Dynamic models of friction wedge dampers

Friction wedges play a central role in the vertical dynamics of railroad freight cars. They also play a role in lateral dynamics and stability. While friction wedges are mechanically very simple, their inherent nonlinearities lead to complications in modeling and dynamics. In this paper we present two simplified models of the fundamental physics of friction wedge dampers in the geometry typical of a three-piece truck. We also review the friction wedge model used in NUCARS and compare the three.