It is well-known that aging track structure is one commonplace causal factor in train derailments. Furthermore, track buckling is observed to be more likely in older tracks. As described in our companion proposal, we are developing a computational track buckling model for deployment by U.S. Railroad Companies as a tool for predicting track buckling. Over the course of the previous year, we have focused much of our attention on predicting the effects of both longitudinal and lateral crosstie-aggregate interfacial friction on rail buckling. We have shown that our model is capable of performing these friction-dependent predictions, but these predictions were made based on a very limited set of experimentally determined friction values. We, therefore, propose to set about the task of determining these complex material properties for a wide range of track structural materials. Obtaining these properties will then allow us to refine our predictive capabilities considerably.
- Coefficient of friction as a function of crosstie type, ballast characteristics, wet and dry conditions, and normal load.
- Vertical deformation during repeated sliding and friction tests.
- The contribution of end ballast as the crosstie is embedded in aggregate.
The work will continue initial efforts that acquired several forms of composite crossties (different manufacturers, dimpled, smooth, etc.) as well as wood and 3 versions of concrete crossties. For friction testing, a 20-inch long crosstie sample is put in aggregate and loaded vertically while frictional sliding moves the crosstie back and forth up to 1000 times (see Figure 1). Testing acquires both the vertical load, which is controlled to hit a target, and the varying horizontal load as the crosstie moves back-and-forth.