拉深筋对板材变形特征和力学性能的影响研究

采用实验方法将金属板材拉过不同尺寸的拉深筋镶块，分析了拉深筋高度、圆角半径以及过筋次数对板材变形特征的影响规律，研究了过筋产生的预应变对板材后续力学性能的影响规律。结果表明：板材流过拉深筋后，流动方向上发生均匀的拉伸变形；过筋产生的预应变随着拉深筋高度增大而增大，随着圆角半径增大而减小，随着过筋次数增加而近似线性增大；预应变越大，材料后续屈服强度和抗拉强度越高，但后续延伸率越小，总延伸率随着预应变增大表现出先减小后增大的趋势。     

一种外LET柔顺半铰的动力学建模与分析

对一种外LET柔顺半铰进行建模与动力学特性分析。采用斜率不连续的绝对节点坐标法（ANCF）建立了该柔顺半铰系统动力学方程；对外力作用下半铰中心线和外轮廓的运动变形进行仿真，与实验结果对比，证明了绝对节点坐标法对柔顺半铰动力学建模的有效性；进一步分析了半铰外形尺寸变化对其变形规律的影响。     

Stability enhancement of induction generator–based series compensated wind power plants by alleviating subsynchronous torsional oscillations using BFOA‐optimal controller tuned STATCOM

In this paper, a STATCOM (static synchronous compensator) is used to encounter the potential SSR (subsynchronous resonance) observed by IG (Induction Generator) based series compensated wind farms. The basic controller used for STATCOM control is identical to that of the literature. An idea of a unique meta‐heuristic swarm‐based optimization technique called BFOA (bacterial foraging optimization algorithm) based optimal‐controller is introduced for optimal parameter selection of the basic controller used in the control scheme of the STATCOM. The investigation is carried out with 500 MW IG‐based wind farm exposed to three‐phase LLL‐G fault close to the PCC (point of common coupling) and implemented with MATLAB in both steady and transient states for the three different cases, namely, without STATCOM, with the basic STATCOM controller, and in the presence of the proposed BFOA‐optimal controller‐based STATCOM. In both the states, the observed eigenvalues of the test system, together with the time domain results of the generator rotor dynamics for three distinct cases, reveals the effectiveness of the suggested BFOA‐optimal controller tuned STATCOM in mitigating the potential SSR.     

YC12VC型高速柴油机发火顺序的分析研究

基于AVL-EXCITE软件搭建了YC12VC发电用高速柴油机轴系动力学模型,其模拟值与试验值吻合性较好,验证了该模型可以较好地模拟不同工况条件下轴系的运动情况。基于平衡性和均匀发火等原则,设计了8种不同的发火顺序,并针对轴承受力、轴承润滑、轴系扭振和转速不均匀性开展影响规律研究。结果表明:通过发火顺序的优化,在保证最大主轴承负荷和最小油膜厚度满足设计要求的前提下,标定工况下的曲轴扭振总振幅从0.465°降低到0.259°,转速不均匀系数从0.018降低到0.009。     

RV减速器扭转刚度计算

扭转刚度是影响机器人运动精度、定位精度和重复定位精度的重要参数之一,本文通过对RV减速器内部齿轮副啮合刚度和各类型轴承刚度理论计算,提出了建立两个RV减速器虚拟样机,即在齿轮传动专业软件Romax中建立虚拟样机1,计算出系统变形引起的扭转刚度K1;同时在通用仿真动力学软件中建立虚拟样机2,计算出RV减速器回滞曲线,通过回滞曲线计算出扭转刚度K2,采用弹簧串联原理,计算了RV减速器扭转刚度K并通过试验验证了此方法的正确性。     

基于曲轴扭振信息识别的柴油机失火气缸判别方法

为解决柴油发动机在高转速、低负荷工况下难以准确判断出发生失火故障的气缸的问题,提出了通过检测曲轴转速信号中的扭振信号起始点来判定失火气缸的故障诊断方法。该方法首先通过分析单缸失火时的转速信号以确定曲轴扭振的自由频率,然后基于该频率构造正弦检测信号,将该检测信号与各缸做功转角范围内的转速信号做内积运算,并得到的内积值作为失火气缸的指示特征。在6缸柴油机上的失火试验证明该方法能够在高转速低负荷情况下准确识别发动机的单缸失火和两缸失火,弥补了传统失火诊断方法工况覆盖率低的不足。     

Development of a probabilistic algorithm of surface residual materials on Si3N4 ceramics under longitudinal torsional ultrasonic grinding

Longitudinal torsional ultrasonic-assisted grinding (LTUG) is one of the main methods to achieve high-quality and high-efficiency machining of high-performance ceramic materials. However, it isn't easy to accurately characterize the three-dimensional (3-D) surface topography due to multiple random factors during LTUG. Aiming at the complex surface features caused by multiple random factors in the LTUG of Si3N4 ceramics, a probabilistic algorithm for the height of residual material on the surface (HRMS) in LTUG of Si3N4 ceramic was proposed, and the prediction model for the 3-D surface topography and 3-D surface roughness parameters of Si3N4 ceramics in LTUG was established by using this algorithm. Simulation and experimental results show that the prediction model of 3-D surface topography and 3-D surface roughness established by the HRMS algorithm can more realistically predict the general characteristics of 3-D surface topography in LTUG under different process parameters, and the error range of the 3-D surface roughness parameter is 0–14.07%, which realizes the high-precision and high-reliability prediction of the 3-D surface topography and 3-D surface roughness parameters of the Si3N4 ceramic under LTUG.     

胀紧套联接的应用

概括地总结了胀套联接的原理、特点及其使用的方式。介绍了胀紧联接套的基本结构 ,并给出了胀紧联接套的受力分析及承载能力的计算方法 ,着重对其应用情况作了介绍。     

钢结构错列桁架体系扭转效应评定

根据钢结构错列桁架的组成特点,推导出评定水平荷载作用下扭转效应系数的计算公式,并通过模型计算考察《高层民用建筑钢结构技术规程》(JGJ99—98)第3.2.2条是否适用于钢结构错列桁架。计算结果表明:规程第3.2.2条的判定条件并不适用于钢结构错列桁架体系,计算时应该考虑结构扭转的影响。     

Lateral–torsional buckling of cold-formed zed-purlins partial-laterally restrained by metal sheeting

This paper presents an analytical model for predicting the lateral–torsional buckling of cold-formed zed-purlins partial-laterally restrained by metal sheeting for both down and uplift loadings. The critical load is determined by using energy methods. The focus of the study is to investigate the individual influences of restraints provided by the sheeting and by interval anti-sag bars, the variation of moment distribution along the longitudinal axis, and boundary conditions on the lateral–torsional buckling behaviour of the purlin.