Ultrasonic Double Refraction in Worked Metals

Abstract

In the first part of this work the double refraction observed while measuring the attenuation of ultrasonic transverse waves in heat-treated 4150 steel was investigated. Although the data are not complete, they suggest that this double refraction phenomenon can be utilized to detect the amount of preferred orientation of the crystallites in rolled steel when this orientation is small. Calculated values of fractional velocity differences are given.In the second part the theory of ultrasonic wave propagation in polycrystalline metal is discussed, and the effect of preferential orientation of crystallites on fractional velocity changes is indicated. The use of ultrasonic double refraction data for determining the extent of preferential orientation is discussed. PART I Ultrasonic Double Refraction in 4150 Steel LTRASONIC double refraction was observed while transverse wave attenuation measurements were being made on blocks of hot-rolled 4150 steel which had been austenitized, quenched, and tempered in preparation for tests concerning temper embrittlement. Differences in the velocities of transverse waves polarized parallel to and perpendicular to the rolling direction in the steel resulted in interference patterns (see Fig. 1) such as those observed from irradiated silicon single crystals• and from "compatible" silicon single crystals at different temperatures? The reader is referred to reference 3 for the theoretical treatment of ultrasonic double refraction.A y-cut transducer was bonded to each specimen with phenyl salicylate, and when the polarization direction of the transducer happened to be approximately 45 ø out of alignment with the rolling direction in the steel, the cancellation due to interference became almost complete at some echoes (see Fig. 1). In such cases the echo numbers at which nodes occurred were noted and the fractional differences in velocity were calculated from the m=0 through m=4 branches of the equation (given in reference 3)' /Xv 1 (2m+l)tA+(--1)r•(2to--t•4) v 2fit 4riots4where m is an integer or 0, v the velocity, to a round trip time in the specimen, t• the travel time to the first apparent node, and tT the travel time to the first true node; f is the ultrasonic frequency. Higher branches were excluded since they would have yielded a difference in velocity well above the minimum difference observ-* Author of Part I. able by the pulse-echo method, and no such difference was observed. The values of/Xv/v appear in Table I. When interference patterns occurred the nodes were recorded, but when there was no interference pattern no attempt was made to produce one by reorienting the crystal. As a result the data are incomplete.The possibility that the observed difference in velocity was due to preferential orientation of the grains in the steel due to rolling was explored. If/Xv/v is due to crystal orientation, it is frequency independent (see reference 3). As can be seen from the table, Av/v must be calculated from the m--0 branch of the formulas in reference 3 since this is the only branch gi...

Stress-acoustic relations for stress measurement by ultrasonic technique.

“…In conventional structural material, however, there exists more or less initial anisotropy, 8,9) such as preferred orientation, which has a significant influence on stress-induced anisotropy. property under stress in terms of higher-order constants, which usually have very complicated components.…”

Simultaneous Determination of Orientation and Thickness in Anisotropic Media

“…Hence, in any direction, there are three possible acoustic velocities corresponding to three possible polarizations of the particle displacement (one longitudinal and two shear). The direction of propagation is specified by two orientation angles e and $) relative to the crystallographic axes where h sin $ cos e h = sin $ sin e b cos $ (2) Therefore, the three possible acoustic velocities can be determined for any orientation of the single crystal. The variation in these velocities in space is often depicted by a velocity surface where the radius represents the velocity in that particular direction.…”

“…While there is considerable research in the use of ultrasonic techniques to characterize texture in polycrystalline metals (1)(2)(3)(4)(5), relatively little work has been done on the problem of orientation determination in single crystal materials. There is one study, which explores the possibility of using an ultrasonic approach to orient single crystals when the material properties are known.…”

Measurement of the stress of steel members using the ultrasonic phase spectrum

“…Similar to photoelasticity theory, when a transverse wave is perpendicularly incident on a stressed solid, it decomposes into two transverse-wave components with mutually perpendicular polarization directions and different propagation velocities. 19,20 Bergman and Shahbender 21 experimentally studied changes in the velocities of ultrasonic waves propagating perpendicular to the direction of applied stress. Shear waves with particle motion along the direction of applied stress and shear waves with particle motion transverse to the direction of applied stress were included.…”

“…The present paper focuses on the shear‐wave method. Similar to photoelasticity theory, when a transverse wave is perpendicularly incident on a stressed solid, it decomposes into two transverse‐wave components with mutually perpendicular polarization directions and different propagation velocities 19,20 . Bergman and Shahbender 21 experimentally studied changes in the velocities of ultrasonic waves propagating perpendicular to the direction of applied stress.…”