大提离下脉冲涡流对铁磁性材料测厚研究

Research on thickness measurement of ferromagnetic materials with pulsed eddy current under large lift

压力管道局部减薄对工业生产造成重大安全隐患,因此用脉冲涡流技术评估带包覆层管道壁厚减薄极为重要。研究主要目的是找到一种有效且易于提取的信号特征以评估壁厚。利用Comsol仿真软件建立测厚有限元模型,分析脉冲涡流时域信号特征,提取检出电压信号峰值、到峰时间特征量,分析电压峰值、到峰时间和试件厚度之间的关系。同时通过20#碳钢阶梯板实验验证,实验结果表明:电压峰值特征量可以评估提离60 mm以下板件厚度变化,到峰时间和板厚呈线性关系,且不受提离变化影响。通过对比发现到峰时间特征量优于电压峰值,该特征量能有效地用于铁磁性材料的厚度检测,且检测范围大。

The local thinning of pressure pipelines poses a major safety hazard to industrial production,so it is extremely important to use pulse eddy current technology to evaluate the thickness reduction of coated pipelines.The main purpose of the research is to find an effective and easy-to-extract signal feature to evaluate wall thickness.The finite element model of thickness measurement was established by Comsol simulation software,the characteristics of the pulsed eddy current signal in the time domain were analyzed,the peak value of the detected voltage signal,the peak time characteristic quantity were extracted,and the relationship between the voltage peak value,the peak time and the thickness of the specimen was analyzed.At the same time,it was verified by 20#carbon steel ladder plate experiment.The experimental results show that the voltage peak characteristic value can evaluate the thickness change of the plate under 60 mm lift-off,and the peak time and the plate thickness show a linear relationship,and are not affected by the lift-off change.Through comparison,it is found that the peak time characteristic quantity is better than the voltage peak value.This characteristic quantity can be effectively used for thickness detection of ferromagnetic materials with a large detection range.