Application of subband adaptive filtering techniques to ultrasonic detection in multilayers

• 来源期刊: 声学学报（英文版）
• 学科: 物理学
• 年，卷（期）: 2003,（1）
• 页码范围: 41-49
• 页数: 9页
• 分类号: O426
• 语种: 英文

摘要

The ultrasonic testing for the defects of complete disbond in multi-layered structure with lower acoustic impedance beneath a high acoustic impedance overburden is one of the difficult problems in ultrasonic nondestructive testing field. A model of a multi-layered steel-rubber composite plate is depicted. Because the acoustic impedance of the steel differs far from that of the couplant water and the rubber, the energy of the signal reflected from the debonded rubber layers is very weak. More over, the flaw echoes are masked by the strong echoes reverberated in the steel plate. It's nearly impossible to identify the debonding echoes directly. The subband adaptive filtering method is discussed in the paper, where the subband decomposition is performed by mutual wavelet packets decomposition on the criterion of maximizing the cross-correlation between the signals. The simulations on both synthetic and real signals are presented. The echoes from the delaminated flaw at the depth of 5 mm in the rubber from the calculated signal, and echoes from the flaw at the depth of 3 mm from the real signal are extracted successfully.