电磁声多界面脱粘检测实验研究
文献类型：学位论文
| 作者 | 宋卫华 |
| 学位类别 | 博士 |
| 答辩日期 | 2007-06-07 |
| 授予单位 | 中国科学院声学研究所 |
| 授予地点 | 声学研究所 |
| 关键词 | 超声检测 电磁声换能器 多界面脱粘 信号处理 |
| 其他题名 | Experimental study on the inspection of multilayer disbonds by electromagnetic acoustic transducer |
| 学位专业 | 声学 |
| 中文摘要 | 本论文围绕电磁声多界面脱粘检测的理论及技术问题进行了探索性实验研究。在充分认识和理解电磁声换能机理的基础上，利用课题组搭建的电磁声实验平台开展了电磁声换能器的实验响应特性分析、电磁声界面回波信号优化和电磁声界面回波信号处理与识别等方面的相关理论和实验研究工作，论文所取得的结果对进一步开展电磁声多界面脱粘检测技术应用研究具有重要参考价值，对高波阻下多层低波阻介质脱粘接触式超声检测中遇到的耦合问题和自动化检测效率问题的解决提供了一种可供选择的途径。 论文探讨了利用载波频率及脉冲个数可调的方波长脉冲激励电磁声换能器进行多界面脱粘检测的可行性；利用实验方法研究了体横波电磁声换能器的响应特性，分析了它们在非铁磁性材料-铝和铁磁性材料-钢上的响应特性规律，利用自适应解卷积方法求解了该种换能器在铝上发射和接收声波时的响应；采用小波去噪方法提高了电磁声信号的信噪比，采用自适应抵消去噪方法消除了感生噪声造成的加长盲区，优化了检测信号；提出利用瞬时图谱进行电磁声多界面脱粘检测信号定性识别，利用瞬时振幅、瞬时相位和瞬时频率等三瞬参数特征矢量进行多界面脱粘检测信号BP神经网络识别等方法；论文最后进行了压电与电磁声横波直探头多界面脱粘检测的对比研究，系统比较了两者在实际应用中的优劣。 |
| 英文摘要 | This thesis aims at the theoretical and experimental study on nondestructive testing of disbonds in a bonding multilayer structure by electromagnetic acoustic transducer (EMAT). Based on the electromagnetic ultrasonic testing system built up by our research group and the knowledge of electromagnetic acoustic wave generation mechanism in solids, the thesis focuses mainly on experimental study covering the response of our electromagnetic ultrasonic testing system, the electromagnetic acoustic signal optimization, the electromagnetic acoustic signal processing and identification of interfacial echoes. The presented results are importance of developing EMAT testing system for disbonds in multilayer adhesion structures and demonstration of possible non-contact way to overcome difficulties in coupling and automatic inspection of bonding by piezoelectric probes for structures consisting of a crust of high acoustic impedance and multi-layers of low acoustic impedances. The thesis made feasibility analysis of our EMAT testing system by squared modulation burst drive signal for inspection of multilayer disbonds from interfacial reflection signals. The responses of our EMAT testing system on an aluminum (non-ferromagnetic material) block and a steel block (ferromagnetic material) were experimentally studied, then the responses of the transmitter and receiver of our EMAT testing system on an aluminum block are experimentally analyzed by adaptive filter deconvolution, respectively. The wavelet filtering and adaptive noise canceling methods were used simultaneously to optimize the detected electromagnetic ultrasonic signals, and the processed results demonstrated that the wavelet filtering enhanced the SNR and the adaptive noise canceling narrowed the dead zone effectively. The instantaneous amplitude, phase and frequency of the detected ultrasonic echoes were composed to form three-dimensional instantaneous spectrum patterns to distinguish the testing signals from different adhesive states qualitatively, and the average instantaneous parameters were used as the input eigenvectors for the BP artificial neural network to identify and classify the electromagnetic ultrasonic interfacial echoes. In the final chapter of the thesis, systematical comparisons for multilayer disbonds testing by piezoelectric shear wave probe and electromagnetic transducer were made. |
| 语种 | 中文 |
| 公开日期 | 2011-05-07 |
| 页码 | 105 |
| 源URL | [http://159.226.59.140/handle/311008/276]  |
| 专题 | 声学研究所_声学所博硕士学位论文_1981-2009博硕士学位论文 |
| 推荐引用方式 GB/T 7714 | 宋卫华. 电磁声多界面脱粘检测实验研究[D]. 声学研究所. 中国科学院声学研究所. 2007. |
入库方式： OAI收割
来源：声学研究所
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