Real-time evaluation of wear condition in aviation self-lubricating bearings based on acoustic emission

基于声发射的航空自润滑轴承磨损状态实时评估

¹ National Key Laboratory of Strength and Structural Integrity, Aircraft Strength Research Institute of China, Xi'an 710065, China
² College of Civil Aviation, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China

Received: 25 March 2025

Abstract

Wear of the self-lubricating liner in aviation spherical plain bearings leads to increased clearance between the inner and outer rings, causing precision degradation of the control mechanism, thereby seriously threatening flight safety. Acoustic emission (AE)-based condition monitoring possesses many advantages such as high sensitivity, early-warning capability, and strong anti-interference performance, which can effectively address the limitation of traditional inspection methods in their inability to real-time characterize bearing operational states. First, a wear test setup with multiaxial loading capability for self-lubricating bearings and a split-type bearing base integrated with embedded AE sensors were designed, ensuring the fidelity of AE signal acquisition. Then, the evolutionary laws of AE signals from self-lubricating bearings in both time and frequency domains were studied, revealing the dual dominant frequency characteristics of AE signals and their dynamic energy evolution mechanism. A method for constructing bearing wear index based on acoustic emission time-frequency features and the multi-criteria feature selection strategy was proposed, enabling real-time assessment of the wear condition of self-lubricating bearings via wear index curves. It was found that the dynamic equilibrium of the PTFE transfer film in the bearing liner influences the energy distribution of AE frequency components. The critical transition interval for the test bearings between the running-in phase and stable wear phase was identified as 9 747 to 10 773 revolutions; and it was determined that the test bearings ultimately remained in the stable wear phase. Finally, the accuracy of the proposed wear index-based condition prediction method was validated using torque data. Furthermore, the micro-wear characteristics of the bearings were characterized through scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The migration behavior of the PTFE transfer film and the interfacial chemical composition under the final wear state demonstrated the consistency of the wear phase determination.

摘要

航空自润滑轴承衬垫磨损导致内外圈间隙增大, 引发操纵机构精度劣化, 从而严重影响飞行安全。声发射状态监测具有高灵敏度、早期预警和抗干扰强等优势, 可有效弥补传统检测方法难以实时反映轴承运行状态的不足。设计了自润滑轴承多轴加载的磨损试验装置及声发射传感器嵌入的分体式轴承底座, 确保了声发射信号采集的保真度。研究了自润滑轴承声发射信号在时域和频域的演变规律, 揭示了声发射信号的双主频特性及其能量动态演化机制, 提出了基于声发射时频特征与多准则特征筛选策略的轴承磨损指数构建方法, 基于磨损指数曲线实现了自润滑轴承磨损状态的实时评估。发现轴承垫层PTFE转移膜的动态平衡影响了声发射频率成分的能量分布; 试验轴承磨合阶段与稳定磨损阶段的临界过渡区间为9 747~10 773转; 判定试验轴承最终处于稳定磨损阶段。基于扭矩数据验证了所提磨损指数状态预测方法的准确性, 进一步通过扫描电镜和能谱分析表征轴承磨损微观特征, 根据最终磨损状态下PTFE转移膜的迁移特性及界面化学组分证明磨损阶段判定的一致性。