铁路货车滚动轴承故障声学诊断研究

针对铁路列车滚动轴承故障在途检测的需要,提出一种轴承故障声学诊断方案,并重点讨论了在时域和频域内选取特征参数分析的故障诊断方法。试验证明此方案可以较高精度地对铁路货车滚动轴承故障进行检测。     

基于声发射技术的铁路重载货车滚动轴承故障诊断研究

通过声发射检测技术对铁路重载货车滚动轴承故障进行不解体诊断,利用小波包分析技术对采集到的声发射信号进行分解和重构,提取故障信号的能量特征向量,将处理后的特征向量输入到BP神经网络进行滚动轴承故障模式识别,进而判断轴承是否发生故障以及故障的类型。经过使用大量的实际滚动轴承实验数据进行验证,其结果都表明了使用本文的方法的有效性。     

Active and passive compliant force control of ultrasonic surface rolling process on a curved surface

Ultrasonic surface rolling process(USRP) is one of the effective mechanical surface enhancement techniques. During the USRP, unstable static force will easily do harm to the surface quality. In order to achieve a higher surface quality on the part with a curved surface, an active and passive compliant USRP system has been developed. The compliant USRP tool can produce the natural obedience deformation along the part surface. Force control based on the fuzzy Proportional-integral-derivative(PID) ...     

大型对日定向装置大开口复合材料主承力架传力设计及验证

根据大型对日定向装置的结构特点和受力特性，调整传力结构，充分利用纤维增强复合材料结构的可设计性，开展优化设计。在保证高刚度和轻量化的同时，克服结构大开口带来的承载能力不足，设计出结构质量与承载比仅为5.2%，集舱段和壳体功能于一体的大型对日定向装置复合材料主承力架结构。建立有限元模型，分别采用Tsai-Wu和最大应变2种纤维增强复合材料的强度失效准则，对其进行校核。开展静力试验，采集应变等信息，与有限元仿真分析结果展开对比。结果表明:其整体趋势一致，顺利通过试验考核。     

高温环境下角接触球轴承磨损寿命分析

针对高温环境下轴承材料性质和润滑状态变化，造成轴承磨损加剧，过早丧失精度的问题。首先开展高温环境下轴承用材料的摩擦磨损试验，获取材料的磨损系数。在此基础上，考虑温度、润滑、轴承材料属性等对轴承磨损性能的影响，建立高温角接触球轴承磨损模型，通过数值求解探讨工况参数和结构参数等对轴承磨损性能的影响，并评估轴承的磨损寿命。结果表明：对于高温轴承材料无磁合金GH05，在高温300 ℃摩擦状态下平均磨损系数为2.5×10^-7 mm²/N；随着载荷、转速、温度的增加，轴承内、外滚道的磨损率均不断增大，其中内圈磨损率大于外圈，内圈磨损特性决定着轴承的磨损寿命；载荷和转速是决定轴承磨损寿命的主要因素，轴承主结构参数对磨损寿命具有重要影响，通过结构优化可提高轴承磨损寿命。     

基于改进的SqueezeNet直升机滚动轴承故障诊断

针对现有基于卷积神经网络的故障诊断方法存在模型参数量和计算量大的问题，提出一种改进的SqueezeNet模型应用于直升机滚动轴承故障诊断。该模型借鉴VGG16模型的思想，在经典的SqueezeNet基础上，采用3个3×3卷积核代替1个7×7卷积核，实现了在相同感知野条件下增加网络容量、增强非线性、减少网络参数量，采用卷积层、池化层和Fire模块、池化层两大结构交替的方式组成模型特征提取层，在保障特征提取能力的情况下，进一步减少了网络参数量。通过轴承数据开展模型故障诊断实验，结果表明该模型诊断精度达到99.65%，与传统卷积神经网络及经典的SqueezeNet模型相比诊断精度相当，而计算量与参数量最大缩减约6倍和36倍。     

某扭力管万向节组件及支撑轴承的正弦振动疲劳研究

本文建立C919某扭力管万向节组件及支撑轴承的有限元模型，对其进行模态分析及正弦分析，推导了正弦振动下的疲劳寿命计算公式并预估了模型的寿命，通过模态试验验证了模型的正确性，通过正弦试验验证了疲劳寿命计算的正确性。该疲劳寿命计算方法可用来预估相关模型的正弦振动疲劳寿命。     

An innovative constraining ring rolling process for manufacturing conical rings with thin sterna and high ribs

Conical rings with thin sterna and high ribs (CRTSHR) are key bearing-load parts of aerospace equipment, which are required to be manufactured with high performance and efficiency. Traditional ring rolling is the most preferred method for manufacturing high-performance ring parts, but it can hardly achieve the forming of CRTSHR due to the extreme geometry of CRTSHR. To solve this difficulty, an innovative constraining ring rolling process (CRR) is proposed in this paper to manufacture CRTSHR. To evaluate the proposed CRR and reveal its deformation behaviors, a thermomechanical coupled FE model for CRR of CRTSHR is established. Then, the experiment for CRR of CRTSHR is performed on a modified ring rolling machine, which proves that CRR of CRTSHR is feasible and the established FE model is reliable. Based on the reliable FE model, the metal flow mode in deformed CRTSHR is analyzed, and the deformation characteristics such as the stress state, strain distribution and the evolution of power parameters in CRR of CRTSHR are revealed. Finally, the influences of key parameters such as the friction factor between ring and molds, the diameter of idle roll and the feed velocity of idle roll on CRR of CRTSHR are investigated by FE simulation.     

Analysis of oil shedding and ligaments formation on bearing rotary elements

For designing efficient lubrication system of an aeroengine bearing chamber, sufficient knowledge on oil/air two-phase flow characteristics is required. When analyzing bearing chamber two-phase flow, the essential prerequisite is quantifying the oil ligaments, which are detached from bearing rotary elements and shed into the bearing chamber. Related investigations are mainly targeted at liquid shedding on the rotating disk as opposed to the bearing rotary elements. Moreover, the research based on bearing rotary elements is conducted by experiment. Due to the limited operating conditions, experimental studies cannot guide engineering applications. To overcome these limitations, a theoretical model is established in this paper, for revealing the mechanism of oil shedding from bearing rotary elements and quantifying the shedding ligaments. The theoretical model is validated against experimental results from classical studies. In addition, the correlation for shedding ligaments number based on aeroengine bearing structural and operational parameters is obtained via theoretical analysis. The analytical results demonstrate that oil shedding and ligaments formation appear at the edge of bearing inner race outer-periphery. The number of shedding ligaments increases with the rise of shaft rotational speed while decreases with the growth of oil viscosity.     

On a plastic instability criterion for ultra-large radial-axial ring rolling process with four guide rolls

A dynamic mechanical model is proposed to describe the complexing actions of all the rolls on the ring during the ultra-large radial-axial ring rolling(RARR) process with four guide rolls. Based on the model, the calculation models for bending moment and normal stress at any section of the ring are deduced by force method. If the maximum section bending normal stress exceeds the yield stress of the ring materials, the ring will be distorted thus leading to the instability of the RARR process. Ac...