注射模脱出螺纹塑料制品脱模力矩的研究

建立了螺纹制品成型时的受力模型,指出由于收缩制件对型芯的正压力主要作用在型芯牙尖顶部及牙尖的一个侧面上,在型芯表面的其余部位压力基本为零,甚至在制品和型芯间存在有间隙。实验证实了上述假设的正确性。在此基础上推导出了新的脱模扭矩计算公式,公式表明,脱模扭矩的大小与塑料的弹性模量、泊松比、脱模时的收缩率、摩擦系数、塑件平均壁厚、螺纹牙尖角、螺牙高、扭径等因素有关。 用螺纹型芯可更换的试验模具,用多种塑料模制螺纹制品,实测其脱模扭矩证明了该公式的正确性     

钉头管自支承式换热器的耦合传热及流场数值模拟研究

对钉头管自支承式换热器的结构进行合理简化,建立数值模型,用FLUENT软件对其温度场和流场进行数值模拟,分析比较了钉头管自支承式换热器对空气、水、润滑油3种介质的强化传热效果。结果表明钉头管自支承式换热器对粘度较小的空气介质效果更明显,其强化传热系数可达光管结构的1.7倍左右,压降为光管结构的1.04-1.08倍。     

一种新的抽油机曲柄销连接结构

曲柄销是抽油机的关键部件,连接失效是曲柄销失效的重要因素之一。介绍了一种新的抽油机曲柄销连接结构和设计方法,该结构可有效地提高曲柄销的强度,减小预紧曲柄销连接所需要的力矩,对提高曲柄销轴的寿命具有重要意义。     

张力节点的试验研究

销接作为一种典型的节点连接形式被广泛地应用在大跨度张力结构体系中。现行国外规范就几何参数对节点力学性能的影响不能给出很好的估计。通过大量的试验研究了几何参数对节点力学性能的影响,可为设计提供一些有益的理论依据。     

CCTV主楼大悬臂钢结构施工关键技术

CCTV主楼为复杂连体结构,连体悬臂结构是结构的核心部分,呈空间“L”形,具有结构施工难度大,悬挑跨度大、结构位形控制要求高、施工安全控制难度大等特点。通过合理制订悬臂钢结构安装方案,采用合龙关键施工技术,包括合龙前的位形分析、合龙构件结构分析及主要施工措施等,确保了悬臂结构合龙顺利完成。     

跨隔射孔测试联作技术研究及应用

论述了跨隔射孔测试联作工艺技术的原理、管柱结构和现场应用情况。它的井下管柱采用双封隔器结构,射孔枪接在两个封隔器之间,用油管把测试工具和射孔枪送入井下并对准油层,负压射孔后立即进行地层测试,录取地层资料,实现射孔和测试的连续施工。应用这项技术能够解决油气井任意选层射孔测试联作的技术难题,减少打、钻桥塞作业,减少井筒储存影响,实现负压射孔,有效地防止井喷,确保安全生产和环境保护。研制开发了双通道剪销封隔器、电子压力计保护托筒等一批新型井下工具。解决了射孔弹爆炸瞬间产生的巨大震动和压力波对井下工具及仪表的冲击破坏问题。     

基于硬件逻辑的微处理器通用开发系统的设计

提出通过硬件逻辑芯片和加载不同的硬件逻辑配置软件,实现控制不同种类微处理器的相关功能管脚能够灵活映射连接到同一外围接口应用电路上.从而达到在不改变开发系统其他任何硬件结构的情况下实现微处理器型号的快速更换,解决了现存的对于不同微处理器需要设计不同开发实验系统的问题.     

Effect of sliding speed and temperature on the tribological behavior of pongamia oil-based blended lubricant

The increase in industrialization has created the demand for petroleum-based lubricants throughout the world. The decrease in availability of mineral oils and their hazards related to the environment created the need to search for the alternate bio-based oils. In this work, the pongamia seed oil is blended with mineral oil (SAE20W40) at 5%, 10%, and 15% ratio for its tribological investigation at different speed and temperature. In terms of coefficient of friction and wear rate, 5% and 10% pongamia oil blends show better results at all sliding speed and temperatures. Fifteen percent of pongamia blend shows the maximum friction and wear among all the blends. Maximum friction coefficient and wear occur at 300 rpm and minimum at 1,500 rpm sliding speed. Minimum drop in the total acid number was also found in the 5% and 10% blends in comparison to 15% blend and conventional mineral. Overall, PB5 and PB10 are suitable lubricants for tribological applications.     

Investigation on lubrication condition of piston pin in real engine block with ultrasonic technique

In situ observations of variations in the lubrication conditions between a piston pin and a pin boss in a real automotive engine block operating under low rotational speeds, such as during activation of the engine, were carried out by measuring the echo height detected by an ultrasonic probe installed into the cylindrical piston pin. It was possible to estimate the oil film thickness directly within an accuracy of 1 µm by the echo height ratio reflected from the piston pin surface. The amplitude of the reflected wave (echo height) under the condition including an air bubble was higher than that without an air bubble, and the phase of the wave approached that of the dry condition. It thus became possible to detect cavitation between the piston pin and the pin boss. In particular, cavitations were continuously observed at the anti‐thrust side in the upstroke under 300 rpm operation. However, it was at least clarified that the lubrication condition in the thrust side of the piston pin supporting a load under a stable condition was sufficient to maintain safe operation, since a continuous oil film without a cavity was formed at the thrust side even for a low rotational speed. Copyright © 2011 John Wiley & Sons, Ltd.     

Pin-cap和NDW对延迟计算精度的影响

由于仿真工具本身及外部一些因素的限制,在特征化时序库时不可能产生出与理想器件完全一致的时序库延时计算模型。为了建立更为精确的延时计算模型,cadence将多输入引脚电容模型与规范化驱动波形的概念引入到有效电流源模型。文中通过使用时序分析工具对时序库进行关键路径仿真,并将分析结果与Spectre仿真结果进行对比,研究在ECSM中标准单元的接收端建立多输入引脚电容模型所带来的时序差异,以及NDW对延迟计算精度的影响。研究表明,ECSM 库若同时结合pin-cap与NDW的使用,将会更有利于延迟的精确计算,从而得到更为实际的时序分析结果。