基于时间编码信号处理与识别的滚动轴承性能退化程度评估

滚动轴承是最常见的机械设备之一,对其进行性能退化评估是实现视情维修的基础。近年来滚动轴承监测技术已经取得了一定的成果,但找到一个能够对轴承故障进行早期预警且具有可信度高、高效率的监测系统是一大挑战。提出了一种基于时间编码信号处理与识别(TESPAR)的设备性能退化评估方法,并将其运用于滚动轴承不同故障程度实验与全寿命实验。结果表明:TESPAR分析不仅能准确分辨不同故障程度,且对轴承故障的变化具有敏感性。     

基于单层SAE与SVM的滚动轴承性能退化评估

滚动轴承是旋转机械设备的常用关键部件之一,其性能退化评估是机械设备状态监测与视情维修的基础和依据。为及时准确掌握滚动轴承性能退化趋势与程度,提出基于单层稀疏自编码学习和支持向量机的滚动轴承性能退化评估方法,研究能够深度挖掘数据各种潜在隐含信息的稀疏自编码学习方法以及基于时频域特征和稀疏自编码学习的轴承状态特征的提取方法;提出基于支持向量机分类算法改进的轴承性能退化评估算法,并应用到滚动轴承的性能退化评估模型中,确定了模型参数寻优的方法;最后将所获得的轴承状态特征输入到轴承性能退化评估模型,得到了轴承性能退化趋势图,并通过滚动轴承实例验证了所提出方法的实用性。     

基于广义S变换与隐马尔可夫的滚动轴承性能评估

考虑到滚动轴承故障信号的非平稳性、强噪声性，导致状态评估结果不确定性高，提出一种基于广义S变换特征提取和变分贝叶斯-隐马尔可夫模型的滚动轴承性能评估方法。针对滚动轴承监测获得的振动信号，对其进行广义S变换后，分别进行时间、频率、时频的信息熵特征值运算，提取健康指数作为性能评估的特征向量，并使用变分贝叶斯-隐马尔可夫模型建立实时性能评估模型，用健康样本训练模型，以模型输出对数似然概率值作为性能退化的评估指标。利用数学模型仿真和辛辛那提大学提供的轴承数据验证特征指标和评估模型的可行性，结果表明广义S变换熵值优于常规的特征指标，在轴承早期微弱故障时灵敏度高，性能评估模型仅需要正常数据就可以准确表征轴承性能退化趋势，为设备的维修和故障检测提供了参考。     

基于多目标和声搜索优化SVM的伺服电机滚动轴承性能退化评估

针对传统的支持向量机(SVM)算法参数往往根据经验设定,难以建立最优模型以准确地检测出伺服电机滚动轴承早期故障的问题,研究一种基于多目标和声搜索优化SVM的伺服电机滚动轴承性能退化评估方法。首先提取轴承振动信号的时域、时频域特征作为原始特征集,采用堆叠稀疏自编码器对原始特征集进行更深层次的特征提取,得到最终的特征向量。之后以轴承退化曲线的趋势性和单调性作为适应度函数,采用多目标和声搜索算法对SVM的参数进行优化,建立最优评估模型,得到轴承的性能退化指标。实验结果表明:该方法能准确地检测出轴承的早期故障,相比于传统的轴承SVM性能退化评估方法具备更好的趋势性和单调性。     

基于小波包能量与模糊C均值聚类的轴承退化状态预测

滚动轴承在发生严重故障前会经历不同的退化状态,针对时域和频域故障特征不能表征早期故障的问题,提出了小波包能量结合高斯混合模型的轴承性能退化指标提取方法。该方法以小波包能量比例值向量作为原始特征,引入高斯混合模型,以计算出的小波包能量比例值对数似然概率作为性能退化指标,通过实验验证该方法能发现早期故障,还能很好的跟踪轴承退化趋势。在此基础上,由于退化状态难以界定识别,利用模糊C均值聚类对性能退化指标模糊聚类,从而识别轴承性能退化状态,通过滚动轴承退化实验验证了该方法的有效性。     

一种基于CNN的滚动轴承退化指标构建方法

针对传统滚动轴承退化指标构建方法高度依赖于人工筛选特征的问题，提出基于卷积神经网络的端到端的滚动轴承性能退化指标构建方法。该方法在Softmax的输出端设置两个节点，分别代表正常和失效状态，以正常状态归一化的幅值谱为训练样本，以待评估数据在正常节点输出概率为基础，构建了滚动轴承性能退化指标。通过在不同实验数据集中的应用，以及与其他指标的对比，验证了该方法的有效性和优越性。     

基于多通道循环平稳特征融合的智能诊断方法

同一监测点的多源通道信号可以为精准故障诊断提供更全面的特征信息，然而多源特征的有效融合仍然具有挑战性。为解决此问题，耦合隐马尔科夫(CHMM)被用来有效融合双通道信息的循环平稳特征，即用快速谱相关(FSC)提取特征，从而为提高滚动轴承智能诊断正确率提供有效多源融合特征向量支撑。FSC分析方法用于滚动轴承同源双通道振动信号的特征提取；参数优化选取后的CHMM对双通道同源特征进行融合，实现滚动轴承的智能诊断。通过滚动轴承常规故障实验和全寿命加速疲劳实验，验证了所述方法不仅能用于滚动轴承故障的智能分类，而且还能用于滚动轴承的有效性能退化评估。此外，通过对比研究验证了所述方法的优越性。     

基于GA随机共振的模糊SVDD轴承性能退化评估

提出了一种基于遗传算法随机共振与模糊支持向量数据描述相结合的轴承性能退化评估方法。首先结合遗传算法,应用稳定约束条件下的自适应随机共振方法对轴承故障微弱信号进行提取,在保证收敛性的条件下得到所需的特征集;然后从得到的特征集中选取多个特征作为模糊支持向量数据描述的输入,利用训练样本得到超球体模型,进一步提出一个轴承退化综合性能评估指标。最后利用不同方法对实验数据进行评估对比验证了该方法能够更早的检测出轴承的性能退化时刻,并且能够更加形象的描述轴承性能退化过程。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.     

电化学噪声数据处理方法概述

综述了常见的电化学噪声数据处理方法,介绍了直流趋势剔除、统计分析、快速傅立叶变换(FFT)法计算功率谱密度(PSD)以及小波变换处理电化学噪声信号的基本过程,并阐释了各种数学处理及所得参数的物理意义。