Thermal stress measurement in continuous welded rails using the hole-drilling method

Abstract

The absence of expansion joints in Continuous Welded Rail (CWR) has created the need for the railroad industry to determine the in-situ level of thermal stresses so as to prevent train accidents caused by rail buckling in hot weather and by rail breakage in cold weather. The development of non-destructive or semi-destructive methods for determining the level of thermal stresses in rails is today a high research priority.This study explores the known hole-drilling method as a possible solution to this problem. A new set of calibration coefficients to compute the relieved stress field with the finer hole depth increments was determined by a 3D Finite Element Analysis that modeled the entire hole geometry, including the mechanics of the hole bottom and walls. To compensate the residual stress components, a linear relationship was experimentally established between the longitudinal and the vertical residual stresses of two common sizes of rails, the 136RE and the 141RE, with statistical significance. This result was then utilized to isolate the longitudinal thermal stress component in hole-drilling tests conducted on the 136RE and 141RE thermally-loaded rails at the Large-scale CWR Test-bed of UCSD's Powell Research Laboratories. The results from the Test-bed showed that the hole-drilling procedure, with the appropriate residual stress compensation, can indeed estimate the in-situ thermal stresses to achieve a ±5F accuracy of Neutral Temperature determination with a 90% statistical confidence, which is the desired industry gold standard.

Stability of continuous welded rails: A state-of-the-art review of structural modeling and nondestructive evaluation

“…Two rounds of experiments were conducted. 30,31 With the first round, a linear relationship between the longitudinal and the vertical residual stresses at the neutral axis of unconstrained 136RE and 141RE rail sections was established. This calibration was used to establish a protocol in which the longitudinal thermal stress is estimated by subtracting, from the total longitudinal relieved stress, the longitudinal residual component that is, in turn, calculated from the vertical relieved stress.…”

Application of Nonlinear Lamb Wave Mixing Method for Residual Stress Measurement in Metal Plate

“…Residual stress measurement techniques can be classified into two categories: destructive and nondestructive methods [5,6]. Destructive methods, such as hole drilling, slicing, or ring coring, facilitate stress release but can cause irreversible damage to the material [7,8]. Recently, nondestructive testing methods, such as X-ray diffraction, digital image correlation, magnetic methods, and ultrasonic methods, have been used widely for detecting residual stress [9,10].…”

Improved Stress Estimation with Machine Learning and Ultrasonic Guided Waves

“…Monitoring stress is thus an important failure prevention mechanism and it may be classified into semi-destructive and nondestructive evaluation methods. In the former case, which is not the focus of the present work, the most commonly used is the hole-drilling method [11][12][13]. Nondestructive evaluation for stress monitoring has been done more recently with the use of strain gauges [14], which are limited in resolution, and digital image correlation [15,16] which are not viable options for real-time continuous monitoring use, in contrast with the solutions based on ultrasonic information [17][18][19][20] that can be conveniently used for stress estimation as it involves cheap and simple equipment that may operate in a large frequency range depending on the load frequencyband characteristic.…”