基于相空间奇异值分解与AFSA-SVM的齿轮故障诊断方法

针对表征齿轮故障信息的特征难提取与支持向量机的结构参数基于经验选取,致使齿轮故障分类模型泛化能力弱、精度差的问题,提出一种基于相空间奇异值分解与AFSA-SVM的齿轮故障诊断方法。该方法首先将齿轮振动信号进行相空间重构,并对重构矩阵进行奇异值分解得到奇异值特征向量;其次,利用人工鱼群算法优化支持向量机的惩罚系数与高斯核宽度系数,建立AFSA-SVM的齿轮故障分类模型;最后,将奇异值特征向量作为模型输入进行齿轮不同故障状态的分类识别。实验结果表明:与基于BP、SVM和PSO-SVM的故障分类方法相比,基于相空间奇异值分解与AFSASVM的齿轮故障诊断方法具有更高的分类精度,更强的泛化能力。     

基于小波包与SVM的滚珠丝杠故障诊断

采取小波包方法对数控机床滚珠丝杠故障信号进行分析,结合时域分析,提取不同故障状态下的特征值,得到支持向量机（SVM）的输入特征向量;研究并确定了应用二叉树算法与RBF核函数,采用遗传算法对SVM的参数寻优,建立了SVM多故障分类器,实现了滚珠丝杠的故障诊断与分类。最后通过实验结果证明了多故障分类器的可行性与有效性。     

LMD和SVM相结合的电机轴承故障诊断研究

为了提高电机轴承故障诊断的准确率,提出了基于粒子群优化的支持向量机(SVM)故障诊断的方法。文章采用局部均值分解(LMD)提取电机轴承振动信号特征作为支持向量机的特征向量;采用粒子群优化算法(PSO)优化支持向量机的核函数参数和惩罚参数,以此建立分类器用于识别电机轴承故障类型。通过仿真实验验证该方法能够有效的识别电机轴承故障状态。     

基于支持向量机的火车滚轴故障诊断

火车故障的60%都是由于滚轴问题引起的,现在的诊断方法都是基于知识的,但故障样本的不足从一定程度上制约了基于知识的方法在实际中的应用,针对这一问题,利用支持向量机在小样本情况下具有较强分类能力的特点,本文提出了一种基于支持向量机的滚轴故障诊断方法.该方法采用小波变换对齿轮的震动信号进行处理来构造特征向量,然后输入到支持向量机分类器中进行模式识别.     

用电弧声信号监测GMAW焊丝干伸长的SVM模型

为了探索电弧声在焊接质量监控中的应用途径,在对短路过渡GMAW电弧声信号频谱分析的基础上提出电弧声道概念,认为声道是受焊接参数、电弧形态等众多因素影响的分布参数系统.电弧声的LPC(线性预测)模型是声道传输特性的一个参数化估计.电弧声频谱与焊丝干伸长密切相关,但呈现出高度复杂性和非线性.利用电弧声LPC预测系数和反射系数构造输入向量,建立了支持向量机(SVM)的焊丝干伸长分类模型.训练和测试结果表明,采用不同形式核函数的SVM(支持向量机)分类器均能实现干伸长的正确分类,其性能明显优于相同条件下的RBF(径向基函数)神经网络分类模型,小样本情况下仍具有较好的推广能力.其中,用反射系数作为输入向量训练三次多项式核函数的SVM分类器性能最优,测试正确率在98%以上.据此认为,利用LPC分析提取电弧声的特征向量,建立SVM模型是一种焊接动态参数监控的可行方法.     

基于特征信息融合的离散小波SVM齿轮故障诊断方法研究

针对齿轮振动信号故障特征微弱及故障样本不足,提出基于特征信息融合的小波-SVM(支持向量机)故障诊断方法,用于多类齿轮故障诊断。该方法采用离散小波变换对齿轮的振动信号进行处理来构造特征向量,将多路信号融合后输入到SVM的多故障分类器中进行故障识别。实验结果表明:该方法能够在训练样本数量少的情况下,快速获得良好的分类结果,且其故障诊断准确率在96.67%以上;峰值和峰值因子对齿轮故障最敏感,以峰值或峰值因子为特征量的多传感器信息融合,其诊断准确率达95%。该方法更适合于实际齿轮故障诊断应用,并为多类齿轮故障快速诊断的进一步创新研究提供了理论基础。     

基于IWT_SE与GA_SVM的齿轮磨损检测

为了实现齿轮运行过程中的磨损程度准确识别,提出了基于改进小波阈值样本熵(IWT_SE)与遗传算法优化支持向量机(GA_SVM)的齿轮磨损程度检测方法。首先,对齿轮振动信号进行改进小波阈值降噪;其次,计算降噪后信号的样本熵,组成特征向量;最后,将特征向量输入基于GA_SVM建立的分类器进行故障识别分类。通过齿轮实验数据分析了算法中的参数选取问题;将该方法用于齿轮实验数据,并与传统小波阈值函数样本熵分别与BPNN,PNN,SVM,PSO_SVM相结合的方法进行对比分析,结果表明,IWT_SE与GA-SVM相结合时识别准确率最高,达95%,证明文中所提方法对齿轮磨损程度识别具有一定实际应用价值。     

基于多类SVM与改进EMD的故障诊断

鉴于传统方法在智能故障诊断中存在着一些不足,提出了一种基于多类支持向量机(SVM)和改进的经验模式分解(EMD)的故障检测与诊断办法。首先通过采用窗口平均法的EMD将原始信号自适应分解到分布在不同频带的基本模式分量(IMF),再用特征归一化处理进行特征提取,然后输入多类SVM分类器进行分类,从而对设备的当前状况作出判断。经过实验证明,本方法可以有效地对轴承设备进行故障诊断。     

改进和声搜索算法优化支持向量机的柴油机故障诊断研究

针对基本和声搜索算法在优化支持向量机参数时,其局部搜索能力不足且后期收敛速度比较慢的缺点,提出利用改进和声搜索算法对支持向量机相关参数进行选择优化(IHS-SVM)的方法。在这一方法中,将原算法中控制参数—记忆库取值概率(HMCR)、微调概率(PAR)和调节宽度(bw)由静态值改进为随迭代次数的不同而进行动态变化。通过对UCI中的2个数据集进行分类正确率测试,并与未优化的支持向量机(SVM)和基本和声算法优化的支持向量机(HS-SVM)测试结果对比,证明了该改进方法的优越性。最后,将其用于柴油机故障诊断,并将分类正确率与未优化SVM和HSSVM分类结果进行比较,进一步说明改进和声搜索算法优化的支持向量机(IHS-SVM)能获得更高的分类结果正确率,即证明了该改进方法的实用性。     

振动监测技术在齿轮裂纹故障诊断中的应用

在对一级齿轮箱的振动信号进行快速傅里叶变换和小波包变换的基础上,提取各个小波包系数的峭度和偏态,并选择分辨率较高的小波包系数的峭度和偏态作为齿轮裂纹的故障特征。最后通过基于粒子群优化算法(Particle swarm optimization, PSO)的支持向量机(Support vector machine, SVM)模型进行齿轮裂纹故障特征分类,其中,PSO主要用来优化SVM模型的核函数的关键参数,避免出现局部最优和过拟合的问题。计算结果表明,和其它算法相比,提出的齿轮裂纹故障诊断方法在分类精度和计算效率方面具有综合优势。     

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.     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

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).     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.     

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.