Nonlinear Dynamic Analysis to Extend the Value of Liquid Rocket Qualification Test

The goal of the methods and project example described is to use analysis to get more out of an engine qualification program. Nonlinearities are one of the reasons that testing is important in final validation of engine designs. An efficient method of modeling discrete nonlinearities was used to extend the understanding and value of both the sinusoidal vibration testing and the linear dynamic analysis that had been done before testing. In the example, discrete nonlinear elements are identified and separated from the overall engine finite element model. The nonlinear system is solved in a multibody dynamic program with the bulk of the engine represented by its modes. Final data recovery for the engine components is done within a linear, dynamic analysis program using the modal time histories from the multibody program.