利用LCR波的单通道耦合检测钢轨应力

本文介绍了利用临界折射纵波 (CriticallyRefractedLongitudinal,LCR)来检测钢轨应力的实验方法 ,建立整套实验系统 ,用耦合单通道采集数据 ,并根据应力与声速的线性关系进行分析 ,其实验误差小于 5 %     

钢轨服役疲劳特性的非线性表面波检测研究

该文利用非线性表面波检测方法对钢轨在不同服役年限后的疲劳特性进行评价,通过推导得到表面波相对非线性系数的测量表达式,选取服役期为0、1、2、5、10和20年的钢轨,采用楔块探头研究非线性表面波在钢轨截面传播特性,以此分析表面波非线性系数的规律。实验结果显示服役初始阶段钢轨的非线性系数的变化很小,随着服役时间的增加钢轨非线性系数变化速率呈现增大的趋势;通过对钢轨微观组织分析,表明位错密度增加所导致的微裂纹是钢轨的非线性系数增大的重要原因。研究将为非线性超声检测钢轨服役疲劳损伤提供理论依据,对预防钢轨因疲劳导致的失效,保证钢轨的安全服役和铁路运行安全提供新的研究方向。     

长钢轨位移测量仪的校准测量

正为满足对长钢轨位移测量仪的校准测量,笔者依托实验室50m激光基线检测平台,提出并设计制作了一套校准装置,通过检测实验并分析测量准确度,验证了长钢轨位移测量仪校准装置可满足日常校准测量需求,有效地保障了量值的溯源。一、长钢轨位移测量仪校准装置长钢轨位移测量仪装置由三部分组成,分别为激光干涉仪系统、50m激光基线和长钢轨位移测量仪标靶移动装置配合使用。图1是长钢轨位移测量仪标靶     

基于FBG反射谱特征的铁路道岔损伤识别试验研究

针对道岔结构性能及安全状态对列车(尤其高速列车)行车安全与运行质量的重要性,提出基于光纤布拉格光栅(FBG)传感技术,利用FBG传感器反射谱特征对铁路道岔钢轨结构进行损伤(裂纹)识别。在带裂纹的道岔钢轨上安装FBG传感器进行静、动态加载室内实验。通过分析FBG传感器反射谱形状精细变化,实现对裂纹的识别。实验结果表明,该基于FBG反射谱特征的损伤识别方法可有效识别铁路道岔钢轨裂纹。     

一种新型的铁路钢轨探伤车

对于钢轨内部伤损的检测,可以采用超声、射线探伤等方法。但在野外作业,最简便、有效、快速的方法,当推超声波探伤。西德、日本、美国、苏联等,都有专用的铁路钢轨探伤车。除了有手推小车外,还有火车头牵引的大型探伤列车。使用探伤车后,钢轨内部伤损可以预先发现而做到预先更换,预先防范,对保证铁路安全起了重要作用。 我国铁路部门,各工务段,都有专业的钢轨探伤组,常年累月对钢轨进行超声探伤。使用的仪器,起初是进口国外的,以后自己制作了JGT—1型(单通道)和JGT—2型(双通道)等专用的钢轨探伤仪。但由于铁路业务日益繁忙,钢轨伤损日益…     

数字式钢轨测温计的常见故障的调修

数字式钢轨测温计是用AD5 90为感温元件,用二次仪表指示温度,测量钢轨温度的铁路专用计量器具,是铁路工务部门路轨养护中不可缺少的测温仪表。数字式钢轨测温计(以下简称轨温计)型号很多,主要有ADT -Ⅰ、ADT -Ⅱ、HDT -Ⅰ、SGW -Ⅱ等。电路大同小异,出现的故障多种多样。本文针     

钢轨垂直振动模态导波频散曲线、波结构及检测应用*

频散曲线和波结构是钢轨导波检测时设计检测方法和分析回波波形的基础。首先介绍了半解析有限元计算任意截面弹性波导中导波传播的频散曲线和波结构的基本方法。然后应用该方法求解了U60型钢轨中垂直振动模态的导波频散曲线和波结构,并讨论了频散曲线和波结构在钢轨轨头缺陷导波检测中的应用。最后采用模态力锤实验及时频联合分析的方法验证了频散曲线数值计算结果。钢轨轨头横向裂纹垂直振动模态导波检测的有限元数值模拟和实验表明该模式导波是检测钢轨轨头缺陷的有效检测模式波型。     

铁路客车提速轴承外圈非基准端面挡边平行度测量仪的研制

铁路客车提速轴承外圈以前只要求测量基准端面挡边平行度，而对非基准端面挡边平行度的测量没有要求。由于近年铁道部对铁路客车提速轴承的检测项目提出了新的要求，因此开发研制了铁路客车提速轴承外圈非基准端面挡边平行度测量仪。该仪器经使用验证效果很好，满足了铁道部对铁路客车提速轴承在该检测项目的要求。     

铁路道岔综合打磨技术的应用和研究

对铁路道岔区段钢轨表面存在的病害进行认真分析，结合道岔钢轨打磨工作存在的问题，有针对性的采用在道岔区段大机打磨与仿形打磨机相结合的综合打磨新方案。该方案实行后大大提高了道岔区钢轨打磨质量，实现了道岔区的全面打磨，降低生产成本。     

利用宽频导波的轨道断轨检测算法

准确检测和定位轨道的断轨位置一直是铁路安全的重中之重,由于导波能沿轨道长距离传播,采用导波的无损检测技术能够一次检测较长距离的钢轨。在反射系数的导波法裂缝检测中;利用宽频导波在断裂处的反射特性以及导波的传播特性进行断轨定位。其间又推导了无限长结构中裂缝位置与导波波幅的数学关系,并根据这一数学关系给出了检测算法和流程。通过2.8 m长钢轨的断裂检测实验表明,在20 k Hz到40 k Hz范围内,如果选择合适的计算频段,该方法能够得到较好的定位结果,定位误差1.2%。     

Advanced ultrasonic method for measuring rail axial stresses with electromagnetic acoustic transducer

This paper explores the feasibility of the acoustoelastic birefringence method for monitoring the axial stresses in the railroad rails. An electromagnetic-acoustic transducer (EMAT) is incorporated with a superheterodyne-phase-sensitive detector to accomplish noncontacting stress measurements. Two different measurement techniques are employed and compared to each other, both of which use the polarized shear waves propagating transversely to the rail axis. One is the pulsed resonance spectroscopy technique applied to the web, where the surfaces are nearly parallel to each other and support the thickness oscillations. The other method detects the small phase shift that occurs along with the stress application. The phase shifts were measured for the discrete reflection echoes that traveled long distances (top-to-bottom echo and multiple echoes in the head of the rail). The compressive axial load was raised up to 60 tons with the Shinkansen (bullet train) rail samples, which exceeds the buckling load of long rails. Both techniques showed a linear response to stress with a sufficient sensitivity and robustness, which promise the development of a practical railroad maintenance technology. The effects of the liftoff and the residual stress distribution are determined.     

弯曲波对钢轨振动特性测试的影响研究

针对钢轨弯曲波的传播及弯曲波反射后对钢轨振动特性测试的影响,对钢轨的弯曲波波速进行了理论推导,并设计了弯曲波波速测试试验,对弯曲波传播波速及其反射波的波速等特性进行了试验验证,同时就钢轨弯曲波对振动特性测试的影响及其解决措施进行了研究。结果表明:钢轨弯曲波的波速不是常数,而是频率的函数,弯曲波的不同频率分量以不同的波速传播,其弯曲波的反射波与入射波波速相同;在有限长的试验段内进行轨道结构振动特性测试时,不可忽略钢轨弯曲波的影响;在钢轨端部安装阻尼设备可有效抑制反射波对钢轨振动特性测试的影响。     

Guided Wave Inspection and Monitoring of Railway Track

Cost-effective NDE of the vast length of aging railway track around the world remains a challenge for the community. Continuously welded rail is installed in tension but temperature changes can result in rail buckling if the initial tension is insufficient or fatigue cracks and ultimately rail breaks if the initial tension is excessive. The NDE challenge therefore includes both the detection of defects and the measurement of axial stress. Since continuously welded railway lines may be thought of as one-dimensional elastic waveguides, they are natural candidates for guided wave ultrasound, which offers the potential to interrogate a large length of rail from a single position. Guided waves have been proposed as a means of detecting the axial stress in rails to prevent buckling and also as a means of detecting complete breakage and cracks prior to breakage. This paper reviews the approaches used and the modeling methods available to support the development of nondestructive inspection and monitoring systems. Possibilities for future systems are also discussed.     

Advanced Ultrasonic Method for Measuring Rail Axial Stresses with Electromagnetic Acoustic Transducer

Abstract

This paper explores the feasibility of the acoustoelastic birefringence method for monitoring the axial stresses in the railroad rails. An electromagnetic-acoustic transducer (EMAT) is incorporated with a superheterodyne-phase-sensitive detector to accomplish noncontacting stress measurements. Two different measurement techniques are employed and compared to each other, both of which use the polarized shear waves propagating transversely to the rail axis. One is the pulsed resonance spectroscopy technique applied to the web, where the surfaces are nearly parallel to each other and support the thickness oscillations. The other method detects the small phase shift that occurs along with the stress application. The phase shifts were measured for the discrete reflection echoes that traveled long distances (top-to-bottom echo and multiple echoes in the head of the rail). The compressive axial load was raised up to 60 tons with the Shinkansen (bullet train) rail samples, which exceeds the buckling load of long rails. Both techniques showed a linear response to stress with a sufficient sensitivity and robustness, which promise the development of a practical railroad maintenance technology. The effects of the liftoff and the residual stress distribution are determined.     

Direct measurement of rail resistance

An experimental technique for directly measuring rail resistance during a railgun firing is described. A simple railgun flux loop is the only additional instrumentation (beyond standard instrumentation) required to determine rail resistance. Several tests were conducted to verify this rail resistance measurement technique. Typical test data for current, dI/dt, flux loop voltage, breech voltage and muzzle voltage are shown. It is concluded that the technique will permit the evaluation of advanced rail and railgun concepts such as cryogenic rail operation and transposed conductor rail performance     

磁性应力测量条件对应力感度的影响

磁性应力测量具有测量速度高,探测深度大(可达数毫米),无辐射危险,携带方便等优点.可以对使用中的构件进行实时实地且安全的测量.但磁性应力测量法只能用于铁磁材料并且对铁磁材料结构等因素也敏感.因此,在磁性应力测量中影响测量精度的原因很多,其中一个最主要的参数就是应力感度.本文主要研究了两种材料的应力感度与材料测定条件的关系,以及测定环境对应力感度的影响,从而在磁性测量的过程中能排除不利条件,正确地确定磁性应力的感度,提高磁性应力测量技术的准确度.     

Taguchi optimization and ultrasonic measurement of residual stresses in the friction stir welding

The main goal of this study is optimization of residual stresses produced by friction stir welding (FSW) of 5086 aluminum plates. Taguchi method is employed as statistical design of experiment (DOE) to optimize welding parameters including feed rate, rotational speed, pin diameter and shoulder diameter. The optimization process depends on effect of the welding parameters on longitudinal residual stress, which is measured by employing ultrasonic technique. The ultrasonic measurement method is based on acoustoelasticity law, which describes the relation between acoustic waves and internal stresses of the material. In this study, the ultrasonic stress measurement is fulfilled by using longitudinal critically refracted (L_CR) waves which are longitudinal ultrasonic waves propagated parallel to the surface within an effective depth. The ultrasonic stress measurement results are also verified by employing the hole-drilling standard technique. By using statistical analysis of variance (ANOVA), it has been concluded that the most significant effect on the longitudinal residual stress peak is related to the feed rate while the pin and shoulder diameter have no dominant effect. The rotational speed variation leads to changing the welding heat input which affects on the residual stress considerably.     

基于磁致伸缩导波的尖轨缺陷检测技术研究

尖轨在其周期性载荷作用下易发生断裂,引发列车事故。为对尖轨缺陷进行检测,文章基于磁致伸缩效应研制了导波检测系统,研究导波在尖轨中的传播特性、导波对尖轨附属件的检测能力以及缺陷的识别能力。采用ABAQUS/Explicit有限元方法研究了不同频率导波在尖轨中的传播特性。所研发的磁致伸缩导波检测系统在尖轨上的检测是可行有效的。使用导波检测系统在尖轨底面激励的水平剪切导波在基本轨和尖轨上可传播的有效距离至少为 12 m,在空轨中至少能传播 16 m。而且低频导波主要沿轨底传播,高频导波主要沿轨腰和轨头传播,多频导波结合能更加准确地对尖轨的检(监)测。     

Diaphragm gauge for measuring explosive impulse

The measurement of shock and stress waves under the action of explosion and impact loading has long been a concern of scientists and engineers. A number of methods have been developed over the years for measuring the physical parameters that are involved in the material dynamics resulting from an explosion. This work describes the development, calibration and validation of a passive copper diaphragm gauge aimed at measuring the impulse acting on it, resulting from an explosion in air. It is found that the diaphragm deformation (central deflection) can be used to measure the impulse, given the calibration curve. Once the gauge is calibrated, it can be used to measure the impulse acting on it in other media (water, soil, etc.). Such gauges are useful in measuring explosion induced impulses acting on structures. This usefulness is the result of the gauge simplicity and reproducibility. It can be used as a passive gauge or, when instrumented with strain gauges, as a passive and active (electronic) gauge.     

Relationship between Rockwell hardness and pearlite lamellar spacing of hardened layer under different cooling rates for U75 V 60 kg m−1 heavy rail

In this study, the heat treatment processes for U75 V heavy rail were studied systematically. Further, a simple and convenient method for measuring pearlite average lamellar spacing in steel by electron probe analysis is introduced, which can make the results closer to the real pearlite average lamellar spacing. This method was used to measure the pearlite average lamellar spacing at different positions of rail head under different heat treatments. Furthermore, the relationship between pearlite average lamellar spacing and Rockwell hardness of U75 V rail steel was determined. This study will provide important theoretical guidance for the formulation of rail heat treatment processes and the measurement of pearlite average lamellar spacing in steel.