基于模具设计与制造专业“双证书”课程的研究与实践

双证融通是职业教育的本质要求,本文通过模具设计与制造专业工作过程分析与职业资格证书标准分析,将职业标准融入课程标准之中,在此基础上,提出模具设计与制造专业双证融通专业培养方案的框架体系。     

浅谈路面工程的基层连铺施工方法

结合沂邳线苍山段路面翻修工程,对路面基层上下两层连铺的施工工艺、重点难点进行了探讨,给出了控制施工质量的方法,分析了这种施工方法的社会经济效益.     

High-frequency random vibration analysis of a high-speed vehicle–track system with the frequency-dependent dynamic properties of rail pads using a hybrid SEM–SM method

A hybrid Spectral Element Method (SEM)–Symplectic Method(SM) method for high-efficiency computation of the high-frequency random vibrations of a high-speed vehicle–track system with the frequency-dependent dynamic properties of rail pads is presented. First, the Williams-Landel-Ferry (WLF) formula and Fractional Derivative Zener (FDZ) model were, respectively, applied for prediction and representation of the frequency-dependent dynamic properties of Vossloh 300 rail pads frequently used in China's high-speed railway. Then, the proposed hybrid SEM–SM method was used to investigate the influence of the frequency-dependent dynamic performance of Vossloh 300 rail pads on the high-frequency random vibrations of high-speed vehicle–track systems at various train speeds or different levels of rail surface roughness. The experimental results indicate that the storage stiffness and loss factors of Vossloh 300 rail pad increase with the decrease in dynamic loads or the increase in preloads within 0.1–10,000?Hz at 20°C, and basically linearly increase with frequency in a logarithmic coordinate system. The results computed by the hybrid SEM–SM method demonstrate that the frequency-dependent viscous damping of Vossloh 300 rail pads, compared with its constant viscous damping and frequency-dependent stiffness, has a much more conspicuous influence on the medium-frequency (i.e. 20–63?Hz) random vibrations of car bodies and rail fasteners, and on the mid- (i.e. 20–63?Hz) and high-frequency (i.e. 630–1250?Hz) random vibrations of bogies, wheels and rails, especially with the increase in train speeds or the deterioration of rail surface roughness. The two sensitive frequency bands can also be validated by frequency response function (FRF) analysis of the proposed infinite rail–fastener model. The mid and high frequencies influenced by the frequency-dependent viscous damping of rail pads are exactly the dominant frequencies of ground vibration acceleration and wheel rolling noise caused by high-speed railways, respectively. Even though the existing time-domain (or frequency-domain) finite track models associated with the time-domain (or frequency-domain) fractional derivative viscoelastic (FDV) models of rail pads can also be used to reach the same conclusions, the hybrid SEM–SM method in which only one element is required to compute the high-order vibration modes of infinite rail is more appropriate for high-efficiency analysis of the high-frequency random vibrations of high-speed vehicle–track systems.     

国内外摩托车ABS制动系统测试方法介绍(1)

随着摩托车行业的发展,人们越来越注重摩托车的安全性能,摩托车制动系统作为衡量摩托车安全性能的关键指标,成为各大摩托车企业关注和科研投入的重点课题,ABS防抱制动系统作为高级制动系统,已经逐渐应用在了中高端摩托车上,随着新系统的应用,世界各国和地区的检测标准也在不断更新,本文重点介绍国内外摩托车ABS制动标准的主要内容和差异,以供大家参考.     

国内外摩托车ABS制动系统测试方法介绍(2)

(上接2015年第5期) d)故障诊断性能:车辆ABS系统的功能状况指示装置应满足GB 15365-2008标准要求,指示符号颜色应为黄色,故障诊断性能检验可通过人为制造ABS系统电源和(或)某个电子控制器断路,使ABS装置失效,目测是否有光学警告信号传递给驾驶员,并确保在白天可见. e) ABS装置失效时制动性能:在ABS装置失效情况下,应在高附着系数路面上进行1次满载状态的干式制动试验,非联动的单独前制动、单独后制动及联动车辆的制动性能要求是相同的,需满足GB 20073-2006标准A.2.1.2.2中满载状态干式单独后轮制动限值要求,如表5所示.     

石家庄六线隧道模型试验相似材料研究

满足相似关系的模型材料是模型试验成功的关键。在调研相似材料研究现状的基础上,依托石家庄六线隧道模型试验项目,应用量纲分析法推导出了相关参数的相似判据。根据相似原则,以粘聚力和摩擦角为主要相似判据,选用重晶石粉、石英砂和凡士林的混合物为模型材料,通过正交设计法研制出了地层相似材料。以抗压强度为相似判据,选用石膏材料为模型材料,研制出了灌注桩和锚索注浆体相似材料。     

基于SS-FB-PFC的纯电动汽车车载充电系统的研究

针对现有车载充电系统的主要问题,提出了一种基于单相单级全桥功率因数校正拓扑的车载充电系统结构和改进型单体电压控制的新型整车充电策略.开发了一台3.6kW的样机,其实验结果表明,该系统具有效率高、体积小、功率因数高和谐波污染少等优点,充电控制策略提升了充电的安全性.     

交互式电子技术手册(IETM)规范体系分析

本文对当今国际上两种IETM主流规范的优缺点和适用范围进行了比较和评述,并指出在IETM的研究与开发中正确评价和应用两种规范的有关问题.     

熊洞湾隧道断层破碎带施工技术

文章对熊洞湾隧道成功通过断层破碎带的施工技术进行了总结,提出了适合断层破碎带施工的原则和技术措施,将预报、监测工作贯穿整个施工过程,以达到稳步掘进,有效地防止坍塌等事故的发生。其成果可为以后断层破碎带的施工提供参考借鉴。     

隧道专用特种压力循环注浆锚固装置及施工工艺的研究

文章针对目前砂浆锚杆存在的问题,介绍了一种具有螺旋杆体、止浆装置和排气管、并可监控注浆压力的锚杆注浆系统。通过模拟试验和现场实践证明,该装置可方便可靠地实现全螺旋砂浆锚杆的有压注浆,具有不失浆、不漏浆以及注浆饱满等特点;且注浆施工工艺操作简单,解决了当前普通砂浆锚杆在施工中不能安装配件和注浆效果差等问题。