基于特征融合与HPO-RVM的滚动轴承剩余寿命预测

为准确预测轴承的剩余使用寿命,提出基于特征融合与猎食者-猎物优化(HPO)算法优化相关向量机的轴承剩余寿命预测方法。提取时域、频域和时频域特征准确描述轴承的退化状态,利用综合评价指标对提取的特征进行筛选得到敏感特征集;采用核熵成分分析对敏感特征进行自适应融合,得到轴承的退化特征;构建混合核函数作为相关向量机的核函数以提高模型预测性能;最后,利用HPO算法得到混合核函数的参数,将寻优得到的参数用于寿命预测模型的训练。通过对轴承加速退化数据集进行实验,结果表明：所构建的寿命预测模型优于BP、ELM、SVM等模型,构造的混合核函数模型优于高斯核函数模型,采用的优化算法优于粒子群、遗传算法等。     

基于主元数据的大型复杂机电设备寿命预测方法

针对单一表征参数的大型复杂机电设备寿命预测方法无法全面表征设备退化轨迹以及多表征参数之间存在相关性从而影响寿命预测准确性的问题，提出一种基于表征参数数据融合的大型复杂机电设备的寿命预测方法。先提出一种加权主成分分析法，对多种表征设备退化的参数进行融合，得到可以表征设备退化且相互之间不存在相关性的主元数据；然后，建立基于主元数据的维纳退化过程模型；最后，选取数控机床进给系统的双向定位精度、双向重复定位精度、反向间隙误差、直线度4种表征参数对应的数据对模型进行了具体的分析和验证。试验结果表明：与基于单一表征参数和多表征参数的寿命预测模型相比，融合后的主元参数能够更好地表征设备的退化过程，从而可以更精确地实现设备的剩余寿命估计。     

基于状态空间模型的加工中心功能铣头实时寿命预测

针对铣头运行过程中退化状态不可直接测量、寿命数据难获取、样本小以及成本高等问题，提出基于状态空间模型的铣头性能退化及实时寿命预测模型。融合最新测定的铣头温度数据，并使用贝叶斯理论计算模型参数，更新铣头退化状态变化率以及剩余寿命的失效概率密度，实现对铣头的在线实时寿命预测。加工中心功能铣头运行过程中的温度数据表明：铣头寿命预测准确率随着测定的温度数据增加而逐渐增加，至运行末期，准确率可达96%以上，同时其退化状态变化率也随着铣头运行时间的增加而逐渐减小。     

基于改进LSTM的航空发动机寿命预测方法研究

发动机剩余寿命(RUL)预测时，进行数据特征提取易导致预测效率低下。为解决此问题，提出一种改进的长短期记忆(LSTM)算法模型。通过引入深度稀疏自动编码器(SDAE)完成时序数据的处理与特征提取，优化LSTM模型，改善航空发动机RUL预测效果。利用SDAE进行特征提取，构建健康因子(HI)曲线；同时考虑运行工况、故障模式和传感器3个因素，并分别训练其权重。利用LSTM模型进行发动机剩余寿命预测。利用涡扇发动机退化过程数据集C-MAPSS开展实验，并与DNN、BiLSTM、单层LSTM进行对比分析。结果表明：与上述3种算法相比，改进后算法的均方根误差和〖JP2〗评分函数值至少分别降低6.6%和39.1%；该方法寿命预测结果和实际寿命曲线拟合度高，验证了该方法的可行性和有效性。     

基于时域和谱峭度特征融合及指数模型的滚动轴承RUL预测

滚动轴承剩余使用寿命（RUL）预测对保障旋转机械设备平稳运行意义重大。针对时域特征预测精度波动大、数据利用率低等问题,提出一种基于时域和谱峭度特征融合及指数模型的滚动轴承RUL预测方法。从时域和谱峭度提取信号的特征进行平滑处理并基于单调性尺度排序,从而选取优势特征通过主成分分析(PCA)构建健康指标。然后,通过3σ准则确定退化点后对数据再处理。最后,基于贝叶斯理论和极大似然函数估计指数退化模型的参数来预测轴承每时刻的RUL,采用XJTU-SY数据集验证所提方法的有效性。结果表明：所提方法可根据当前观测轴承进行小样本数据潜在信息的挖掘,并能在强噪声背景下准确地表征非平稳信号的退化过程,提升RUL预测的精度。     

基于冲击的涡扇发动机退化建模与下发预测

为解决多性能参数模型无法描述不同起飞推力下发动机性能退化的问题,利用单性能参数结合极端冲击模型描述起飞时发动机全功率运转对热端部件的热冲击影响,利用线性退化模型描述发动机自然退化过程,建立发动机性能可靠度退化模型。利用V2500发动机全寿命EGTM数据,结合最大似然估计给出性能可靠度表达式与模型参数,最后利用机队中同型V2500发动机非完整EGTM数据验证模型,预测下发时间,结果表明此模型预测下发时间和实际下发时间的误差小于3%,证明了模型的有效性。     

基于相关系数和BP神经网络的轴承剩余寿命预测

为了评估机械设备的退化状态,准确掌握轴承剩余寿命信息,提出了一种基于相关系数和BP神经网络(BP Neural Network,BPNN)模型的轴承剩余寿命预测方法。该方法包括线上和线下两个步骤,首先利用相关系数法对预测模型的输入特征进行约简,其次线下步骤是通过机器学习来构建轴承的退化模型,而线上步骤则是利用退化模型来预测轴承剩余寿命。通过对轴承的全寿命退化实验数据进行分析预测,该方法与传统的技术相比能降低预测误差,表明该方法能够有效地模拟轴承退化过程并预测轴承剩余有效寿命(RUL)。     

基于多信息融合与GRU的轴承剩余寿命预测

为解决单一传感器信号易受干扰且能提取的退化信息有限，导致轴承剩余寿命预测精度低的问题，提出一种基于双通道信息融合与门控单元(GRU)神经网络的轴承剩余寿命预测方法。进行轴承寿命试验时，在振动传感器采集信号的基础上增加声发射传感器，弥补单一信号易受干扰的缺点；使用卷积神经网络自动挖掘出包含轴承退化信息的特征，避免传统算法过分依赖专家判断的弊端；通过归一化处理对信息进行融合；最后使用这些数据训练GRU神经网络，利用训练好的门控单元神经网络预测高铁牵引电机轴承的剩余寿命。结果表明：相比单通道数据，双通道数据训练出的门控神经网络模型的预测结果更为准确；门控单元神经网络相比长短时记忆神经网络有更高的轴承寿命预测精确度。     

基于DTW相似度和Bi-LSTM的滚动轴承寿命预测

针对现有的滚动轴承退化指标单调性差,对轴承异常不敏感导致基于数据驱动的深度学习算法难以实现轴承寿命准确预测的问题,提出一种基于动态时间规整算法(DTW)和双向长短期记忆神经网络(Bi-LSTM)的滚动轴承剩余寿命预测算法。利用信息熵提取滚动轴承的退化特征,构造连续的时间序列;划分时间序列并构造出参考模板及测试模板,采用DTW算法计算模板间的相似度,将它作为健康指标表征轴承的退化程度;用健康指标训练Bi-LSTM网络并预测轴承的寿命。采用法国IEEE PHM 2012的全寿命数据进行研究,结果表明：经过DTW算法优化信息熵指标后所构造的健康指标可更好地反映轴承的退化过程;当进行寿命预测并保持预测算法不变时,经过优化后的指标较优化前相比,能明显提高轴承寿命预测的准确度。     

工程机械用液压马达剩余寿命预测

为了进行工程机械用液压马达剩余寿命预测,基于容积效率、Wiener过程以及支持向量机回归,提出一种剩余寿命预测方法。开展液压马达全寿命试验,运用非线性支持向量机回归算法处理原始数据,基于极大似然估计法和贝叶斯更新策略建立Wiener过程模型,完成液压马达剩余寿命预测。结果表明：液压马达容积效率随冲击次数变化有明显下降趋势;非线性支持向量机回归在考虑退化数据随机性的基础上提高了规律性;基于Wiener过程的剩余寿命预测方法能够准确、可靠地预测液压马达的剩余服役寿命。     

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。