Characterization of Microstructural Evolution by Ultrasonic Nonlinear Parameters Adjusted by Attenuation Factor

Weibin Li,Younho Cho,Xinlin Qing,Bingyao Chen

doi:10.3390/met9030271

Abstract

The use of an acoustic nonlinear response has been accepted as a promising alternative for the assessment of micro-structural damage in metallic solids. However, the full mechanism of the acoustic nonlinear response caused by the material micro-damages is quite complex and not yet well understood. In this paper, the effect of material microstructural evolution on acoustic nonlinear response of ultrasonic waves is investigated in rolled copper and brass. Microstructural evolution in the specimens is artificially controlled by cold rolling and annealing treatments. The correlations of acoustic nonlinear responses of ultrasonic waves in the specimens corresponding to the microstructural changes are obtained experimentally. To eliminate the influence of attenuation, which was induced by microstructural changes in specimens, experimentally-measured nonlinear parameters are corrected by an attenuation correction term. An obvious decrease of nonlinearity with the increase of grain size is found in the study. In addition, the influences of material micro-damages introduced by cold rolling on the acoustic nonlinear response in specimens are compared with the ones of grain boundaries controlled by heat treatment in specimens. The experimental results show that the degradation of material mechanical properties is not always accompanied by the increase of acoustic nonlinearity generated. It suggested that the nonlinear ultrasonic technique can be used to effectively characterize the material degradations, under the condition that the variations of grain sizes in the specimens under different damage states are negligible.

Highlights

The use of nonlinear ultrasonics for characterizing the material property degradation due to fatigue, creep, aging, and thermal damage has been intensively investigated [1,2,3,4,5,6]
Second harmonic generation of ultrasonic wave propagation was used to quantify the amount of nonlinearity in a material by several groups [9,10,11,12]
The objective of this paper is to investigate the effect of microstructural evolution on acoustic nonlinear response in copper and brass

Summary

Introduction

The use of nonlinear ultrasonics for characterizing the material property degradation due to fatigue, creep, aging, and thermal damage has been intensively investigated [1,2,3,4,5,6]. It has been widely accepted that material nonlinearity could be attributed to micro-structural defects, such as lattice deformation or dislocation motion [7,8]. Any process that alters the local atomic potential or impedes the movement of dislocations will change the microstructure and material nonlinearity. Second harmonic generation of ultrasonic wave propagation was used to quantify the amount of nonlinearity in a material by several groups [9,10,11,12]. It is convenient that the acoustic nonlinear response of second harmonic generation is related to the material micro-structural changes. According to the authors’ literature survey, most previous efforts have been limited to the use of nonlinear ultrasonic approach for qualitatively characterization of material microstructure.

Objectives

Results

Conclusion