| There are many bolt joined structures in the aero-engine,which have great influence on the dynamic characteristics of it.In the traditional joint modeling,the material parameters of the joined part are obtained through the modal test of the actual structure.But in the early design stage of the aero-engine,without a physical prototype,it is the biggest challenge for designers to establish the joined model accurately and to predict the dynamic characteristics of the aero-engine.This paper takes the assembled aero-engine casing as the object of study,aims at establish the accurate joint model,presents a method to calculate the analytical solution of joint parameters and the zonal sectionalized thin-layer element modeling method.Those methods are applied to the process of building the finite element model of the aero-engine casing.In this paper,the stiffness theory of bolted joints based on supermodel and the fractal contact theory are studied.The method of obtaining material parameters based on supermodel and the modeling method of the thin-layer elements are studied.Secondly,taking the cylindrical joined structure as the research object,the super-model of the cylinder joined casing is established as the reference model,the simplified models of the ordinary thin layer element and the sectionalized thin-layer element are established respectively.Their frequency difference comparing to the super-model is 4.38% and 2.81% respectively,which indicates that the sectionalized thin-layer element modeling method is more accurate than the ordinary thin-layer element modeling method.To further improve the accuracy of the model,the sectionalized thin-layer element model was verified with a super-model.Thirdly,the super-model and the sectionalized thin-layer element model are verified with the test data.At the same time,the modal frequency prediction analysis is carried out on the supermodel and the sectionalized thin-layer element model after verification.Finally,the sectionalized thin-layer element modeling method is applied to a more complex engine-case to further verify the feasibility of the modeling method.The bolted joint modeling method proposed in this paper helps to study the dynamic characters of the assembled aero-engine casing in the early design stage without a physical prototype,which can shorten the design period and save the cost. |
