基于结构光视觉的钢轨波磨检测与定位方法研究

钢轨波磨的高精度测量是研究钢轨波磨问题的基础。基于钢轨波磨检测与定位问题,提出了一种结合结构光视觉、波磨横向测量线以及连续小波变换的波磨测量系统。建立基于结构光视觉的钢轨轮廓测量模型,提出依据11条波磨测量线来提取轨面不平顺并运用连续小波变换时频分析方法,实现了波磨的横向与纵向位置定位。通过搭载测量系统的波磨小车对实际线路进行测试,结果表明,该曲线内轨曲中点和缓圆点处均存在波磨,且曲中点处波磨幅值大于缓圆点处;外轨曲中点和缓圆点处轨面在所有测量线处无周期性,不存在波磨。该曲线波磨纵向位置在K19+555~K19+650范围内,横向位置在B-B测量线上,波长约为200mm,横向定位后的轨面不平顺水平要比未经定位的轨面不平顺水平大4.2dB。波磨测量系统实现了钢轨波磨的精确定位与测量。     

金属拱型波纹屋盖结构足尺模型试验研究

设计并实施了 16组金属拱型波纹屋盖结构足尺模型试验。通过这些破坏性试验 ,对这种结构在全跨及半跨荷载作用下的力学性能有了一个直观认识。试验得出的结论不仅可作为建立结构分析理论的依据 ,而且可用于指导这种结构的工程实践     

热处理对Hf-基非晶合金力学性能的影响

采用铜模浇铸法制备Hf44.5Cu27Ni13.5Ti5Al10块体非晶合金,并对其进行等温退火处理。利用X射线衍射仪（XRD）和透射电镜（TEM）对非晶合金的晶化行为进行了分析,并通过MTS810实验机及场发射扫描电子显微镜（FESEM）研究了等温退火对合金力学性能的影响。结果表明,该非晶合金等温退火相转变进程为：非晶→非晶＋Al16 Hf6Ni7→非晶＋Al16 Hf6Ni7＋CuTi2→CuHf2＋CuTi2。合金断裂强度随退火温度的升高先增大后减小。743 K等温退火后,合金断裂强度达到最大值2400 MPa,弹性应变为3.0%。在Hf44.5Cu27Ni13.5Ti5Al10块体非晶合金压缩断口上观察到纳米级韧窝及周期性条纹结构。随着退火温度的升高,周期性条纹间距逐渐减小直至消失,断口形貌呈现为脆性解理断裂的河流状花样。     

皱纹外导体泡沫PE绝缘RF同轴电缆的衰减特性

衰减是射频(RF)同轴电缆最重要的传输特性.外导体皱纹深度及泡沫聚乙烯(PE)的介质损耗角正切tg δ是影响皱纹外导体泡沫PE绝缘同轴电缆衰减的主要因素.浅皱纹结构及净化介质材料是降低该电缆衰减值的有效途径.     

Effect of Temperature on Grain Size in AA6063 Aluminum Alloy Subjected to Repetitive Corrugation and Straightening

The influence of processing temperature on grain size reduction in AA 6063 aluminum alloy subjected to repetitive corrugation and straightening(RCS)is investigated in this work.The aluminum alloy was processed by RCS at different temperatures(room temperature,100 ℃,200 ℃ and 300 ℃)till the maximum number of passes possible before failure and the mechanical properties such as tensile strength and hardness were measured.The grain size and their misorientation of grains of the processed samples were analyzed using the electron backscattered diffraction.The results indicated that the transformation of low-angle grain boundaries to high-angle grain boundaries and dislocation tangles were highly dependent on the strain imparted,which could be controlled by selecting the proper processing temperature.As a result,the mechanical properties are affected.In particular,the room temperature tensile strength and hardness values of the processed material decrease with increasing processing temperature.     

Study on the Effect of Track Curve Radius on Friction-Induced Oscillation of a Wheelset–Track System

Abstract

The purpose of this article is to investigate the correlation between the friction-induced oscillation of a wheelset–track system and curve radius and to explain a general phenomenon of rail corrugation based on the viewpoint of friction-induced oscillation. The typical phenomenon of rail corrugation in metros is that corrugation generally arises when the curve radius is quite small, whereas it rarely occurs when the curve radius is larger or on a straight track. Different multibody models of the vehicle–track system and finite-element models of the multiple-wheelset–track system with different curve radii are established, respectively. According to the creep force analyses and unstable vibration analyses, the correlation between the creep force and friction-induced oscillation can be identified. Then the effect of the track curve radius on the friction-induced oscillation of the wheelset–track system can be summarized, which provides an explanation of the typical phenomenon of corrugation.     

地铁轨道波浪形磨耗检测系统研究

钢轨波浪形磨耗(简称"波磨"),已经成为地铁轨道损伤的主要形式之一。在了解国内外各种检测方法的基础上,采用惯性基准法,设计地铁轨道波磨在线检测系统。基于SIMPACK仿真软件,模拟地铁车辆在波磨轨道上的运行状态,采集轴箱加速度,计算出轨道波磨,对该系统进行理论指导、验证。     

Short pitch corrugation of railway tracks with wooden or concrete sleepers: An enigma solved?

British Railways (BR) in the 1970s observed an increased level of short pitch corrugation after the electrification of the West Coast main line, which involved (among other things) the change from wooden to concrete sleepers. Here, using a simple model for the two systems, we find a different sensitivity to lateral creepage, a doubled growth at the “pinned-pinned” resonance regime shifted from about 600 to about 1000 Hz, but a reduced growth in the 300-600 Hz range, where most data for both systems seem to lye. Hence, despite it would be tempting to associate the increased corrugation simply to the increased (doubled) peak of normal load, there is discrepancy in the corresponding wavelength predicted by the model. Hence, there is still an “enigma” about the reasons for the enhanced corrugations.     

Numerical investigation on flow and heat transfer characteristics of corrugated tubes with non-uniform corrugation in turbulent flow

Based on finite volume method, the pressure drop and heat transfer characteristics of one smooth tube and ten different axisymmetric corrugated tubes, including two with uniform corrugation and eight with non-uniform corrugation, have been studied. A physical model of the corrugated tube was built, then the numerical simulation of the model was carried out and the numerical simulation results were compared with the empirical formula.The results show that: the friction factor decreases with the increase of Reynolds number ranging from 6000 to 57000, the value of which in the corrugated tubes with non-uniform corrugation(tube 03–10) are smaller than those with uniform corrugation(tube 01–02). The geometry parameters of tube(01) have advantages on the heat transfer enhancement in low Reynolds number flow region(from 6000 to 13000) and tube(07–08)have advantages on the heat transfer enhancement in high Reynolds number flow region(from 13000 to 57000). The vortex, existed in each area between two adjacent corrugations called second flow region, is the root of the enhancement on heat transfer in the corrugated tubes. The effectiveness factor decreases with the increasing of Reynolds number and the performances of the corrugated tubes with pitch of 12.5 mm have advantages than these of 10 mm under the same corrugation geometric parameter.     

波纹腹板工字钢强度数值分析

对一种新型结构型材———波纹腹板工字钢进行静载强度及刚度的数值分折,通过分析波纹腹板在静载作用下的主要强度及刚度性能并与普通平腹板进行比较,揭示波纹腹板在静载作用下的应力分布及刚度特点,为型材结构的研究开发提出一种新的设想,并为进一步开展这方面的研究提供参考。