On the thermally-induced seizure in bearings: A review

This paper presents a state-of-the-art survey of papers reported on the nature of a troublesome failure mode in bearings known as seizure. This mode of failure is thermally-induced and it occurs in both journal and rolling element bearings. To gain insight, particular attention is given to reported experimental observation, various mechanisms involved, and available prediction methodologies.     

拧紧力矩和热应力对螺纹插装阀的影响分析

在分析螺纹插装阀整体结构和工作原理的基础上,建立螺纹插装阀阀套与阀芯间隙变化量在拧紧力矩和热应力作用下的理论计算模型,通过理论计算分析其间隙的变化规律,同时结合有限元分析结果对计算模型进行初步验证。结果表明:该计算模型可以用于分析螺纹插装阀在热应力下的使用性能,对螺纹插装阀的设计使用具有一定的指导意义。     

Machining accuracy for shearing process of thin-sheet metals—Development of initial tool position adjustment system

In the shearing process, clearance has a significant effect on machining accuracy. However, the relationship between uneven clearance caused by misalignment of tool position and machining accuracy remains unclear. This is attributed to the fact that, previously, the effect was small because the thickness of the workpiece was not so thin, and a method for precisely measuring and adjusting the tool position had not been established. Therefore, in the present study, a new method of adjusting the initial tool position is developed. In addition, punching experiments are conducted under the condition that the initial tool position is adjusted to an accuracy of 2 μm or better, and the effects of clearance on machining accuracy, shape of cross-section, and diameter of hole, are investigated in three types of materials. From these results, the importance of adjusting the initial tool position is clarified.     

An experimental study for the effect of different clearances on burr, smooth-sheared and blanking force on aluminium sheet metal

In this study, an experimental study was carried out to examine the effect of different clearances on smooth-sheared depth, burr height and blanking force. Aluminium sheet metals with 0.8, 1, and 1.5 mm thicknesses were used in the experiments. These experiments were carried out in circular blanking dies to 6, 8, 10, and 12 mm diameters. Six different clearances (0.009, 0.064, 0.12, 0.175, 0.231 and 0.287 mm) were used for every material and diameter. The results of the experiment show that burr, smooth-sheared and punch force is strongly related to the clearance value. The results are in agreement with the results of previous theoretical and experimental work in the literature.     

运用一元回归分析法预测柴油机压缩比

本文利用一元回归分析法，对大修柴油机的余隙容积进行了预测．具体做法是通过测量机体平面到活塞顶面的距离、运用一元回归直线方程以及选用不同厚度的缸盖垫片来保证柴油机的余隙容积，从而保证压缩比．     

一起主变保护误动事故的分祈与处理

通过一次保护误动原因查找和分析，发现了电气回路存在的问题并对定值商榷，从而纠正了运行中的缺陷，保证电网的安全稳定运行。     

多间隙平面机械系统动态性能分析

在考虑多间隙的条件下,对机械系统的动态性能进行了分析。首先,建立了转动副考虑间隙时的运动学模型,其次,选取了Flores接触力模型建立了间隙关节元素之间的法向接触力,并利用修正的"Coulomb"摩擦力模型计算了摩擦力。最后,以平面曲柄滑块机构为例,在机械系统中分别考虑单个间隙和多间隙进行了对比分析,并对不同尺寸的间隙关节进行了分别仿真,数值结果证明机械系统中引入间隙关节越多且间隙尺寸越大其动力学性能越恶化。     

浅析火花塞点火间隙对发动机性能影响

火花塞间隙的大小,直接关系到两极间跳火的强弱。间隙过小会使火花变弱,也更容易使两点击发生跨连,不利于发动机工作,其间隙过大,不易使两级产生火花,所需点火能量就愈大。     

具有间隙的风力机变桨距系统模糊自整定PID控制

因加工、安装和磨损的原因,大型风力机的变桨距电液控制机构铰链处不可避免的存在间隙,过大的间隙会使得变桨过程超调量增大,调节过程震荡次数过多,甚至引起叶片与塔架共振,最终导致风力机停机事故。分析了变桨距机构铰链处间隙的形成机制,提出了用模糊自整定PID控制算法对间隙进行补偿的方法,依据间隙的振-冲模型制定模糊推理规则,对PID控制器参数进行自适应整定。在间隙分别为0.2、0.4、0.6和0.8 mm时对常规PID控制器与模糊自整定PID控制性能进行对比研究。结果表明:相比常规PID控制器,模糊自整定PID控制方法使得变桨距控制系统超调量和震荡次数显著减小,有效地避免了系统变桨冲击。     

含间隙机构动力学研究若干问题

综合评述了含间隙机构的动力学建模方法、求解方法及其近几年在非线性动力学领域的发展,以及此类机构在控制方面的主要研究成果,同时本文对含间隙机构的未知领域提出了展望,提出了未来研究的主要方向。