Study Of The Stiffness Of Aeroengine Casing With Bolted Joints

The casing is the major bearing structure of the aeroengine. And its mechanical properties play a crucial role to the reliability and longevity of the engine. Aeroengine casings are mainly connected by bolts, which will cause the discontinuity and nolinear of the tensile stiffness.The bolt connection also has significant influence on vibration characteristics of casing. The research on bolt connection has also became a hotspot in recent years?In the dynamics analysis of aeroengine casing, traditional dynamics analysis of the bolt connection was usually ignored, for which makes the result cannot reflect the true dynamics characteristics of casing structure. Using ANSYS,the finite element models for local and overall structure casing with portrait flange which is connected by bolts are established in this thesis. These models primarily include rigid connection model, frictional contact model and nodes coupling simplified model. For the modal test part, hammering method is used.Comparing the results of those three different models with the results of modal test, frictional contact model which has the highest precision to finish the finite element analysis is finally chosen in this thesis. The method to study the influence of bolt pre-tightening force on the natural frequency of overall casing structure which is only under the bolt pre-tightening force is based on experimental and numerical calculation. With the numerical calculation, the influence law of various geometric parameters on the structural natural frequencies under the bolt pre-tightening force is explored. As for the relation of tensile rigidity, pre-tightening force and internal pressure for the overall casing structure which is under the case of internal pressure,it is confirmed indirectly through the numerical natural frequency analysis. In the casing structure,the influence of the three major geometric parameters on tensile rigidity,flexural rigidity and both of their stiffness-mass ratios are analysed.Through the study of this thesis, a train way of thought for the numerical simulation of complex structure with bolted joints and some references for the design of casing with bolted joints are provided.