金属构件空气耦合声谐振检测方法研究

Study on air-coupled acoustic resonance detection technique for metal component

针对天然气长输管道易发生腐蚀减薄等损伤,采用常规漏磁和接触式超声方法难以进行中低压天然气管道内检测的问题,本文提出了一种空气耦合声谐振检测方法,利用空气作为耦合介质,结合声谐振技术,实现了非接触、大提离条件下的金属构件壁厚和局部腐蚀检测。通过建立数值模型和试验验证,分析了单频正弦激励和宽频线性调频激励下声场分布及回波时频域响应信号的差异特征,对比聚焦型和平面型换能器的空气耦合声谐振检测能力,并基于界面回波信号差分法,开展了构件壁厚测量和平底孔缺陷检测试验。模拟和试验结果表明,该方法能有效提高回波能量强度,准确测量金属构件壁厚,可实现31 mm提离高度下金属构件壁厚及局部腐蚀的检测误差控制在±0.5 mm内,对于保障管道安全运行具有重要的实际应用价值。

Natural gas pipelines are prone to corrosion and thinning damage.Conventional magnetic flux leakage and contact ultrasonic methods are not suitable for internal inspection of medium-and low-pressure natural gas pipelines.In this study,an aircoupled acoustic resonance detection method was proposed.By using air as the coupling medium and combining with acoustic resonance technology,non-contact detection of wall thickness and local corrosion of metal components under large liftoff conditions were achieved.The differences in the distribution of the sound field and the time-frequency domain response of the echo under single-frequency sinusoidal excitation and wide-band linear frequency modulation excitation were analyzed through numerical modeling and experimental verification.The detection capabilities of focused and planar transducers for air-coupled acoustic resonance were compared,and experiments on wall thickness measurement and flat-bottom hole defect detection were conducted based on the interface echo signal differential method.Simulation and experimental results demonstrate that this method can effectively enhance the intensity of echo energy and accurately measure the wall thickness of metal components.It is capable of controlling the detection error of metal component wall thickness and local corrosion within±0.5 mm even under a lift-off height of 31 mm,which holds significant practical application value for ensuring the safe operation of pipelines.