Degree Type

Dissertation

Date of Award

1991

Degree Name

Doctor of Philosophy

Department

Aerospace Engineering

First Advisor

Lester W. Schmerr

Abstract

Flaw classification (determination of the flaw type) and flaw sizing (prediction of the flaw shape, orientation and sizing parameters) are very important issues in ultrasonic nondestructive evaluation of materials. In this work, new techniques for both classification and sizing are described;In the area of flaw classification, a methodology is developed which can solve classification problems in weldments using probabilistic neural networks. In the area of flaw sizing, four new approaches are presented including (1) the determination of distance-gain-size (DGS) curves and frequency response curves for flat-bottom holes based on a theoretical ultrasonic scattering model, (2) a time-of-flight equivalent (TOFE) sizing method for relatively large (>1 mm) flaws in materials, (3) an amplitude-based equivalent (ABE) sizing method and (4) a first moment (FM) sizing method. Both the third and fourth methods are shown to be new viable techniques for sizing relatively small (<1 mm) flaws in materials.

DOI

https://doi.org/10.31274/rtd-180813-12199

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Sung-Jin Song

Language

en

Proquest ID

AAI9212192

File Format

application/pdf

File Size

199 pages

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