基于小波分解表面波的涂层平板表面缺陷检测方法研究

激光照射在涂层平板表面产生的超声表面波传播时会产生色散现象,该现象会影响表面缺陷检测精度。针对表面波的色散问题,采用有限元仿真分析表面波在涂层平板表面的传播规律,利用Morse小波分解多频表面波信号,提取最大幅值单一频率的缺陷时域信号从而确定表面缺陷位置。在此基础上通过扫描缺陷附近检测点的方式,分析缺陷前沿入射波和缺陷后沿透射波时域信号之间的关系构建缺陷深度量化公式。数值研究表明:采用小波分解多频表面波信号的方法有效避免了表面波的色散影响,提高了缺陷位置检测精度；当缺陷深度在1~2 mm范围时,根据缺陷深度量化公式计算得到的缺陷深度与实际缺陷深度较为吻合且误差百分比控制在8 %以内,验证了提出的缺陷深度量化公式的有效性,为应用表面波实现涂层平板表面缺陷检测提供了新的工具。

Research on surface defect detection method of coating plate based on wavelet decomposition surface wave

The surface wave produced by laser irradiation on the surface of coating plate will produce dispersion phenomenon when it propagates,which will affect the precision of surface defect detection.In order to solve the dispersion problem of surface wave,finite element simulation is used to analyze the propagation rule of propagation surface wave on the surface of coating plate surface.Morse wavelet is used to decompose the multi-frequency surface wave signal and the time domain signal of the maximum energy amplitude in the single frequency of surface wave is extracted to determine the location of surface defect.Based on this,the relationship between the incident wave at the defect front and the transmitted wave at the defect rear by scanning the detection points near the defect are analyzed,and the defect depth quantization formula is constructed.Numerical research show that:The wavelet decomposition method can effectively avoid the influence of surface wave dispersion and improve the precision of defect location detection.When the defect depth is within the range of 1~2 mm,the defect depth calculated according to the defect depth quantization formula is consistent with the actual defect depth and the error percentage is controlled within 8 %,which verifies the effectiveness of the proposed defect depth quantization formula.It provides a new tool for surface defect detection of coating plate by surface wave.