Thermo-mechanical coupled simulation and validation of heterogeneous connection interfaces in an attitude-control thruster based on measured surface form errors

Abstract

To analyze the non-uniform stress and coaxiality variation at the composite-metal heterogeneous connection interface of an attitude-control thruster, a thermo-mechanical coupled finite element model considering measured surface form errors and temperature-dependent material parameters was established for an N2O/NH3 bipropellant attitude-control thruster. A three-dimensional measured-error assembly model was constructed based on measurement data from key mating surfaces. By comparing the ideal geometric model with the measured-error model, the influence of surface form errors on the initial contact state and local stress distribution was investigated. The variations in interfacial contact pressure, equivalent stress, and co-axiality under the ground hot-fire loading and on-orbit thermal environments were further analyzed. The results show that measured surface form errors transform nominally uniform contact into local discontinuous contact, leading to significant increases in maximum contact pressure and equivalent stress. Ground hot-fire loading causes interfacial contact release and load redistribution, leading to a significant increase in co-axiality error. Under on-orbit conditions, the external thermal environment has a more significant influence on coaxiality variation than short-duration pulse firing. Ground hot-fire test results show good agreement with the simulation in terms of temperature distribution, heating trend, and post-firing co-axiality variation, verifying the effectiveness of the proposed model.