Failures of Locomotive Axles

FAILURES OF LOCOMOTIVE AXLES

caused by overheated traction-motor support bearings are discussed in this article. These failures are of interest because the analysis shows an example of what can be done when the fracture face and origin are destroyed during the failure incident. In most failure analyses of broken components, it is generally assumed that conclusive results cannot be obtained if the fracture and the fracture origin cannot be identified and examined. In many failures this is true. However, the failures described in this article possess some unique characteristics that permit successful analysis despite the lack of a preserved fracture face and origin.

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Failure Analysis - Service Problems

Intergranular SCC in 4340 Alloy Steel

Aqueous saturated picric acid, with 1% HCl and a wetting agent, Nacconol
90G, at 80°C revealed the prior-austenite grain boundaries. The hardness was too high, 35-38 HRC, making the steel sensitive to Cl-ion stress- corrosion cracking.

SCC Failures of ASTM A325 Bolts in the Piscataqua Bridge

Fracture appearance of a typical failed bolt; arrows point to the origin at the surface. There is some corrosion on the surface (3x, 6x)

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Failure Analysis - Materials and Manufacturing Problems

Failure Analysis - Materials and Manufacturing Problems

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Conducting the Failure Examination

Not all failures are catastrophic. Many failures involve a gradual degradation of properties or excessive deformation or wear until the component is no longer functional. Failures due to wear or general corrosive attack usually are not spectacular failures, but account for tremendous material losses and downtime every year. Of course, early failures of the spectacular catastrophic order capture the most attention and rightly so. Nevertheless, all failures deserve the attention of the investigator because they reduce production efficiency, waste critical materials, and increase costs.

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Conducting the Failure Analysis

Non-Fracture Failures

  • Ductile Deformation
  • Creep
  • Distortion
  • Wear
  • General Corrosion
  • Leakage, e.g., Selective Leaching, Pitting, Crevice Corrosion

Causes of Failure

  • Poor Design
  • Imperfections in Materials
  • Imperfections in Manufacture/Fabrication
  • Overloading/Service Abuse
  • Improper Maintenance or Repair
  • Environmental Effects
  • Combinations of the above

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resourcesThe articles and presentations that can be down-loaded from this web site are based upon work done by GFV while employed at Bethlehem Steel (1967-1983), Carpenter Technology (1983-1996), Buehler Ltd. (1996-2009) and Struers (2009-Present) and from the authors consulting work for companies such as, Latrobe Steel, Scot Forge, etc., and from his litigation work. GFV's bylined articles appearing in various issues of the ASM Handbook series have been listed here courtesy of ASM International, Materials Park, Ohio.

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