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.
Xuan Zhu, Francesco Lanza di Scalea, and Mahmood Fateh, "Thermal stress measurement in continuous welded rails using the hole-drilling method," Proc. SPIE 9803, Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2016, 98031C (Presented at SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring: March 22, 2016; Published: 20 April 2016); https://doi.org/10.1117/12.2218664.
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