A Novel Ultrasonic Method for Accurate Characterization of Microstructural Gradients in Monolithic and Composite Tubular Structures

Thumbnail Image
Date
1999
Authors
Roth, Don
Carney, Dorothy
Baaklini, George
Bodis, James
Rauser, Richard
Major Professor
Advisor
Committee Member
Journal Title
Journal ISSN
Volume Title
Publisher
Authors
Research Projects
Organizational Units
Journal Issue
Is Version Of
Versions
Series
Series
Review of Progress in Quantitative Nondestructive Evaluation
Center for Nondestructive Evaluation

Begun in 1973, the Review of Progress in Quantitative Nondestructive Evaluation (QNDE) is the premier international NDE meeting designed to provide an interface between research and early engineering through the presentation of current ideas and results focused on facilitating a rapid transfer to engineering development.

This site provides free, public access to papers presented at the annual QNDE conference between 1983 and 1999, and abstracts for papers presented at the conference since 2001.

Department
Abstract

Prior studies have shown that ultrasonic velocity/time-of-flight imaging that uses back surface echo reflections to gauge volumetric material quality is well suited (perhaps more so than is the commonlyused peak amplitude c-scanning) for quantitative characterization of microstructural gradients. Such gradients include those due to pore fraction, density, fiber fraction, and chemical composition variations [11–15]. Variations in these microstructural factors can affect the uniformity of physical performance (including mechanical [stiffness, strength], thermal [conductivity], and electrical [conductivity, superconducting transition temperature], etc. performance) of monolithic and composite [1,3,6,12]. A weakness of conventional ultrasonic velocity/time-of-flight imaging (as well as to a lesser extent ultrasonic peak amplitude c-scanning where back surface echoes are gated [17] is that the image shows the effects of thickness as well as microstructural variations unless the part is uniformly thick. This limits this type of imaging’s usefulness in practical applications. The effect of thickness is easily observed from the equation for pulse-echo waveform time-of-flight (2τ) between the first front surface echo (FS) and the first back surface echo (B1), or between two successive back surface echoes where: 2τ=(2d)V (1) where d is the sample thickness and V is the velocity of ultrasound in the material. Interpretation of the time-of-flight image is difficult as thickness variation effects can mask or overemphasize the true microstructural variation portrayed in the image of a part containing thickness variations. Thickness effects on time-of-flight can also be interpreted by rearranging equation (1) to calculate velocity: V=(2d)2τ (2) such that velocity is inversely proportional to time-of-flight. Velocity and time-of-flight maps will be affected similarly (although inversely in terms of magnitude) by thickness variations, and velocity maps are used in this investigation to indicate time-of-flight variations.

Comments
Description
Keywords
Citation
DOI
Copyright
Fri Jan 01 00:00:00 UTC 1999