Abstract
The ultrasonic nonlinearity parameter is used to evaluate the nonlinear elasticity of a material, which is determined from the displacement amplitude of the fundamental and second-order frequencies components in an ultrasonic wave propagating through a material. However, the displacement amplitude of the second-order harmonic component generated during propagation through a material is very weak because it is easily affected by measurement conditions such as surface roughness. In this study, we analyzed the influence of surface roughness on the measurement of the ultrasonic nonlinearity parameter. For this purpose, Al6061-T6 and SUS304 specimens were prepared with different surface roughness ranging from 0.5 to 2.9 μm. Then, the absolute and relative ultrasonic nonlinearity parameter measurements were conducted using a through-transmission technique involving two cases: both surfaces being rough, and one being a rough surface and the other being a smooth surface. The experimental results showed that the surface roughness had a lesser influence on the absolute measurement than on the relative measurement and that the transmission surface was less affected by the reception surface. These results were similar regardless of the types of specimens. Therefore, to perform accurate measurements, it is desirable to measure the nonlinearity parameter after polishing the material surface.
Highlights
The ultrasonic nonlinear technique is considered a promising nondestructive evaluation method to evaluate material degradation [1]
Al6061-T6 specimens with one rough surface and one smooth surface were prepared to analyze the influence of surface roughness by varying the surface roughness of the surface where the ultrasound wave is transmitted
This study analyzed the influence of the surface roughness on ultrasonic nonlinearity parameter measurements
Summary
The ultrasonic nonlinear technique is considered a promising nondestructive evaluation method to evaluate material degradation [1]. The results showed that the amplitude decreases markedly and that the frequency spectra change as the surface roughness increases These studies analyzed only the linear ultrasonic characteristics. Na et al [20] investigated the influence of surface roughness on the ultrasonic nonlinearity parameter measurements for 410Cb stainless steel with rough surfaces on both sides of the specimens using the piezoelectric method. The experimental results showed that the ultrasonic nonlinearity parameter decreased as the surface roughness increased; they conducted measurements only 410Cb stainless steel with both surfaces were rough. We investigated the influence of the surface roughness on the ultrasonic nonlinearity parameter measurements For this purpose, Al6061-T6 and SUS304 specimens with different surface roughnesses of 0.5–2.9 μm on both sides were prepared. The influence of the surface roughness on the ultrasonic nonlinearity parameter measurement for each case was analyzed
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