United States Department of Transportation
i
Load environment of rail joint bars - phase I, effects of track parameters on rail joint stresses and crack growth.
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2013-04-01
[PDF-1.41 MB]
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NTL Classification:NTL-RAIL TRANSPORTATION-RAIL TRANSPORTATION
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Abstract:The load environment of joint bars was assessed under a variety of loading and track conditions. Bending stresses, thermal stresses, and residual stresses were measured on commonly used joint bars. Crack growth rates from artificially induced cracks were also monitored. This study provides the relevant data and analysis results needed for developing more comprehensive models for joint bar failure, fatigue life, crack growth, and inspection interval optimization. The data provided will also help railroads to design more reliable and safer joint bar designs.
Bending stresses in joint bars vary widely in local foundation and loading conditions. Stresses too low to cause fatigue damage and stresses large enough to cause joint bar breakage were measured. Thermal stresses in insulated joint bars are similar to those found in rail. Data also shows that once one joint bar of a standard joint is broken because of fatigue or manufacturing defect, the other joint bar carries all of the longitudinal and bending loads from the broken bar. This puts high stresses on the remaining bar, which sometimes breaks. This is consistent with the fact that in many cases both joint bars are found broken on inspection. The data also shows that thermal stresses can increase significantly because of maintenance operations, such as surfacing and under cutting.
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