基于相轨迹分析的电涡流无损检测方法研究

发布时间：2018-03-30 00:11

本文选题：电磁涡流　切入点：无损检测　出处：《天津工业大学》2017年硕士论文

【摘要】：电磁涡流无损检测技术利用施加于电磁线圈上的交变电流产生磁场,继而在被测导体上产生交变的电涡流,交变的电涡流又产生了涡流场,通过检测涡流场即可间接获取被测导体的特征参数。提离噪声和集肤效应是电磁涡流无损检测技术存在的主要问题。文本基于电磁涡流无损检测系统的等效变压器模型,通过理论分析证明了等效变压器模型中励磁电流相位与耦合系数无关。在电磁涡流无损检测系统的等效变压器模型中,励磁电流代表着被测材料表面的磁通密度,而提离高度则是影响耦合系数的重要因素。因此,这一结论表明磁通密度的相位信息不受提离高度的影响。在理论分析的基础上进行了仿真研究,仿真结果证明,在被测金属材料表面特定位置上检测出的法向磁通密度BZ与提离高度呈现出良好的线性特征,且该点也是法向磁通密度的极值点,证明在该点处的磁通密度数据与理论分析的等效变压器模型具有最优的近似性。绘制不同提离高度下BZ在极值点pmax处的相轨迹,其斜率代表了 BZ的相位信息。分别对无缺陷、表面缺陷、亚表面缺陷和内部缺陷材料进行仿真研究发现,该方法可有效识别存在于被测金属材料不同位置的缺陷信息。进一步将该方法扩展至多频激励的情况,数据分析结果表明,相轨迹的频率响应特性可有效区分被测材料缺陷的深度信息。最后,设计了适合本文所述相轨迹方法的实验系统,通过实验验证了理论分析的正确性。
[Abstract]:Electromagnetic eddy current is applied to the electromagnetic coil to produce magnetic field, and then alternating eddy current is generated on the tested conductor, and the alternating eddy current produces the eddy current field. The characteristic parameters of the tested conductor can be obtained indirectly by detecting the eddy current field. The lifting noise and skin effect are the main problems in the electromagnetic eddy current nondestructive testing technology. The text is based on the equivalent transformer model of the eddy current nondestructive testing system. It is proved by theoretical analysis that the phase of excitation current in the equivalent transformer model is independent of the coupling coefficient. In the equivalent transformer model of electromagnetic eddy current nondestructive testing system, the excitation current represents the flux density on the surface of the measured material. Therefore, this conclusion shows that the phase information of magnetic flux density is not affected by the lift height. Based on the theoretical analysis, the simulation results show that the phase information of the magnetic flux density is not affected by the lift height. The simulation results show that the phase information of the magnetic flux density is not affected by the lift height. The normal flux density BZ and the lift height detected on the surface of the metal material tested show a good linear characteristic, and this point is also the extreme point of the normal flux density. It is proved that the magnetic flux density data at this point have the optimal approximation with the equivalent transformer model analyzed in theory. The phase trajectories of BZ at the extreme point pmax at different lift heights are plotted, and its slope represents the phase information of BZ. The simulation of surface defect, subsurface defect and internal defect material shows that the method can effectively identify the defect information existing in different positions of the metal material under test, and further extend the method to the case of multi-frequency excitation. The data analysis results show that the frequency response characteristics of the phase trajectory can effectively distinguish the depth information of the material defect. Finally, an experimental system suitable for the phase trajectory method described in this paper is designed, and the correctness of the theoretical analysis is verified by experiments.
【学位授予单位】：天津工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG115.28

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