基于声压反射系数相位谱的涂层密度和纵波声速双参数反演

Simultaneous Inversion of Density and Longitudinal Wave Velocity of Coatings Based on Ultrasonic Reflection Coefficient Phase Spectrum Matching Analysis

提出一种基于声阻抗测量,采用相关系数法对涂层的声压反射系数相位谱二元非线性方程进行双参数反演,同时确定涂层密度和纵波声速的方法。采用超声脉冲回波法,采集厚度为1.929mm铝板和厚度为0.2~0.5mm、掺杂质量百分比30%~50%铁粉的环氧树脂涂层的超声回波信号,在有效频带范围内采用相关系数法对试样理论和试验声压反射系数相位谱进行匹配分析,利用声阻抗条件约束相关系数矩阵,约束后的相关系数矩阵最大值对应的密度和纵波声速即为涂层的最优表征结果,纵波声速和密度的反演误差均在±3.2%以内。

An inversion method based on ultrasonic reflection coefficient phase spectrum （URCPS） combined with acoustic impedance constraint was proposed to simultaneously measure density and longitudinal wave velocity of thin coatings. Ultrasonic pulse echo method was employed on aluminum alloy plate with thickness of 1.929 mm and epoxy resin coatings containing 300.2-0.5mm iron powder with thickness between 0.2- 0.5 mm to obtain ultrasonic signals. Then an inverse algorithm based on the correlation coefficient method was introduced to retrieve the density and longitudinal wave velocity by comparing the theoretical and experimental URCPS and searching maximum in correlation coefficient matrix constrained by acoustic impedance measured by ultrasonic method. The relative errors of the retrieved density and longitudinal wave velocity were less than ＋3.2 %.