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Keywords: rail surface defect, white etching layer, martensite, pearlite, rolling contact fatigue, wheel slide/skid, X-ray diffraction, XRD, scintillator.

Summary

One of the typical rolling contact fatigue (RCF) defects called squats is caused on the running band of a rail surface posed a problem during the 1970s in many countries. Currently, the impact of the white etching layer (WEL) on crack initiation of multiple-type squats is considered. The thickness of the WEL is investigated on the Japanese railways. The thickness of the WEL is not so large but some ten microns thick which should be suitable for X-ray penetration to investigate. On the other hand, it is very important but not so easy to establish any measures to prevent the WEL forming. Generally it will be effective to grind off the WEL as soon as it is checked. However the WEL is not easily determined by visual inspection and appropriate methods have not been so far developed. The authors have investigated the use of X-ray diffraction (XRD) to study the WEL formed on the surface of a rail. In this paper, the fundamental experimental set up of XRD are used to establish the use of dynamic XRD for the measurement. It is anticipated that the dynamic measurement would be installed on a rail flaw detection vehicle travelling speed at about 40km/h. The parameters such as: the distance between the X-ray tube and the surface of rail, the power of the X-ray tube, the size of the scintillator crystal, the sampling frequency of the signal, the target size of the WEL and the filtering function of the noise were combined and arranged mutually to improve the resolution of the system installing an appropriate number of scintillators at more effective places for averaging the obtained data (i.e. the XRD intensity). Comparing the difference of the experimental results between the two different experimental arrangements, the possibility of developing an on-board system for the XRD method to monitor any Martensite formed on the surface of rail was investigated. Further study will be important for better practice and rail integrity.

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Front Page Browse CCP CSETS CTR IJRT Other Authors Search Purchase Guide FAQ Contact us	Civil-Comp Proceedings ISSN 1759-3433 CCP: 110 PROCEEDINGS OF THE THIRD INTERNATIONAL CONFERENCE ON RAILWAY TECHNOLOGY: RESEARCH, DEVELOPMENT AND MAINTENANCE Edited by: J. Pombo Paper 253 Dynamic Detection of the White Etching Layer for Prevention of Multiple Crack Initiation M. Ishida¹ and Y. Maruyama² ¹Nippon Koei Co., Ltd., Tokyo, Japan ²Pulstec Industrial Co. Ltd., Shizuoka, Japan doi:10.4203/ccp.110.253 purchase the full-text of this paper Full Bibliographic Reference for this paper M. Ishida, Y. Maruyama, "Dynamic Detection of the White Etching Layer for Prevention of Multiple Crack Initiation", in J. Pombo, (Editor), "Proceedings of the Third International Conference on Railway Technology: Research, Development and Maintenance", Civil-Comp Press, Stirlingshire, UK, Paper 253, 2016. doi:10.4203/ccp.110.253 Keywords: rail surface defect, white etching layer, martensite, pearlite, rolling contact fatigue, wheel slide/skid, X-ray diffraction, XRD, scintillator. Summary One of the typical rolling contact fatigue (RCF) defects called squats is caused on the running band of a rail surface posed a problem during the 1970s in many countries. Currently, the impact of the white etching layer (WEL) on crack initiation of multiple-type squats is considered. The thickness of the WEL is investigated on the Japanese railways. The thickness of the WEL is not so large but some ten microns thick which should be suitable for X-ray penetration to investigate. On the other hand, it is very important but not so easy to establish any measures to prevent the WEL forming. Generally it will be effective to grind off the WEL as soon as it is checked. However the WEL is not easily determined by visual inspection and appropriate methods have not been so far developed. The authors have investigated the use of X-ray diffraction (XRD) to study the WEL formed on the surface of a rail. In this paper, the fundamental experimental set up of XRD are used to establish the use of dynamic XRD for the measurement. It is anticipated that the dynamic measurement would be installed on a rail flaw detection vehicle travelling speed at about 40km/h. The parameters such as: the distance between the X-ray tube and the surface of rail, the power of the X-ray tube, the size of the scintillator crystal, the sampling frequency of the signal, the target size of the WEL and the filtering function of the noise were combined and arranged mutually to improve the resolution of the system installing an appropriate number of scintillators at more effective places for averaging the obtained data (i.e. the XRD intensity). Comparing the difference of the experimental results between the two different experimental arrangements, the possibility of developing an on-board system for the XRD method to monitor any Martensite formed on the surface of rail was investigated. Further study will be important for better practice and rail integrity. purchase the full-text of this paper (price £22) go to the previous paper go to the next paper return to the table of contents return to the book description purchase this book (price £85 +P&P)
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