Continuous welded rail has become the standard in modern railway track construction around the world because it alleviates well-documented disadvantages of rail joints in a track. Continuous welded rail practice results in long segments of continuous rail in track that will develop significant thermal longitudinal stresses due to the absence of expansion joints. Before a continuous welded rail is laid, the rail is free of thermal stresses; the temperature at that time is known as the rail neutral temperature. The design rail neutral temperature is calculated based on local climate projections. As a continuous welded rail is laid, it may be stretched or compressed if the current temperature is not within the calculated design rail neutral temperature range, prior to anchoring the rail down. Upon anchoring, as temperatures deviate from the rail neutral temperature, significant tensile or compressive longitudinal stresses develop, leading to a track buckling or rail pull-apart that compromise the integrity of the track and the safety of train operation. Existing methods to estimate the rail neutral temperature and determine the state of stress in the rail have significant shortcomings related to the ease of implementation, system complexity, practicality, reliability, simplicity, cost, and instrumentation demands. We propose a novel concept for measuring stress in rail segments and determining the rail neutral temperature. The proposed method is based on measurements of nonuniform deformations of the rail under thermal loading, as observed in computer simulations and laboratory investigations. The implementation uses thermal imaging and three-dimensional stereo-digital image correlation technology to acquire full-field deformations. The acquired data are processed to estimate rail neutral temperature and quantify the longitudinal stress in the rail. This article presents the analytical and experimental work that led to the conception of the method and introduces the systematic approach to develop the method along with verification and validation studies.

中文翻译：

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用于轨道中性温度和应力测量的非接触式系统：概念开发

连续焊接钢轨已成为世界各地现代铁路轨道建设的标准，因为它减轻了轨道中钢轨接头有据可查的缺点。连续焊接钢轨的做法会导致轨道中的长段连续钢轨由于没有伸缩缝而产生显着的纵向热应力。在铺设连续焊接钢轨之前，钢轨没有热应力；当时的温度称为轨道中性温度。设计轨道中性温度是根据当地气候预测计算的。在铺设连续焊接钢轨时，如果当前温度不在计算的设计钢轨中性温度范围内，则在将钢轨固定下来之前，它可能会被拉伸或压缩。锚定后，当温度偏离轨道中性温度时，会产生显着的纵向拉伸或压缩应力，导致轨道弯曲或轨道拉开，从而危及轨道的完整性和列车运行的安全性。现有的估计轨道中性温度和确定轨道应力状态的方法在实施的难易性、系统复杂性、实用性、可靠性、简单性、成本和仪器需求方面存在显着缺陷。我们提出了一种测量轨道段应力和确定轨道中性温度的新概念。正如在计算机模拟和实验室调查中所观察到的那样，所提出的方法基于对热载荷下钢轨不均匀变形的测量。该实现使用热成像和三维立体数字图像相关技术来获取全场变形。处理获得的数据以估计钢轨中性温度并量化钢轨中的纵向应力。本文介绍了导致该方法概念的分析和实验工作，并介绍了开发该方法的系统方法以及验证和验证研究。