重型起重电机振动的研究与健康评价标准的确定

由于港口重型起重机电机的振动具有高速、重载、大冲击等特点,针对难以准确提取信号中有效信息的难题,建立了电机振动的分析模型,并提出基于经验模态分解(EMD)的小波包量化分析方法。该方法不仅能够有效的提取出高频背景下的信号特征,而且能够对数据进行量化。实例选取上海某集装箱码头公司的大型桥式起重机(编号:#8115)的电机振动信号,分析处理后建立振动信号的健康评价标准,为实时评估重型起重电机的健康状态提供了可靠依据。     

基于小波包与倒频谱分析的风电机组齿轮箱齿轮裂纹诊断方法

为实现风电机组齿轮箱及时有效地监测和维护,提出基于小波包与倒频谱分析的风电机组齿轮箱齿轮裂纹诊断方法。该方法针对齿轮裂纹振动信号为转速频率对啮合频率及其倍频调制的特点,利用小波包分解来识别振动信号中的故障特征,通过小波包频带能量监测得到故障部位的啮合频率范围;考虑到倒频谱可以分离和提取难以识别的密集调制信号的周期成分,基于倒频谱识别故障部位的转速频率,综合利用两种频谱分析方法得到的啮合频率和转速频率,能诊断故障部位和类型。实验研究表明,该方法能精确地诊断齿轮裂纹故障,并可以实现对风电机组齿轮在复杂环境中退化状态的监测,预防断齿等重大故障的发生。     

基于DTCNN-SVM的工业循环水系统供水泵故障诊断EI北大核心CSCD

工业循环水系统供水泵的工作状态是影响工业过程安全生产的重要因素,为及时准确地识别供水泵的工作状态,提出一种基于深度迁移卷积神经网络和支持向量机(deep transfer convolutional neural network-support vector machine,DTCNN-SVM)的故障诊断方法。将与工作状态强相关的振动信号进行信号-图像预处理,实现振动时序信号的二维灰度图化;在此基础上,采用融合迁移学习与残差神经网络的深度迁移卷积神经网络模型提取振动信号灰度图特征,并基于模糊不一致性度量对深度学习特征进行约简;采用支持向量机法建立供水泵故障诊断模型。试验结果表明,所提方法在少量样本数据和模型参数下能有效识别供水泵工作状态。     

基于圆域分析的大型回转支承初期故障诊断

为解决真实工况下大型回转支承振动信号背景噪声大、常用故障诊断方法难以适用的问题,提出了一种基于圆域分析的振动信号处理方法。将时域信号进行圆域转换,并按一定角度将转换后的圆域信号划分成多个区域;判断各区域信号邻域相关离散点拟合椭圆的倾角方向,得到回转支承整圈对应的多个异常向量;以异常向量的平均向量作为圆域分析的特征向量,分析其均值、方差、歪度和峭度指标的变化情况,实现回转支承的故障诊断。对某型号回转支承进行了加速寿命试验,结果表明,该方法能够有效诊断出回转支承滚道的区域滑移、点蚀等初期故障,相比常见的时域特征、小波分析等方法准确度更高,故障可识别度更强,因此可以用于实际工况下回转支承的故障诊断。     

海洋平台油气管道疲劳裂纹AE信号特征提取及识别研究

为了将声发射(AE)技术实际应用到监测海洋平台油气管道疲劳裂纹中,需要解决管道振动干扰以及疲劳裂纹AE信号有效特征提取的问题,而问题的关键在于对管道结构疲劳裂纹AE信号特征提取及识别算法的研究。在已有研究的基础上,提出了一种基于经验模态分解(EMD)为特征提取的疲劳裂纹识别方法,将管道振动干扰问题和疲劳裂纹AE信号有效特征提取问题联系在一起,对特征元素进行优化并剔除无效噪声干扰信息,通过概率神经网络(PNN)对疲劳裂纹信号进行识别。试验结果表明,PNN结合基于EMD为特征提取的疲劳裂纹识别法能够取得良好的效果,为声发射技术监测海洋平台油气管道疲劳裂纹提供了试验和理论依据。     

基于磁记忆方法的抽油杆裂纹扩展监测

基于拉-拉疲劳实验,利用磁记忆检测仪监测了抽油杆试件疲劳裂纹扩展的整个过程,提取了表征应力集中程度的磁信号合成梯度极限状态系数指标;并结合有限元方法计算了裂纹尖端的断裂力学参量,得到不同裂纹长度所对应的应力强度因子。结果表明:基于实验数据和仿真结果所建立的磁记忆信号特征指标与应力强度因子之间具有很好的一致性,可以有效反映疲劳裂纹的扩展过程以及累积损伤,为再制造前的毛坯筛选提供理论依据。     

斗轮式堆取料机回转支承故障诊断研究

斗轮式堆取料机回转支承因故障引起的振动是超低频信号，采用一般的分析方法难于确定其故障特征频率。利用共振解调技术，可精确分析出超低频故障特征频率，再结合时域分析方法，准确诊断出该回转支承的故障。     

基于小波包能量矩阵的轴承信号特征提取

为通过振动信号识别轴承的工作状态,结合小波包变换和矩阵特征值理论,提出了一种新的轴承信号特征提取方法。引入了能量值方法,对小波包分解信号进行分层分段能量计算,组成能量特征矩阵,求得矩阵特征值;定义基于特征值的振动信号特征参数,并探讨了特征参数与轴承运行状态间的联系。最后在特征提取基础上,提出了故障早期模式识别的对应系数相乘方法。结果表明：最大值特征参数能够敏感的反映轴承工作性能的变化,可作为轴承状态监测特征量;对应系数相乘法可以作为故障部位诊断的有效方法。     

复杂变速箱齿根裂纹诊断

本文针对齿轮出现裂纹后其振动信号特征，选用时域同步平均参数法和倒频谱的方法，对某型坦克变速箱的齿轮裂纹信号进行了分析。结果表明，在无载荷条件下，时域同步平均后的时域参数法较倒频谱法对齿根裂纹诊断更有效。     

矿用斜轴式轴向柱塞泵故障诊断的实验研究

分析了ZB-107型斜轴泵的振动特性及典型故障的特性,利用试验模态分析方法确定了振动响应的传递路径及敏感位置,并通过振动响应信号的分析,讨论了斜轴泵在正常工作状态下和典型故障情况下的特征,提出了对斜轴泵典型故障进行诊断的指标.     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Synthesis of Alumina-Zirconia Nanocomposites by Solgel Process

Al₂O₃-ZrO₂ nanocomposites were developed starting with the solgel process. Composite alumina-zirconia nanopowders were synthesized from metallorganic precursors (Aluminium secondary butoxide and zirconium Iso propoxide) using the solgel process. The parameters affecting the synthesis—solvent, concentration of precursor, R/H ratio (i.e., dilution of water in solvent)—were varied as also the temperature and pH. BET and TEM were used to measure nanosize. Diffuse reflectance spectroscopy and also qualitative optical absorption led to identical particle size estimate. The variation of process parameters was used to study the effect and interdependence of process parameters. Artificial Neural Networks was used to rigorously analyze the process. Although this led to confirmation of interdependence of parameters, the presence of a single overwhelming solvent variable was also established. Then the optimal process was used to synthesize more nanopowder. To produce bulk nanocomposite the nanopowders were sintered by varying the temperature and time period. The sintered lithoids were probed with a vickers hardness tester to measure elastic modulus, hardness, and fracture toughness. The results showed high elastic modulus, modest hardness, and very high fracture toughness.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.