The time domain Born approximation for ultrasonic scattering from volume flaws in an elastic medium is described. Results are given both for the direct and the inverse problem. The time domain picture leads to simple intuitive formulas, which we illustrate by means of several simple examples. Particular emphasis is given to the front surface echo and its use in reconstructing the properties of the flaw.

https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=4771&context=qnde

Time domain Born approximation

In order to interpret measurements of the scattered wave field resulting from sonification of an object, the effects of the measurement system must be removed from the measured data. In ultrasonic nondestructive evaluation, estimation of the farfield scattering amplitude for a flaw in a material, e.g., a crack, void, or inclusion, involves removing the measurement system effects in the presence of electronic noise and noise due to the scattering of sound from inherent material features such as grain boundaries. The purpose of the work reported here was to evaluate an optimal Wiener filtering approach to scattering amplitude estimation. The filter was shown to determine an optimal estimate as the weighted average of the information derived from measurement of the scattered wave field and prior information about the flaw distribution. The optimal Wiener filter was evaluated and compared to a nonoptimal form of the Wiener filter. The optimal Wiener filter was shown to provide improved scattering amplitude es...

https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=9876&context=rtd

A prior knowledge based optimal Wiener filtering approach to ultrasonic scattering amplitude estimation

The increasing use of quantitative techniques for characterizing flaws in materials often requires accurate measurement of flaw properties over a wide range of frequencies despite t he presence of noise and despite the variability of the properties of the transducer, electronics, etc. In this paper, we provide a statistical treatment of the problem of extracting the scattering amplitude of a flaw from measured data. A technique is derived for achieving extended bandwidth by combining data from two or more transducers.

https://ieeexplore.ieee.org/iel5/10280/32713/01534472.pdf

Optimum Measurement of Broadband Ultrasonic Data

Test Bed for Quantitative NDE — Inversion Results

There is an increasing need for the characterization of small flaws in ceramic components. This project is concerned with detecting and characterizing flaws in the bulk of ceramic parts. Cylindrical tensile test specimens of hot pressed Si3N4 are being prepared and, when available, will be inspected. In preparation for the arrival of the samples, measurement techniques have been developed for inspection of cylindrical shaped samples, signal processing techniques have been de vel oped for obtaining flaw scattering data over a broad range of frequencies and analysis techniques have been developed to automatically extract flaw characteristics from measured data.

https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1026&context=cnde_yellowjackets_1981

Low Frequency Characterization of Flaws in Ceramics

http://ieeexplore.ieee.org/iel5/10280/32713/01534458.pdf

J.M. Richardson

Papers

Semi-Adaptive Approach to the Extraction of Low-Frequency Properties from Scattering Measurements