Experimental Measurement of Residual Stress Distribution in Rail Specimens Using Ultrasonic LCR Waves

Young-In Hwang,Man Yong Choi,Yong-Il Kim,Jeong-Hak Park,Geonwoo Kim,Ki-Bok Kim

doi:10.3390/app11199306

Abstract

Longitudinal critically refracted (LCR) waves are considered bulk longitudinal waves and penetrate into an effective depth beneath the surface parallel to the material surface. Such LCR waves can be employed to measure residual stresses because the acoustoelastic effect is the basis for ultrasonic residual stress measurements. This effect is described by the relationship between change of wave travel time and stress applied when such waves propagate in a stressed medium. In this paper, stresses applied in a rail were evaluated by using a developed LCR probe. With this transducer, it was verified how the difference in the arrival times of the LCR waves showed a trend as the tensile stresses increased. The acoustoelastic coefficients were calculated using the relationship between the stresses and the travel times, and the residual stresses of the used rails were measured using these coefficients. In addition, the difference in residual stress distribution according to the characteristics of the wheel-rail contact surface was analyzed from the obtained residual stress value. It was concluded that this non-destructive evaluation technique using LCR waves could be employed for accurate stress measurement of rails because differences in stress applied to the rail can be detected.

Highlights

Residual stress refers to the stress remaining inside materials after the manufacturing process when they are not in use and are not subjected to any thermal gradients or external loads
The main objective of this study was to confirm the potential for application of a new ultrasonic method for the non-destructive measurement of residual stress in rails
The measurement of residual stress of rails was carried out using longitudinal critically refracted (LCR) waves

Summary

Introduction

Residual stress refers to the stress remaining inside materials after the manufacturing process when they are not in use and are not subjected to any thermal gradients or external loads. Engineering properties of industrial equipment, notably brittle fracture, corrosion resistance, dimensional stability, distortion, and fatigue life, can be significantly affected by residual stress [1]. Residual stress is a factor affecting the fatigue and fracture characteristics of rails. This stress is formed during the manufacturing and heat treatment of the rails, and it is caused by vertical loads applied to a wheel due to the weight of the vehicle it supports. Techniques to evaluate and analyze the residual stress in rails accurately are very important because this can have a direct effect on accidents affecting safety

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Conclusion