Evaluation of Thermomechanical Damage of a Slipper and Rail in a Rocket Sled System

摘要

During the rocket sled test, slippers and rail experience high-speed sliding contact causing critical damage on the surfaces. Because of the significant temperature rise on the contacting surfaces, its fracture mechanism relies on the temperature-dependent material properties. In this study, the thermomechanical damage of the slipper and the rail is systematically investigated through 3D finite-element analysis (FEA) model and simulations. The sliding velocity consisted of 20 m/s, 200 m/s, and 1500 m/s, whereas the vertical velocity (bouncing speed of the slippers) was assumed to be 1.1 m/s. The unique method of including the aerodynamic bounce by allowing the rail to move vertically is quite different from other models explored by collaborating authors. The process of material thermal softening by adiabatic and frictional heat generation is applied to the modeling. From the simulation results, it is found that the damage process and pattern of the slipper and the rail asperity is very dependent upon the sliding velocity and the slipper temperature. For the sliding velocity of 20 m/s, the damage rate of the slipper gradually increases with the elapsed contact time, where the slipper surface produces a plowing type of damage pattern (continuous scratch). However, when the sliding velocity increases beyond 200 m/s, the slipper surface starts showing a gouging type of damage pattern along with a chopping material removal in the rail asperity.