超薄双层胶结复合结构低频超声类兰姆波定征方法

提出用低频超声类兰姆波定征方法来估计超薄双层胶结复合结构各层的纵波声带、横波声速、厚度和密度等参数，采用超声耦合剂耦合方式，结合超声漏类兰姆波频哉分析方法获取复合结构类兰姆波色散曲线，提出以色散特性为基础的低频超声类兰姆波定征方法和在最小二乘意义下以色散同工线为基础的反向算法对超薄双层胶结复合结构进行参数估计，进上步分析了影响估计准确性的各种因素，研究了低频超声类兰姆波定征方法对超薄双层胶结复合结

Low Frequency Ultrasonic Method for Characterizing Ultra-Thin Bi-Layer Composite

A low frequency ultrasonic (Lamb like) wave method is used for characterizing the shear, longitudinal wave velocities, the thickness, and the density of ultra thin two layered bonding composite . The layer thickness is only a fraction of the ultrasound wavelength so that the echoes from the front and back surfaces cannot be separated in the time domain. The least square method and the secant algorithm are applied to determine the governing parameters basing on the measured dispersion curve of the low frequency Lamb wave propagating along the composite. The reasons for evaluation error of the parameters and the sensitivity of the method for different parameters are analyzed. The technique is employed experimentallly to characterize the ultra thin aluminum and brass layers of the aluminum/brass composite with thickness down to five percent of the ultrasonic wavelength by using a pair of broadband longitudinal wave transducers of 2 MHz. It is observed that the nominal value agrees well with the estimation.