基于小波分析的樟子松表面和内部声发射信号频域研究

为准确计算樟子松断裂时在表面和内部传播的声发射（acoustic emission,AE）信号传播速度，对樟子松表面和内部传播AE信号的有效频段进行研究。为得到樟子松断裂时候产生的AE信号，使用万能力学试验机进行三点弯曲压断试验，并在试件表面相距固定距离的2个点采集原始AE信号。为得到不同频段的AE信号，对原始AE信号进行小波分解并重构AE波形。针对不同频段的AE信号，采用信号相关性分析法计算信号到达2个传感器的传播时差，以此计算AE信号的传播速度。根据AE信号在不同介质中的传播规律以及AE信号的传播速度判断AE信号的传播介质和AE信号的主要频率。结果表明，当AE信号在樟子松表面传播时，AE信号的有效频段为15~62 kHz。当AE信号在樟子松内部传播时，AE信号的有效频段为125~250 kHz。使用有效频段内信号计算AE信号的传播速度，可显著提升计算得到的AE信号传播速度的准确性。

Frequency Domain Identification of Acoustic Emission Signals on Surfaceand Interior of Pinus sylvestris var.mongolica Based on Wavelet Analysis

In order to accurately calculate the propagation speed of acoustic emission (AE) signals propagating on the surface and interior of Pinus sylvestris var.mongolica wood,the effective frequency band of AE signals propagating on the surface and interior of P.sylvestris var.mongolica was studied.First of all,in order to obtain the AE signal generated when the wood strip of P.sylvestris var.mongolica was fractured,a universal testing machine was used to perform a three-point bending and crushing test,and the original AE signal was collected at two points at a fixed distance on the surface of the strip specimen.Then,in order to obtain the AE signal of different frequency bands,the original AE signal was wavelet decomposed and the AE waveform was reconstructed.In order to obtain the AE signals of different frequency bands,the signal correlation analysis method was used to calculate the propagation time difference of the signals reaching the two sensors,so as to calculate the propagation speed of the AE signal.Finally,the propagation medium of the AE signal and the main frequency of the AE signal were judged according to the propagation law of the AE signal in different media and the propagation speed of the AE signal.The test results showed that when the AE signal propagated on the surface of the wood strips,the effective frequency range of the AE signal was 15-62 kHz.When the AE signal propagated interior the wood strips,the effective frequency band of the AE signal was 125-250 kHz.Using the signal in the effective frequency band to calculate the propagation speed of the AE signal can significantly improve the accuracy of the calculated propagation speed of the AE signal.