中文摘要：

相控阵超声无损检测技术近年来在无损检测领域得到了越来越广泛的应用。但当前相控阵超声检测基于传统线性超声，对于材料或结构的微缺陷、微裂纹等缺陷不敏感。研究基于超声的非线性效应的非线性超声无损检测技术对于克服线性超声相控阵技术的不足具有积极的意义。本文设计和开发了基于非线性超声相控阵的无损检测系统，并利用超声检测的标准试件对该系统的性能进行了检验。对比测试了常规线性超声方法、基于滤波的非线性超声方法以及基于反相脉冲的非线性超声方法对于钨丝线靶、超声仿体以及碳钢试块的检测效果。测试结果表明，非线性超声相控阵无损检测技术与传统线性超声相控阵无损检测相比具有空间分辨力高、缺陷分辨力强等优点，而基于反相脉冲的非线性相控阵超声无损检测在空间分辨力上比基于滤波的非线性超声检测方法又有比较显著的提高。

英文摘要：

Phased array ultrasonic nondestructive tesing （NDT） has been more widely applied in recent years due to its flexibility, high efficiency and accuracy. However, the conventional phased array ultrasonic NDT technique is based on linear acoustic response of testing medium, and has inadequate spacial resolution and sensitivity for detection of small cracks and defects. Nonlinear phased array ultrasonic NDT technique, which is based on detection of the nonlinear acoustic response of the medium, is a possible solution. In this work, a nonlinear phased array ultrasonic NDT system was developed, and its performance was systematically examined. Conventional phased array imaging, filter-based nonlinear phased array imaging, and pulse-inversion nonlinear phased array imaging were conducted for three standard specimens： a tungsten wire phantom, a high frequency tissue phantom and a steel test block. Comparison of imaging results indicates that relative to the conventional phased array method, both nonlinear phased array imaging methods show significant improvement on spacial resolution. Furthermore, in all cases, relative to the filter-based nonlinear method, the pulseinversion nonlinear method shows remarkable improvement of resolution along both lateral and axial direction.