Quantitative ultrasonic techniques for determining the serviceability of structural components are reviewed. Particular emphasis is placed on the use of forward and inverse elastic wave scattering theory as a fundamental foundation for predicting such engineering parameters as the probability of flaw detection and for developing improved techniques for flaw sizing. Ultrasonic measurement techniques for the determination of distributed failure-related properties such as residual stresses are discussed, and the status of the prediction of failure by the detection of acoustic emission precursors is reviewed.

https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1143&context=ameslab_pubs

Quantitative Ultrasonic Nondestructive Evaluation Methods

Flaw signals measured in ultrasonic testing include the effects of the measurements system and are corrupted by noise The measurement system response is both bandlimited and frequency dependent within the bandwidth, resulting in measured signals which are blurred and distorted estimates of actual flaw signatures The Wiener filter can be used to estimate the flaw's scattering amplitude by removing the effect of the measurement system in the presence of noise A method is presented for implementing an optimal form of the Wiener filter that requires only estimates of the noise distribution parameters The theoretical error for scattering amplitude estimation, assuming various levels of available prior information, is analyzed Three estimation techniques, one a maximum-likelihood based method and the other two residual-sum-of-squares methods, are formulated and tested The results demonstrate that any of the three approaches could be used to optimally implement the alternative form of the Wiener filter with limited prior information >

Flaw signature estimation in ultrasonic nondestructive evaluation using the Wiener filter with limited prior information

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

Grain noise power spectrum estimation for weak scattering polycrystalline materials using experimentally estimated backscatter coefficients: oblique incidence

In order to perform quantitative ultrasonic NDE measurements, it is necessary to make those measurements independent of the characteristics and settings of the pulser-receiver used and the choice of the transducer employed. The combined effects of those parts of the ultrasonic system on the measured signal can be described mathematically in terms of a single system “efficiency” factor.

Model-Based Calibration of Ultrasonic System Responses for Quantitative Measurements

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

B. Addison

Papers

Optimum Measurement of Broadband Ultrasonic Data