Crack Fault Diagnosis and Location Method for a Dual-Disk Hollow Shaft Rotor System Based on the Radial Basis Function Network and Pattern Recognition Neural Network

The crack fault is one of the most common faults in the rotor system,and researchers have paid close attention to its fault diagnosis.However,most studies focus on discussing the dynamic response characteristics caused by the crack rather than estimating the crack depth and position based on the obtained vibration signals.In this paper,a novel crack fault diagnosis and location method for a dual-disk hollow shaft rotor system based on the Radial basis function(RBF)network and Pattern recognition neural network(PRNN)is presented.Firstly,a rotor system model with a breathing crack suitable for a short-thick hollow shaft rotor is established based on the finite element method,where the crack's periodic opening and closing pattern and different degrees of crack depth are considered.Then,the dynamic response is obtained by the harmonic balance method.By adjusting the crack parameters,the dynamic characteristics related to the crack depth and position are analyzed through the amplitude-frequency responses and waterfall plots.The analysis results show that the first critical speed,first subcritical speed,first critical speed amplitude,and super-harmonic resonance peak at the first subcritical speed can be utilized for the crack fault diagnosis.Based on this,the RBF network and PRNN are adopted to determine the depth and approximate location of the crack respectively by taking the above dynamic characteristics as input.Test results show that the proposed method has high fault diagnosis accuracy.This research proposes a crack detection method adequate for the hollow shaft rotor system,where the crack depth and position are both unknown.

Eigen value analysis of composite hollow shafts using modified EMBT formulation considering the shear deformation along the thickness direction

Composite hollow shafts are used in power transmission applications due to their high specific stiffness and high specific strength.The dynamic characteristics of these shafts are important for transmission applications.Dynamic modelling of these shafts is generally carried out using Equivalent Modulus Beam Theory(EMBT)and Layerwise Beam Theory(LBT)formulations.The EMBT formulation is modified by considering stacking sequence,shear normal coupling,bending twisting coupling and bending stretching coupling.It is observed that modified EMBT formulation is underestimating the shafts stiffness at lower length/mean diameter(l/dm)ratios.In the present work,a new formulation is developed by adding shear deformation along the thickness direction to the existing modified EMBT formulation.The variation of shear deformation along the thickness direction is found using different shear deformation theories,i.e.,first-order shear deformation theory(FSDBT),parabolic shear deformation theory(PSDBT),trigonometric shear deformation theory(TSDBT),and hyperbolic shear deformation theory(HSDBT).The analysis is performed at l/d_(m) ratios of 5,10,15,20,25,30,35,and 40 for carbon/epoxy composites,E-glass/epoxy composites,and boron/epoxy composite shafts.The results show that new formulation has improved the bending natural frequency of the composite shafts for l/d_(m)<15 in comparison with modified EMBT.The effect of new formulation is more significant for the second and third bending modes of natural frequencies.

Functional Outcomes of Adult Tibia Shaft Fractures Treated with Solid Intramedullary Nails versus Hollow Nails: A Systematic Review

Introduction: The management of fractures of the tibia shaft is an important aspect of orthopaedic care, and the selection of the surgical method for fixation can substantially impact patient outcomes. The current review aims to compare the outcomes of adult tibia fractures treated with solid nails to those treated with hollow nails. Methods: A search on Scopus, PubMed, and Cochrane Library, using three keywords (Outcome, Tibia shaft fractures, Nail) was conducted in April 2023. Results were compiled and two independent reviewers screened and selected eligible articles After removing duplicates, titles and abstracts were read to exclude ineligible studies. Full-text articles of the remaining papers were read to select eligible studies which were further critically appraised to ascertain their methodological quality. The data extracted from the selected papers were synthesized using a combination of pooling of results, tests of statistical difference (t-test and chi-square) and narrative synthesis methods. Results: A total of 2295 articles were obtained from the databases and citation searching. A total of 9 papers were identified as eligible and included in the review. Findings revealed that there is no statistical difference in the outcomes of tibia fractures treated with either solid or hollow nail groups such as duration of surgery (p = 0.541), rate of delayed and non-union (p = 0.342), and rate of surgical site infections (p = 0.395). Conclusion: Intramedullary nailing of tibia shaft fractures with either solid or hollow nails have similar functional outcomes.

An effective crack position diagnosis method for the hollow shaft rotor system based on the convolutional neural network and deep metric learning

In recent years, the crack fault is one of the most common faults in the rotor system and it is still a challenge for crack position diagnosis in the hollow shaft rotor system. In this paper, a method based on the Convolutional Neural Network and deep metric learning(CNN-C) is proposed to effectively identify the crack position for a hollow shaft rotor system. Center-loss function is used to enhance the performance of neural network. Main contributions include: Firstly, the dynamic response of the dual-disks hollow shaft rotor system is obtained. The analysis results show that the crack will cause super-harmonic resonance, and the peak value of it is closely related to the position and depth of the crack. In addition, the amplitude near the non-resonant region also has relationship with the crack parameters. Secondly, we proposed an effective crack position diagnosis method which has the highest 99.04% recognition accuracy compared with other algorithms. Then,the influence of penalty factor on CNN-C performance is analyzed, which shows that too high penalty factor will lead to the decline of the neural network performance. Finally, the feature vectors are visualized via t-distributed Stochastic Neighbor Embedding(t-SNE). Naive Bayes classifier(NB) and K-Nearest Neighbor algorithm(KNN) are used to verify the validity of the feature vectors extracted by CNN-C. The results show that NB and KNN have more regular decision boundaries and higher recognition accuracy on the feature vectors data set extracted by CNN-C,indicating that the feature vectors extracted by CNN-C have great intra-class compactness and inter-class separability.

永磁无刷直流空心轴电机定子槽参数减振优化

为了保证永磁无刷直流空心轴电机的输出性能和抑制电磁振动,提出了一种基于非线性多元回归的修正代理模型优化方法.首先,通过AE(Audze-Elglajs)准则确定最优空间填充抽样,并采用核主成分分析(Kernel Principal Components Analysis,KPCA)算法筛选出4个主要变量用于构建代理模型;其次,采用非线性多元回归构建代理模型,决定系数R^(2)值均大于0.9,验证了代理模型的精度;最后,采用鲁棒多目标遗传算法求解代理模型,获得了最优定子槽参数.结果表明,通过优化定子槽参数,电机平均转矩降低了1.3%,不影响输出性能,电机空载、额定负载时最大振动加速度分别降低19%和34.5%,有效地降低了电磁振动,验证了优化方法的有效性和可靠性.

薄壁四点接触球轴承-腕部关节系统接触动力学分析

在机器人实际工况中,针对含有薄壁四点接触球轴承的机器人腕部关节系统的运动稳定性问题,对腕部系统模型进行了简化设计和仿真研究。在考虑薄壁结构的弹性变形和动态接触作用耦合影响的基础上,建立了刚柔耦合工业机器人腕部关节系统模型,分析了不同受载工况和正反转驱动下的变形规律和动态特性。首先,基于多体动力学和Hertz接触理论,设计了包含薄壁四点接触球轴承和中空轴及基座的腕部关节系统刚柔耦合接触动力学仿真模型;然后,考虑薄壁中空轴、基座、轴承套圈和保持架的结构弹性变形、钢球和套圈滚道、保持架的动态接触作用,研究了机器人腕部关节系统两种实际工况对保持架和钢球角速度、保持架和薄壁基座振动位移、钢球与套圈的动态接触力的影响;最后,计算分析了两种工况下腕部关节系统的动态载荷规律和振动响应特性。研究结果表明:在相对较大的径向载荷作用下,保持架和钢球会出现打滑现象,速度呈现周期波动,保持架和基座具有更好的运动稳定性,其薄壁轴承内部载荷降低,主副接触对均承担联合载荷,轴承内部载荷稳定性也更好。该仿真模型及结果可以为薄壁腕部关节系统的动力学分析与设计提供参考。

轻量化多孔空心轴结构设计与分析

为了进一步提高轴的比强度,在传统空心轴的基础上进一步提出并研究了一种基于增材制造技术的多孔空心轴。通过仿真分析并经实验验证,在相同质量时,多孔空心轴与传统空心轴相比,承载能力更佳。在某典型扭转工况下,强度能提高22.5%;在某弯曲工况下,强度能提高9.8%。

新能源汽车空心电机轴径向锻造生产线设计

新能源汽车空心电机轴受力复杂,径向锻造是其最佳成形方式。本文分析了空心电机轴成形工艺流程,提出了生产线关键技术参数,介绍了关键设备组成,讨论了该生产线的技术特点。

Elastic and viscoelastic solutions to rotating functionally graded hollow and solid cylinders

Analytical solutions to rotating functionally graded hollow and solid long cylinders are developed. Young＇s modulus and material density of the cylinder are assumed to vary exponentially in the radial direction, and Poisson＇s ratio is assumed to be constant. A unified governing equation is derived from the equilibrium equations, compatibility equation, deformation theory of elasticity and the stress-strain relationship. The governing second-order differential equation is solved in terms of a hypergeometric function for the elastic deformation of rotating functionally graded cylinders. Dependence of stresses in the cylinder on the inhomogeneous parameters, geometry and boundary conditions is examined and discussed. The proposed solution is validated by comparing the results for rotating functionally graded hollow and solid cylinders with the results for rotating homogeneous isotropic cylinders. In addition, a viscoelastic solution to the rotating viscoelastic cylinder is presented, and dependence of stresses in hollow and solid cylinders on the time parameter is examined.

卧式螺旋卸料沉降离心机螺旋空心轴内表面磨损的研究

针对卧式螺旋卸料沉降离心机螺旋空心轴因磨损产生的偏心、振动、甚至漏料等问题,通过试验和数值模拟研究螺旋空心轴内表面上微凸和微凹缺陷对壁面磨损的影响。结果表明,微凸起处的磨损区主要分布在其迎流面处的底部和微凸起进料端附近壁面,且微凸起上的磨损率在其轴向位置上呈两端高、中间低的分布,距离进料端位置的磨损率更高,磨损率与处理量呈正相关。如进料流量从1.37 m^(3)/h增加至2.74 m^(3)/h时,微凸起磨损率峰值从6.20×10^(-4)kg/(m^(2)·s)增加至1.63×10^(-3) kg/(m^(2)·s);下凹缺陷的磨损区主要分布在其背流面,磨损率峰值随着缺陷直径增加而变大。如缺陷直径从1 mm增加至2 mm时,缺陷处磨损率峰值从3.77×10^(-4)kg/(m^(2)·s)增加至6.02×10^(-4)kg/(m^(2)·s),且下凹缺陷处存在明显的磨损集中现象。研究结果可为螺旋空心轴的防磨设计提供依据。

新能源汽车全空心电机轴径向锻造数值模拟优化

目的利用Simufact–Forming计算机模拟软件,开发汽车全空心电机轴径向锻造工艺。方法分析了不同锤头入模角、坯料转速以及径向下压量对成形等效应变的影响,并基于实验结果建立了正交实验模型,引入了指标隶属度和综合成形质量系数。结果得到了最佳工艺参数组合如下:径向下压量为1.25 mm,锤头入模角为8°,坯料转速为40 r/min,轴向进给量为3 mm。结论根据最佳工艺参数组合进行了产品生产验证,得到了内外表面均较光滑且无折叠情况发生的电机轴产品,其内部金属流动方向性明显,为实现全空心新能源汽车电机轴的批量化生产提供了经验依据。

轴段空心度对舰船复杂推进轴系动力学特性影响分析及多目标优化研究

轴系动力学特性直接影响到舰船航行的安全性、隐蔽性和可靠性,为分析清楚轴段空心度对舰船推进轴系动力学特性的影响,以某复杂推进轴系为研究对象,基于有限元法建立其动力学分析模型;采用雷诺方程计算轴承油(水)膜刚度,基于螺旋桨升力线理论近似计算螺旋桨轴承力作为振动激励,研究得到螺旋桨轴、艉轴及中间轴空心度变化对轴系校中及振动特性的影响规律;在此基础上,以各轴段空心度为变量,应用多目标优化算法开展轴系动力学特性综合优化。优化结果表明:轴系前后艉轴承负荷差减小了4.1kN,回旋振动和纵向振动的最大振幅均有所减小,轴系动力学特性得到改善。

飞轮储能系统电机转子散热研究进展

电机是飞轮储能系统实现电能-动能转换的关键部件,其小体积、大功率的设计特点以及真空运行环境导致电机转子温升问题突出,常规的定子水套冷却已不能满足高功率密度电机转子的散热降温需求。本文首先阐述了飞轮储能电机转子发热的原因及危害,分析了转子涡流损耗、电机温度场的计算方法。回顾了飞轮电机转子被动冷却、主动冷却的研究进展,其中被动冷却包括热辐射与导热,主动冷却包括空心轴内通流冷却与热管冷却,并评估了各种方法的飞轮储能适用性。综合分析表明,强化电机定、转子内部绝缘材料导热以及增强热辐射可以一定程度上防止电机内部热量积聚,降低电机的温度梯度;热管易于安装、集成度高、传热性能优异,但其随轴的旋转传热缺乏验证;空心轴内流冷却技术成熟度高、设计制造简单、传热效果好,可作为高功率密度飞轮电机转子冷却的首选方案。针对MW飞轮储能电机转子散热难题,提出了中空轴内通流冷却的新方案。

基于可靠性优化的空心半轴轻量化设计

转向驱动桥空心半轴是保障汽车的驱动性能和运行稳定性的关键零部件,针对轻量化设计过程中目标响应与约束响应复杂非线性建模和可靠性偏低的问题,文中运用支持向量机回归(Support Vector Regression, SVR)代理模型构建目标响应并验证其有效性,同时考虑多种不确定性因素,增加了形变及应力引起的失效概率在一定范围内的约束条件,从而较好地解决了轻量化设计过程中失效的难题。结果表明:可靠性轻量化设计后的空心半轴比初始设计改善了2.4%(减少了54.4 g),最大形变量的可靠度增加了15.6%(减少了0.2 mm),等效应力的可靠度提升了15.0%(降低了47.1 MPa)。

球磨机机筒的应力有限元分析

针对球磨机工作环境恶劣且工作时间长的工况,机筒为其薄弱环节,容易发生断裂或更大事故的问题,在对球磨机结构和载荷分析的基础上,基于ANSYS软件建立球磨机机筒的三维模型,并完成材料属性和网格划分的设置,重点对球磨机机筒应力有限元和中空轴与端盖元应力进行充分仿真分析,为后续球磨机机筒结构的优化奠定基础。

基于AK-MCS法的新能源电动汽车转向驱动桥空心半轴可靠度分析

新能源汽车转向驱动桥半轴采用空心设计,与燃油汽车的结构形式有很大区别,针对电动汽车转向驱动桥空心半轴的最大等效应力与设计变量呈隐式复杂非线性关系的可靠度分析难题,文中通过将Kriging模型与蒙特卡洛(Monte Carlo Simulation,MCS)法相结合,提出了基于AK-MCS(Active Learning Kriging-Monte Carlo Simulation)法的新能源电动汽车转向驱动桥空心半轴可靠度分析方法。首先,采用Kriging代理模型构建新能源电动汽车转向驱动桥空心半轴的最大等效应力的初始代理模型;其次,通过Kriging提供的学习函数和收敛准则逐步增加样本点,从而对初始最大等效应力的Kriging模型进行更新;最后,对更新后的Kriging代理模型计算新能源电动汽车转向驱动桥空心半轴的可靠度。结果表明:与MCS方法相比,基于AK-MCS方法的可靠度分析在时间上缩短2000余倍;与Kriging+MCS方法相比,基于AK-MCS方法的可靠度分析误差减小了50%。由此验证了基于AK-MCS方法空心半轴可靠度分析的高效性和准确性,为电动汽车转向驱动桥空心半轴可靠性的研究提供了理论依据,具有一定的工程意义。

架悬式永磁直驱转向架轮对更换的研究与分析

针对某型架悬式永磁直驱转向架轮对轴箱及驱动系统总成的更换工艺进行了分析研究,侧重于拆解流程、恢复流程、设备需求、工装设计、更换方案、操作流程等方面进行研究,详细阐述更换过程中需要关注的细节,并且针对轮对轴箱及驱动系统总成具体结构提出与其相匹配的适用工装。本更换方案已在实车检修中应用,具有更换速度快、拆卸无损伤、人员易操作等优势。为该型转向架轮对轴箱及驱动系统总成的更换提供了可选方案,填补了同时具有抱轴式电机和空心轴六连杆传动这两种特质转向架分解和组装工艺的空白。

采用小齿轮空心轴驱动装置的三轴转向架技术方案研究

小齿轮空心轴驱动装置可应用于1050 mm轮径的高速机车转向架,其特点是可有效减轻轮对驱动装置。文中对采用小齿轮空心轴驱动装置的三轴转向架进行了研究,该转向架基于某集成式双源机车的运用需求,针对三轴转向架中间轮对横动量较大的特点,明确了转向架设计目标,重点阐述驱动装置的结构、联轴器的选型、电机顺置和对置的对比分析以及转向架的主要结构组成等。研究结果表明,转向架各项性能均能满足设计要求,相较于采用1250 mm轮径、轮对空心轴驱动结构的轮对驱动装置,每条轮驱减重2 t以上,轻量化效果显著。

空心轴类件楔横轧仿真及壁厚变化规律

基于Deform-3D软件,建立了平楔楔横轧成形空心轴类件三维刚-塑性大变形热应力耦合有限元模型。通过模拟仿真与实验数据对比,验证了该模型的正确性,并在此模型基础上,应用楔横轧各工艺参数的正交试验,分析了空心坯料的成形性及壁厚的变化规律。结果表明:所轧空心轴类件的壁厚对比度与成形角、展宽角成正比,与断面收缩率成反比。研究结果对轧制空心阶梯轴的应用以及准确预测空心轴类件壁厚的变化具有指导意义和实用价值。

楔横轧成形等内径空心轴的椭圆度影响规律

采用二次回归正交旋转组合设计法,对楔横轧成形等内径空心轴的椭圆度影响规律进行有限元模拟分析和轧制实验,得到了具有较高参考价值的回归方程。依据回归方程和模拟结果,得出了工艺参数对等内径空心轴椭圆度的影响规律,以及各因素对椭圆度的影响程度主次和工艺参数的最优组合。研究结果为实现等内径空心轴类零件的楔横轧精确成形,以及优化模具设计和工艺参数的合理确定,提供了理论依据。