Kim Jongbeom, Song Dong-Gi, Jhang Kyung-Young
Department of Mechanical Convergence Engineering, Hanyang University, 222 Wangsimni-ro, Seongdong-gu, Seoul 04736, Republic of Korea.
School of Mechanical Engineering, Hanyang University, 222 Wangsimni-ro, Seongdong-gu, Seoul 04736, Republic of Korea.
Ultrasonics. 2017 May;77:197-202. doi: 10.1016/j.ultras.2017.02.013. Epub 2017 Feb 17.
The ultrasonic nonlinearity parameter (β) is determined from the particle displacement amplitudes of the fundamental and second-order harmonic components in an ultrasonic wave propagated through a material. This parameter is generally referred to as the absolute parameter. However, measuring the second harmonic component is especially difficult because its amplitude is usually much smaller than those of signals in typical ultrasonic measurements. For this reason, most studies use the relative parameter determined using the measured electric signal amplitudes of the fundamental and second harmonic ultrasonic waves. However, in many occasions, the absolute parameter is needed for a quantitative assessment of material degradation. This study proposes a method to estimate the absolute parameter from a measured relative parameter along with a proportionality constant between normalized absolute and relative parameters. This method is based on the observed fact that the ratio of between normalized relative and absolute parameters is identical after compensating proportionality constant. The method was experimentally validated for Al6061-T6 alloy specimens heat-treated for different aging times. The parameter determined through the proposed method were compared with the absolute parameters which were measured separately. The results show that these two parameters were close to each other within the measurement errors.
超声非线性参数（β）是根据在穿过材料传播的超声波中基波和二阶谐波分量的粒子位移幅度来确定的。该参数通常被称为绝对参数。然而，测量二次谐波分量特别困难，因为其幅度通常比典型超声测量中的信号幅度小得多。因此，大多数研究使用根据基波和二次谐波超声波的测量电信号幅度确定的相对参数。然而，在许多情况下，需要绝对参数来对材料降解进行定量评估。本研究提出了一种方法，可根据测量的相对参数以及归一化绝对参数和相对参数之间的比例常数来估计绝对参数。该方法基于这样一个观察到的事实，即在补偿比例常数后，归一化相对参数与绝对参数之间的比率是相同的。该方法通过对不同时效时间进行热处理的Al6061-T6合金试样进行了实验验证。将通过所提出的方法确定的参数与单独测量的绝对参数进行了比较。结果表明，在测量误差范围内，这两个参数彼此接近。
