Research On The Mechanical And Thermal Transfer Characteristics And The Vibration Performance Of The Discontinuous Structures On Aeroengines

In the design and manufacture process of modern aero-engine, the components of the aero-engine, especially the cases, are not continuous in structure because of the limitation of the manufacturing technique. The discontinuous structures may have influence on the transfer characteristics of both force and heat, which affects the vibration performance of the aero-engine cases.In traditional simulation, both the bolt joint structures and temperature are ignored when analyzing the vibration performance of the aero-engine cases. However, the irrespective of bolt joint structures and temperature may lower the accuracy of the finite element model, which affects the reliability of the simulation results. This paper mainly focuses on searching for a modeling and calculation approach which can be applied to analysis the vibration performance of the discontinuous aero-engine cases subject to temperature field. After setting up the dynamical model of the discontinuous cases, the vibration performance of the aero-engine cases is analyzed.First, the modeling methods of bolted joints were studied and some common methods such as virtual material parameter method, multi-point constraints method and spring-damping method were compared to find a suitable modeling method for bolted joints. The chosen method was used for setting up the finite element model of the bolt joins. And then the contact stiffness and thermal contact resistance at the joint interface were studied, which can be applied to analyze mechanical and thermal transfer characteristics of the bolt joints of the aero-engine cases. Concerning mechanical transfer characteristics of the interface, study on how bolt parameters like the bolt preloads, the distribution of bolts and the number of bolts affected the bending stiffness and vibration frequency was done. When considering the thermal transfer characteristics of the interface, the study focused on how temperature and geometrical morphology at the interface affects the contact thermal resistance. Finally, a finite model of a certain aero-engine case was set up which took the bolt joints into consideration. Both contact stiffness and contact thermal resistance were applied in this finite element model, which all owed us to analyze how the bolt joints and temperature affected the vibration performance of the aero-engine case.Several conclusions can be obtained from the study. The stiffness of the engine case would decrease when the bolt joints were took into consideration. The bolt preloads, the distribution of bolts and the number of bolts can affect the bending stiffness and vibration frequency of the engine case. Both temperature and the surface morphology at the interface can affect the thermal conduct resistance. It’s necessary to take the bolt joint structures and temperature into account when analyzing the vibration performance of the aero-engine cases, for it allows a more accurate simulation. The conclusions in this paper can be applied in the design and fault diagnosis of aero-engine, and it’s valuable in engineering practice.