Research On Lightweight Design Method Of Casing Structure Under Internal Pressure

Gearbox is a common type of parts in aeroengine,which is used for supporting rotor,fixing stator,channel contour and other purposes.For aeroengine,the main indexes such as thrust weight ratio and fuel consumption are directly related to the structure weight.For this reason,the lightweight design method of casing has been widely concerned by designers.However,the structural integrity of the casing directly affects the safety of the engine,and lightweight design often brings risks to the structural integrity.Therefore,the lightweight design of the casing needs to be very careful.Because of its perfect theoretical basis and good maneuverability,structural optimization design technology is more and more used in the field of aerospace in recent years.For the casing structure,the design process needs to consider the structural response under various loads,including internal pressure,axial force,bending moment,torque,etc.In addition,some casing also needs to consider temperature load,vibration load,etc.Among them,the satisfaction of structural performance indexes under axial force,bending moment,torque,temperature load and vibration load can be achieved not only by modifying the structural design,but also by reasonably designing the force transmission path,reasonably designing the connection structure and adding damping.However,for the satisfaction of structural performance indexes under internal pressure load,changing the structural design method is a more effective measure.On the other hand,taking too many structural performance indexes into account in structural optimization design will lead to the discontinuity of design domain.In order to overcome this problem,the common measure is to optimize the overall structure design based on the main performance indicators,and then check whether other indicators meet or slightly adjust the structure design.In this paper,the lightweight design method for the casing structure with the main structural performance index under the internal pressure load is studied.The main research contents are as follows:First of all,a simple and effective lightweight design method of the casing under internal pressure is proposed.Different from the traditional structural optimization application,this paper does not only use a specific structural optimization method,but divides the design process into the conceptual design stage and the detailed design stage,and introduces the applicable structural optimization design method in the two stages.At the same time,in order to connect the conceptual design stage with the detailed design stage,this paper proposes a simple and easy-to-use parametric solid geometry modeling method.In order to enhance the usability and reliability of the method,all the design steps of the proposed method can be realized by commercial finite element software without developing programs.Finally,the design method is applied to the lightweight design of a certain casing,and the weight reduction is about 16% when the stress constraints are met.Secondly,the feasibility of the inner boss reinforcement measures applied to the casing structure is studied.Under the action of internal pressure load,the stress concentration near the opening of casing is easy to occur,which brings hidden danger to the safety of engine.Considering the local stress concentration at the edge of the hole,this paper adopts the internal boss to overcome the problem of stress concentration.Combined with numerical analysis and experimental test,it is found that the inner boss configuration has a good ability to restrain the stress at the hole edge,and the amount of material required for the inner boss configuration is small,so it is feasible to apply it to the structural design of the casing.