Method for predicting free shape of retainer ring of aero-engine based on displacement constraint

Abstract

The invention relates to a displacement constraint-based method for predicting the free shape of an aero-engine retainer ring. The method comprises the specific steps of 1, analyzing part design requirements; 2, preparing a model; step 3, setting boundary conditions; step 4, applying initial displacement; step 5, statics simulation under large displacement; step 6, data analysis; 7, adjusting the initial displacement; step 8, post-processing the model; and 9, establishing a free-state retainer ring model. According to the method, Abaqus finite element analysis is applied to machining of large-diameter high-precision thin-wall aero-engine clamping ring parts with the elasticity requirement, the machining period is shortened, the product stability is greatly improved, and the part deformation controllable requirement needed by service is met.

Description

Technical Field

[0001] The invention relates to the technical field of computer-aided machining, and in particular to a method for predicting the free shape of an aero-engine collar based on displacement constraints. Background Art

[0002] Aircraft engine clamp ring parts have irregular openings, bosses and other structures. In the restricted state, except for the opening and boss structure, which are perfect circles, the opening is larger in the free state and is approximately elliptical. This type of part works in a restricted state. It is installed in the clamp ring groove and generates a large elastic force by closing the opening. It is used to block the blades and withstand high temperatures and rotation speeds. The design drawing usually specifies the dimensions in the restricted state and the opening dimensions in the free state. The commonly used processing method is heat setting. The parts are processed according to the dimensions in the restricted state, and then the opening is expanded to the free size required by the design through a heat treatment fixture. The high temperature causes deformation and setting, but there is unpredictable rebound after the parts are removed from the fixture. Generally, heat treatment tests are required before formal processing to determine the parameters and expansion dimensions. The processing cycle is long, the part qualification rate is low, and the part life is short.

[0003] In the prior art, Yuan Heling et al. proposed a reverse processing method for an outer sealing expansion ring. The outer and inner diameters in the free state are calculated by the formula "D from outside = (πD sealing outside + L opening) / π, D from inside = (πD sealing outside + L opening) / π-2T", and the contour processing in the free state is realized. The part structure of this method is relatively simple, and it can be assumed that the part is circular in the free state. It is mainly processed by grinders and wire-cutting equipment. Ye Wenlong et al. used finite element analysis software to load the elastic force of the elastic expansion ring opening to obtain a non-structural elliptical model. For this model, finite element analysis was proposed to obtain the displacement cloud map of the expansion ring before the force was applied, and through matrix calculation, it was input into UG software for outer circle point cloud fitting (without considering Z-direction displacement deviation). This type of parts used for spindle lubricating oil sealing have tangential load requirements and outer ring light transmittance requirements, but no opening size requirements in the free state. Due to different functions, the technical requirements and emphasis of clamping ring parts are different from those of the above-mentioned elastic expansion rings. The above method cannot simultaneously meet the size requirements in the free state and the restricted state for the clamping ring described in this article. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a method for predicting the free shape of an aircraft engine collar based on displacement constraints; the specific technical solution is as follows:

[0005] A method for predicting the free shape of an aero-engine collar based on displacement constraints comprises the following steps:

[0006] Step 1: Analyze part design requirements

[0007] Analyze the process characteristics, structural properties, and dimensional accuracy requirements of the clamping ring, and determine the processing equipment, process route, clamping scheme, and single-side allowance for fine processing;

[0008] Step 2: Model preparation

[0009] According to the known dimensions of the collar in the final restricted state, the outer contour is offset to the outside of the part by the finishing allowance of step 1 using CAD software to establish an initial model, and the formed STP model entity is imported into Abaqus software to define the material properties according to the collar material;

[0010] Step 3: Boundary condition setting

[0011] Load fixed constraints according to the process characteristics and structural characteristics of the collar to ensure consistency with the constraints of the parts assembly limit state;

[0012] Step 4: Apply initial displacement

[0013] Apply inward displacement of the vertical end surface at both ends of the opening;

[0014] Step 5: Statics simulation under large displacement

[0015] Select tetrahedral elements for meshing, establish analysis steps, set the type of the analysis step to "Static, General", set Nlgeom to "on", and submit the calculation task;

[0016] Step 6: Data Analysis

[0017] Check the reaction force RF at the opening after displacement is applied and compare it with the technical requirements of the clamp ring

[0018] When the load range required by the technical documents or the error ε from the calculated value F0 is met If the calculated value is within 10%, perform step 8 model post-processing, otherwise perform step 7 to adjust the initial displacement;

[0019] Step 7: Adjust the initial displacement

[0020] When the reaction force is greater than the design requirement / calculated value, adjust the initial displacement down within the opening size tolerance range; when the reaction force is less than the design requirement / calculated value, adjust the initial displacement down within the opening size tolerance range, and then repeat steps 5 to 6 until the technical requirements are met or the error is within 10% of the calculated value;

[0021] Step 8: Model post-processing

[0022] Convert the final result odb file into a two-dimensional STP solid model;

[0023] Step 9: Establish a free state clamping ring model

[0024] Import the two-dimensional model obtained in step eight into the CAD software, perform feature processing, obtain the free state clamp ring model, and perform programming processing according to the model.

[0025] The above-mentioned method for predicting the free shape of an aircraft engine clamp ring based on displacement constraints has a preferred embodiment that, in step three, the boundary conditions are set as follows: a full constraint is loaded on the boss opposite to the clamp ring opening to constrain all its degrees of freedom; an axial constraint is loaded on the upper or lower surface of the clamp ring, wherein the axial direction refers to the displacement degree of freedom in the thickness direction.

[0026] The preferred solution of the displacement-constrained free-form prediction method for an aero-engine collar is as follows: in step 4, the specific process of applying the initial displacement is as follows: constructing a displacement expression:

[0027]

[0028] Wherein L1 is the opening size in the free state, L2 is the opening size in the restricted state, and a is the single-side allowance for finishing described in step 1).

[0029] The preferred solution of the displacement-constrained aero-engine clamp free shape prediction method is that in step 6, the specific calculation method of the calculated value F0 is:

[0030]

[0031] Where: F0 = tangential elastic force of the collar; m = opening size of the collar in the free state; k = ratio of the collar's restricted state diameter to radial thickness; E = elastic modulus of the material; h = axial thickness of the collar.

[0032] The preferred embodiment of the free shape prediction method of an aero-engine clamp ring based on displacement constraints is as follows: in step eight, the specific process of the model post-processing is as follows: since an axial constraint is imposed in step three, the part model can be determined by extracting any axial section, the final result odb file obtained in step five is re-imported into the Abaqus software, the surface elements are extracted using the geometry editing function, all mesh elements are selected and deleted using the mesh editing function, and a two-dimensional STP solid model is exported.

[0033] Beneficial Effects

[0034] Compared with the prior art, the present invention applies Abaqus finite element analysis to the free shape prediction of large-diameter, high-precision, thin-walled aerospace engine collar parts with elastic requirements for the first time. The calculation is simple and the results are reliable. It solves the problems of the traditional heat setting method of processing according to the limited force shape and then opening the part opening to the free shape size through heat treatment, long processing cycle, unpredictable springback after heat treatment, and low product qualification rate. This technical solution greatly improves product stability, shortens the processing cycle, and meets the controllable deformation requirements of parts required for service; this technology can be applied to the manufacturing process of elastic components such as aerospace engine collars, expansion rings, and elastic rings, and has strong versatility and practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The flowchart of the free shape prediction method of the aero-engine collar based on displacement constraints is shown;

[0036] Figure 2 The mesh model of the clamp ring in the restricted state and the schematic diagram of the opening displacement constraint direction;

[0037] Figure 3 The grid diagram of the collar model in the free state obtained by calculation;

[0038] Figure 4 Schematic diagram of the two-dimensional clamp ring model after post-processing. DETAILED DESCRIPTION

[0039] The following is combined with Figure 1-4 The present invention is described in detail, but the protection scope of the present invention is not limited by the accompanying drawings.

[0040] Taking the free shape prediction of a primary clamp ring as an example, the present invention is further described in combination with the accompanying drawings and implementation process. A method for predicting the free shape of an aircraft engine clamp ring based on displacement constraints comprises the following steps:

[0041] Step 1: Analyze part design requirements

[0042] The first-level clamping ring includes non-parallel openings, radial bosses, and rounded chamfer structures. Since the clamping ring is made of high-temperature alloy, the outer circle size requires high precision, and the opening is narrow in the restricted state, it is not suitable for heat setting processing. The free shape milling + machining in the restricted state after milling can meet the accuracy required by the design. The finishing allowance is set to 0.5mm, and the process holes are reserved on both sides of the opening to achieve clamping in the restricted state of finishing machining;

[0043] Step 2: Model preparation

[0044] Draw the clamp ring limit state model according to the design requirements, use CAD software to offset the outer contour 0.5mm outside the part, and design the opening ends as follows Figure 2The process platform shown in the figure is used to establish an initial model, and then converted into an STP model entity and imported into the Abaqus software to define material properties. This technical solution adopts a linear elastic constitutive model, and the parameters set are elastic modulus and Poisson's ratio.

[0045] Step 3: Boundary Condition Setting

[0046] Load the full constraint ENCASTRE at the center line of the outer arc surface of the boss opposite to the opening, and load the axial constraint on the lower surface of the collar. In this example, the displacement in the X-axis direction is 0, and the coordinate system constraint XSYMM is selected to ensure that it is consistent with the part assembly limit state constraint;

[0047] Step 4: Apply initial displacement

[0048] Considering the free state opening size L1, the restricted state opening size L2, and the machining allowance a, the calculation formula is:

[0049]

[0050] The calculation shows that d = 34 in this example. A displacement of 34 mm perpendicular to the opening end surface is applied to both ends of the opening. In this example, it is in the Y direction and -Y direction. Fill in U2 = 34 and U2 = -34 respectively. Figure 2 As shown;

[0051] Step 5: Statics simulation under large displacement

[0052] Select tetrahedral elements, set the element side length to approximately 1, perform meshing, establish analysis steps, set the type of the analysis step to "Static, General", set Nlgeom to "on", and submit the calculation task after completing all the above settings; the following is obtained: Figure 3 The deformed model shown;

[0053] Step 6: Data Analysis

[0054] Check the reaction force RF at the opening after displacement is applied = 13.44, and compare it with the technical requirements of the clamp ring; the design document of this example does not require a load range, and the calculation formula is used to obtain

[0055]

[0056] Where: the elastic modulus E of the material is taken as the room temperature constant 204000;

[0057] Error ε If the calculated value is within 10%, perform model post-processing in step eight, otherwise, perform initial displacement adjustment in step seven;

[0058] Step 7: Adjust the initial displacement

[0059] When the reaction force is greater than the design requirement / calculated value, the initial displacement is adjusted down within the tolerance range of the opening size; when the reaction force is less than the design requirement / calculated value, the initial displacement is adjusted down within the tolerance range of the opening size, and then the static simulation and data analysis under the five large displacements are repeated until the technical requirements are met or the error is within 10% of the calculated value;

[0060] Step 8: Model post-processing

[0061] Import the final result odb file back into Abaqus software, use the geometry editing function to extract the surface elements, use the mesh editing function to select and delete all mesh elements, and export the available two-dimensional STP solid model as follows: Figure 4 .

[0062] Step 9: Create a free state clamping ring model

[0063] Import the two-dimensional STP solid model into the CAD software, perform feature processing, and obtain a free-state clamp ring model, which can be programmed and processed according to the model.

[0064] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

[0065] Parts of the present invention that are not described in detail belong to common knowledge among those skilled in the art.

Claims

1. A method for predicting the free shape of an aero-engine collar based on displacement constraints, characterized in that: The steps include: Step 1: Analyze part design requirements Analyze the process characteristics, structural properties, and dimensional accuracy requirements of the clamping ring, and determine the processing equipment, process route, clamping scheme, and single-side allowance for fine processing; Step 2: Model preparation According to the known dimensions of the collar in the final restricted state, the outer contour is offset to the outside of the part by the finishing allowance of step 1 using CAD software to establish an initial model, and the formed STP model entity is imported into Abaqus software to define the material properties according to the collar material; Step 3: Boundary condition setting Load fixed constraints according to the process characteristics and structural characteristics of the collar to ensure consistency with the constraints of the parts assembly limit state; Step 4: Apply initial displacement Apply inward displacement of the vertical end surface at both ends of the opening; Step 5: Statics simulation under large displacement Select tetrahedral elements for meshing, establish analysis steps, set the type of the analysis step to "Static, General", set Nlgeom to "on", and submit the calculation task; Step 6: Data Analysis Check the reaction force RF at the opening after displacement is applied and compare it with the technical requirements of the clamp ring When the load range required by the technical documents or the error with the calculated value F0 is met If the calculated value is within 10%, perform step 8 model post-processing, otherwise perform step 7 to adjust the initial displacement; Step 7: Adjust the initial displacement When the reaction force is greater than the design requirement / calculated value, adjust the initial displacement down within the opening size tolerance range; when the reaction force is less than the design requirement / calculated value, adjust the initial displacement down within the opening size tolerance range, and then repeat steps 5 to 6 until the technical requirements are met or the error is within 10% of the calculated value; Step 8: Model post-processing Convert the final result odb file into a two-dimensional STP solid model; Step 9: Establish a free state clamping ring model Import the two-dimensional model obtained in step eight into the CAD software, perform feature processing, obtain the free state clamp ring model, and perform programming processing according to the model.

2. The method for predicting the free shape of an aircraft engine collar based on displacement constraints according to claim 1, characterized in that: In step three, the boundary conditions are set as follows: full constraints are applied to the boss opposite to the opening of the clamp ring to constrain all its degrees of freedom; axial constraints are applied to the upper or lower surface of the clamp ring, where the axial direction refers to the displacement degrees of freedom in the thickness direction.

3. The method for predicting the free shape of an aircraft engine collar based on displacement constraints according to claim 1, characterized in that: In step 4, the specific process of applying the initial displacement is: constructing a displacement expression: Wherein L1 is the opening size in the free state, L2 is the opening size in the restricted state, and a is the single-side allowance for finishing described in step 1).

4. The method for predicting the free shape of an aircraft engine collar based on displacement constraints according to claim 1, characterized in that: In step 6, the specific calculation method of the calculated value F0 is: Where: F0 = tangential elastic force of the collar; m = opening size of the collar in the free state; k = ratio of the collar's restricted state diameter to radial thickness; E = elastic modulus of the material; h = axial thickness of the collar.

5. The method for predicting the free shape of an aircraft engine collar based on displacement constraints according to claim 1, characterized in that: In step eight, the specific process of the model post-processing is as follows: since the axial constraint is applied in step three, the part model can be determined by extracting any axial section, the final result odb file obtained in step five is re-imported into the Abaqus software, the surface elements are extracted using the geometry editing function, all mesh elements are selected and deleted using the mesh editing function, and the two-dimensional STP solid model is exported.

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