, Rockwell International

Thousand Oaks, CA

12:00 AM

Frequency analysis of acoustic emission spectra has been done by our group and others for several years now. Lloyd Graham presented some of the results in a previous paper. One would like, of course, to extract as much information as possible from these spectra. We hope, for example, that at least some fracture or failure processes, microscopic failure processes, will have distinctive frequency signatures: perhaps certain kinds of phase transformations or, as has been discussed, microcrack initiation by brittle fracture of intermetallic particles.

Transducers Applied to Measurements of Velocity Dispersion of Acoustic Surface Waves

Harold M. Frost, United States Air Force
Thomas L. Szabo, United State Air Force

Thousand Oaks, CA

12:00 AM

This talk concerns two new acoustic surface wave (SAW) transducer units developed and applied to the field of nondestructive testing. We confine ourselves here to tone burst transduction of Rayleigh waves (at MHz frequencies), although CW operation and (for example) Lamb and bulk waves are also possible.

Ultrasonic Reference Blocks and Characterized Fatigue Cracks

Donald G. Eitzen, National Bureau of Standards
Daniel J. Chwirut, National Bureau of Standards

Thousand Oaks, CA

12:00 AM

The National Bureau of Standards initiated an identifiable program in nondestructive testing about a year and a half ago. Up until that time there was significant effort in areas affecting NDT, but the focus of these efforts was not nondestructive testing.

I will describe only a couple of the facets of the current NOT program at NBS. The program is growing, and by now is approaching the size of about 3/4 of a million dollars per year. The aim of the program is to bring direct impact on nondestructive activities through better test methods, through standards, and through measurement services and interpretive methodologies.

I will describe progress on an activity aimed at near term improvements in ASTM type reference blocks and also on an effort aimed at producing characterized flaws. I will also very briefly touch on some work we are doing towards establishing measurement techniques for determining the characteristics of ultrasonic and acoustic emission transducers. The ASTM reference block work is supported by the Air Force, NASA and the Army, and the work on characterized flaws and transducers is supported by in-house funding.

Ultrasonic Samples Using Diffusion Bonding Techniques

N E. Paton, Rockwell International

Thousand Oaks, CA

12:00 AM

The objective of this part of the ARPA/AFML program was to produce a set of standard samples which would be suitable for NDE testing and characterization of different NDE techniques. The idea was to have a standard set of samples that could be used to compare results of various investigators and various techniques. In addition to internal defects it was decided, that in order to couple the previous work, the standard flat bottom hole type of defect should also be produced and so we have done this.

Ultrasonic Wave Interactions with Interfaces

George Alders, Rockwell International
Lloyd Graham, Rockwell International

Thousand Oaks, CA

12:00 AM

The objective of the work that I will describe was to determine experimentally how a sound wave interacts with a layer whose thickness is measured in atomic sized units. That is, the interface layers are measured in hundreds of angstroms and are thus much, much thinner than any of the millimeter or tenths of millimeter kinds of wave lengths that we ordinarily have, or can hope to have to interrogate the bond line.

The question we must address is; How does a very long wave length ultrasonic wave interact with a very thin layer or collection of layers? Or; When we get a signal back from an interface, how should we unfold it to learn something about the nature of the interface?

Welcome

C J. Meechan, Rockwell international

Thousand Oaks, CA

12:00 AM

It's a pleasure to welcome you on behalf of Rockwell International and the Science Center to this symposium. We're very happy to join with Dr. Ed VanReuth and Dr. Mike Buckley in sponsoring this symposium.

Nondestructive evaluation or nondestructive testing, as some of you would call it, is a fantastica lly important subject to us, both to the company and we believe as a country. We're performing a little experiment with NASA and the Soviet Union today, and that little program has .a lot of dependence on nondestructive evaluation.