Method for analyzing shape maintaining requirement and shape maintaining effect of large-opening structure in aircraft assembly

Abstract

The invention discloses a method for analyzing the shape-preserving requirement and the shape-preserving effect of a large-opening structure in aircraft assembly, which comprises the following steps of: 1, under the condition of not influencing the actual deformation trend and the deformation magnitude, determining the material attribute of each part of an aircraft cylinder section, and establishing an aircraft cylinder section finite element calculation model; 2, setting two intersecting diagonal lines for a large opening structure at each cylinder section frame in the airplane cylinder section model; step 3, acquiring the deformation condition of each large-opening structure by adopting an aircraft cylinder section finite element calculation model so as to judge whether the aircraft cylinder section model needs shape maintenance or not, and determining the assembly working condition needing shape maintenance after determining that shape maintenance is needed; 4, determining the position of a large opening structure needing shape maintenance in the airplane cylinder section model according to the relative displacement of two points of each diagonal line according to the assembly working condition needing shape maintenance; and 5, after the shape maintaining tool is installed on the large-opening structure needing shape maintaining, the shape maintaining effect of the shape maintaining tool is judged on the basis of relative displacement of two points of a diagonal line.

Description

Technical Field

[0001] This invention relates to, but is not limited to, the field of aircraft manufacturing process equipment technology, and particularly to a method for analyzing the shape retention requirements and shape retention effects of large opening structures in aircraft assembly. Background Technology

[0002] In aircraft assembly, a segmented assembly method based on process separation surfaces is generally adopted. Before segment docking, the docking surfaces of the forward, mid, and aft fuselage sections, or the openings in the wing-fuselage docking area, are temporary, large-scale process opening structures. These opening structures lack the overall rigidity support of a closed structure during the docking waiting and hoisting assembly stages. Under the influence of their own weight, the tension of process joints, and external factors, they are prone to deformation exceeding process tolerances. This further leads to mismatch in the docking surface contour, excessive clearance or step difference during segment docking. Forced assembly generates excessive assembly stress, severely affecting assembly quality and structural performance, and even impacting aircraft safety. Therefore, in the aircraft segment assembly process, effective shape-preserving control of the large-scale opening structures formed by process separation surfaces is a crucial step in ensuring precise, efficient, and low-stress docking.

[0003] Currently, the determination of conformity requirements, such as whether large openings at the process separation surface need to be conformed to and the specific location of conformity, mainly relies on the experience of designers. This highly subjective decision-making model, which lacks quantitative criteria, may lead to ambiguity in the judgment of the necessity of conformity and key areas. In other words, it is impossible to objectively and quantitatively judge the necessity of conformity, key conformity areas, and conformity effects, thereby affecting assembly quality. Summary of the Invention

[0004] The purpose of this invention is to solve the above-mentioned problems by providing a method for analyzing the conformability requirements and conformability effects of large opening structures in aircraft assembly. This method addresses the issue that traditional conformability design methods for large opening structures at process separation surfaces rely on experience and cannot objectively and quantitatively determine the necessity of conformability, key conformability areas, and conformability effects, thereby affecting assembly quality.

[0005] The technical solution of this invention is as follows: This invention provides a method for analyzing the shape retention requirements and shape retention effects of large opening structures in aircraft assembly, including:

[0006] Step 1: Without affecting the actual deformation trend and magnitude, simplify the aircraft tube segment model according to actual needs, determine the material properties of each component of the aircraft tube segment, and establish a finite element calculation model of the aircraft tube segment; wherein, the aircraft tube segment model includes multiple tube segment frames, each tube segment frame has a large opening structure, and two lifting points are set on the upper part of the large opening structure located at the docking surface.

[0007] Step 2: Set two intersecting diagonals for the large opening structure at each segment frame in the aircraft segment model; based on the diagonals set on the large opening structure, apply working conditions to the aircraft segment model, obtain the relative displacement of two points on each diagonal before and after applying the working conditions, and obtain the deformation of the large opening structure.

[0008] Step 3: Combine the actual assembly scenario and use the aircraft tube segment finite element calculation model to obtain the deformation of each large opening structure in order to determine whether the aircraft tube segment model needs to maintain its shape. After determining that it needs to maintain its shape, determine the assembly conditions that require shape maintenance.

[0009] Step 4: For the assembly conditions that require protection, determine the position of the large opening structure that requires protection in the aircraft tube section model based on the relative displacement of the two points on each diagonal.

[0010] Step 5: After installing the conforming fixture on the large opening structure that needs to maintain its shape, judge the conforming effect of the fixture based on the relative displacement between the two diagonal points. Compared to before conforming, the greater the decrease in relative displacement of the large opening structure after applying the assembly condition, the better the conforming effect.

[0011] Optionally, in the above-described method for analyzing the shape retention requirements and shape retention effects of large opening structures in aircraft assembly, step 1 includes:

[0012] Step 11: For the aircraft tube section model, delete bolts, rivets, and clips, and replace all connectors with binding constraints.

[0013] Step 12: Fill in the holes in the model, and delete the marks and rounded corners;

[0014] Step 13: Identify and delete non-load-bearing components in the model;

[0015] Step 14: Based on the required calculation time, using the results of the stiffness and strength analysis, and taking the actual deformation trend and magnitude as the design objective, delete non-critical load-bearing structures.

[0016] Optionally, in the above-described method for analyzing the shape retention requirements and shape retention effects of large opening structures in aircraft assembly, step 2, which involves setting diagonal lines for the large opening structures at each segment frame in the aircraft segment model, includes:

[0017] Step 21: Identify the major opening structures of the aircraft tube segment model. Each tube segment frame has a major opening structure, and the major opening structure located at the end is the major opening structure located at the docking surface. Number the major opening structures in a certain order.

[0018] Step 22: Determine two intersecting diagonals on the large opening structure at the docking surface based on the lifting point positions on the aircraft tube model. This includes: determining the upper points of two diagonals based on the two lifting point positions, and taking the intersection of the floor frame and the side wall panel as the lower points of the corresponding diagonals within the same tube frame.

[0019] Step 23: For large opening structures at other tube frame sections other than the large opening structure at the docking surface, project the upper diagonal point of the docking surface onto the other large opening structures and set it as the upper diagonal point of the other large opening structures; the intersection point of the floor frame and the side wall panel of the large opening structures within the same tube frame is the lower diagonal point of the corresponding large opening structure.

[0020] Optionally, in the above-described method for analyzing the shape retention requirements and effects of large opening structures in aircraft assembly, the method for obtaining the deformation of each large opening structure in step 2 includes:

[0021] Apply a working condition to the aircraft tube segment model, and subtract the lengths of each diagonal before and after applying the working condition. The result is the relative displacement between the two points on the diagonal, which is used to represent the deformation of the major opening structures in the aircraft tube segment model.

[0022] Optionally, in the above-described method for analyzing the shape retention requirements and effects of large opening structures in aircraft assembly, the calculation method for the relative displacement of the two points on each diagonal before and after the applied working condition in step 2 is as follows:

[0023] ΔL1=L ′ 1-L1;

[0024] ΔL2=L ′ 2-L2;

[0025] Among them, the intersecting diagonals in each of the major opening structures are diagonal 1 and diagonal 2, L1 and L2, respectively. ′ 1 represents the length of diagonal 1 before and after the applied load condition, L2 and L ′ 2 represents the length of diagonal 2 before and after the applied working condition. ΔL1 and ΔL2 are the relative displacements of diagonal 1 and diagonal 2, respectively, representing the deformation inside the large opening structure.

[0026] Optionally, in the above-described method for analyzing the shape retention requirements and shape retention effects of large opening structures in aircraft assembly, step 3 includes:

[0027] Step 31: Based on the actual assembly scenario, determine the assembly conditions involved in the aircraft tube section model. The assembly conditions include ground placement conditions and hoisting conditions. The hoisting conditions include deflection conditions and torsion conditions.

[0028] Step 32: Calculate the stiffness simulation results for each assembly condition, including: using the finite element calculation model of the aircraft tube section for simulation, calculating the relative displacements ΔL1 and ΔL2 of diagonals 1 and 2 in the major opening structures to determine the deformation.

[0029] Step 33: If the deformation of the major opening structures does not exceed the deformation design requirements under all assembly conditions, the aircraft tube section model does not need to maintain its shape; if there are major opening structures that exceed the deformation design requirements, the condition is determined to be an assembly condition that requires shape maintenance.

[0030] Optionally, in the above-described method for analyzing the shape retention requirements and shape retention effects of large opening structures in aircraft assembly, step 4 includes:

[0031] Step 41: For the assembly conditions that require protection, calculate the relative displacement values ​​ΔL1 and ΔL2 of the two diagonals of each large opening structure.

[0032] Step 42: Sort the relative displacement values ​​ΔL1 and ΔL2 of the two diagonals of each large opening structure, and comprehensively identify the diagonal with the larger relative displacement, as well as the position of the large opening structure where the diagonal is located.

[0033] Step 43: Divide the aircraft tube section into two sections along the heading. Based on the shape retention requirement of selecting at least one large opening structure in each section, determine the position of at least one large opening structure in each section according to the deformation amount of the diagonal in each section.

[0034] Optionally, in the above-described method for analyzing the shape retention requirements and shape retention effects of large opening structures in aircraft assembly, step 5 includes:

[0035] Step 51: Install the conformal fixtures onto the large opening structures that need to be conformed to, as determined in Step 4.

[0036] Step 52: For each assembly condition requiring shape preservation determined in Step 3, calculate the relative displacement values ​​ΔL1 and ΔL2 of the two diagonals of each large opening structure after the shape preservation fixture is installed.

[0037] Step 53: For each assembly condition requiring shape preservation, compare the relative displacement values ​​of the two diagonals of the large opening structure before and after shape preservation to determine the shape preservation effect of the shape preservation tooling; among them, after applying the assembly condition, the greater the decrease in relative displacement of the large opening structure after shape preservation, the better the shape preservation effect.

[0038] The beneficial effects of this invention are as follows: Addressing the highly subjective and quantitatively unreliable design process for maintaining the shape of large opening structures in current aircraft assembly, this invention proposes a method for analyzing the shape-maintaining requirements and effects of large opening structures in aircraft assembly. First, without affecting the actual deformation trend and magnitude, the aircraft cylindrical segment model is simplified, the material properties of each component of the segment are determined, and a finite element analysis model of the aircraft cylindrical segment is established. Second, two intersecting diagonals are set for the large opening structures at each segment frame in the aircraft cylindrical segment model. This allows for the application of these diagonals to the aircraft cylindrical segment model. The process involves several steps. First, the relative displacements of two points on each diagonal before and after applying the working condition are obtained to determine the deformation of each large opening structure. Second, a finite element analysis model of the aircraft tube segment is used to obtain the deformation of each large opening structure to determine whether the aircraft tube segment model needs to maintain its shape. After determining that shape maintenance is required, the assembly working condition that requires shape maintenance is identified. For the assembly working condition that requires shape maintenance, the position of the large opening structure that needs to maintain its shape in the aircraft tube segment model is determined based on the relative displacements of two points on each diagonal. After installing the shape-maintaining fixture on the large opening structure that needs to maintain its shape, the shape-maintaining effect of the fixture is judged based on the relative displacements of two points on the diagonal.

[0039] The method for analyzing the conformability requirements and effects of large opening structures in aircraft assembly provided by this invention can use quantitative indicators to determine the necessity of conformability protection, key conformability protection areas, and conformability protection effects. This provides scientific and robust support for conformability protection schemes, avoiding tooling redundancy caused by "overprotection" and conformability protection failures caused by "underprotection," significantly improving assembly quality and process reliability in aircraft manufacturing. Compared to before conformability protection, after applying the assembly conditions using the method provided by this invention, the greater the relative displacement reduction of the large opening structure, the better the conformability protection effect. Attached Figure Description

[0040] The accompanying drawings are provided to further understand the technical solutions of the present invention and constitute a part of the specification. They are used together with the embodiments of this application to explain the technical solutions of the present invention and do not constitute a limitation on the technical solutions of the present invention.

[0041] Figure 1 : Schematic diagram of the three-dimensional structure of the mid-fuselage and the location of the large opening;

[0042] Figure 2 : Schematic diagram of the intersecting diagonals of the large opening structure in the mid-fuselage;

[0043] Figure 3 : Schematic diagram of the formal conformal frame structure of the mid-fuselage;

[0044] Figure 4 : Schematic diagram of conformal frame structure in comparison with mid-fuselage;

[0045] Figure 5 Comparison of relative displacements along diagonal 1 under deflection conditions: no shape preservation, normal shape preservation, and comparative shape preservation.

[0046] Figure 6 Comparison of relative displacements along the diagonal 2 under deflection conditions: no shape preservation, normal shape preservation, and comparative shape preservation.

[0047] Figure 7 Comparison of relative displacements between the optimal shape-preserving position and the comparative shape-preserving position of diagonal 1 under deflection conditions;

[0048] Figure 8 Comparison of relative displacements between the optimal shape-preserving position and the comparative shape-preserving position of diagonal 2 under deflection conditions;

[0049] Figure 9 A flowchart illustrating the method for analyzing the shape retention requirements and shape retention effects of large opening structures in aircraft assembly.

[0050] Explanation of reference numerals in the attached figures:

[0051] Figure 1 The numbers 1-9 represent nine large opening structures. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

[0053] As explained in the background section above, the determination of conformity requirements, such as whether the large opening structure at the process separation surface needs to maintain its shape and the specific location of the shape maintenance, mainly relies on the experience of the designers. This highly subjective decision-making mode, which lacks quantitative criteria, may lead to ambiguity in the judgment of the necessity of shape maintenance and key areas.

[0054] Specifically, on the one hand, overprotection can occur due to overly conservative judgments, leading to the design and application of structurally redundant, bulky, and excessively heavy conformal tooling. This not only significantly increases manufacturing costs, occupies assembly space, and reduces operational efficiency, but the excessive weight of the conformal tooling may also cause further product deformation. On the other hand, underprotection can occur due to insufficient experience or oversights, failing to effectively identify deformation areas, resulting in conformal tooling failure or insufficient effectiveness, thus affecting assembly quality. In addition, existing conformal processes lack objective and quantitative evaluation methods for conformal solutions, making it impossible to intuitively judge the deformation-inhibiting effect of conformal tooling.

[0055] To address the aforementioned issues, this invention provides a method for analyzing the shape retention requirements and effects of large opening structures in aircraft assembly. This method is applicable to the scientific and precise assessment of the necessity, key shape retention areas, and shape retention effects of temporary large opening structures in aircraft assembly processes.

[0056] The present invention provides the following specific embodiments, which can be combined with each other. For the same or similar concepts or processes, they may not be described again in some embodiments.

[0057] This invention provides a method for analyzing the shape retention requirements and shape retention effects of large opening structures in aircraft assembly, characterized by the following steps:

[0058] Step 1: Without affecting the actual deformation trend and magnitude, simplify the aircraft tube segment model according to actual needs, determine the material properties of each component of the aircraft tube segment, and establish a finite element calculation model of the aircraft tube segment; wherein, the aircraft tube segment model includes multiple tube segment frames, each tube segment frame has a large opening structure, and two lifting points are set on the upper part of the large opening structure located at the docking surface.

[0059] Step 2: Set two intersecting diagonals for the large opening structure at each segment frame in the aircraft segment model; based on the diagonals set on the large opening structure, apply working conditions to the aircraft segment model, obtain the relative displacement of two points on each diagonal before and after applying the working conditions, and obtain the deformation of the large opening structure.

[0060] Step 3: Combine the actual assembly scenario and use the aircraft tube segment finite element calculation model to obtain the deformation of each large opening structure in order to determine whether the aircraft tube segment model needs to maintain its shape. After determining that it needs to maintain its shape, determine the assembly conditions that require shape maintenance.

[0061] Step 4: For the assembly conditions that require protection, determine the position of the large opening structure that requires protection in the aircraft tube section model based on the relative displacement of the two points on each diagonal.

[0062] Step 5: After installing the conforming fixture on the large opening structure that needs to be conformed to, judge the conforming effect of the fixture based on the relative displacement of the two diagonal points.

[0063] The following describes the embodiments of the present invention in further detail, taking a fuselage component of an aircraft as an example and in conjunction with the accompanying drawings. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0064] The method for analyzing the shape retention requirements and shape retention effects of large opening structures in aircraft assembly provided in this embodiment includes the following steps:

[0065] Step 1: Delete bolts, rivets, clips and other connecting parts, and replace them with binding constraints; fill in the weight reduction holes, observation windows and other holes on the mid-fuselage section model, and eliminate the floor frame imprint, rounded corners of the stringer edges and other structures; identify and delete non-load-bearing components in the model, including brackets, gaskets and so on.

[0066] Step 2: Based on the required calculation time, using the stiffness analysis results, and without affecting the actual deformation trend and magnitude, non-critical load-bearing structures are appropriately deleted, ultimately retaining only the stringers, floor supports, and skin structure. All parts are made of T7451 type 7050 grade aluminum alloy. Finally, a finite element calculation model of the mid-fuselage section is established, as shown in the following form. Figure 1 As shown;

[0067] Step 3, as follows Figure 1 As shown, the large opening structure of the mid-fuselage section model is a frame structure. The nine large opening structures are numbered 1-9, with the negative Z-axis as the direction. Figure 1 As shown;

[0068] Step 4, as follows Figure 1 As shown, the red funnel-shaped symbols on frames 1 and 9 represent fixed constraints. The positions of these constraints are the lifting point positions. Further, the upper diagonal points are determined based on these lifting point positions. Specifically, the model's heading direction (the negative Z-axis) is used to connect the two lifting points, forming a connecting line. The projection of this connecting line onto frames 1-9 of the mid-fuselage model is taken as the upper diagonal point. Within the same frame, the intersection of the floor frame and the side panel is taken as the lower diagonal point. Connecting these two points forms a diagonal. The two intersecting diagonals within the same frame are diagonal 1 and diagonal 2. Figure 2 As shown;

[0069] Step 5: During the assembly of the fuselage, the actual assembly scenarios are mainly divided into two types. One is to place the model on the ground using a bracket for riveting, cleaning excess materials, and precision machining of landing gear intersections. The other is to hoist the model to the next workstation for three-section docking. Therefore, the model needs to consider two working conditions: ground placement and hoisting. Considering that a straight-line hoisting method is used during hoisting, and the possibility of torsion, the working conditions to be considered are finally divided into four types: ground bracket placement (bracket fixed constraint), balanced hoisting (four hoisting points fixed constraint), hoisting imbalance 1 (two hoisting points on the negative X side are fixed constraint, and two hoisting points on the other side are unconstrained), and hoisting imbalance 2 (two hoisting points on the positive X side are fixed constraint, and two hoisting points on the other side are unconstrained). In this example, it is only necessary to explain the necessity of shape preservation, key shape preservation areas, and shape preservation effect judgment. Therefore, only hoisting imbalance 1 and balanced hoisting are selected for explanation.

[0070] Step 6: Calculate the simulation results of stiffness and strength for each assembly condition, and calculate the relative displacements ΔL1 and ΔL2 of diagonal 1 and diagonal 2 to determine the deformation. The calculation method is as follows:

[0071] ΔL1=L ′ 1-L1;

[0072] ΔL2=L ′ 2-L2;

[0073] Among them, L1 and L ′ 1 represents the length of diagonal 1 before and after the applied load condition, L2 and L ′ 2 represents the length of diagonal 2 before and after the applied load condition. ΔL1 and ΔL2 are the relative displacements of diagonals 1 and 2, respectively, representing the deformation inside the large-opening structure. The relative displacements for the balanced hoisting condition are calculated as follows:

[0074] The relative displacements under lifting imbalance condition 1 are as follows:

[0075]

[0076] From the two tables above, it can be observed that the maximum relative displacement in the balanced lifting condition is only 0.3mm, and the displacement of most frames is around 0.1mm, with the actual maximum displacement being only 0.9202mm. In the unbalanced lifting condition 1, the maximum relative displacement is 6.6mm, and most frames exhibit significant relative displacement, with the actual maximum displacement reaching 120mm. Therefore, considering all factors, the mid-fuselage section model does not require shape preservation in the balanced lifting condition, while shape preservation is necessary in the unbalanced lifting condition 1.

[0077] Step 7: For lifting imbalance condition 1, according to the relative displacement table of lifting imbalance condition 1 above, it can be concluded that the relative displacement of the large opening positions 1 and 9 is larger, whether it is diagonal 1 or 2. Therefore, the large opening positions 1 and 9 are selected as the positions that need to be maintained.

[0078] Step 8: Select two different forming frames, one is a formal forming frame, the structure of which is as follows: Figure 3 As shown, another type is a conformal retainer, the structure of which is as follows: Figure 4 As shown. Taking the lifting imbalance condition 1 as the calculation condition, and the large opening positions 1 and 9 as the conformal positions, the stiffness simulation is performed for the two types of conformal frames. The relative displacement of the large opening structure at each position of the fuselage section model is calculated under the conformal frames of the two types. The comparison of the relative displacement of diagonal 1 is shown in the figure. Figure 5 As shown in the diagram, the relative displacement comparison of diagonal 2 is as follows: Figure 6As shown in these two figures, it is clear that both conformal frames and the non-conformal frame provide better conformal protection for large openings in the mid-fuselage compared to the non-conformal frame, with the conformal frame showing significantly superior conformal protection.

[0079] Step 8: In Step 7, positions 1 and 9 with large openings were selected as the optimal conformal positions. To further prove that these positions are optimal, positions 2 and 8 with large openings were selected as the comparison conformal positions. Using the lifting imbalance condition 1 as the calculation condition, positions 2 and 8 with large openings as conformal positions, and the formal conformal frame as the conformal frame, a stiffness simulation was performed. The relative displacements of the large opening structures at various positions on the fuselage section model were calculated when the conformal frame was located in the comparison conformal positions, and compared with the optimal positions. The relative displacement comparison diagram of diagonal 1 is shown below. Figure 7 As shown in the diagram, the relative displacement comparison of diagonal 2 is as follows: Figure 8 As shown, the surface conformity preservation effect at the optimal conformity preservation position is significantly better than that at the comparison position.

[0080] To address the highly subjective and quantitatively unreliable design process for maintaining the form of large opening structures in aircraft assembly, this invention proposes a method for analyzing the form-keeping requirements and effects of such structures in aircraft assembly. First, without affecting the actual deformation trend and magnitude, the aircraft cylindrical segment model is simplified, the material properties of each component within the segment are determined, and a finite element analysis model of the aircraft cylindrical segment is established. Second, two intersecting diagonals are set for the large opening structures at each segment frame in the aircraft cylindrical segment model. Based on these diagonals, working conditions are applied to the aircraft cylindrical segment model to obtain... The relative displacements of two points on each diagonal before and after the applied working condition are used to obtain the deformation of each large opening structure. Furthermore, a finite element analysis model of the aircraft tube segment is used to obtain the deformation of each large opening structure to determine whether the aircraft tube segment model needs to maintain its shape. After determining that shape maintenance is required, the assembly conditions requiring shape maintenance are identified. For the assembly conditions requiring shape maintenance, the positions of the large opening structures requiring shape maintenance in the aircraft tube segment model are determined based on the relative displacements of two points on each diagonal. After installing shape-maintaining fixtures on the large opening structures requiring shape maintenance, the shape-maintaining effect of the fixtures is judged based on the relative displacements of two points on the diagonal.

[0081] The method for analyzing the conformability requirements and effects of large opening structures in aircraft assembly provided by this invention can use quantitative indicators to determine the necessity of conformability protection, key conformability protection areas, and conformability protection effects. This provides scientific and robust support for conformability protection schemes, avoiding tooling redundancy caused by "overprotection" and conformability protection failures caused by "underprotection," significantly improving assembly quality and process reliability in aircraft manufacturing. Compared to before conformability protection, after applying the assembly conditions using the method provided by this invention, the greater the relative displacement reduction of the large opening structure, the better the conformability protection effect.

[0082] The above examples illustrate in detail the significant role of the method for analyzing the shape retention requirements and effects of large opening structures in aircraft assembly, as described in this invention, in determining the necessity of shape retention for large openings in aircraft, key shape retention areas, and the judgment of shape retention effects.

[0083] The foregoing description illustrates and describes preferred embodiments of the present invention. As previously stated, it should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the inventive concept described herein through the foregoing teachings or techniques or knowledge in related fields. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A method for analyzing the shape retention requirements and shape retention effects of large opening structures in aircraft assembly, characterized in that, Includes the following steps: Step 1: Without affecting the actual deformation trend and magnitude, simplify the aircraft tube segment model according to actual needs, determine the material properties of each component of the aircraft tube segment, and establish a finite element calculation model of the aircraft tube segment; wherein, the aircraft tube segment model includes multiple tube segment frames, each tube segment frame has a large opening structure, and two lifting points are set on the upper part of the large opening structure located at the docking surface. Step 2: Set two intersecting diagonals for the large opening structure at each segment frame in the aircraft segment model; based on the diagonals set on the large opening structure, apply working conditions to the aircraft segment model, obtain the relative displacement of two points on each diagonal before and after applying the working conditions, and obtain the deformation of the large opening structure. Step 3: Combine the actual assembly scenario and use the aircraft tube segment finite element calculation model to obtain the deformation of each large opening structure in order to determine whether the aircraft tube segment model needs to maintain its shape. After determining that it needs to maintain its shape, determine the assembly conditions that require shape maintenance. Step 4: For the assembly conditions that require protection, determine the position of the large opening structure that requires protection in the aircraft tube section model based on the relative displacement of the two points on each diagonal. Step 5: After installing the conforming fixture on the large opening structure that needs to be conformed to, judge the conforming effect of the fixture based on the relative displacement of the two diagonal points.

2. The method for analyzing the shape retention requirements and shape retention effects of large opening structures in aircraft assembly according to claim 1, characterized in that, Step 1 includes: Step 11: For the aircraft tube section model, delete bolts, rivets, and clips, and replace all connectors with binding constraints. Step 12: Fill in the holes in the model, and delete the marks and rounded corners; Step 13: Identify and delete non-load-bearing components in the model; Step 14: Based on the required calculation time, using the results of the stiffness and strength analysis, and taking the actual deformation trend and magnitude as the design objective, delete non-critical load-bearing structures.

3. The method for analyzing the shape retention requirements and shape retention effects of large opening structures in aircraft assembly according to claim 1, characterized in that, The method of setting diagonal lines for the large opening structures at each segment frame in the aircraft segment model in step 2 includes: Step 21: Identify the major opening structures of the aircraft tube segment model. Each tube segment frame has a major opening structure, and the major opening structure located at the end is the major opening structure located at the docking surface. Number the major opening structures in a certain order. Step 22: Determine two intersecting diagonals on the large opening structure at the docking surface based on the lifting point positions on the aircraft tube model. This includes: determining the upper points of two diagonals based on the two lifting point positions, and taking the intersection of the floor frame and the side wall panel as the lower points of the corresponding diagonals within the same tube frame. Step 23: For large opening structures at other tube frame sections other than the large opening structure at the docking surface, project the upper diagonal point of the docking surface onto the other large opening structures and set it as the upper diagonal point of the other large opening structures; the intersection point of the floor frame and the side wall panel of the large opening structures within the same tube frame is the lower diagonal point of the corresponding large opening structure.

4. The method for analyzing the shape retention requirements and shape retention effect of large opening structures in aircraft assembly according to claim 3, wherein the method for obtaining the deformation of large opening structures in step 2 includes: Apply a working condition to the aircraft tube segment model, and subtract the lengths of each diagonal before and after applying the working condition. The result is the relative displacement between the two points on the diagonal, which is used to represent the deformation of the major opening structures in the aircraft tube segment model.

5. The method for analyzing the shape retention requirements and shape retention effect of large opening structures in aircraft assembly according to claim 4, characterized in that, The method for calculating the relative displacement of the two points on each diagonal before and after the applied working condition in step 2 is as follows: ΔL1=L ′ 1-L1; ΔL2=L ′ 2-L2; Among them, the intersecting diagonals in each of the major opening structures are diagonal 1 and diagonal 2, L1 and L2, respectively. ′ 1 represents the length of diagonal 1 before and after the applied load condition, L2 and L ′ 2 represents the length of diagonal 2 before and after the applied working condition. ΔL1 and ΔL2 are the relative displacements of diagonal 1 and diagonal 2, respectively, representing the deformation inside the large opening structure.

6. The method for analyzing the shape retention requirements and shape retention effects of large opening structures in aircraft assembly according to claim 5, characterized in that, Step 3 includes: Step 31: Based on the actual assembly scenario, determine the assembly conditions involved in the aircraft tube section model. The assembly conditions include ground placement conditions and hoisting conditions. The hoisting conditions include deflection conditions and torsion conditions. Step 32: Calculate the stiffness simulation results for each assembly condition, including: using the finite element calculation model of the aircraft tube section for simulation, calculating the relative displacements ΔL1 and ΔL2 of diagonals 1 and 2 in the major opening structures to determine the deformation. Step 33: If the deformation of the major opening structures does not exceed the deformation design requirements under all assembly conditions, the aircraft tube section model does not need to maintain its shape; if there are major opening structures that exceed the deformation design requirements, the condition is determined to be an assembly condition that requires shape maintenance.

7. The method for analyzing the shape retention requirements and shape retention effects of large opening structures in aircraft assembly according to claim 6, characterized in that, Step 4 includes: Step 41: For the assembly conditions that require protection, calculate the relative displacement values ​​ΔL1 and ΔL2 of the two diagonals of each large opening structure. Step 42: Sort the relative displacement values ​​ΔL1 and ΔL2 of the two diagonals of each large opening structure, and comprehensively identify the diagonal with the larger relative displacement, as well as the position of the large opening structure where the diagonal is located. Step 43: Divide the aircraft tube section into two sections along the heading. Based on the shape retention requirement of selecting at least one large opening structure in each section, determine the position of at least one large opening structure in each section according to the deformation amount of the diagonal in each section.

8. The method for analyzing the shape retention requirements and shape retention effects of large opening structures in aircraft assembly according to claim 1, characterized in that, Step 5 includes: Step 51: Install the conformal fixtures onto the large opening structures that need to be conformed to, as determined in Step 4. Step 52: For each assembly condition requiring shape preservation determined in Step 3, calculate the relative displacement values ​​ΔL1 and ΔL2 of the two diagonals of each large opening structure after the shape preservation fixture is installed. Step 53: For each assembly condition requiring shape preservation, compare the relative displacement values ​​of the two diagonals of the large opening structure before and after shape preservation to determine the shape preservation effect of the shape preservation tooling; among them, after applying the assembly condition, the greater the decrease in relative displacement of the large opening structure after shape preservation, the better the shape preservation effect.

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