窄带脉冲信号测量横波衰减系数-频率曲线的方法

提出一种测量材料超声横波衰减-频率曲线(αs-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...

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

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 f2.93 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.