Location

La Jolla, CA

Start Date

1-1-1987 12:00 AM

Description

In general, the ultrasonic attenuation in polycrystalline materials at room temperature (RT) is described in terms of scattering losses and absorption losses. Ultrasonic scattering is caused by the grain structure of the material whereas the interaction of the ultrasonic wave with lattice imperfections (e. g. dislocations, Bloch walls) leads to energy absorption. Usually, it is impossible to separate the different contributions by using conventional pulse-echo techniques which measure the total ultrasonic attenuation plus some artificial attenuation due to specimen geometry and sound-field divergence. Only if special assumptions on the frequency dependence of each contribution can be made, a separation might be possible /1/. Recently, several techniques have been proposed in order to measure ultrasonic absorption directly. One technique is based on resonance measurements in small cylindrical specimens by exciting standing waves at frequencies below 1.2 MHz /2/. A second technique uses the infrared detection of the heat produced by the ultrasonic absorption /3/, and a third technique is based on ultrasonic diffusion measurements /4/. This paper presents a new method for direct absorption measurements in polycrystalline materials by measuring ultrasonic reverberation. The method is especially appropriate in the case of large scattering contributions usually present in coarse grained steels.

Book Title

Review of Progress in Quantitative Nondestructive Evaluation

Volume

6A

Chapter

Chapter 1: General Techniques—Fundamentals

Section

Other Techniques

Pages

473-481

DOI

10.1007/978-1-4613-1893-4_54

Language

en

File Format

application/pdf

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Jan 1st, 12:00 AM

A New Method for the Measurement of Ultrasonic Absorption in Polycrystalline Materials

La Jolla, CA

In general, the ultrasonic attenuation in polycrystalline materials at room temperature (RT) is described in terms of scattering losses and absorption losses. Ultrasonic scattering is caused by the grain structure of the material whereas the interaction of the ultrasonic wave with lattice imperfections (e. g. dislocations, Bloch walls) leads to energy absorption. Usually, it is impossible to separate the different contributions by using conventional pulse-echo techniques which measure the total ultrasonic attenuation plus some artificial attenuation due to specimen geometry and sound-field divergence. Only if special assumptions on the frequency dependence of each contribution can be made, a separation might be possible /1/. Recently, several techniques have been proposed in order to measure ultrasonic absorption directly. One technique is based on resonance measurements in small cylindrical specimens by exciting standing waves at frequencies below 1.2 MHz /2/. A second technique uses the infrared detection of the heat produced by the ultrasonic absorption /3/, and a third technique is based on ultrasonic diffusion measurements /4/. This paper presents a new method for direct absorption measurements in polycrystalline materials by measuring ultrasonic reverberation. The method is especially appropriate in the case of large scattering contributions usually present in coarse grained steels.