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1975
Wednesday, January 1st
12:00 AM

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.

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.

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.

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.

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.

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.