A comparison of liquid hydrocarbon calibration standards in piston cylinders and standard cylinders with eductor tubes

Natural gas liquid standards consist of various components primarily in the C1-C6 range; they are available in three types of cylinder packages: piston cylinders and two other types of standard cylinders with eductor tubes. The three cylinder packages have different operation conditions and thus a sample may behave differently in each of the packages. The piston cylinder maintains the components in a single liquid phase at a constant pressure, while the standard cylinders maintain the components as a two-phase mixture. Typically, the components may distribute between the two phases in different concentrations depending on the various thermodynamic variables, such as temperature, pressure, and volume. This study will examine the integrity of the sample in the three cylinder packages during a controlled cylinder depletion. The results for the various cylinders will be compared with a theoretical model of the experiments.     

The Interaction of Rigid Cylinders in a Low Reynolds Number Pulsational Flow

The interaction of two rigid cylinders with parallel axes in a viscous liquid subjected to translational vibrations perpendicular to the plane containing the cylinder axes is considered in the framework of the low Reynolds number approximation. It is shown that the interaction type substantially depends on the distance between the cylinders. If this distance exceeds the viscous Stokes length, then the vibrations lead to the cylinder attraction. For the distances shorter than the Stokes length, the behaviour is opposite.     

Torsional buckling of elastic cylinders with hard coatings

The torsional buckling characteristic of an elastic cylinder with a hard surface coating layer is addressed in this paper. Deformations of the core and surface layer are obtained analytically through the Navier??s equation and thin shell model, respectively. Both infinitely and finitely long cylinders are studied and the effects of the surface layer??s stiffness, thickness, residual stresses, as well as the cylinder lengths on the critical torsional angle and buckling morphologies, are discussed. It is found that either the surface rippling or global buckling mode may occur when there exist residual stresses within the surface layer. The critical torsional angle increases when the surface layer becomes stiffer and thinner. In addition, higher-order rippling modes frequently occur for a finite-length cylinder with stiffer and thinner surface layer.     

一种基于流形学习和 KNN算法的柴油机工况识别方法

不同负荷状态下的柴油机振动、温度、转速等信号显著不同,而机组故障信号特征往往淹没在随负荷变化而剧烈变化的信号中,因此变负荷状态下的柴油机故障监测诊断难度较大,一直困扰着柴油机的实际故障诊断工作。本文提出了一种基于流形学习和KNN算法的柴油机工况识别方法,为柴油机变负荷工况下故障监测预警打下基础。方法融合机组的多源信号特征构建特征向量,通过流形学习t-分布邻域嵌入算法（t-SNE）实现特征向量的维数约简和敏感特征提取,采用K最近邻分类算法（KNN）完成柴油机运行负荷状态的自动分类。正常及故障状态下的柴油机信号验证了方法的有效性和实用性。     

活塞式气体流量标准装置活塞缸内径测量及不确定度评估

针对活塞缸自身结构特点对测量器具的限制,提出了三坐标测量机测量活塞缸内径的方法。以名义内径为19mm、45mm、140mm的活塞缸为例,对活塞缸的内径、外径和厚度进行测量,比较不同方法测量得到的活塞缸内径的差异,验证了三坐标测量机测量活塞缸内径的可靠性。此外,分析了活塞缸的形状特征对其内径测量不确定度的影响,得到活塞缸内径测量结果分别为18.999mm、44.983mm、139.975mm,测量相对不确定度分别为0.016%、0.015%、0.010%。     

Influence of cylinder compression methods on the deformation of the piston pair of a high-pressure manometer

The influence of methods of compression of high-pressure cylinders on the deformation of a piston pair as well as the effect of pressure on the flanks of steel and hard-alloy cylinders are considered. The magnitudes of the deformation of the cylinder channels are preented and the influence of the pressure exerted on the cylinder flanks on the effective area of high-pressure piston pairs is given.     

Stresses in cross-ply laminated circular cylinders of axially variable thickness

Summary This paper presents the results from an analytical investigation of the behavior of composite circular cylinders subjected to internal and external surface loading. The present cylinder consists of a number of homogeneous ply groups of axially variable thickness. Each ply group forming a layer is treated as an individual thin elastic cylinder of generally orthotropic material with interfacial stresses on the inner and outer surfaces of the layer as boundary loading. The deformation and stresses in each layer can be expressed in terms of interfacial stresses along the exterior surfaces of each layer. All displacement and stresses throughout the composite cylinder can be determined subsequently after satisfying boundary conditions at the inside and outside surfaces of the cylinder in conjunction with the recurrence relationship among interfacial stresses. Numerical results are presented for different values of the inner-to-outer ratio, number of layers, stacking sequence, axially-variable-thickness parameter, and load factor. Based on the presented results, conclusions can be drawn concerning the cylinder behavior and its sensitivity to different parameter variations.     

Positive Effect of Periodic Micropatterns on Compression Ring Friction

Internal combustion engines are increasingly regulated in regard to efficiency and environmental impact, which requires advanced optimization strategies of engine components. The contact between the top ring and the cylinder liner is critical to the efficiency of an internal combustion engine. As shown in a previous study, an amorphous carbon coating can greatly improve the friction properties of piston rings. This work expands on these results by fabricating laser-interference-induced microchannels on the coating perpendicular to the direction of movement with a mean depth of 0.97 and 3.13 μm spatial period to further optimize the tribology. Fired single-cylinder engine measurements of the microtextured rings show a significant reduction in mean piston assembly friction of 5% for operation points that are relevant for urban transportation and up to 10% for specific operation points. Subsequent multibody elastohydrodynamic simulations prove that measured friction changes result from the compression ring microtexture. In particular, the microtexture increases the hydrodynamic pressure, reduces hydrodynamic losses, and leads to 20% lowered compression ring losses for an entire combustion cycle of the investigated operation point. In the future, such tribological concepts can be deployed in internal combustion engines that are powered by sustainable hydrogen or methanol.     

Polar shear-lag analysis of a composite of concentric cylinders with longitudinal cracks: Application to internal checking in wood

Composites of concentric cylinders can fail by microcracks that span the thickness and length of one cylinder but arrest at the boundary to adjacent cylinders. This failure mode was analysed by developing a new polar shear-lag analysis for stresses in a cross-section of a concentric-cylinder composite. The analysis can accurately calculate stresses in each cylinder in the presence of microcracks. These stresses were used to calculate the energy release rate for formation of a new microcrack as a tool for predicting the microcracking process due to any source of applied or residual stresses. The target problem was to model internal checking in certain species of trees. In a tree, the alternating regions of early- and late-wood that form the growth rings are the concentric cylinders. Internal checking is microcracking in the early-wood layers. The shear-lag analysis was used to predict the propensity of growth rings to form internal checks.     

Root Cause Analysis of Cracking in Shaft End and Coupling of a High-Power Generator

Failure analyses and root cause determination were carried out on the rotor of a high-power generator of gas–diesel dual fuel which presented cracking due to torsional fatigue in its end (region of section change and coupling), after 30,000 h of service. The generator of 307 MW–3000 rpm has a rotor (shaft of 400 mm Ø) manufactured in a proprietary steel grade equivalent to ASTM A470 type, Class 7 of high hardenability. It was reported that the equipment control system showed, in service, a high level of vibrations, not admissible for continuing the operation. First, and during the equipment shutdown for inspection, the presence of cracks, slant to the rotor shaft, was detected by means of visual inspection and dye penetrant test. The failure region corresponds to the zone of coupling–shaft joint, linked by means of fixation by interference, whereas the cracking spread on two fracture planes at 45° with respect to the rotor shaft. On this zone, where cracking started, a severe fretting corrosion damage was evidenced. The characterization and identification of present damage mechanisms were conducted through macrographic, fractographic, SEM, EDS, chemical analyses, and mechanical tests. It was recognized that from the damage by fretting corrosion, fatigue micro-cracks were produced that spread due to service tensions by a mechanism of fretting fatigue. The fatigue fracture propagation was developed into two orthogonal planes at 45° from the longitudinal shaft, which reveals an inversion in the loading condition, only justifiable by torsional vibrations that were assigned to a torsional resonance typical of the system dynamics. It was considered that the torsional vibrations cause micro-movements between components, promoting fretting corrosion and the subsequent fretting fatigue that finally induced the failure by high-cycle torsional fatigue with low-stress amplitude.     

The vibration of rotating elastic membrane cylinders

Using membrane theory we first investigate the finite deformation of a right circular cylinder of compressible hyperelastic material rotating about its axis. A necessary and sufficient condition for axial shortening to accompany rotation is given. Secondly we consider small amplitude vibrations propogating on such a finitely deformed cylindrical membrane. The same equations are shown to govern both the compressible and incompressible cases. For axi-symmetric vibrations analytical results are obtained and are used to show that neither pure torsional nor pure longitudinal vibrations can propagate in a rotating cylinder. Numerical results are given for a variety of different forms of vibration for a particular realistic material model.     

Static stress analysis of carbon nano-tube reinforced composite (CNTRC) cylinder under non-axisymmetric thermo-mechanical loads and uniform electro-magnetic fields

Static stresses analysis of carbon nano-tube reinforced composite (CNTRC) cylinder made of poly-vinylidene fluoride (PVDF) is investigated in this study. Non-axisymmetric thermo-mechanical loads are applied on cylinder in presence of uniform longitudinal magnetic field and radial electric field. The surrounded elastic medium is modeled by Pasternak foundation because of its advantages to the Winkler type. Distribution of radial, circumferential and effective stresses, temperature field and electric displacements in CNTRC cylinder are determined based on Mori–Tanaka theory. The detailed parametric study is conducted, focusing on the remarkable effects of magnetic field intensity, elastic medium, angle orientation and volume fraction of carbon nano-tubes (CNTs) on distribution of effective stress. Results demonstrated that fatigue life of CNTRC cylinder will be significantly dependent on magnetic intensity, angle orientation and volume fraction of CNTs. Results of this research can be used for optimum design of thick-walled cylinders under multi-physical fields.     

利用机体表面振动信号诊断活塞环失效的研究

建立了活塞环失效时活塞－缸套撞击的力学模型，通过理论计算证明活塞环失效后活塞组的撞击参数将会改变。分析了活塞环振动和悬浮的条件。给出了活塞环径向振动固有频率范围的计算式。通过两种机型对活塞环失效故障诊断进行了模拟试验。得到了利用机体表面振动信号诊断活塞环失效的方法；当从机身外表面监测到的振动参数在低频段出现了与单环径向振动固有频率相近的特征频率，该特征频率处谱值显著增大，含该特征频率的窄带内功率也显著增大，可认为有活塞环（通常是第一道环）失效了。     

基于ANSYS的柱塞副间隙自动补偿技术研究

柱塞和缸孔配合间隙的大小直接影响水液压柱塞泵的容积效率.利用工程塑料PEEK具有良好弹塑性和密封性的优势,提出了一种新型柱塞副间隙自动补偿结构,用于柱塞与缸孔之间的密封．通过ANSYS仿真软件,分析了不同宽度的环形槽在周期性变化的压力下,对应的柱塞套变形量．结果表明,该结构不仅能有效降低柱塞/缸孔副的泄漏,而且材料的应力幅值大为降低,能够很好地延长柱塞副的使用寿命．     

Torsion of composite cylinder containing crack terminating at bimaterial interface

Considered in this paper is the Saint-Venant's torsion of a cylinder containing a dissimilar circular bar and a slanted crack. The authors gave a warping function that satisfies automatically the interface bonded condition, and reduced the torsional problem to a pair of mixed-type integral equations that could be evaluated numerically. The nature of stress singularity for a slanted crack terminating at the interface is studied, and it is shown that the power of singularity is not –0.5 at the interface tip of a crack. The expressions of singular stress around this tip are derived. For two typical composite cylinders, some numerical results giving mode III stress intensity factors, singular stresses, and torsional rigidities are presented.     

Measurement of residual stresses in thick composite cylinders by the radial-cut-cylinder-bending method

Thick fabric composite cylinders for nozzle parts in solid rocket motors should be designed to endure the extreme temperature and pressure of combustion gas. As the thickness of the composite cylinder increases, fabricational residual stresses due to the anisotropic thermal expansion or shrinkage of fabric composites also increase, which induces inter-laminar failures. Therefore, the accurate estimation of the residual stresses is indispensable for the development of thick fabric composite cylinders.

In this paper, the residual stresses in thick cylinders made of carbon fabric phenolic composites were measured by a new radial-cut-cylinder-bending method. To obtain the residual stresses from the measured relative strains during the radial-cut operation, a bending test of the cylinder with the radial-cut was performed instead of measuring the material properties with respect to radial positions. The thermal residual stresses were also calculated by finite element method considering shear deformation of fabric layers, and compared with the measured residual stresses by the new method, from which it was found that the new simple method estimated the residual stresses pretty well. Also the inter-laminar tensile strength at the position of maximum radial residual stress could be obtained from the bending test.     

诊断内燃机各缸作功均匀性的曲轴简谐扭振反算法

简要介绍了各种诊断内燃机各缸作功均匀性的方法及其局限性；依据内燃机动力学的基本理论，提出了一种利用轴系一个惯量的扭振信号多谐次分量反算内燃机各缸作功均匀性的新方法；详细推导和说明了该方法的基本原理；以某6L240柴油机为对象，进行了选用3个谐次的扭振简谐分量准确反算出各缸作功均匀性的仿真研究。理论分析和仿真研究表明．新方法只需以各缸停缸实验得到的扭振幅频特性参数为基础，利用一个惯量的扭振信号多谐次分量就可反算出内燃机各缸平均有效压力。方法简便准确，既不依靠轴系结构参数等较难获得的先验知识，又适用于内燃机轴系存在扭振的情况。     

气缸缓冲特性计算机辅助测试系统

 为研究气缸缓冲特性计算机辅助测试(CAT)系统，设计了气动回路、电磁阀驱动电路。配置了虚拟仪器的硬件，用LabVIEW 设计虚拟仪器的软件． 此CAT 系统可以测试气缸的压力、输出力、位移和振动加速度，并绘制相应的实验结果曲线．实验表明此CAT 系统操作简便、测量精度高、实用性强，可对缓冲特性、速度特性、瞬态特性等多种气缸性能进行检测．     

WAW-500微机控制电液伺服试验机的故障诊断与修复

简述了WAW-500微机控制电液伺服试验机的故障现象,分析讨论了试验机负荷示值呈非线性偏差的原因与诊断方法,并据此对试验机的主机刚性框架进行了修复,用调整试验机工作油缸活塞间位置的方法解决了工作油缸之间产生的摩擦,并使之重新投入使用.说明了试验机活塞之间产生的摩擦会造成负荷测量产生严重的非线性偏差,因此应该定期对拉伸试...