站场工艺管道小口径支管角焊缝相控阵超声检测工艺

小口径支管是站场工艺管道重要组成部分,受其管径小、结构复杂等因素的影响,目前的无损检测技术有效性不高,大量小口径支管角焊缝的安全状况不明,是站场工艺管道的安全隐患。采用CIVA仿真软件对典型规格的小口径接管角焊缝模型进行仿真,分析不同工艺参数下焊缝内部声场的特点及变化规律,优化了相控阵无损检测工艺,并在模拟试件上开展5种典型缺陷的试验验证,验证结果表明,提出的相控阵检测工艺可以有效检测出模拟试件中的典型缺陷,缺陷实测尺寸误差在10%以内。

基于CANopen协议的双轴伺服系统控制研究

由于伺服系统精度高、稳定性好、响应迅速等优点,已经在工业控制的各个领域被广泛应用,但是随着工业自动化的不断发展,单一的伺服系统已经无法满足需求。现场总线采用数字信号通信的方式,具有数据传输速度快,抗干扰性好等优点。因此,将现场总线技术应用到伺服系统中是运动控制领域的研究热点之一。提出了一种基于CANopen协议的与伺服控制系统相结合的CANopen主从控制方案,实现对双轴伺服电机的精确控制。研究结果表明,通过上位机界面发送报文对伺服系统控制的方法操作简单、数据准确、实时性好,用户通过上位机界面接收伺服电机的反馈信息,可以很好地对电机进行实时监控。

Evaluation of cable tension sensors of FAST reflector from the perspective of EMI

The active reflector of FAST(five-hundred-meter aperture spherical radio telescope) is supported by a ring beam and a cable-net structure,in which nodes are actively controlled to form series of real-time paraboloids.To ensure the security and stability of the supporting structure,tension must be monitored for some typical cables.Considering the stringent requirements in accuracy and longterm stability,magnetic flux sensor,vibrating wire strain gauge and fiber bragg grating strain gauge are screened for the cable tension monitoring of the supporting cable-net.Specifically,receivers of radio telescopes have strict restriction on electro magnetic interference(EMI) or radio frequency interference(RFI).These three types of sensors are evaluated from the view of EMI/RFI.Firstly,these fundamentals are theoretically analyzed.Secondly,typical sensor signals are collected in the time and analyzed in the frequency domain,which shows the characteristic in the frequency domain.Finally,typical sensors are tested in an anechoic chamber to get the EMI levels.Theoretical analysis shows that Fiber Bragg Grating strain gauge itself will not lead to EMI/RFI.According to GJB151 A,frequency domain analysis and test results show that for the vibrating wire strain gauge and magnetic flux sensor themselves,testable EMI/RFI levels are typically below the background noise of the anechoic chamber.FAST finally choses these three sensors as the monitoring sensors of its cable tension.The proposed study is also a reference to the monitoring equipment selection of other radio telescopes and large structures.

Study and application of vibrating wire strain gauge in monitoring cable tension of FAST cable-net

A cable net structure is selected to support its reflecting triangular aluminum panels of FAST(five-hundred-meter aperture spherical radio telescope).To ensure the security and stability of the supporting structure,cable force of typical cables must be monitored on line.Considering the stringent requirements in installation,accuracy,long-term stability and EMI(Electromagnetic interference),most of the commonly used cable force measurement methods or sensors are not suitable for the cable force monitoring of the supporting cable-net of FAST.A method is presents to accomplish the cable force monitoring,which uses a vibrating wire strain gauge to monitor the strain of linear strain area at the anchor head.Experiments have been carried out to verify the feasibility.The method has a series of advantages,such as high reliability,high accuracy,good dynamic performance and durability,easiness of maintenance,technical maturity in industry and EMI shielding.Theoretical analysis shows that there is a linear relationship between the cable body force and anchor head surface strain,and experimental results proves a good linear relationship with excellent repeatability between the cable body force and anchor head surface strain measured by the vibrating wire strain gauge,with a linear fit better than 0.98.Mean square error in practical measuring is 2.5t.The relative error is better than 4%within the scope of the cable force in FAST operation which meets practical demand in FAST engineering.

水封隧道内油气管道补口材料的应用效果

通过6条水封隧道内油气管道补口的检测数据,总结了热熔胶型热收缩带补口、液体环氧补口、黏弹体胶带+聚合物外护带补口的应用效果,分析了水封隧道内不同补口材料的失效原因。结果表明:热收缩带补口大面积整体失粘导致密封失效,主要原因是施工质量控制不严;液体环氧补口在水封隧道内应用效果偏差,主要原因是水渗透进入涂层与基体界面处,造成液体环氧涂层鼓泡和附着力严重下降;黏弹体胶带在不同水封隧道内的应用效果差异较大,个别隧道内黏弹体胶带出现搭接、压接不实导致补口密封失效。

油气阀室接地网状态的冲击检测方法研究

我国某长输管道所属站场曾发生雷击造成站内设备损坏事件,给站内安全生产造成严重影响,而接地装置是泄放雷击电流的重要设施,接地装置连接状态不良将影响其冲击接地阻抗。首先测量了阀室不同位置的冲击阻抗和工频接地电阻,对二者的关系进行了对比分析,研究发现:阀室各测点的实际冲击阻抗远大于工频接地电阻,不能用工频接地电阻乘冲击系数评估其冲击阻抗。利用冲击阻抗时变曲线不仅可以去判断接地网整体是否连接良好,还可以去分析不同测点之间是经过拓扑分支相连还是直接相连的;发现A阀室接地网整体接地良好,B阀室接地网存在个别接地不良,如测点1及测点4。该方法不仅可用于测量阀室的冲击阻抗,还可以用于检测各测点连通性。

基于宽板拉伸的错边环焊缝应力集中试验与模拟

应力状态是环焊缝合于使用评价的关键因素,而错边会引起环焊缝结构的不连续性,导致焊缝所受应力状态发生变化。为了探讨含错边环焊缝在外加载荷下的力学行为以及应力分布情况,通过宽板拉伸试验对含错边的环焊缝应力集中现象进行研究,建立有限元模型对其进行验证,对比了BS 7910-2013《金属结构中缺陷验收评定方法导则》和GB/T 19624—2004《在用含缺陷压力容器安全评定》推荐方法所得的计算结果。研究表明:错边会导致明显的焊缝应力集中,BS 7910-2013计算得到的应力集中系数与宽板和有限元模拟得到的结果相比保守度较为合理。含错边管道环焊缝现场缺陷合于使用评价时,推荐采用BS 7910-2013对错边进行应力集中等效处理。

台湾高等技职教育的评鉴制度及其影响分析

台湾高等技职校院包括科技大学、技术学院以及专科学校,其创办至今已有30年历史,一直扮演着应用学术理论于实务技术、培育精深产业技术人才以及引导整体技职教育发展的重要功能。高等技职校院办学质量的评鉴旨在协助各校检视其办学效能和建立发展特色,同时也是提供教育行政主管单位有效掌握全台湾技职教育质量的重要依据,以期共同提升教育的效能。本论文旨在分析台湾在近十年来实施高等技职校院评鉴之后,学校在办学的质与量方面确实提升的具体现象;尤其介绍与分析了台湾高等技职校院评鉴的实施模式与评鉴内容,针对台湾高等技职教育的评鉴制度与实施进行反思与后设分析,通过反思而发现评鉴的实施所促使高等技职校院发展朝向一致化的发展趋势。具体言之,本文讨论的议题包括:(1)台湾高等技职教育的发展与现况;(2)教育评鉴的相关理论;(3)台湾高等技职教育评鉴的实施方式;(4)台湾高等技职教育的评鉴指标;(5)评鉴的实施对于高等技职校院办学质量影响的综合省思。