基于超声导波SC-DTW的金属板微损检测方法

针对金属板材的质量控制与服役性能评估问题,在对金属板材微损伤进行超声导波检测的基础上,结合形状上下文(shape context,SC)与动态时间规整方法对其损伤劣化程度进行量化评估.该方法以无损Lamb波信号为基准,采用动态时间规划(dynamic time warping,DWT)算法对损伤信号进行相似匹配分析对比,确定基准信号与损伤信号的最佳匹配路径.引入SC的轮廓识别方法对Lamb波的局部波形信息进行统计分析,以波形形状距离代替传统欧氏距离匹配方法,解决DTW相似匹配中的病态对齐问题.最后,将无损Lamb波与损伤Lamb波信号间SC-DTW匹配距离作为损伤程度的量化指标,采用随机闭合裂纹的有限元仿真模型和铝板弯折实验对所提出方法进行验证,结果表明,基于Lamb波SC-DTW的损伤量化指数对铝板早期裂纹具有较高的敏感性和较好的量化表征能力.该方法无需对波包进行识别,也不必进行复杂的特征提取,具有简单高效和抗噪声能力强等优点,在金属板服役性能评估与质量控制中有较好的实用性和推广价值.

Detection of micro-damage in metal plates based on SC-DTW of guided waves

Aiming to the quality control and service performance evaluation of metal plates, a dynamic time warping of guided waves method based on shape context is proposed to quantify the micro-damage in aluminum plates. Using the Lamb wave signal of the intact metal plate as the baseline, the dynamic time warping(DWT) algorithm is applied to match the damage signal to the baseline so as to determine the optimal warping path. The shape context(SC) contour recognition method is introduced to statistically analyze the local waveform information of Lamb waves. The shape distance of waveform is used to replace the traditional Euclidean distance, and the ill alignment problem in the DTW similarity matching is solved. Finally, the SC-DTW matching distance between damaged signal and baseline is used as a quantitative index to describe the damage degree. The finite element simulation model of random closed cracks and bending test of aluminum plates are used to verify the proposed method. The results show that the damage quantification index based on the Lamb wave SC-DTW has high sensitivity and good quantitative characterization ability for the early crack of the aluminum plate. This method does not need to identify the wave packet, and does not need to deal with the feature extraction, which has the advantages of simplicity, high efficiency and strong anti-noise ability, and has good practicability and popularization value in the quality control and service performance evaluation of metal plates.