基于声发射多特征融合的搅拌摩擦焊缺陷监测

Defecting monitored of friction stir welding based on acoustic emission multi-feature fusion

搅拌摩擦焊(friction stir welding,FSW)是一个多物理场耦合过程,焊接过程中声发射信号与焊接缺陷具有关联性.基于声发射检测与多特征融合研究FSW缺陷监测方法,实时检测固态介质中的声发射信号,利用短时傅里叶变换、小波变换、梅尔频谱对声发射信号进行分析,确定焊接缺陷与声发射信号之间的相关性,最后通过concat融合方法构建多特征向量.结果表明,FSW在预制缺陷处具有不同的声发射信号特征.短时傅里叶、小波变换的主要频段集中在20 kHz,出现缺陷时功率分别达到-40,0.8 dB以上,梅尔频谱的主要频段集中在3.5 kHz出现缺陷时功率达到-40 dB以上.应用多层神经网络分别建立基于单特征、多特征向量的焊接缺陷识别模型,多特征向量的焊接缺陷识别模型在数据集中的平均识别率达到97%,比基于单一特征缺陷识别模型提高18%.研究的多特征缺陷识别模型能更准确地对焊接状态进行识别与监测.

Friction stir welding(FSW) is a multi-physical field coupling process. The acoustic emission signal in the welding process is directly related to the welding defects.Based on acoustic emission detection and multi-feature fusion,the defecting monitored of FSW method is studied. Experiments of prefabricated defect FSW are carried out. The acoustic emission signal in the solid medium is detected in real time,and analyzed by short-time fourier transform, wavelet transform and Mel spectrum which explore the correlation between welding defects and acoustic emission signal. Finally, multifeature vectors are constructed by the concat fusion method. It is indicated that FSW has different acoustic emission signal characteristics at the prefabricated defects. Short-time fourier and wavelet time-frequency analysis shows that the frequency of acoustic emission signal is concentrated in 20 kHz and the power at prefabricated defects is more than-40 and 0.8 dB respectively. Mel time-frequency analysis shows that the frequency of acoustic emission signal is mainly concentrated in3.5 kHz and the power is more than-40 dB at prefabricated defects. The multi-layer neural network is applied to establish the welding defect recognition model based on single feature and multi-feature vector respectively. The average recognition accuracy of the multi-feature welding defect recognition model is 97% in the dataset, which is 18% higher than the single-feature defect recognition model. The multi-feature welding defect recognition model can more accurately recognize and monitor the welding state.