page_title: Rail inspection
section_title: Defects and location
hierarchical_section_title: Rail inspection / Defects and location
caption_attribution_description: A damaged piece of rail on a line belonging to Union Pacific going through Santa Cruz.
context_page_description: Rail inspection is the practice of examining rail tracks for flaws that could lead to catastrophic failures. According to the United States Federal Railroad Administration Office of Safety Analysis, track defects are the second leading cause of accidents on railways in the United States. The leading cause of railway accidents is attributed to human error. The contribution of poor management decisions to rail accidents caused by infrequent or inadequate rail inspection is significant but not reported by the FRA, only the NTSB. Every year, North American railroads spend millions of dollars to inspect the rails for internal and external flaws. Nondestructive testing methods are used as a preventive measures against track failures and possible derailment.
context_section_description: There are many effects that influence rail defects and rail failure.  These effects include bending and shear stresses, wheel/rail contact stresses, thermal stresses, residual stresses and dynamic effects.
  Defects due to contact stresses or rolling contact fatigue (RCF):
  tongue lipping
  head checking (gauge corner cracking)
  squats - which start as small surface breaking cracks
  Other forms of surface and internal defects:
  corrosion
  inclusions
  seams
  shelling
  transverse fissures
  wheel burn
  One effect that can cause crack propagation is the presence of water and other liquids.  When a fluid fills a small crack and a train passes over, the water becomes trapped in the void and can expand the crack tip.  Also, the trapped fluid could freeze and expand or initiate the corrosion process.
  Parts of a rail where defects can be found:
  head
  web
  foot
  switchblades
  welds
  bolt holes
  A majority of the flaws found in rails are located in the head, however, flaws are also found in the web and foot.  This means that the entire rail needs to be inspected.
caption: Damaged rail
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