Identification Of Connection State Of Low Pressure Turbine Shaft In Aeroengine

With the development of aerospace technology in China,it is necessary for the further development of aviation industry to systematically analyze the design and production process of various components of aero-engine and to improve the overall performance of aero-engine.As one of the important parts of aeroengine,low-pressure turboshaft is one of the core components to transfer engine power.Its performance will directly affect the overall performance of the engine,and once a fault occurs,it will also directly affect the safe and reliable operation of the engine.This paper takes low-pressure turboshaft as the research object,and focuses on its assembly performance.On the one hand,it studies the change of preload of single bolt in multi-bolt assembly with the idea of fault diagnosis,and the identification model is trained with different signal processing methods and feature extraction methods to realize pretightening force identification;at the same time,the dynamic stiffness of the joint of the low-pressure turbine shaft is studied by collecting the vibration signal of the shaft,the dynamic stiffness of the joint is obtained by using relevant theoretical calculation,and finally get the accurate dynamic stiffness of the joint by using simulation.The specific content of this paper mainly includes the following three parts:(1)Research on identification method of pre-tightening force of single-bolt and multi-bolt connection structure: For the bolted connection structure,the function of the bolt is to assemble the connecting part and the connected part into a whole.In engineering practice,in addition to the structure and material of the connection structure,the most simple and direct control means is to directly control the bolt pre-tightening force,to ensure the reliability of the connection structure,so the change of bolt pre-tightening force will greatly affect the overall performance of the connection structure.In the first part of this paper,starting from the influence of the change of bolt pre-tightening force on vibration signal,based on the idea of fault diagnosis,the vibration signal is analyzed with different pre-tightening force connection regard as different faults,and finally propose three identification methods of bolt pre-tightening force.In this paper,the vibration signals of single-bolt and multi-bolt connection structures under different pre-tightening conditions are collected,and the vibration signals are processed by VMD method.Singular value decomposition,independent component analysis,damage index and other methods are used to extract the features.Thesupport vector machine is used to analyze and train the single-bolt and multi-bolt connection structures.Finally,proposing three method of identification method of preload for the single-bolt and multi-bolt connection structures: Pre-tightening force identification method based on singular value decomposition and support vector machine,pre-tightening force discrimination method based on independent component analysis and support vector machine,pre-tightening force identification method based on damage coefficient and support vector machine,all three method have achieved good identification results.(2)Identification of dynamic stiffness of joint of single bolted connection structure:Because of its own structural characteristics,it is difficult to obtain parameters of joint stiffness and damping directly.How to obtain accurate dynamic stiffness of joint simply and effectively is the difficulty of relevant research.In this paper,the substructure synthesis method is proposed to calculate the dynamic stiffness of the joint directly through the vibration signals collected from the test.Based on the simulation analysis,the spring-damper element model and the virtual material model are established for parametric modeling,so as to realize the optimization and correction of the calculation results.The single bolt test results show that the proposed method can effectively identify the dynamic stiffness of the joint.(3)Identification of the connection state of low-pressure turbine shaft: The final research object of this paper is the low-pressure turbine shaft of aero-engine.Therefore,the last part takes the low-pressure turbine shaft as the object of study,and identifies the connecting state of low-pressure turbine shaft by using the pre-tightening force identification method and the dynamic stiffness identification method of the joint.For multi-bolted low-pressure turbine shaft disc,the preload identification of single bolt is studied,the experimental results show that the three preload identification methods proposed in this paper can accurately identify the change of single bolt preload of low-pressure turbine shaft disc.At the same time,the dynamic stiffness of the joint is identified by taking low-pressure turbine shaft disc as the object.By substituting the dynamic stiffness of the joint calculated from the test data into the virtual material model for parametric modeling,the more accurate dynamic stiffness of the joint can be obtained more quickly.