Research On Design Method Of Bolt Connected Flange For Engine Casing

With the development of advanced aero-engines,the working environment is unique and the working load is very complicated.Specially,the structure of bolt connected flange for thin-walled casing should have sufficient capacity to resist the structural damage,deformation,fatigue,and the better of sealing and stability.In the design of traditional engine casing structure,the empirical formula based on the aero-engine design manual was mainly used to check.This method can ensure the strength of the bolt connected flange for casing and reduce the structural vibration,but it is difficult to optimize the structure,strength and weight.With the rapid improvement of numerical simulation technology,traditional design methods can not satisfy the higher design requirements of advanced aero-engines.Therefore,in the design stage of bolt connected flange for thin-walled casing of modern aero-engine,which is particularly important to consider the comprehensive optimization technology of the structural vibration,strength and weight.In this paper,the bolt connected flange of thin-walled casing structure is taken as the study object,and using finite element software Ansys Workbench to establish five finite element model,and the dynamic characteristics was researched respectively.By comparative analysis found that the standard bolt connected of structure has better strength and vibration performance.In this respect,the height and thickness of the flange,casing thickness and bolt numbers were selected as design variables;the structural mass,first natural frequency and maximum equivalent stress were determined as objective functions.The second-order response surface model was established according to the sample points by Box-Behnken method and the finite element calculation results.The weight coefficients were obtained by Analytic Hierarchy Process,and the genetic algorithm was adopted to achieve the multi-objective optimization of the casing.Finally,the modal tests and the finite element verification were performed on the optimization results.The modal test was performed on test model by the hammering method to obtain natural frequency and corresponding vibration mode.Besides,the maximum equivalent stress and structural mass were calculated.The study indicates that the error between the modal test results and the finite element calculation is less than 6%.Meanwhile,the optimization has greatly increased the first natural frequency and reduced the structural mass and maximum equivalent stress by 5.28% and 13.64% respectively,which verifies the effectiveness and the feasibility of the optimization method proposed in this paper.