贯流式水轮发电机集电环短路原因分析及改善措施

白石窑水电厂1～4号发电机组在投运初期,集电环曾多次出现绝缘降低甚至短路的非正常现象。通过分析,引发故障的原因主要是碳刷架、集电环绝缘结构设计欠妥、运行环境恶劣以及机组的振动过大。针对上述原因,改进了绝缘结构设计上的不足,加强巡视和维护检查,装设工业电视监控,加装碳粉回收装置,对受油器进行防漏油或喷油技术处理,加强清污力度、提高发电水头以便减少机组振动,从内外因加以防范和改善后,问题得到了标本兼治,取得了理想的效果。     

大块式动力基础的振动分析与加固处理

根据一大块式曲柄连杆机构的机器钢筋混凝土基础的振动测试与振动分析 ,诊断了基础发生工程事故的原因 ,并结合工程特点 ,在不改变基础设计的动力参数的情况下 ,确定了灌浆加固处理方法 ,并介绍了灌浆加固处理的效果。     

Failure of a stationary pump engine piston

Piston failures are not a common occurrence, but they do occur, and failure is usually associated with fatigue crack growth. Most failures initiate at the gudgeon pin hole or in the skirt of the piston. Occasionally they fail elsewhere. In the example covered in this paper, failure initiated in the crown and progressed down to the gudgeon pin before final failure occurred. This paper outlines the cause and mode of failure and shows that small metallurgical discontinuities can contribute to these failures under the right circumstances.     

MEMS运动件的芯片外机械驱动方法

研究MEMS微结构的片外机械式驱动问题 ,介绍了在MEMS硅芯片背面贴合一块宏观尺度PZT片的驱动思想即PZT产生机械运动 ,在硅固定件与微运动件之间产生动量耦合 ,从而驱动微运动件。重点探讨脉冲驱动、振动驱动两大类基本驱动方法及其特点 ,介绍国外代表性研究结果 ,并提出对该方法进一步研究的观点与设想。     

Quantitative assessment of preferential fatigue initiation sites in a multi‐phase aluminium alloy

Complex multi‐phase Al–Sn–Si alloys are commonly employed in the manufacture of small automotive plain bearings. The fundamental fatigue initiation behaviour of this class of alloys is currently not well understood. A range of analytical techniques were applied to investigate preferential initiation site location and to attempt to identify critical microstructural features. It was apparent from experimental studies that points of fatigue crack initiation are associated with the Si secondary phase. Using tessellation approaches and subsequently both adaptive numerical modelling and micro‐scale finite element modelling allowed the identification of features affecting the probability that a given Si phase would initiate a fatigue crack.     

Simulation by Slepian method of plastic displacements of Gaussian process excited multistory shear frame

The object of study is a stationary Gaussian white noise excited multi-degree-of-freedom (MDOF) linear elastic, ideal plastic, linearly damped, statically determinate oscillator with several potential elements of ideal plastic yielding. Specifically the study is exemplified for a plane multistory shear frame with rigid traverses where all the connecting columns except the columns in one or more of the bottom floors have finite symmetrical yield limits. The white noise excitation acts on the mass of the first floor making the movement of the elastic bottom floors simulate a ground motion that interacts with the structure above the bottom floors. The method of study is so-called Slepian model simulation and is in principle the same for other statically determinate MDOF elasto-plastic oscillators of the considered type. The method is fast as compared to direct simulation and provides results that give good insight in the behavior of the plastic displacement response process.     

Dynamic stiffness vibration analysis using a high‐order beam model

This work presents the derivation of the exact dynamic stiffness matrix for a high‐order beam element. The terms are found directly from the solutions of the differential equations that describe the deformations of the cross‐section according to the high‐order theory, which include cubic variation of the axial displacements over the cross‐section of the beam. The model has six degrees of freedom at the two ends, one transverse displacement and two rotations, and the end forces are a shear force and two end moments. Using the dynamic stiffness matrix exact vibration frequencies for beams with various combinations of boundary conditions are tabulated and compared with results from the Bernoulli–Euler and Timoshenko beam models. Copyright © 2003 John Wiley & Sons, Ltd.     

机器人骨骼-肌肉系统工程模拟的动态分析

用振动学理论对仿人机器人骨骼-肌肉系统工程模型进行了分析，并提出了一种控制振动的方法，提高仿人机器人运动精度和缩短达到稳定的时间，同时阐述了这种方法的可行性。     

The wheel–rail interface—some recent accidents

The importance of the wheel–rail interface to the safe operation of railways is discussed. Some aspects of the history of rails and wheels are introduced. Several recent accidents involving the wheel–rail interface are described. The great importance of operating both vehicles and track as a system is emphasized, together with the necessity of maintaining both in good condition.     

现场双面动平衡在离心式多级叶轮风机上的应用

对离心式多级叶轮风机进行振动频谱分析，认为叶轮存在动不平衡，造成风机振动超标，采用现场双面动平奢技术消除了风机转轴动不平衡。