Study On Pre Tightening Force For Connecting Bolts Of Aeroengine Low Pressure Rotor

The aero engine is the "heart" of the aircraft,and the low pressure rotor is an important part of the transmission power.The low pressure rotor is connected by the low pressure turbine cone wall and the shaft disk through the bolt group containing 36 bolts.The connection performance of the bolt group bolts of the low pressure rotor directly affects the service energy of the whole machine.The domestic engine design work started late.The previous research focused on the design of the blade and other structural parts.The research on the fastening assembly is still in the initial stage.With the increasing improvement of the domestic engine design,the fastening and assembly has attracted wide attention.Many factors such as the structure of the connector,the number of bolts,the size of the bolt and the pre tightening force of the bolt will affect the connection performance.In this paper,the effect of bolt pretightening force is considered only by the relevant project requirements.The pre tightening force of the bolt is divided into two kinds: 1,to ensure that the engine meets the requirements in the service process.This pretightening force is called service pretightening force.2,in the process of fastening and assembly,the pretightening force is caused by the process and other factors.This article is called the process pretightening force,and the final need is to get service.The pre tightening force is composed of pre tightening force and pre tightening force.This paper will discuss the influencing factors and determining methods of service pre tightening force and technological preload respectively,and finally get assembly preload.Contents of the abstract.The second chapter of this paper introduces the test method of bolt pretightening force and surface pressure,mainly using fiber grating sensor,combined with related bonding technology,through a large number of calibration tests,accurate,multi point and on-line measurement of bolt pretightening force and surface pressure,at the same time,it also has small damage to the structure.Advantage。 The measurement method of pre tightening force is mainly used in elastic interaction experiment,short term relaxation experiment,bolt group stiffness experiment,bolt group connection natural frequency experiment and so on.The measurement method combined with surface pressure is mainly used in the elastic positive action experiment.In the third chapter,through the establishment of a finite element simulation model,the influence law of the elastic negative effect is studied.It is found that the elastic positive effect will reduce the pre tightening force of the bolt,mainly due to the deformation of the matrix of the connector,which is related to the increment of the pretightening force.Compared with the elastic positive work,the influence range is smaller.The law of the elastic negative effect is verified on the eight bolt hole flange joint,and it is found that the elastic positive effect is caused by the effect of the warping force.It will make the bolt pretightening force larger,which is mainly related to the constraint.The tightening sequence of the bolt will affect the elastic positive effect.Finally,the tightening sequence,the tightening step and the tightening step length are analyzed.For the influence of elastic interaction,a set of better tightening process is put forward.In the fourth chapter,according to the separation criterion,stiffness criterion,dynamic criterion and fatigue criterion,the service pretension of bolt group bolts with low pressure rotor is designed to meet the requirements of high load,high speed,high environment temperature,high reliability and big weight ratio during the service of low pressure rotor of aero engine.In the fifth chapter,combined with the conclusion of the actual structure of low pressure rotor and the elastic interaction mechanism of the previous article,the experiment of positive and negative effects of the low pressure rotor is carried out respectively.Combined with the experimental results,the method of two step tightening is used to minimize the dispersion of bolt group bolts,and the maximum change of bolt pretightening force is obtained.Finally,the change of bolt pre tightening force is obtained.Combined with the effect of short-term relaxation on bolt pretightening force,the pretightening force of the bolt is determined,and the pretightening force of service pretightening force and process pretightening force is combined to make up the assembly pretightening force.