Jeong Hyunjo
Department of Mechanical Engineering, Wonkwang University, Iksan 54538, Republic of Korea.
Materials (Basel). 2023 Jul 2;16(13):4777. doi: 10.3390/ma16134777.
In nonlinear ultrasonic testing, the quadratic and more recently cubic nonlinearity parameters are frequently measured as a quantitative indicator of damaged material state. Application of higher-order harmonics can improve the sensitivity of detection and monitoring for damages and microstructures due to their higher values of nonlinearity parameters. The excitation and reception of higher-order harmonics, so-called superharmonics, which use the third to fifth harmonics arising from nonlinear wave propagation, is not sufficiently investigated and applied. The purpose of this communication is to develop a highly sensitive superharmonic nondestructive technique that efficiently generates and receives third- and fifth-order harmonics using the odd harmonic resonances of a single piezoelectric crystal. The method focuses on the measurement of fifth harmonic generation and reception, and the calculation of the relative quintic nonlinearity parameter (δ'). The method also addresses the issue of source nonlinearity that may be contained in the measured fifth harmonic amplitude. The measurement results of δ' for a series of precipitation heat-treated samples clearly show a much better sensitivity than the results of the cubic nonlinearity parameter (γ'). The proposed method enables a highly sensitive and true pulse-echo mode nonlinear ultrasound testing.
在非线性超声检测中，二次及最近的三次非线性参数经常被测量，作为材料损伤状态的定量指标。由于高阶谐波的非线性参数值较高，应用高阶谐波可以提高对损伤和微观结构的检测及监测灵敏度。利用非线性波传播产生的三次到五次谐波的高阶谐波（即所谓的超谐波）的激发和接收，尚未得到充分研究和应用。本通讯的目的是开发一种高灵敏度的超谐波无损检测技术，该技术利用单个压电晶体的奇次谐波共振有效地产生和接收三次和五次谐波。该方法侧重于五次谐波产生和接收的测量以及相对五次非线性参数（δ'）的计算。该方法还解决了测量的五次谐波幅度中可能包含的源非线性问题。一系列沉淀热处理样品的δ'测量结果清楚地表明，其灵敏度比三次非线性参数（γ'）的结果要好得多。所提出的方法能够实现高灵敏度和真实脉冲回波模式的非线性超声检测。
