01145898

Monograph

http://onlinepubs.trb.org...ail/HSR-55Final_Report.pdf

As part of an infrastructure subject to increased magnitude and frequency of loads, railroad track systems require regular inspection to assure high reliability for the safety of the public and passengers and the safe and efficient movement of goods. A key high-performance element in the system is the rail. In high-speed rail and heavy haul operations, these issues of risk and attendant costs have become more critical. This report summarizes the efforts of WavesInSolids LLC to develop a rail inspection technology to detect and characterize the condition of the rail surface and subsurface. Unattended traffic-hardened layers on the surface of the rails are operational hazards due to the inevitability of rolling contact fatigue cracks and larger transverse defects. In this Innovations Deserving Exploratory Analysis (IDEA) project, the higher order surface wave, or Sezawa wave, was evaluated as the detection and measurement mechanism for traffic-hardened layers in used rails. Hardness tests were conducted on rail specimens with known traffic volume (in terms of million gross tons (MGT)) to determine surface and subsurface hardness gradients, prior to ultrasonic testing using angled beam wedge transducers. Metallographic analyses were also undertaken on these rail specimens. The tests using the Sezawa wave technology demonstrated the ability to interrogate and resolve traffic-hardened layers in the depth ranges of 0-1 mm, 1-3 mm, and 4-7 mm. The minimum Brinell Hardness (HB) gradient, between the hardened layer and underlying rail, required to support Sezawa wave generation was also investigated and determined to be greater than 20 HB. The technology was also tested on lubricated rail showing Sezawa waves, unlike Rayleigh waves, can travel on such surfaces with excellent signal-to-noise ratio and, therefore, can be applied to inspection of dry as well as lubricated rails. Finally, work was carried out to determine the feasibility of using electromagnetic acoustic transducers (EMATs) to generate Sezawa waves in the rails. If successful, this technology would then be incorporated into a non-contact system that could be mounted on a rail inspection vehicle that could be operated at speeds up to 25 mph. This effort was unsuccessful due mainly to insufficient coupling of ultrasonic energy generated from the non-contact EMATs into the Sezawa wave mode. A commercial product based on the outcome of this project has been developed. It is a handheld device using contact transducers based on Sezawa wave technology that is capable of detecting and resolving traffic-hardened depths in the millimeter range.

This HSR-IDEA Project was conducted by WaveinSolids LLC, State College, Pennsylvania. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved

HSR-IDEA Project 55

English

29p

2008-8

High-Speed Rail IDEA Program Project Final Report

Final Report

August 2006-August 2008

Print

Figures; Glossary; Photos; References (4) ; Tables (8)

Defects; Fatigue cracking; Hardness; High speed rail; Inspection; Maintenance of way; Metallography; Railroad tracks; Rolling contact; Technological innovations; Ultrasonic tests

Innovations Deserving Exploratory Analysis (IDEA) (Program)

Electromagnetic acoustic transducers; Surface wave tests

Maintenance and Preservation; Railroads; Terminals and Facilities; I22: Design of Pavements, Railways and Guideways; I61: Equipment and Maintenance Methods

TRIS, TRB

Dec 4 2009 10:17AM