Connection structure robustness evaluation method of intermediate bearing supporting structure

Abstract

The invention belongs to the technical field of bearing structure damage failure, and particularly relates to a connecting structure robustness evaluation method for an intermediary bearing supporting structure, which comprises the following steps of: 1, preliminarily designing the intermediary bearing supporting structure according to a design requirement; 2, performing deformation coordination evaluation under a centrifugal load, interface contact damage evaluation under a working load and interface contact damage evaluation under a periodic impact load on the intermediate bearing supporting structure; 3, when all the evaluation results meet the interface contact damage control requirement, skipping to the step 4, and otherwise, skipping to the step 1; 4, performing rigidity dispersion evaluation on the intermediate bearing supporting structure; and 5, when the rigidity dispersity evaluation meets the rigidity requirement, generating an evaluation report, otherwise, skipping to the step 1. According to the method, the interface contact damage of the intermediate bearing supporting structure in the complex load environment can be quantitatively evaluated.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of bearing structure damage failure, and particularly relates to a connection structure robustness evaluation method of a middle bearing supporting structure. BACKGROUND

[0002] In the structural design of a small bypass ratio turbofan engine, a middle bearing double-rotor design scheme is often adopted, and the high-pressure rotor is directly supported on the low-pressure rotor through the middle bearing, so as to reduce the number of load-bearing frames and improve the engine thrust-to-weight ratio. With the continuous improvement of the working load and structural efficiency of an aero-engine, as a key structure for transmitting the bearing point dynamic load of the high-pressure rotor, the middle bearing and the related supporting structure will bear various complex loads, mainly including assembly load, temperature load, centrifugal load, bearing point dynamic load generated by rotor rotation inertia load, and collision impact load caused by the gap between the bearing and the bearing seat. Under the combined action of the above static load and dynamic load, different forms of contact damage will occur at the contact interface of the connection structure of the middle bearing-supporting system. With the increase of working cycles, the interface contact damage will continuously accumulate and make the mechanical properties of the structural system gradually deviate from the design state, that is, the robustness of the structural system is poor, and finally deformation is too large or fracture occurs, resulting in failure of the middle bearing supporting structure. In the independent development of advanced aero-engines, several serious middle bearing damage failures have occurred. The existing research on bearing structure damage failure mostly takes the bearing with a fixed outer ring and a rotating inner ring as the research object, and mainly focuses on the contact fatigue and wear damage of a single component of the bearing, and less considers the connection structure of the bearing-supporting system, especially the influence of multi-mode damage at the interface of the connection structure on the mechanical properties of the supporting constraint. There is still a lack of systematic and effective evaluation method for the interface damage of the connection structure and the robustness of the mechanical properties. SUMMARY

[0003] In order to solve the above problems, a connection structure robustness evaluation method of a middle bearing supporting structure is provided, comprising: Step 1: initially design the middle bearing supporting structure according to the design requirements; Step 2: evaluate the deformation compatibility of the middle bearing supporting structure under centrifugal load, evaluate the interface contact damage under working load, and evaluate the interface contact damage under periodic impact load; Step 3: when the deformation compatibility evaluation result, the interface contact damage evaluation result under working load, and the interface contact damage evaluation result under periodic impact load all meet the preset requirements, jump to step 4, otherwise jump to step 1; Step 4: evaluate the stiffness dispersion of the middle bearing supporting structure; Step 5: When the rigidity dispersion evaluation meets the rigidity requirement, output the deformation coordination evaluation result, the interface contact damage evaluation result under the working load, the interface contact damage evaluation result under the periodic impact load, and the rigidity dispersion evaluation result, otherwise jump to step 1.

[0004] Preferably, the interface contact damage is evaluated by a contact fatigue damage evaluation model, a displacement constraint failure evaluation model, and a wear damage evaluation model.

[0005] Preferably, the evaluation parameter of the contact fatigue damage evaluation model is a fatigue strength parameter ; the evaluation parameter of the displacement constraint failure evaluation model is a maximum relative sliding distance ; and the evaluation parameter of the wear damage evaluation model is a friction work .

[0006] Preferably, the fatigue strength parameter is calculated by the following formula: ; is a normal stress of the interface in an initial assembly state, is a normal stress of the interface after a load is applied, is a change amplitude of the normal stress of the interface.

[0007] Preferably, the maximum relative sliding distance is calculated by the following formula: Step 11: Obtain a normal alternating load received by the interface and a tangential alternating load received by the interface. Step 12: When is greater than , the interface has a slip, otherwise the maximum relative sliding distance is 0, wherein is a static friction coefficient of the interface. Step 13: When the interface has the slip, calculate a sliding friction force : ; Calculate an acceleration of the slip :

[0008] wherein is a dynamic friction coefficient, and m is a mass of a slip member. Step 14: Calculate the maximum relative sliding distance by a uniform variable speed formula.

[0009] Preferably, the friction work The calculation method is: Step 21: Use the displacement constraint failure assessment model to determine whether the interface has slip. If not, then =0, if there is slip, proceed to step 22; Step 22: Obtain the load on the interface in its initial assembly state , the maximum load on the interface , maximum interface friction stress , relative displacement of the two contact surfaces ; Step 23: Calculate the friction work using the following formula : .

[0010] Preferably, the working load includes assembly load, centrifugal load, fulcrum dynamic load and lateral impact load.

[0011] The advantages of this application include the following: Three quantitative evaluation parameters are proposed to quantitatively assess the interface contact damage of intermediate bearing support structures under complex load environments. A corresponding robustness assessment method and process for interface contact damage are proposed to evaluate the deformation coordination, interface contact damage, and stiffness dispersion of intermediate bearing support structures under complex load environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a flow chart of a method for evaluating the robustness of a connection structure of a bearing support structure in a preferred embodiment of the present application.

[0013] Figure 2 It is the interface contact hysteresis loop under load in the viscous / semi-viscous state; Figure 3 It is the interface contact hysteresis loop of the interface under load in the slip state. DETAILED DESCRIPTION

[0014] To make the technical solution and its advantages of the present application clearer, the technical solution of the present application will be described in further detail below in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only some embodiments of the present application and are only used to explain the present application, not to limit the present application. It should be noted that, for ease of description, only the parts related to the present application are shown in the accompanying drawings, and other related parts can refer to the general design. In the absence of conflict, the embodiments of the present application and the technical features in the embodiments can be combined with each other to obtain new embodiments.

[0015] A method for robustness assessment of the connection structure of an intermediate bearing support structure, such as Figure 1 Shown, including: Step 1: preliminary design of the intermediate bearing support structure according to design requirements; Step 2: deformation compatibility evaluation of the intermediate bearing support structure under centrifugal load, interface contact damage evaluation under working load, and interface contact damage evaluation under periodic impact load; the working load includes assembly load, centrifugal load, fulcrum dynamic load, and transverse impact load.

[0016] Step 3: when the deformation compatibility evaluation result, the interface contact damage evaluation result under working load, and the interface contact damage evaluation result under periodic impact load all meet the preset requirements, jump to Step 4, otherwise jump to Step 1; Step 4: stiffness dispersion evaluation of the intermediate bearing support structure; Step 5: when the stiffness dispersion evaluation meets the stiffness requirement, output the deformation compatibility evaluation result, the interface contact damage evaluation result under working load, the interface contact damage evaluation result under periodic impact load, and the stiffness dispersion evaluation result, otherwise jump to Step 1.

[0017] In some optional embodiments, the interface contact damage is evaluated by a contact fatigue damage evaluation model, a displacement constraint failure evaluation model, and a wear damage evaluation model.

[0018] Fatigue damage mainly manifests as the initiation and propagation of cracks in the interface material under internal force. It is caused by damage accumulation under cyclic load and can be divided into high-cycle fatigue and low-cycle fatigue. The contact fatigue damage that may occur in the intermediate bearing support structure mainly occurs on the installation edge centering cylindrical surface and the positioning end surface. When the internal cracks of the material propagate to a certain extent, fatigue fracture may occur, causing the radial constraint stiffness of the intermediate bearing support structure to decrease or even fail.

[0019] Because the interface contact stress is relatively complex, the size and direction of the principal stress will change with the load, so a multi-axial fatigue parameter is needed to predict the initial life of the fatigue crack. Currently, the critical plane method is commonly used to study the interface fatigue damage characteristics, and the SWT model is a commonly used fatigue damage life model. The present application uses the SWT model to evaluate the local fatigue characteristics of the interface.

[0020] The evaluation parameter of the contact fatigue damage evaluation model is the fatigue strength parameter The calculation formula of the fatigue strength parameter is as follows: ; is the normal stress of the interface in the initial assembly state, is the normal stress of the interface after the load is applied, is the amplitude of the normal stress of the interface.

[0021] The evaluation parameter of the displacement constraint failure evaluation model is the maximum relative slip distance , its principle is: Displacement constraint failure primarily manifests as a change in the tangential relative positional relationship between interfaces. This occurs when interfacial friction, under complex loads, is unable to constrain incompatible deformation or displacement between interfaces. Relative slip between mating interfaces reduces their displacement constraint capacity, leading to a deterioration in mechanical properties such as the support stiffness of the supporting structure. Analysis of the load environment of intermediate bearing support structures reveals that the loads borne by the contact interface primarily include static and alternating loads, which can be categorized as normal and tangential loads based on their direction of action. During steady-state engine operation, the axial compression of the interface generates a constant normal force. Simultaneously, under centrifugal loads, due to the uncoordinated radial deformation of the components on either side of the stop, the end faces tend to slide radially relative to each other, resulting in a constant tangential force on the interface. During transient engine startup and shutdown, centrifugal and temperature loads vary. Due to significant differences in the structural configuration and material parameters of different structural units, the interface experiences relative displacement or a tendency to shift relative to each other. When the engine is subjected to lateral overload or a hard landing, the mounting edge of the intermediate bearing outer ring undergoes significant lateral displacement, altering the centering of the mating interface and leading to relative slip between the end faces. The fundamental cause of this interfacial slip during this deformation process lies in the inharmonious deformation of the structural units. When the connection structure is subjected to alternating loads, such as those generated by rotational inertia excitation, the interface experiences alternating normal and tangential loads, potentially causing relative slip, impacting the interface contact state and shifting the relative position of the components.

[0022] Relative maximum relative slip distance In order to quantitatively evaluate the displacement constraint failure of the structural system interface under external loads, the maximum relative slip distance is used to to quantitatively evaluate.

[0023] In some optional embodiments, the maximum relative sliding distance The calculation method is: Step 11: Obtain the normal alternating load on the interface The tangential alternating load on the interface ; Step 12: When Greater than When the interface has slip, otherwise the maximum relative slip distance is 0, where is the interfacial static friction coefficient; Step 13: Calculate the sliding friction when the interface has slip : ; Calculating the acceleration of slip :

[0024] in, is the coefficient of kinetic friction, m is the mass of the sliding member; Step 14: Calculate the maximum relative slip distance using the uniform speed formula .

[0025] The evaluation parameter of the wear damage evaluation model is friction work Friction work The calculation method is: Step 21: Use the displacement constraint failure assessment model to determine whether the interface has slip. If not, then =0, if there is slip, proceed to step 22; Step 22: Obtain the load on the interface in its initial assembly state , the maximum load on the interface , maximum interface friction stress , relative displacement of the two contact surfaces ; Step 23: Calculate the friction work using the following formula : .

[0026] The derivation process is: In order to quantitatively evaluate the interface wear of the intermediate bearing support structure under external load, the friction work law based on Archard is used to describe the interface wear damage under external load changes. The traditional friction work expression is shown in formula (1), where: is the friction work, is the friction force between two components pressed against each other, It is the maximum relative sliding distance, specifically the maximum relative sliding distance between two components pressed against each other.

[0027] (1) For the aero-engine rotor system, under cyclic loads, Equation (1) needs to be changed to an integral form to be more accurate.

[0028] (2) The reasons why it can be rewritten into the above form are as follows, Figures 2-3 As shown, it is the hysteresis regression curve of the interface during the load application process. Figures 2-3 They correspond to different contact state areas of the contact interface, the load on the interface in the initial assembly state, the maximum load on the interface, the friction stress difference between the load on the interface in the initial assembly state and the maximum load on the interface, the relative displacement change of the two contact surfaces, the slip amount of the stick segment, the slip amount of the slip segment. Figure 3 It can be seen that the hysteresis regression curve has a stick segment (inclined curve) and a slip segment (horizontal curve), the stick segment represents that the contact interface still remains in a stick state under low load, the contact stress is linearly related to the slip amount, the inclination angle of the stick segment is determined by the tangential stiffness of the contact interface, the slip segment represents that the driving force is greater than the maximum friction force under high load, the contact interface slips, the slip amount rapidly increases, and the friction stress remains unchanged at the maximum value, and the friction work is and the area surrounded by the curve and the abscissa. As shown in Figure 2 for the stick / semi-stick region, since the interface almost has no slip and no horizontal segment, the hysteresis regression line tends to be a straight line, and the friction work is almost 0. In summary, the friction work between the contact pairs under a single load cycle can be written in the form of equation (2).

[0029] Generally, the tangential contact stiffness of the contact interface is high, and the slip amount of the stick (inclined) segment is much smaller than the slip amount of the slip (horizontal) segment. To simplify the calculation of the friction work between the contact pairs of the interface, the friction work of the contact pairs can be approximately processed by the following formula according to the contact state of each part of the contact region of the contact pairs: (3) That is, when the contact pairs are in a stick state, the friction work generated at this position is ignored. When the contact pairs slip, only the friction work under the condition of the maximum load on the interface is used to calculate the friction work. The upper limit of the friction work can be obtained by the approximate formula (3). It is worth noting that the maximum load on the interface refers to the maximum friction stress state, not necessarily the load in the maximum working speed state.

[0030] The advantages of the present application include: three quantitative evaluation parameters are proposed, which can quantitatively evaluate the interface contact damage of the intermediate bearing supporting structure under complex load environment. The corresponding interface contact damage and robustness evaluation method and process are proposed to evaluate the deformation coordination, interface contact damage of the intermediate bearing supporting structure under complex load environment, and the dispersion of the stiffness of the supporting structure under severe load.

[0031] ​The above merely provides the specific implementation of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method of evaluating the connection structure robustness of an intermediate bearing support structure, characterized by, The method comprises the following steps: Step 1: preliminarily design the intermediate bearing support structure according to design requirements; Step 2: evaluate the deformation compatibility of the intermediate bearing support structure under centrifugal load, evaluate the interface contact damage under working load, and evaluate the interface contact damage under periodic impact load; Step 3: when the evaluation results of the deformation compatibility, the interface contact damage under working load, and the interface contact damage under periodic impact load all meet the preset requirements, jump to Step 4, otherwise jump to Step 1; Step 4: evaluate the stiffness dispersion of the intermediate bearing support structure; Step 5: when the stiffness dispersion evaluation meets the stiffness requirement, output the evaluation results of the deformation compatibility, the interface contact damage under working load, the interface contact damage under periodic impact load, and the stiffness dispersion evaluation result, otherwise jump to Step 1.

2. The method of evaluating the robustness of the connection structure of the intermediate bearing support structure according to claim 1, characterized by, The interface contact damage is evaluated by a contact fatigue damage evaluation model, a displacement constraint failure evaluation model, and a wear damage evaluation model.

3. The method of claim 2, wherein The evaluation parameters of the contact fatigue damage assessment model are fatigue strength parameters ; The evaluation parameter of the displacement constraint failure evaluation model is the maximum relative slip distance ; The evaluation parameter of the wear damage evaluation model is friction work .

4. The method of evaluating the robustness of the connection structure of the intermediate bearing support structure according to claim 3, characterized in that, Fatigue strength parameter The formula for calculating the fatigue strength parameter is: ； the normal stress to which the interface is subjected in the initial assembled state, the normal stress to which the interface is subjected after the load is applied, the amplitude of the variation of the normal stress to the interface.

5. The method of claim 3, wherein the connection structure robustness evaluation method of the intermediate bearing support structure is characterized by, Maximum relative slip distance The calculation method is: Step 11: Get the normal alternating load on the interface and the tangential alternating load on the interface ; Step 12: When is greater than , the interface has slip, otherwise the maximum relative slip distance is 0, where is the interface static friction coefficient; Step 13: Calculate the sliding friction force when the interface has slip : ； Acceleration of the slip is calculated : wherein, is the dynamic friction coefficient and m is the mass of the sliding member; Step 14: Calculate the maximum relative slip distance using the uniform velocity formula .

6. The method of evaluating the robustness of the connection structure of the intermediate bearing support structure according to claim 5, characterized by, Friction work The calculation method is: Step 21: judge whether the interface has slip by using displacement constraint failure evaluation model, if not, then =0, if yes, then step 22; Step 22 obtains the initial assembly state of the interface , the maximum load on the interface , the maximum friction stress on the interface , the relative displacement of the two contact surfaces ; Step 23: Calculate the friction work according to the following formula : 。 7. The method of evaluating the robustness of the connection structure of the intermediate bearing support structure according to Claim 1, characterized by, The working load includes assembly load, centrifugal load, fulcrum dynamic load, and transverse impact load.

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