DYNAMIC ANALYSIS OF A SLED TRAVELING ALONG A ROUGH RAIL (TEST, SIMULATION, POWER SPECTRAL DENSITY (PSO), MODAL SUPERPOSITION).

摘要

Rocket sleds are commonly used for simulation of special environments for testing purposes. The motion of a sled on the track induces large quasi-steady-state and dynamic forces on the sled. Design of sleds requires knowledge of these forces and of established techniques for application of measured and theoretical forcing functions to proven mathematical structural simulations. The prediction of the quasi-steady-state sled loads is relatively straightforward and requires few specialized techniques. Dynamic force prediction on the other hand is somewhat of a black art. Several techniques have been theorized but the results have been extremely marginal at best. This research is intended to find a reliable force prediction tool that is not extremely cumbersome to use.;Simulation results were successfully correlated to existing measured sled slipper data for both dual rail and monorail sleds, in both the vertical and lateral directions. The Test Track now has a viable design tool in DASTARR for predicting sled track interaction forces.;The sled track interaction process through the slipper gap constitutes a nonlinear spring problem. When the slipper is in rail contact, linear static theory applies. The approach taken to the problem is based on the assumption that the linear portion of the structural system can be decoupled into two components and their associated responses. The decoupled components are the suspension assembly and the rest of the structure through its modal response. The suspension response is commonly referred to as the rigid body response. A three-dimensional nonlinear computer code was developed to solve for the dynamic force contributions. This was accomplished by numerical integration of the equations of motion through the time domain based on the input parameters defining the suspension, structural modal participation, track roughness, quasi-steady-state forces, and the nonlinearity of the sled track interface. The result of the program is the time history response of each slipper throughout the simulation.