Research On Dynamical Characteristics Of Accessory Transmission Shaft Of Aero-Engine To Aircraft

In order to improve maneuverability of aircraft and reduce frontal area of aero-engine, theaccessory of an engine was separated with that of the aircraft in a modern combat aircraft, so that thetransmission shaft of the aircraft accessory is met to run safely under the environment of high speed,high power, large deformation, and large maneuver overload. The accessory shaft acts as a keycomponent which connects aero-engine accessory with aircraft accessory, so the requirements aboveconditions must be satisfied for its dynamic characteristics and reliability. Vibration mode, criticalspeeds, strength, life and experiment were analyzed for the transmission shaft with diaphragmcoupling connecting aero-engine with aircraft accessory in a new generation in this paper. The workof this paper supplied theory foundation and test certification for the subsequent design and practicaluse of the accessory transmission shaft. The main contents of this paper are as follows:(1) Vibration modal analysis: the model of the transmission shaft with the diaphragm couplingwas established by using finite element method. The influence of diaphragm type and material tostructure vibration mode was researched. Based on the results, diaphragm coupling of type Ⅰ andTC4material was chosen for the accessory transmission shaft. Test results were identical with theorycalculation for accessory transmission shaft with the diaphragm coupling, so the correctness of theorycalculation and the finite element model were verified.(2) Critical speeds analysis: critical speeds of the model of the transmission shaft with thediaphragm coupling for the aero-engine to aircraft accessory were calculated by transfer matrixmethod and finite element method in the same time to ensure credibility of the results. The results ofthe two methods were identical and showed that critical speed will not appear within working speedrange of the shaft, so the accessory transmission shaft could satisfy requirements of the dynamicalcharacteristics under working conditions. At the same time, the critical speeds characteristics of theshaft in the tester were analyzed by theory calculation and verified by sweeping frequency test, so asto ensure the safety for ground test of the transmission shafting with the diaphragm coupling. Theboth results showed that critical speeds and harmful vibration would not appear within experimentspeed range for the shaft in the tester. The dynamical characteristics of the shaft in the tester cansatisfy the requirements of experiment.(3) Strength and life analysis: the static strength of the accessory transmission shaft withdiaphragm coupling was analyzed by finite element method with the model verified under the load conditions, displacement compensation and maneuver overload given. The safety factors at thedangerous points were all greater than3and it showed that the accessory transmission shaft with thediaphragm coupling could meet the requirements of the static strength. The fatigue life of theaccessory transmission shaft with the diaphragm coupling was analyzed under the load conditions.The calculation results showed that the accessory transmission shaft with the diaphragm coupling hasinfinite life under the load spectrum given. Durability test of the accessory transmission shaft with thediaphragm coupling has been finished the ground tester under the simulation load spectrum given, andthe number of cycles was greater than108for the accessory transmission shaft with the diaphragmcoupling. The shaft fatigue breakage hasn’t created, so it showed that the calculation results wereeffective and credible.