窄带脉冲信号测量横波衰减系数-频率曲线的方法  

Measuring frequency-dependent attenuation coefficient curve of ultrasonic shear wave using a narrowband pulse-echo method

作　　者：张广栋 李天骥 李雄兵[1] 张书增[1] ZHANG Guangdong;LI Tianji;LI Xiongbing;ZHANG Shuzeng(School of Traffic and Transportation Engineering ,Changsha 410075)

机构地区：[1]中南大学交通运输工程学院,长沙410075

出　　处：《声学学报》2022年第1期105-113,共9页Acta Acustica

基　　金：国家自然科学基金项目(51805554);湖南省自然科学基金项目(2019JJ50771)资助。

摘　　要：提出一种测量材料超声横波衰减-频率曲线(α_(s)-f)的方法:应用窄带脉冲驱动接触式横波探头的脉冲反射方式,采用石英晶体作为耦合块,通过测量耦合块和被测试块耦合界面的声压反射和透射系数,并在衍射修正下测量得到单频率下的超声横波衰减系数;在探头有效带宽内改变发射频率并重复测量,得到不同频率下超声横波衰减系数数值;利用非线性最小二乘拟合方法得到其α_(s)-f曲线。采用该方法对铝合金6061材料的衰减系数进行测量,得到α_(s)-f曲线结果为α_(s)(f,2z)=0.32f2.93,皮尔逊相关系数R为0.9864。测量结果与现有方法所得结果进行对比,本方法在单频率下的结果与现有方法吻合,表明本方法测量的有效性,而多频率测量的方法对研究材料α_(s)-f关系具有重要意义。A narrowband pulse-echo method accompanied by multi-frequency measurements is proposed to determine the frequency-dependent attenuation coefficient curve(α_(s)-f) of the ultrasonic shear wave.A narrowband toneburst signal is used to drive the contact shear wave transducer,which transmits shear waves through a coupling block before entering the sample made of quartz crystal,and signals reflected from the upper and bottom surfaces of the sample are collected.When the acoustic pressure-based reflection and transmission coefficients are determined and the diffraction correction is considered,the attenuation coefficient of ultrasonic shear waves at a single frequency can be obtained.Experiments are repeated using different driving frequencies within the effective bandwidths of the transducers,and attenuation coefficients of ultrasonic shear waves at different frequencies are determined.The α_(s)-f curve is then obtained from these measured results using a nonlinear least-squares fitting method.The frequency-dependent attenuation coefficient for aluminum alloy 6061 is measured by using the proposed method,and the α_(s)-f curve is determined as α_(s)(f,2 z)=0.32 f;with the Pearson correlation coefficient R of 0.9864.The attenuation coefficients obtained in this work are compared with those measured using the traditional method,and it is shown that results agree well with each other at the effective bandwidth.It is also shown that the multi-frequencies measurement method is also benefit to determine the α_(s)-f curve accurately.

关 键 词：石英晶体 非线性最小二乘拟合 皮尔逊相关系数 频率曲线 衰减系数 发射频率 有效带宽 反射和透射系数 

分 类 号：TB302[一般工业技术—材料科学与工程]