Location

La Jolla, CA

Start Date

1-1-1998 12:00 AM

Description

Developing a quantitative understanding of ultrasonic beam propagation in engineering materials such as Ti-6A1-4V is important because flaw signals can be altered greatly by the macrostructure that the ultrasonic beam propagates through between the transducer and the flaw. Two consequences of the macrostructure are particularly important: 1) back scattered noise which competes with flaw signals and 2) forward scattered signals and the associated beam profile fluctuations which can modulate the strength of flaw signals [1,2,3], These effects are particularly important when ultrasonic beams are used to detect subtle defects such as unvoided, uncracked hard-alpha inclusions (regions with a high content of interstitial nitrogen or oxygen), because the flaw signal is inherently weak due to a small mismatch of acoustic impedance. Each of these effects is controlled by the inherently complex macrostructure which develops during routine processing. Current theories suggest that the most important physical feature which controls noise is the two-point correlation of elastic constants, which is in turn controlled by local variations in crystallographic orientation [4]. Therefore, in order to quantify the effects of the macrostructure on ultrasonic beam propagation, one must determine the elastic constants on a microscopic level with length scales less than the ultrasonic wavelength, approximately 600 μm at 10 MHz.

Book Title

Review of Progress in Quantitative Nondestructive Evaluation

Volume

17A

Chapter

Chapter 1: Standard Techniques

Section

Elastic Wave Scattering/Backscattering

Pages

89-96

DOI

10.1007/978-1-4615-5339-7_11

Language

en

File Format

application/pdf

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Jan 1st, 12:00 AM

Use of Electron Backscatter Diffraction in Understanding Texture and the Mechanisms of Backscattered Noise Generation in Titanium Alloys

La Jolla, CA

Developing a quantitative understanding of ultrasonic beam propagation in engineering materials such as Ti-6A1-4V is important because flaw signals can be altered greatly by the macrostructure that the ultrasonic beam propagates through between the transducer and the flaw. Two consequences of the macrostructure are particularly important: 1) back scattered noise which competes with flaw signals and 2) forward scattered signals and the associated beam profile fluctuations which can modulate the strength of flaw signals [1,2,3], These effects are particularly important when ultrasonic beams are used to detect subtle defects such as unvoided, uncracked hard-alpha inclusions (regions with a high content of interstitial nitrogen or oxygen), because the flaw signal is inherently weak due to a small mismatch of acoustic impedance. Each of these effects is controlled by the inherently complex macrostructure which develops during routine processing. Current theories suggest that the most important physical feature which controls noise is the two-point correlation of elastic constants, which is in turn controlled by local variations in crystallographic orientation [4]. Therefore, in order to quantify the effects of the macrostructure on ultrasonic beam propagation, one must determine the elastic constants on a microscopic level with length scales less than the ultrasonic wavelength, approximately 600 μm at 10 MHz.