Session: Track 2-1: Rolling Stock and Dynamics

Paper Number: 133616

133616 - Load Environment Characterization of Tank Car Stub Sill During Revenue Operations 

Fractures in the stub sills of tank cars pose a significant problem for the rail industry due to the potential for damage to the tank structure and eventual release of the contents.  Previous research revealed that high magnitude coupling forces that occur in yard operations have the potential to exceed yield limits of mild steel and initiate stub sill damage.  These high force events in yards may be mitigated by informing railroads with limiting combination of coupling speed and impacting mass limits.

In 2018, the Federal Railroad Administration’s (FRA’s) Office of Research, Development and Technology (RDT) conducted a series of impact tests for different tank car configurations at various coupling speeds.  The objective of this research study was to characterize the load environment on tank cars during yard operations.  ENSCO, Inc. (ENSCO) instrumented a tank car loaned to FRA by Union Tank with multiple transducers and a data collection system that supported high sampling rates required for impact testing.  ENSCO conducted a series of impact tests simulating various coupling conditions at Amsted Rail’s test facility in Camp Hill, PA.    ENSCO collected over 700 impact tests for different car configurations, end-of-car units, and coupling speeds.  The results showed that coupling speed and the type of end-of-car units employed on the cars have the most influence on the peak longitudinal impact force, whereas anvil and hammer configurations have limited effect on the peak impact force.  Results also showed that different end-of-car units yielded different in impact forces for different speed ranges. 

In 2022, FRA, Union Tank Car, and ENSCO conducted a cooperative test program to better characterize the load environment of the tank car operations in both mainline and yard operations.  Main operations consist of all train movements as a single consist including on mainline, sidings, and on yards.  Yard operations consist of all train movements (or impacts) while assembling train consists.  This effort also helped evaluate how the results from previous impact test program apply to real revenue service yard operations.  Under this effort, ENSCO instrumented the tank car loaned to FRA by Union Tank Car with same multiple transducers and data collection system as the previous impact testing.  The data consisted of acceleration, force, speed, and strain data.  ENSCO collected continuous data over 10 months and 14,000 miles.  A comprehensive statistical data analysis was conducted to investigate the effect of different parameters, particularly the effect of mainline versus yard operations.  The following major conclusions were drawn from the data analysis:

─        Yard operations (1830 kip maximum) have slightly larger longitudinal coupler forces than main operations (1000 kip maximum) but similar magnitudes.  Longitudinal coupler forces had similar magnitudes for both the autonomous testing and the previous impact testing (1540 kip maximum).

─        Vertical coupler forces had similar magnitudes for both main operations (51 kip maximum) and yard operations (58 kip maximum) but about half of the previous impact testing (117 kip maximum). 

─        The rosette strains had similar magnitudes overall between main operations (670 µε to 1110 µε maximums) and yard operations (650 µε to 1720 µε maximums) with some locations higher and some lower.  The rosette strains had similar magnitudes between autonomous testing and the previous impact testing (570 µε to 2440 µε maximums) but also with some variation with some locations higher and some lower.

─        The in-board strain location had the highest values for both autonomous testing (1720 µε maximum) and the previous impact testing (2440 µε maximum).

This testing showed that the train dynamics from mainline and yard operations are nearly equally important for longitudinal coupler forces and the resulting stub sill strains. This finding will help determine important areas of future research and identify recommendations for the railroads to improve safety. Part of this process should be improvements to both mainline and yard operation scenarios.

Presenting Author: Timothy Martin ENSCO, Inc.

Presenting Author Biography: Timothy Martin is a project manager at ENSCO, Inc., where he has worked for the past 28
years. He specializes in vehicle dynamic testing including wheel and coupler forces,
accelerations, displacements, and many other related signals. He also works with track
geometry and vehicle simulations. He has a M.S. degree in Mechanical Engineering from
Clemson University and a B.S. degree in Mechanical Engineering from Virginia Tech.

Authors:

Timothy Martin ENSCO, Inc.
Francisco González, Iii Federal Railroad Administration