Technology Digests / Modeling RNT Changes from Train Operations after Welding

TD26-024

Date Posted: October 12, 2026
Authors
  • Stephen Wilk
  • Ryan Alishio
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Key Findings

  • MxV Rail used the results of multiple field tests to develop a method to model how train operations redistribute longitudinal rail stresses and decrease high-RNT pockets or increase low-RNT pockets after welding.
  • Accounting for RNT redistribution from train operations can help prioritize RNT adjustments during seasonal work.
  • The results of a sensitivity study regarding common variations during welding did not show significant sensitivity, and most cases fell within the range of the predicted base case.
  • This research is based on common tangent track conditions. Curved track RNT changes will require further study.

Modeling RNT Changes from Train Operations after Welding

MxV Rail developed a method to model how train operations “redistribute” rail longitudinal stresses away from high- or low-rail neutral temperature (RNT) pockets after welding. If a rail break occurs in cold weather, it may not be practical to re-establish the target RNT at that time, and railroads sometimes opt to install a temporary repair at a lower RNT and then readjust the RNT later by installing a final repair at target RNT before summer. Railroads have observed that the RNT at the temporary repair can increase after train operations and seasonal changes. Estimating the changed RNT can be important for readjustment prioritization. Alternatively, electric flash butt (EFB) welding during the summer months can sometimes produce higher RNTs since EFB welding consumes rail during the process, thereby increasing tensile stresses in the rail. In 2025 and 2026, field testing at the Facility for Accelerated Service Testing (FAST®) created both low-…