基于改进邻域粗糙集与S_Kohonen神经网络的滚动轴承故障诊断研究

针对现有滚动轴承故障诊断技术中,存在输入属性冗余过多、故障识别率不高等缺点,提出了基于改进邻域粗糙集与S_Kohonen神经网络的故障诊断方法。由于传感器采集的故障信息大多为数值型数据且数据维数较大,文中引入邻域粗糙集理论并对基于邻域粗糙集的经典前向贪心算法进行改进,利用改进算法约简故障数据,大大减小了算法复杂度;对Kohonen神经网络进行改进,在其原有结构基础上添加输出层构成S_Kohonen神经网络,使其输出类别满足给定分类要求;分别采用前向贪心算法、改进算法约简故障数据,将约简前、后的故障数据分别输入S_Kohonen神经网络、BP神经网络识别滚动轴承故障状态,试验结果证明邻域粗糙集可有效消除属性之间的重复信息,改进算法提取故障属性信息更能反映故障状态的本质,S_Kohonen神经网络具有良好的故障识别能力,两者配合使用,改进邻域粗糙集——S_Kohonen神经网络模型具有很好的故障诊断能力。     

粗糙集及主元分析的机械故障诊断研究

针对粗糙集理论方法与主成分分析方法的特点,引入了一个启发式函数,提出了一种将两种方法相结合的算法.运用粗糙集理论建立了信息系统的分辨矩阵,通过主元分析方法得到了各主成分的表达式和主成分贡献率,通过启发式算法得到了决策信息表的最佳属性约简和故障诊断规则,并通过算例分析验证了该算法的优越性.研究表明该算法在处理机械故障诊断中数据量大、变量多的数据时,具有很好的效果.     

基于粒子群的粗糙集属性约简与数控机床故障诊断研究

数控机床故障诊断的核心任务是根据故障征兆,经过推理计算,自动识别故障发生原因,文章把粒子群算法和粗糙集运用于机械设备的故障诊断中,提出了基于粒子群的粗糙集约简的故障诊断知识获取、规则优化和故障识别。首先介绍了粗糙集属性约简,并把粒子群算法应用于粗糙集属性约简算法中,最后从对相关数据集的约简实验结果角度证明了算法的正确性和优越性。     

制造过程质量决策粗糙集模型

针对当前企业对获取的制造信息进行深层次挖掘的需求,提出了制造过程质量决策粗糙集模型.分析了制造过程状态参数与质量之间的作用关系;基于粗糙集理论,提出了从制造数据中获取质量知识的最优规则集算法,研究了制造信息和决策知识确定性的度量方法.最后,以实际生产中的轴加工为例验证了模型的正确性和有效性.     

基于粗糙集数据挖掘算法的决策分析

介绍了粗糙集理论的基本概念和特点,研究了基于概念泛化和粗糙集的数据挖掘算法(CRCG)的决策分析,并以拉深模具为例,将其应用于模具质量评价和诊断,使模具质量控制的决策更科学、合理。     

粗糙集的约简算法在涡流传感器设计中的应用

用粗糙集理论从传感器设计的大量数据中提取最小规则集，约简过程表明，核属性中只有测量参数，即涡流传感器结构参数对灵敏度的影响是通过与测量参数的配合而起作用的，应用粗糙集约简算法，不仅获得了传感器的设计规则，而且揭示了影响传感器性能的因素之间的关系，为涡流传感器设计提供了新的知识。     

基于变精度粗糙集的铝合金焊接接头疲劳寿命预测

采用变精度粗糙集方法对铝合金焊接接头疲劳寿命预测进行建模,采用基于联合熵的离散化算法和属性约简算法对信息进行处理,获取能预测铝合金焊接接头疲劳寿命的动态模型,并对该方法的主要步骤和关键问题做了阐述.基于试验室获取的小批量试验数据对该模型进行试验分析,结果表明,该模型既具有一定的噪声容忍度又具有较高的正确度和覆盖度.该方法拓展了粗糙集理论的应用领域,并为铝合金焊接接头疲劳寿命的预测提供了一种新方法,具有较大的应用潜力.     

基于粗糙集理论的冲模设计隐性知识发掘的研究(英文)

为了克服目前在基于规则推理(Rule-Based Reasoning,RBR)系统中获取和更新规则的困难以及加快基于事例推理(Case-Based Reasoning,CBR)系统中的事例检索过程,文章提出了一种基于模糊集和粗糙集理论、从冲压模具设计库中发掘隐性设计知识的技术。所发掘的知识以规则的形式表达。该知识发掘过程包括:(1)冲压零件基于特征的模糊表达;(2)冲压事例的模糊聚类;(3)基于粗糙集的规则获取。为了进行验证,文章在原型系统中建立了一个包含53个事例的原型事例库,并从中自动发掘出了38条规则。通过事例聚类和属性约减,CBR系统的检索速度可以得到较大的提高。此外,由于所发掘的规则以产生式规则的形式表达,RBR系统可以利用这种技术建立和更新规则。     

基于粗糙集理论与聚类算法的加工中心可靠性综合评价研究

针对数控机床可靠性综合评价中指标选取不一、需要大量先验知识等不足，提出一种粗糙集与K-means聚类算法相结合的评价方法。建立原始评价指标体系，通过K-means聚类算法与Silhouetta指标对各指标值进行离散化处理，并运用粗糙集理论约简冗余指标，构造动态评价指标体系。根据属性重要度定义对约简后的指标客观赋权，构建粗糙集聚类可靠性综合评价模型。结果表明：所提出的方法合理、有效。     

漏焊智能检测系统中的知识获取

在智能系统中，知识获取是极为重要的，它在一定程度上反映了系统智能水平的高低。在知识获取的过程中应用计算方法是当前国内外研究人员的研究热点。粗糙集理论作为一种新兴的计算方法具有极大的应用潜力，已经广泛应用于模式识别、医疗诊断、医疗数据分析、图像处理、质量控制、故障诊断、数据挖掘和过程控制等许多领域中。在本检测系统中，由于具体条件的限制和人为因素的影响，传统的方法不能满足要求，必须用智能的方法加以解决。而解决问题的关键在于如何有效地获取检测过程中的知识，从而实现智能检测。将粗糙集理论应用于相关初步知识的获取，再由神经网络对所获取的初步知识进行优化，可以提高知识获取的效率。本文给出了该智能检测系统中运用粗糙集理论获取相关初步知识的方法。     

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.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

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.