陶瓷基复合材料粘接构件超声特征研究方法

新型航天器机体外层陶瓷基复合材料隔热构件在粘贴过程中会产生缺陷,不利于航天器的飞行安全.针对一种陶瓷基多孔复合材料粘接结构构件,利用自主研制的超声C扫描自动检测系统,研究构件粘接层缺陷的超声检测特征.考虑材料多孔性和各向异性会导致超声数据多噪音,采用自适应小波阈值算法对超声信号进行去噪,从而提高透射声波的信噪比.在此基础上,提出采用Hilbert-Huang变换(HHT)和伪Wigner-Ville分布(PWVD)相结合的方法对透射声波进行时频分析,得到时间、频率和幅值的三维分布,从而获得超声透射波最大幅值和对应的时间和频率.通过对比缺陷处与非缺陷处超声透射信号的时频域分布,揭示了该类新型陶瓷基复合材料粘接缺陷对超声信号的影响特点.

Ultrasonic Features Study Method of Bonded Ceramic Matrix Composite

The outer layer of the ceramic matrix composite insulation member of the spacecraft machine will produce defects during the pasting process,which is not conducive to the flight safety of the spacecraft.Aiming at a ceramic-based porous composite bonded structural member,ultrasonic detection characteristics of component bonding layer defects are studied by using the self-developed ultrasonic C-scan automatic detection system.Considering the porosity and anisotropy of the material,the ultrasonic data is more noisy.The adaptive wavelet threshold algorithm is used to denoise the ultrasonic signal,thereby improving the signal-to-noise ratio of the transmitted acoustic wave.On this basis,a time-frequency analysis of transmitted acoustic waves is carried out by using Hilbert-Huang transform (HHT) and Pseudo Wigner-Ville Distribution(PWVD).The three-dimensional distribution of time,frequency and amplitude is obtained,thereby obtaining the maximum amplitude of the ultrasonic transmission wave and the corresponding time and frequency.By comparing the time-frequency distribution of the ultrasonic transmission signal between the defect and non-defective,the influence characteristics of the bonding defects of the new ceramic matrix composites on the ultrasonic signal are revealed.