人工槽模拟GH4169涡轮盘表面裂纹缺陷的微磁检测

针对航空发动机涡轮盘表面裂纹缺陷,提出一种地磁场环境下的微磁无损检测(NDT)方法。磁化试验测得了广泛使用的镍基高温合金GH4169材料的磁化特性曲线,通过磁性分析,证明该材料的相对磁导率略大于空气的相对磁导率,为弱顺磁性物质。理论分析了微磁检测适用于涡轮盘试件的检测原理和缺陷处的磁异常特征,通过对预置人工槽缺陷的涡轮盘试块进行检测,验证了理论分析的正确性。检测结果表明,随着涡轮盘表面裂纹宽度和深度的增加,磁异常的宽度和峰值也相应增加,裂纹宽度相同时,深度越深,或者说深宽比越大,磁异常越明显,且裂纹产生的位置对定位精度存在一定的影响。该微磁检测方法为涡轮盘表面裂纹缺陷的有效检测提供了新的思路,能进一步推广应用于飞机发动机的其他部件,如转子叶片、涡轮轴等,以及飞机机身上具有相似磁学特性的材料的无损检测。

Micro-magnetic NDT for surface crack defect in a GH4169 turbine disc simulated by artificial groove

This study proposes a micro-magnetic nondestructive testing (NDT) method in the geomagnetic field to detect the surface crack defect in a turbine disc. The magnetization characteristic curve of extensively used nickel base superalloy GH4169 is obtained by magnetized test. It is proved that the relative permeability of the material is slightly greater than the relative magnetic permeability of the air through the magnetic analysis. Thus, GH4169 is a weak paramagnetic substance. The mechanism of the micro-magnetic NDT method suitable for turbine disk specimen and magnetic anomaly characteristics of the defect are analyzed. The correctness of the theoretical analysis is verified through the testing of a turbine disk contained artificial crack defects. Test results show that the width and peak of the magnetic anomalies increase along with the increase of width and depth of surface crack. When the widths of cracks are the same, the deeper the depth, or the larger the deep width ratio, the greater the magnetic anomaly, and the position of crack has a certain influence on the positioning accuracy. The micro-magnetic NDT method provides new thoughts for the detection of surface crack defects of a turbine disc. The method can be further popularized and applied to other parts of the aeroengines, such as rotor blades, turbine shaft and the aircraft fuselage with similar magnetism features.