This study uses a nonlinear multibody dynamics model of a railway vehicle with three-piece trucks to perform a parametric study on a wide range of parameters influencing the performance of the truck on tangent track. One of the major disadvantages of the three-piece truck is that its performance can be greatly influenced due to worn parts or contaminants on friction surfaces, such as the friction wedge. The influence of worn parts is modeled as increased gap between bodies, using dead-band springs. The influence of environmental contamination is modeled as change in coefficients of friction. Lateral accelerations, measured at the center of gravity of the leading axle of the leading truck (Axle 1) are used for the hunting performance of the vehicle. For the baseline case, an eigenvalue analysis of a linearized model is used to evaluate the effect of speed on damping ratio and lateral motion frequency. A comparison of the linear model and non-linear time series analysis show that the linear model is less conservative, in that it predicts that the onset of hunting occurs at higher speeds.
The results indicate a direct relationship between various coefficients of friction and hunting velocity of the rail vehicle. Increasing the gap between the pedestal legs and bearing housing does not influence hunting velocity, but reduces lateral acceleration magnitudes during hunting. The weights of the carbody and cargo also has a direct relationships with hunting velocity, meaning that hunting occurs at lower speeds for unloaded car and at higher speeds for a loaded car.