Solid-State Welding of Signal Wire Attachment

An essential component of railroad signaling systems is the attachment of signal wires to the rail. Railroad signaling systems detect track failures, prevent derailments, and alert signal crossing stations to approaching traffic. If these safety-critical attachments fail, rail traffic slows and crews must investigate and repair these systems. More reliable signal wire attachments can reduce uncertainty, improve safety, and reduce operational costs. The Federal Railroad Administration (FRA) and EWI have worked together to investigate the causes of failures at these attachments and develop an alternative signal wire-to-rail attachment process. Early research findings are published on FRA’s eLibrary: In the developed solid-state joining technique, called friction welding, a brass stud is welded to rail at temperatures too low to form martensite, a brittle and undesireable steel microstructure that can form with other high-heat attachment processes. EWI designed and fabricated a prototype portable friction welder for use on 136RE rail. This battery-powered system allows for studs to be attached to the web and head of rails. In this research, EWI modified an earlier design of the brass stud to reduce the weld area and then developed new friction welding process conditions for the new design. The smaller weld area enabled the design of a small and lighter second-generation prototype welder. The design of the studs also allowed for wires to be removed and reattached during maintenance activities, without the need to produce an additional weld. Friction-welded stud attachments tests were made on the FAST track at the Transportation Technology Center (TTC) in Pueblo, Colorado. In-track testing during the spring 2020 heavy-haul session saw no attachment failure after 66 million gross tons (MGT). The test attachments were torque tested at 25 ft-lbf every 10 MGT with no failures. Electrical resistance was measured between evenly spaced pairs of the stud attachments throughout the session. All measurements met AREMA signal wire attachment standards. EWI is currently seeking railroads for revenue service testing of the attachments and commercialization partners to take the solid-state signal stud attachment technology to market.


  • English

Media Info

  • Media Type: Digital/other
  • Features: Photos; References;
  • Pagination: 4p
  • Serial:
    • Research Results
    • Issue Number: RR 21-02
    • Publisher: Federal Railroad Administration
  • Publication flags:

    Open Access (libre)

Subject/Index Terms

Filing Info

  • Accession Number: 01768658
  • Record Type: Publication
  • Created Date: Mar 19 2021 2:26PM