Reliability Guarantee Theory Research Of Clearance Of Aero-engine Main Shaft Bearings

A bearing of aero-engine main shaft is the pivot bearing of engine rotor, and it is one of the most significant components of aero-engine, thus its working performance will have an immediate effect on the engine's performance and the aeroplane's safety. The main shaft bearings work in severe environment for its high speed?alternate loadings and severe vibration. The working life and reliability of main shaft bearings have already been the obstacles to raise the thrust-weight ratio of aero-engine.The clearance is the key parameter of rolling bearings, which has a close connection to the working life and reliability, and it is affected by various random factors. Initial clearance is the clearance while the bearing leaves the factory. Initial clearance is a random variable, which is affected by various random factors like design?processing?assembling and gauging, and whose distribution pattern and distributed parameter can be got through statistics. People always use the fixing method of "interference fit for inner ring and transition fit for outer ring" when the main shaft bearing is assembled to the engine, and this clearance is called fit clearance. The decrease of clearance after the bearing is assembled is a random variable, for that it has a relation with the random factors like shrink range and the surface quality of fit. The clearance changes randomly again because the main shaft bearing is affected by the random factors like thermal deformation?centrifugal force?shaft load?rub and lubricating, which is called working clearance.The working clearance design is one of the difficulties in designing bearings for it affects bearings' multiple failure modes. It's an important means of studying the clearance with reliability method to improving the bearings' life. Based on reliability theory, this paper studies the bearings of aero-engine main shaft. This paper first studies the statistical rules of random factors affecting the bearing clearance, and establishes the probabilistic model between these random variables and clearance. Then with the studies of the contact fatigue failure mode of bearings based on quasi-static analysis method of rolling bearings, and the studies of the nonlinear dynamic stability failure mode of rotor-bearing system based on bifurcation theory, this paper provides theory for determining a confidence interval of optimal bearing working clearance. Finally, the paper gives reliability plans of selecting initial clearance and ensuring working clearance of main shaft bearings based on a generalized stress-strength interference model.This paper provides basic reliability design data and theory to bearing manufactures, also, it provides reliability using standard to users.