A Quantitative Analysis Method for Interface Slip Damage of a Flange-Bolt Connection Structure of an Aeroengine

Abstract

The present invention discloses a method for quantitatively analyzing the interfacial slip damage of a flange-bolt connection structure of an aero-engine. The steps include: dividing the rotor bolt connection structure into local sectors, analyzing the mechanical process of interfacial slip damage of the rotor bolt connection structure, extracting four evaluation parameters, namely the relative interfacial slip distance, the absolute structural slip distance, the effective contact area coefficient, and the non-viscous area coefficient, and analyzing the interfacial slip damage reflected by the above evaluation parameters. The method of the present invention can accurately analyze and evaluate the interfacial slip damage of the flange-bolt connection structure of an aero-engine in practical engineering applications, and is of great significance for the analysis of interfacial slip damage and structural improvement of the rotor bolt connection structure in engineering practice.

Description

Technical Field

[0001] The present invention relates to the technical field of aero-engine rotor connection structures, and particularly to a method for quantitatively analyzing interface slip damage of a flange-bolt connection structure of an aero-engine. Background Art

[0002] Limited by the existing manufacturing process level, the rotor structure system of modern aero-engines is composed of components with different materials and geometric structures connected and combined through different forms of connection structures. Under the action of complex working loads, due to the differences in the deformations of each component, there is a tendency of relative slip between the interfaces. In the case of poor interface constraint conditions, with the increase of load cycles, the above-mentioned interface slip damage gradually accumulates, resulting in changes in the mechanical properties of the connection structure, and then causing the rotor dynamic characteristics to deviate from the design point. Among them, flange-bolt connection (hereinafter referred to as bolt connection) is a typical connection form in the aero-engine rotor connection structure. Under high rotational speeds, it will be subjected to the combined action of working loads such as centrifugal load, aerodynamic load, temperature load, and axial tug-of-war force, resulting in axial relative slip of the centering cylindrical surface of the connection structure. On the one hand, this phenomenon will cause frictional work to be generated, leading to wear damage of the interface. On the other hand, due to the irreversible axial deformation of the flange edge, local angular deformation of the connection structure will be caused, which greatly affects the local deformation of the rotor and the rotor unbalance state. For the purpose of paying attention to and analyzing the interface slip mechanical behavior and slip damage under working loads, it is urgent to establish an analysis method for interface slip damage of the connection structure applicable to the aero-engine rotor structure system to improve the design and assembly control level of the aero-engine connection structure. Summary of the Invention

[0003] To solve the problem of the lack of a detailed analysis method for the interface slip mechanical behavior of the rotor bolt connection structure under working loads in the prior art, the present invention provides a method for quantitatively analyzing interface slip damage of a flange-bolt connection structure of an aero-engine, and establishes a quantitative analysis method for interface damage of the connection structure.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] A method for quantitatively analyzing interface slip damage of a flange-bolt connection structure of an aero-engine, comprising the following steps:

[0006] Step 1, divide the local sector of the rotor bolt connection structure, and divide the entire circumferential rotor bolt connection structure into several local fan-shaped regions according to the number of bolts;

[0007] Step 2: Conduct a simulation analysis of the mechanical process of relative interface slippage. Based on the solid finite element model of the rotor connection structure, apply the same bolt pre-tightening force, axial force, centrifugal load, and temperature boundary as the real rotor, and based on this, conduct a simulation analysis of the relative sliding and deformation occurring on the centering cylindrical surface / positioning end face of the connection structure during the loading process;

[0008] Step 3: Extract the characterization parameters of interface slip damage of the connection structure. Based on the calculation results of interface slip and deformation of the rotor connection structure, extract four parameters: relative interface slip distance, absolute structure slip distance, effective contact area coefficient, and non-viscous area coefficient. These four parameters are called the characterization parameters of interface slip damage of the connection structure;

[0009] Step 4: Quantitatively analyze the interface damage of the connection structure. Based on the obtained characterization parameters of interface slip damage of the connection structure, quantitatively analyze the interface slip damage and its possible additional angular deformation under external loads, and obtain the change of each interface contact characteristic characterization parameter of a solid finite element model under the assembly, maximum working, and unloading states, as well as the variation laws of the end face axial slip distance and working state slip distance with the rotational speed based on the calculation results of the connection structure deformation and contact characteristics.

[0010] Furthermore, in Step 2, in the solid finite element model, contact elements are added at the connection interface position to consider the interface contact characteristics, and the local mesh of the connection structure interface is refined to accurately capture the local contact characteristics of the interface.

[0011] Furthermore, in Step 3, the effective contact area coefficient C val is:

[0012]

[0013] In the formula, A sticking is the viscous area of the interface, A sliding is the slip area of the interface, and A total is the nominal contact area of the interface;

[0014] The non-viscous area coefficient C no-sticking is the ratio of the area occupied by the non-viscous state of the interface to the nominal contact area of the interface, and its expression is as follows:

[0015]

[0016] The beneficial effects of the present invention compared with the prior art are as follows:

[0017] (1) The present invention can effectively and clearly obtain the interface contact state under complex loads, providing a clear improvement direction for the design and assembly control of the connection structure of the aero-engine rotor system.

[0018] (2) The present invention further determines the slip state and residual deformation of the centering cylindrical surface by focusing on the change amount of the interface deformation in the working state relative to the interface position in the initial assembly state, providing a reliable basis for judging whether the interface deformation will have an adverse impact on the rotor unbalance state in practical engineering applications. Description of the Drawings

[0019] Figure 1 is the analysis flow chart of the present invention according to an embodiment of the present invention;

[0020] Figure 2 is the schematic diagram of the typical rotor bolt connection structure and the load received according to an embodiment of the present invention;

[0021] Figure 3 is the axial slip mechanical process of the bolt connection structure according to an embodiment of the present invention;

[0022] Figure 4 is the change of the interface contact characteristic characterization parameters under the assembly - maximum working - unloading states according to an embodiment of the present invention;

[0023] Figure 5a is the curve of the change of the end - face axial slip characteristics with the rotational speed according to an embodiment of the present invention;

[0024] Figure 5b is the curve of the change of the end - face axial slip characteristics with the rotational speed in the working state according to an embodiment of the present invention. Detailed Embodiment

[0025] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. If not specifically specified, the technical means used in the embodiments are conventional means well - known to those skilled in the art.

[0026] The main purpose of the present invention is to solve the lack in the current existing technologies of the detailed analysis of the interface slip mechanical behavior of the rotor bolt connection structure under working loads and to propose corresponding characterization parameters, and to establish a quantitative analysis method for interface damage of the connection structure.

[0027] As Figure 1 shown, the quantitative analysis method for interface slip damage of the flange - bolt connection structure based on an aero - engine according to an embodiment of the present invention includes the following steps:

[0028] Step 1: Divide the local sector of the rotor bolt connection structure;

[0029] As Figure 2The typical bolt connection structure shown consists of the rear flange A of the drum, the sealing labyrinth disc B with a spigot structure C, and the aircraft material bolt D. At a high rotational speed ω, this typical bolt connection structure will be subjected to working loads such as centrifugal / temperature loads. In addition, the assembly pre-tightening force F1 generated by the bolts and the tug-of-war force F2 caused by aerodynamic forces will affect the contact state of the connection structure interface. To explore the local deformation of the structure caused by slip damage and simplify the calculation workload, considering that the rotor bolt connection structure has a central symmetry feature with respect to the rotor central axis, the entire rotating rotor bolt connection structure can be divided into several local sector regions according to the number of bolts.

[0030] Step 2: Conduct a simulation analysis of the mechanical process of relative slip at the interface.

[0031] First, for the structure and load state of the above rotor bolt connection structure, analyze the mechanical process of relative slip at the bolt connection structure interface. As Figure 3 shown, the rear flange A of the drum undergoes axial sliding during the loading process, changing its contact state and generating a sliding friction force F3. This sliding friction force F3 will offset part of the tug-of-war force F2 caused by aerodynamic forces, thereby suppressing the axial deformation of the spigot structure C. During the unloading process, the column shell flange edge that has already undergone bending deformation will have a tendency of elastic recovery (the slip direction is opposite to the direction of the sliding friction force F3). However, due to the insufficient elastic recovery force, under the hindering effect of the sliding friction force F3 generated at the interface, the axial deformation of the rear flange A of the drum cannot be completely restored to the initial assembly state, that is, the axial slip is irreversible. When the bolt connection structure undergoes relative slip in the axial direction during the working process, in addition to generating frictional work and causing wear damage to the interface, the non-recoverable axial deformation of the flange edge will cause local deformation of the connection structure. Subsequently, based on the above analysis, an entity finite element model based on the rotor connection structure is established, and the same bolt pre-tightening force, axial force, centrifugal load, and temperature boundary as the real rotor are loaded. Based on this, a simulation analysis is carried out on the relative sliding and deformation of the centering cylindrical surface of the connection structure during the loading process;

[0032] Step 3: Extract the corresponding characterization parameters of interface slip of the connection structure. Due to the non-continuous distribution of the bolt pre-tightening load along the circumferential direction, the contact state and stress distribution of the connection interface are non-uniform. In addition, when the working load changes, different components have different deformation characteristics due to different structural forms, resulting in a deformation trend of relative displacement between the interfaces, causing changes in contact characteristics such as the contact state and stress distribution of the connection interface.

[0033] To quantitatively describe and analyze the deformation and slip characteristics of the connection interface, two deformation and slip characteristic characterization parameters, namely the relative slip distance of the interface and the absolute slip distance of the structure, are defined.

[0034] The relative interface slip distance: It is used to quantitatively describe the interface slip distance. The difference between the interface slip distance at a given rotational speed and the initial assembly state is defined as the relative interface slip distance. This parameter is used to quantitatively characterize the interface slip deformation under the influence of working loads. In the numerical example, the relative interface slip distance of the centering cylindrical surface in the axial direction is focused on.

[0035] Regarding the absolute structural slip distance: For multiple connection interfaces in the rotor structure, with the change of working loads, each interface slips. When multiple interface slips occur simultaneously, the total deformation of the structure is defined as the absolute structural slip distance. In the numerical example, the absolute structural slip distance of the connection structure sector in the axial direction is focused on.

[0036] Regarding the effective contact area coefficient: In contact analysis, the interface contact state is divided into four contact states: Sticking, Sliding, Near, and Far. Among them, only in the Sticking and Sliding states, there is a normal pressure acting between the contact surfaces. These two states are called effective contact states. The interface only has the functions of positioning, bearing, and force transmission in the area of effective contact. Therefore, when analyzing the interface contact state, the effective contact area coefficient can be used for quantitative analysis. This parameter is defined as the ratio of the interface effective contact area to the interface nominal contact area, denoted by the symbol C val as shown in Equation (1). Due to the requirement of the robustness of the connection structure, it is usually necessary to ensure that the connection interface has a relatively high effective contact area coefficient

[0037]

[0038] where A sticking is the interface sticking area, A sliding is the interface sliding area, and A total is the interface nominal contact area.

[0039] Regarding the non-sticking area coefficient: To avoid large macroscopic slips at the interface, it is required that the area of the connection interface in the non-sticking state be as small as possible. Therefore, the non-sticking area coefficient C no-sticking is defined as the ratio of the area of the interface in the non-sticking state to the interface nominal contact area, and its expression is as shown in Equation (2):

[0040]

[0041] Step 4, quantitatively analyze the interface damage of the connection structure. Based on the obtained characterization parameters of the interface slip damage of the connection structure, quantitatively analyze the interface slip damage under the external load and the possible angular deformation of the connection structure. Obtain the changes in the characterization parameters of the contact characteristics of each interface of the above-mentioned solid element model under the assembly, maximum working, and unloading states, and the variation laws of the relative slip distance and the absolute slip distance of the structure with the rotation speed based on the calculation results of the connection structure deformation and contact characteristics.

[0042] Specifically, in the solid finite element model of Step 2, contact elements are added at the connection interface position to consider the interface contact characteristics (the friction coefficient is set to 0.15), and the local mesh of the connection structure interface is refined to accurately capture the local contact characteristics of the interface. By applying the tug-of-war force F2 caused by the aerodynamic force on the front side of the drum shaft E (as Figure 2 shown) to simulate the axial tug-of-war force acting on the connection structure in the working state, the loading of this axial tug-of-war force is divided into three steps. During the loading process of the first load step, the axial force is kept at 0, while in the second to the N + 1 load steps, the axial force is gradually increased to the axial force in the maximum state by linear interpolation to simulate the load loading process, and then gradually decreased to 0 in the M load steps to simulate the unloading process;

[0043] By Figure 2 the rotation speed ω shown to simulate the influence of the centrifugal load on the force-deformation state of the connection structure, its loading is also divided into three steps, that is, the rotation speed is kept at 0 in the first load step, and then the rotation speed is linearly increased to the maximum rotation speed in N load steps, and then the rotation speed is decreased to 0 in M load steps;

[0044] Solve the temperature distribution state in the connection structure through steady-state thermal analysis, and thus the influence of the equivalent temperature load on the load-deformation state of the structure. The loading of the temperature load is divided into three steps. Among them, during the loading process of the first load step, each temperature boundary is kept at the ambient temperature, while in the second to the N + 1 load steps, the temperature at each boundary position is gradually increased to the maximum temperature by linear interpolation, and then gradually decreased to the ambient temperature in M load steps.

[0045] Based on the above steps, solve the interface slip damage of the connection structure to obtain the changes in the slip characterization parameters of each interface of the model under the assembly, maximum working, and unloading states as Figure 4 、 Figure 5a 、 Figure 5b shown.

[0046] Those skilled in the art can easily understand that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A quantitative analysis method for interfacial slip damage of a flange-bolt connection structure of an aeroengine, characterized in that, It includes the following steps: Step 1: Divide the local sectors of the rotor bolt connection structure, and divide the entire circumferential rotor bolt connection structure into several local sector regions according to the number of bolts; Step 2: Conduct a simulation analysis of the mechanical process of relative slip at the interface. Based on the solid finite element model of the rotor connection structure, apply the same bolt pre-tightening force, axial force, centrifugal load, and temperature boundary as the real rotor, and based on this, conduct a simulation analysis of the relative slip and deformation that occur on the centering cylindrical surface / positioning end face of the connection structure during the loading process; Step 3: Extract the characterization parameters of interface slip damage of the connection structure. Based on the calculation results of interface slip and deformation of the rotor connection structure, extract four parameters: the relative interface slip distance, the absolute structure slip distance, the effective contact area coefficient, and the non-viscous area coefficient. These four parameters are called the characterization parameters of interface slip damage of the connection structure; The relative interface slip distance is used to quantitatively describe the interface slip distance. Define the difference between the interface slip distance at a given rotational speed and the initial assembly state as the relative interface slip distance, which is used to quantitatively characterize the interface slip deformation under the influence of working loads; Regarding the absolute structure slip distance, for multiple connection interfaces in the rotor structure, as the working load changes, slip occurs at each interface. Define that when multiple interface relative slips occur simultaneously, the total deformation of the structure is the absolute structure slip distance; In step 3, the effective contact area coefficient is as follows: (1) In the formula, is the interfacial viscous area, is the interfacial slip area, is the interfacial nominal contact area; The non-sticky area coefficient is the ratio of the area of the non-sticky state of the interface to the nominal contact area of the interface, and its expression is as follows: (2) Step 4: Quantitatively analyze the interface damage of the connection structure. Based on the obtained characterization parameters of interface slip damage of the connection structure, conduct a quantitative analysis of the interface slip damage and its possible additional angular deformation under external loads, and obtain the change of the characterization parameters of the contact characteristics of each interface of a solid finite element model in the assembly, maximum working, and unloading states, as well as the variation laws of the axial slip distance of the end face and the working state slip distance with the rotational speed based on the calculation results of the connection structure deformation and contact characteristics; 2. The quantitative analysis method for interfacial slip damage of the flange-bolt connection structure of an aero-engine according to claim 1, characterized in that In Step 2, in the solid finite element model, consider the interface contact characteristics by adding contact elements at the connection interface position, and refine the mesh at the local position of the connection structure interface to accurately capture the local contact characteristics of the interface.

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