摘要
变厚度板因其轻量化等结构优势在航空航天、核能工程等重要领域具有广泛应用,其缺陷检测对保障服役安全具有重要意义。然而,变厚度板的几何非均匀性会显著影响其中Lamb波的传播特性,导致Lamb波传播行为复杂、频散效应加剧,并使得常规适用于等厚度波导结构的Lamb波缺陷成像方法失效。针对变厚度板缺陷检测问题,提出一种基于波形相关因子加权的Lamb波全聚焦成像方法,用于变厚度板中缺陷的定位成像。该方法首先构建了Lamb波在变厚度板中传播的理论模型,将厚度渐变波导等效为一系列局部均匀的等厚度短波导的组合。其次,利用基于传播路径的虚拟反向传播技术对缺陷散射波包进行频散补偿,修正波形畸变。在此基础上,计算频散补偿后各通道信号的波形相关系数,作为权重因子与经典全聚焦方法的幅值叠加机制复合,构建基于权重因子的幅值成像指标。该成像指标通过波形相关因子加权抑制了非相关噪声对幅值叠加的贡献,提升了缺陷成像的信噪比。在线性变厚度铝合金板中的数值仿真结果表明,所提出的方法能实现缺陷的有效定位成像,且最大缺陷中心定位误差<4 mm,成像背景噪声幅值显著低于传统全聚焦方法,实验结果进一步验证了该方法的有效性。本研究可为变厚度板中的缺陷检测与成像提供有益参考。
Variable-thickness plates are widely used in critical fields such as aerospace and nuclear engineering due to their structural advantages like lightweight properties,making defect detection crucial for ensuring operational safety.However,the geometric non-uniformity of variable-thickness plates significantly affects the propagation characteristics of Lamb waves,leading to complex wave behavior,intensified dispersion effects,and rendering conventional Lamb wave defect imaging methods designed for uniform-thickness waveguides ineffective.To address the defect detection challenges in variable-thickness plates,this study proposes a Lamb wave total focusing method based on waveform correlation factor weighting for defect localization and imaging.The method first establishes a theoretical model of Lamb wave propagation in variable-thickness plates by approximating the thickness-varying waveguide as a series of locally uniform,short waveguides with constant thickness.Subsequently,a propagation-path-based virtual backpropagation technique is employed to perform dispersion compensation on defect-scattered wave packets,correcting waveform distortion.Building on this,the waveform correlation coefficients of the dispersion-compensated signals from each channel are calculated and used as weighting factors,which are combined with the amplitude superposition mechanism of the classical total focusing method to construct a weighted amplitude imaging metric.This metric suppresses the contribution of uncorrelated noise to amplitude superposition through waveform correlation factor weighting,thereby improving the signal-to-noise ratio of defect imaging.Numerical simulations on a linearly varying-thickness aluminum alloy plate demonstrate that the proposed method achieves effective defect localization,with a maximum defect center localization error of less than 4 mm.The imaging background noise amplitude is significantly lower than that of traditional total focusing method.Experimental results further validate the effectiveness of the method.This study provides a valuable reference for defect detection and imaging in variable-thickness plates.Variable-thickness plates are widely used in critical fields such as aerospace and nuclear engineering due to their structural advantages,such as lightweight properties,making defect detection essential for ensuring operational safety.However,the geometric non-uniformity of such plates significantly affects the propagation characteristics of Lamb waves,leading to complex wave behavior,intensified dispersion effects,and rendering conventional Lamb wave defect imaging methods designed for uniform-thickness waveguides-ineffective.To address the defect detection challenges in variable-thickness plates,this paper proposes a Lamb wave total focusing imaging method weighted by waveform correlation factors for defect localization and imaging.First,a theoretical model of Lamb wave propagation in variable-thickness plates is established by approximating the thickness-varying waveguide as a series of locally uniform,constant-thickness short waveguides.Then,a propagation-path-based virtual backpropagation technique is employed to perform dispersion compensation on defect-scattered wave packets,correcting waveform distortions.On this basis,the waveform correlation coefficients of the dispersion-compensated signals from each channel are calculated and used as weighting factors,which are integrated with the amplitude superposition mechanism of the classical total focusing method to construct a weighted amplitude imaging metric.By introducing the waveform correlation factor,this metric suppresses the contribution of uncorrelated noise to amplitude superposition,thereby improving the signal-to-noise ratio of defect imaging.Numerical simulations on a linearly varying-thickness aluminum alloy plate demonstrate that the proposed method can achieve effective accurate defect localization,with a maximum defect center localization error of less than 4 mm,and the imaging background noise amplitude is significantly lower than that of the conventional total focusing method.Experimental results further verify the effectiveness of the proposed approach.This study provides a valuable reference for defect detection and imaging in variable-thickness plates.
作者
黄尹
王旗
许才彬
邓明晰
Huang Yin;Wang Qi;Xu Caibin;Deng Mingxi(College of Aerospace Engineering,Chongqing University,Chongqing 400044,China)
出处
《仪器仪表学报》
北大核心
2025年第6期348-360,共13页
Chinese Journal of Scientific Instrument
基金
国家自然科学基金(12374430,12134002)项目资助。
关键词
LAMB波
缺陷成像
变厚度
全聚焦
波形相关因子
Lamb wave
defect imaging
variable thickness
total focusing method
waveform correlation
