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A three-piece bogie acts as a support for the freight train car bodies so that they can run on straight and curved tracks. It also absorbs the vibrational energy generated by the track. The three main parts of a traditional three-piece bogie are two side frames and a bolster. The side frames run parallel to the rails and are connected to each other by the bolster, which runs perpendicular to the rail. The side frames are connected to the axles, which are directly connected to the wheels that run on the track through the primary suspension. The primary suspension includes the bearing adapter and pedestal roof. The secondary suspension, which includes the friction wedge and load coils, connects and provides damping on each end of the bolster at its intersection with the side frame. Moreover, the friction wedge aids in warp resistance of the bogie. Because of the wedge’s non-linear frictional characteristics and load sensitive behavior, accurately capturing its dynamics in a computational model proves difficult. Previous work at the Railway Technology Laboratory (RTL) at Virginia Tech focused on better capturing the dynamics of the friction wedge modeled as a 3D rigid body. The current study extends that work to a half-truck model treated as an application of multibody dynamics with unilateral contact to model the friction wedge interactions with the bolster and the side frame. The half-truck model created in MATLAB is a 3D, dynamic, stand-alone model comprised of four rigid bodies: a bolster, two friction wedges, and a side frame assembly. The model allows each wedge four degrees of freedom: vertical displacement, longitudinal displacement (between the bolster and side frame), pitch (rotation around the lateral axis), and yaw (rotation around the vertical axis). The bolster and the side frame have only a vertical translation degree of freedom. The geometry of these bodies can be adjusted for various simulation scenarios. The bolster can be initialized with a pre-defined static yaw (rotation around the vertical axis) and the side frame may be initialized with a predefined pitch/toe geometry (rotation around the lateral axis). The model simulation results have been compared with results from NUCARS®, an industrially used train modeling software developed by the Transportation Technology Center, Inc., for similar inputs.

The design of the freight train truck has gone relatively unchanged over the past 150years. There has been relatively little change to the fundamental railway truck design because of the challenges of implementing a cost effective and reliable modification to designs that have proven effective in decades of operation. A common U. S. railway truck consists of two sideframes, a bolster, two spring nests, and four friction wedges. The two sideframes sit on the axels. The bolster rides on springs on top of the sideframes. The friction wedges also ride on springs on top of the sideframe, and are positioned between the bolster and sideframe, acting as a damping mechanism. Better understanding the dynamic behavior and forces on the bodies are critical in reducing unnecessary wear on the components, along with potential negative behavior such as loss of productivity and increase in operating costs. This thesis will investigate the dynamic behavior of the truck under warping conditions using a stand-alone model created in Virtual.Lab. This research covers two main areas.First, the full-truck model will be developed and its simulation results will be compared to test data from the Transportation Technology Center, Inc. (TTCI). Data was provided from warp testing performed at the TTCI facilities in the spring of 2008. Once validated, the model will be used to gain a better understanding of the forces and moments that are propagated through the system, and of the dynamics of all bodies. Due to costs and physical constraints, not every bogie component can be instrumented during test, so the computer model will be able to provide valuable information not easily obtained otherwise.iii Second, full-truck models using different contact geometry between the wedges, sideframes, and bolster will be compared. A model with extremely worn sideframes will allow for investigation into the effects of wear on the damping abilities and warp stiffness of the truck. Another model using split wedges will be compared with the previous model to investigate into the behavior differences in the truck using different types of wedges. By understanding the impact of different geometries on the overall performance of the truck, better decisions on design and maintenance can be made in the future.After creating the models, we found that the full-truck model created in LMS® Virtual.Lab compared well with the test data collected by TTCI. In the comparison with NUCARS® we determined that the stand-alone model, which incorporates the wedges as bodies, captures the warp dynamics of the truck better than NUCARS®, which models the wedges as connections. By creating a model with severely worn sideframes, we were able to determine that the truck loses its abilities to damp bounce in the system as well as to prevent warping when the components become sufficiently worn. The split-wedge model behaved similarly to the standard full-truck model for bounce inputs, but had a significantly different behavior in warp. Further development will be needed on the s...