Advanced Magnetic Barkhausen Noise for Residual Stress Measurement in Aircraft Landing Gear

残馀应力会导致飞机起落架部件的灾难性失效。目前，还没有可靠的无损检测技术来测量在役构件上的残余应力而不去除涂料。X射线衍射法需要去除油漆和金属电镀，然后对母材进行蚀刻。目前的磁巴克豪森噪声(MBN)技术只需要去除油漆。然而，虽然MBN已经被用来检测飞机起落架中的高残余应力区，只使用一个测量参数，但它被发现在目前的形式下是不可靠的。在控制用于产生巴克豪森噪声的激励场产生的磁通量方面的最新进展表明，有可能提高测量的重复性，以及提供对相对磁性的额外表征。此外，相互正交场激励的发展有可能提供对组件的各向异性磁性的快速评估，这可能与其应力状态相关。信号分析技术也得到了改进，包括MBN能量、巴克豪森噪声包络和脉冲高度分布的评估。需要进一步发展MBN技术，以识别和补偿可能影响测量结果的重要参数。例如，涂层厚度变化的影响，喷丸引起的压缩表面应力状态的变化，以及钢中塑性变形的影响。还需要优化探头设计，以适应独特的几何形状，如紧曲率半径。促进对影响MBN信号产生的参数的理解和补偿是拟议工作的一部分。此外，还将开发用于残余应力测量的先进的MBN信号分析方法。有限元模型将被用来设计和预测塑性变形飞机起落架中残余应变场的大小和方向。这项拟议的工作是与位于安大略省阿贾克斯的赛峰着陆系统公司合作的，该公司生产飞机起落架。

Residual stress can lead to catastrophic failure of aircraft landing gear components. Currently, there is no reliable non-destructive inspection technology for residual stress measurement on in-service components without paint removal. X-Ray diffraction (XRD) requires both paint and metal plating removal, followed by etching of the base metal. Current Magnetic Barkhausen noise (MBN) technology only requires paint removal. However, while MBN has been employed to detect areas of high residual stress in aircraft landing gear using only a single measurement parameter, it has been found to be unreliable in its current form. Recent advances in control of the magnetic flux generated by the excitation field used to generate Barkhausen noise havedemonstrated a potential for improving measurement repeatability, as well as providing additional characterization of relative magnetic properties. Furthermore, development of mutually orthogonal field excitation has prospects to provide rapid evaluation of a component's anisotropic magnetic properties, which may be correlated with its stress state. Signal analysis techniques have also been advanced, including evaluation of MBN energy, Barkhausen noise envelope and pulse height distribution. Further development of MBN technology is required to identify and compensate for significant parameters that may affect measurement outcomes. Examples include effects of paint thickness variation, variability in compressive surface stress state induced by shot peening and the effects of plastic deformation in steel. Probe designoptimization is also required, in order to accommodate unique geometries, such as tight curvature radii. Advancement in the understanding and compensation for parameters that affect MBN signal generation is part of the proposed work. In addition, advanced MBN signal analysis methodology for residual stress measurement will be developed. Finite element modelling will be used for probe design and prediction of magnitude and direction of residual strain fields in plastically deformed aircraft landing gear. The proposed work is in collaboration with Safran Landing Systems Inc., located in Ajax Ontario that manufactures aircraft landing gear.