基于磁轭结构的脉冲涡流热成像激励效果比较

Comparative study of pulsed eddy current thermography excitation effect based on magnet yoke structure

针对目前脉冲涡流感应热成像无损检测中激励线圈加热不均匀、受提离影响大的问题,将导线缠绕在磁轭装置上加载电流,分析其激励效果。为确定线圈缠绕位置对激励效果的影响,比较了不同装置激励时裂纹两端和底部的涡流分布及温度分布。结果表明,引入磁轭装置后系统的能量传递效率得到很大提高,同时激励的不均匀性减弱。激励线圈均匀分布在磁轭装置横梁及两极靴时激励效果最好。利用最优激励模型对不同方向的裂纹进行检测,结果表明,铁磁材料表面各个方向角的裂纹都可以被检测到,非铁磁材料方向角较小的裂纹不能被检测到。根据试件表面最高温度随裂纹方向角增大而线性增加的特点可以识别裂纹的方向角。

For uneven heating and great influence of lift-off of excitation coil in pulsed eddy current thermography,we wounded the coil on a magnet yoke structure to applied excitation and analyzed the excitation effect.In order to test he impact of the position of the wound coil,we compared the distribution of eddy current and temperature on the ends and ottom of the crack under different excitation means.It showed that,after the introduction of the magnet yoke structure,he energy transfer efficiency of the system is greatly improved and unevenness of excitation is weakened.The best effect btained when the coil uniformly distributed on beam and pole pieces.Using the optimal model to detect cracks in ifferent directions,the results showed that,cracks with any angle on ferromagnetic material can be detected while small ngle fractures on non-ferromagnetic can't be discovered.It is possible to identify the direction of the crack because the aximum temperature of the specimen surface is linearly increased with the increase of crack angle.