Simulation-based forward design method for field shape maintenance scheme of large-opening structure

Abstract

The invention belongs to the technical field of mold production, and discloses a simulation-based large-opening structure field shape maintenance scheme forward design method, which comprises the following steps of: 1, simplifying a large-opening structure and establishing a high-fidelity finite element simulation model; deformation of the large-opening structure under the actual working condition is simulated, the elastic deformation degree of the large-opening structure is calculated and evaluated based on the surface shape variance, and a shape maintaining tool supporting point position is selected according to the elastic deformation degree; 2, designing and optimizing a shape-preserving tool model by considering a deformation factor of a large-opening structure and a shape-preserving tool volume factor according to a shape-preserving tool supporting point position; 3, installing the shape-preserving tool model into the high-fidelity finite element simulation model, carrying out large-opening structure deformation simulation analysis in a shape-preserving state, and calculating a surface shape variance in the shape-preserving state; 4, selecting a force control shaft at the tail end of the supporting point position of the shape maintaining tool, designing simulation to obtain the contact force of the force control shaft and the surface shape variance of the supporting point position, and establishing a mathematical model between the contact force of the force control shaft and the surface shape variance of the supporting point position; 5, in the field shape maintaining process, the laser tracker is used for measuring the position error of the shape maintaining tool supporting point position, the surface shape variance of the shape maintaining tool supporting point position is evaluated, and the contact force is calculated based on a mathematical model between the force control shaft contact force and the surface shape variance of the supporting point position.

Description

Technical Field

[0001] The invention belongs to the technical field of forward design of flexible shape-keeping tooling, and in particular relates to a forward design method of an on-site shape-keeping solution for a large opening structure based on simulation. Background Art

[0002] In the overall design and functional requirements of the aircraft, it is generally necessary to arrange more door openings on the fuselage, so more opening areas are formed in the fuselage compartment. These large opening cabin structures connected by the opening frame and other areas with other components cause a sharp change in the rigidity and force transmission of the fuselage structure, making it easy for the wing-body docking area to be twisted and deformed during the assembly process, and at the same time causing serious displacement deviations in the wing-body joint, affecting the assembly coordination of the wing-body joint, causing assembly difficulties, and forced assembly will produce greater assembly stress. Therefore, the docking assembly process of large components determines the final quality of the aircraft, and during the assembly process, it is necessary to ensure high-precision installation combinations when the continuous large opening components are docked with other groups and components.

[0003] In the actual product component assembly process, on the one hand, affected by its own structure and assembly process, the large opening structure is a typical unstable and deformable structure under the action of uneven stress, and the assembly deformation state is difficult to control; on the other hand, the large opening docking structure generally has the characteristics of large size, variable curvature, and variable thickness. Under the action of positioning error, manufacturing error, and load, it will cause assembly errors such as positioning gap and warping, making it difficult for the large-size open cabin structure of the aircraft to meet the requirements of coaxiality, aerodynamic shape accuracy, and assembly coordination accuracy. Therefore, due to the combined effects of the molding error, tooling manufacturing error, positioning error and assembly deformation of the large opening structure, the deformation of the continuous large opening structure during posture adjustment, positioning and transfer transportation is difficult to control, and the existing assembly process can only maintain the opening shape by installing two layers of traditional standard shape-keeping frames or special assembly tooling on the end face of the large opening structure. The design of the shape-keeping tooling often relies on design experience, and lacks theoretical analysis of the structural form, strength, and support point selection of the shape-keeping tooling, which makes the shape-correcting effect of the shape-keeping tooling poor, and it is difficult to solve the problems of excessive local deformation and uncoordinated assembly of the large opening structure, and it is difficult to meet the design requirements of lightweight shape-keeping tooling.

[0004] Therefore, there is an urgent need for a forward design method for flexible shape-preserving tooling for large-opening structures, which can meet the needs of deformation control of large-opening structures during assembly, lightweight design of shape-preserving tooling, and automatic adjustment of flexible tooling, and support the digitization and automation of the assembly process of large-opening structures. Summary of the invention

[0005] Purpose of the invention: In order to solve the above problems, the present invention proposes a forward design method for on-site conformal solutions for large opening structures based on simulation. First, the local deformation of the large opening structure is analyzed by the finite element simulation method, and a topological optimization design method for the large opening structure considering local conformal constraints is proposed to achieve lightweight design of flexible tooling. Then, partial least squares regression is used to establish a mathematical model with the deformation of the tooling conformal point as the independent variable and the tooling force adjustment control axis as the dependent variable. Finally, based on the deformation results of the conformal tooling support points measured on-site, the contact force required for the conformal adjustment of each force control axis is determined. Summary of the invention:

[0007] A simulation-based forward design method for a large opening structure on-site shape-preserving solution, the steps are as follows:

[0008] Step 1: Simplify the large opening structure and establish a high-fidelity finite element simulation model; simulate the deformation of the large opening structure under actual working conditions, evaluate the elastic deformation degree of the large opening structure based on the surface variance calculation, and select the support points of the shape-preserving tooling according to the elastic deformation degree;

[0009] Step 2: According to the support points of the shape-conserving tooling, the shape-conserving tooling model is designed and optimized by considering the deformation factor of the large opening structure and the volume factor of the shape-conserving tooling;

[0010] Step 3: Install the shape-preserving tooling model into the high-fidelity finite element simulation model, carry out deformation simulation analysis of the large opening structure under the shape-preserving state, and calculate the surface shape variance under the shape-preserving state;

[0011] Step 4: Select the end of the conformal structure positioning support as the force control axis, design simulation to obtain the data of the contact force of the force control axis and the deformation of the conformal point under working conditions such as lifting and transportation, and establish a mathematical model between the two;

[0012] Step 5: During the on-site conformal process, a laser tracker is used to measure the position error of the positioning support end of the conformal tooling to evaluate its degree of deformation. The mathematical model established in the previous section is used to calculate the adjustment force of the corresponding adjustable positioning support end to achieve deformation control of the large opening structure.

[0013] Further, in step one, the specific process is as follows:

[0014] 1.1. Extract the large opening structure based on the actual large opening cabin 3D model, remove the parts that have no effect on the structural simulation analysis results in the large opening cabin model, simplify the tiny features, and complete the establishment of a high-fidelity finite element simulation model of the large opening structure;

[0015] 1.2, according to the actual working conditions of the large opening structure, set different analysis steps to simulate the assembly process of the large opening structure, divide the grid, set the load and boundary conditions in turn, and perform finite element simulation analysis and calculation of the large opening structure after completing the model condition setting;

[0016] 1.3. After the simulation is completed, the deformation and stress distribution data of the opening frame are extracted, and the surface variance R of the contact end surface with the conformal tooling is calculated. 2 , the expression is as follows;

[0017]

[0018] Where {Δu i}={u′ i}-{u i},{u′ i} is the displacement of node i, {u i} is the rigid body displacement of node i, N is the number of control nodes corresponding to the local area; in the calculation, the actual displacement of node i {u′ i} is obtained through finite element analysis, the rigid body displacement {u i}It is obtained by solving and calculating its translation and rotation;

[0019] 1.4, select the horizontal right side as the 0° direction, divide the opening frame into regions along the directions of 45°, 135°, 225° and 315°, calculate the surface variance of the divided local areas respectively, so as to quantitatively characterize the degree of elastic deformation under actual working conditions, compare the deformation results of the local areas equidistant in the four directions, and select the local area with the largest surface variance as the positioning support position of the shape-preserving tooling.

[0020] Further, in step 2, the specific process is as follows:

[0021] 2.1. Establish an optimizable finite element analysis model of the conformal fixture, analyze the design domain and non-design domain of the structure, take the positioning support end of the conformal fixture for the large opening cabin structure as the non-design domain, and the main structure as the design domain, and define the boundary conditions and external loads;

[0022] 2.2, taking the strain energy of the structure as the optimization target, considering the deformation and quality requirements, imposing the upper limit of the surface variance and volume constraints in the conformal area, and using the solid isotropic material penalty method to perform structural topology optimization;

[0023] 2.3. After the optimization is completed, the tooling optimization model is exported. First, the topology optimization results are sliced ​​to obtain the cross-sectional curve, which is then fitted using a straight line. Then, considering the manufacturability of the structure, the hollow truss structure is selected to fit the tooling shape to obtain the preliminary reconstruction result.

[0024] 2.4. After the reconstruction is completed, the model is imported, meshed, materials, sections, specified sections, boundary conditions and loads are defined in sequence. The reconstructed model is statically analyzed using Abaqus software to verify the static strength of the conformal tooling.

[0025] Further, in step 4, the specific process is as follows:

[0026] 4.1, the positioning support end of the reconstructed shape-keeping tooling is designed as an adjustable mechanism, and the force control axis is selected at the end of the support point;

[0027] 4.2. Design orthogonal simulation to simulate the deformation of the opening frame in the large opening cabin structure under different loads, obtain the contact force between the positioning support end face and the opening frame and the deformation of the positioning support end face, and calculate the surface variance of the positioning support end face of the conformal tooling;

[0028] 4.3, based on the acquired data, a mathematical model is established using the least squares regression method with the surface variance of the positioning support end face as the independent variable and the contact force between the positioning support structure and the opening frame as the dependent variable.

[0029] Further, in step five, the process is as follows:

[0030] 5.1. Use the instrument to perform an all-round scan of the large opening structure and conformal tooling to be measured, and switch multiple scanning modes to scan different areas to obtain the three-dimensional point cloud data of the structure. Use the adaptation software to perform three-dimensional reconstruction of the scanned point cloud data to obtain the scanned three-dimensional model of the large opening structure and conformal tooling;

[0031] 5.2. Import the 3D digital model of the structure into the measurement software, match the coordinate system between the 3D digital model and the 3D model obtained by scanning after loading, analyze the deviation between the two, and use it as the position error of the positioning support end of the conformal tooling, so as to calculate the surface variance of the area;

[0032] 5.3. Based on the mathematical model between the surface variance of the positioning support end of the conformal tooling and the contact force between it and the conformable structure, the surface variance obtained by scanning calculation is used as input to calculate the force required for the conformal adjustment of the adjustable end of the conformal tooling. By manually or automatically adjusting the adjustable end, the contact force between the positioning support end surface of the conformal tooling and the conformal surface of the large opening cabin structure meets the requirements;

[0033] 5.4. After the conformal tooling is adjusted, repeat steps 5.1-5.3 and perform multiple feedback adjustments until the deformation of the conformal surface of the large opening cabin structure is reduced by 30% compared to before adjustment.

[0034] Furthermore, the mathematical model of the solid isotropic material penalty method is as follows:

[0035] Find:ρ i =i=1…N

[0036]

[0037] K(ρ i )U=F

[0038]

[0039] 0.0001≤ρ i ≤1,i=1…n

[0040] Where i is the unit number, ρ is the design variable, K, U, F are the overall stiffness matrix, displacement vector and external force vector respectively, u and k are the stiffness matrix and displacement vector of a single unit respectively, C represents the total strain energy of the structure, v i Represents the volume of the corresponding unit, V0 is the design volume of the total volume, R 2 represents the surface variance of the local area, Represents the local area surface variance before optimization.

[0041] Furthermore, in 1.1, the parts that are not affected include: bolts and skin.

[0042] Furthermore, in 1.1, the micro features include: chamfers and holes.

[0043] The beneficial effects of this application are:

[0044] The present invention proposes a simulation-based forward design method for large opening structure on-site shape-preserving schemes to achieve deformation control of large opening structures. It realizes the lightweight design of shape-preserving tooling, establishes a force-displacement equilibrium control mathematical model, enhances the adjustability of assembly tooling, and greatly improves the assembly quality and efficiency of aircraft. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a flow chart of the forward design method of the on-site shape-preserving scheme for large opening structures based on simulation;

[0046] Figure 2 It is a schematic diagram of a typical structural simulation model with a large opening frame;

[0047] Figure 3 A simplified diagram for explaining the selection of shape-preserving points for a large opening frame;

[0048] Figure 4 The flowchart of lightweight design of shape-conserving tooling considering local displacement constraints;

[0049] Figure 5 Schematic diagram of the reconstruction results for shape-preserving tooling design;

[0050] Figure 6 This is the relationship curve between the deformation of the shape-preserving tooling and the contact force mathematical model. DETAILED DESCRIPTION

[0051] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0052] The terms "first", "second", etc. in the specification and claims of the present invention are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention can be implemented in an order other than those illustrated or described herein, and the objects distinguished by "first", "second", etc. are generally of the same type, and the number of objects is not limited. For example, the first object can be one or more. In addition, "and / or" in the specification and claims represents at least one of the connected objects, and the character " / " generally indicates that the objects associated with each other are in an "or" relationship.

[0053] The human body image analysis method provided by the embodiment of the present invention is described in detail below through specific embodiments and application scenarios in conjunction with the accompanying drawings.

[0054] In order to achieve accurate control of the deformation of large opening structures by shape-preserving tooling during the actual assembly process, the present invention proposes a forward design method for large opening structure on-site shape-preserving scheme based on simulation, such as Figure 1 As shown, the steps are as follows:

[0055] 1. By reasonably simplifying the large opening structure, a high-fidelity finite element simulation model is established to simulate the deformation of the large opening structure under actual working conditions. The elastic deformation degree of the opening frame is evaluated based on the surface variance calculation, and the larger deformation area is selected as the support point of the shape-preserving tooling.

[0056] 1.1 The large opening structure is extracted based on the actual three-dimensional model of the large opening cabin. The bolt fasteners, connecting plates and other components that have little impact on the simulation analysis results are removed from the large opening cabin model. The chamfers, holes and other small features are simplified. On the basis of taking into account both calculation efficiency and calculation accuracy, a high-fidelity finite element simulation model of the large opening structure is established.

[0057] 1.2 According to the actual working conditions of the large opening structure, different analysis steps are set to simulate the assembly process of the large opening structure, and the grid is divided, the load and boundary conditions are set in turn. After completing the model condition setting, the finite element simulation analysis and calculation of the large opening structure are carried out.

[0058] 1.3 After the simulation analysis is completed, the deformation and stress distribution data of the opening frame are extracted, and the surface variance of the end face in contact with the conformal tooling is calculated, which is used as the local deformation field of the opening frame when it is assembled under actual working conditions.

[0059] The surface variance can describe the degree of elastic deformation in the local area, and its expression is as follows:

[0060]

[0061] Where {Δu i}={u i ′}-{u i},{u i ′} is the displacement of node i, {u i} is the rigid body displacement of node i, and N is the number of control nodes corresponding to the local area. In the calculation, the actual displacement of node i {u′ i} is obtained through finite element analysis, the rigid body displacement {u i} is obtained by solving and calculating its translation and rotation.

[0062] According to the theory of elasticity, the rigid body displacement of an object can be expressed as:

[0063] u x =u 0x +ω y ×z-ω z ×y

[0064] u y =u 0y +ω z ×x-ω x ×

[0065] u z =u 0z +ω x ×y-ω y ×

[0066] The matrix form is expressed as:

[0067]

[0068] where ω x ,ω y ,ω z represents the rigid body rotation around each axis, u x 、u y 、u z represents the displacement along the x, y, and z directions, u 0x ,u 0y ,u 0z Rigid body translation along the x, y, and z directions.

[0069] make Then the above formula can be written as {u}={u0}+{T}{ω}.

[0070] By calculation, we can get {Δu i}={u′ i}-{u0}-{T i}{ω}, by which the actual displacement of the node, the rigid body translation in the local area, the rigid body rotation and the surface variance expressed by the node coordinates can be calculated.

[0071] 1.4 Select the horizontal right side as the 0° direction, divide the area along the opening frame in the counterclockwise directions of 45°, 135°, 225° and 315°, calculate the surface variance of the divided local areas respectively, so as to quantitatively characterize the degree of elastic deformation under the actual working conditions, and compare the deformation results of the local areas equidistant in the four directions, and select the local area with the largest surface variance as the positioning support position of the shape-preserving tooling.

[0072] 2. Comprehensively consider the deformation factors of the shape-conforming area of ​​the opening frame and the volume factors of the shape-conforming tooling, and carry out the topological optimization design of the shape-conforming tooling with the displacement and volume of the shape-conforming area as constraints.

[0073] 2.1 Establish an optimizable finite element analysis model of the conformal tooling, analyze the design domain and non-design domain of the structure, take the positioning support end of the conformal tooling for the large opening cabin structure as the non-design domain, and the main structure as the design domain, and define the boundary conditions and external loads.

[0074] 2.2 Taking the strain energy of the structure as the optimization target, considering the deformation and quality requirements, the surface variance and volume constraint upper limits of the conformal area are imposed to perform structural topology optimization, so that the optimized conformal tooling can control the material usage and the warping deformation of the conformal area within a certain range, seek the optimal distribution of materials, and achieve the minimization of structural flexibility under given boundary conditions and external forces.

[0075] The optimization mathematical model of the solid isotropic material penalty method (SIMP) used is as follows:

[0076] Find:ρ i =i=1…N

[0077]

[0078] K(ρ i )U=F

[0079]

[0080] 0.0001≤ρ i ≤1,i=1…n

[0081] Where i is the unit number, ρ is the design variable, K, U, F are the overall stiffness matrix, displacement vector and external force vector respectively, u and k are the stiffness matrix and displacement vector of a single unit respectively, C represents the total strain energy of the structure, v i Represents the volume of the corresponding unit, V0 is the design volume of the total volume, R 2 represents the surface variance of the local area, Represents the local area surface variance before optimization.

[0082] 2.3 After the optimization is completed, the tooling optimization model is exported. First, the topology optimization results are sliced ​​to obtain the cross-sectional curve, which is then fitted using a straight line. Then, considering the manufacturability of the structure, the hollow truss structure is selected to fit the tooling shape and obtain the preliminary reconstruction result.

[0083] 2.4 After the reconstruction is completed, the model is imported, meshed, materials, sections, specified sections, boundary conditions and loads are defined in sequence. The reconstructed model is statically analyzed using Abaqus software to verify the static strength of the conformal tooling.

[0084] 2.5 Install the optimized shape-preserving tooling into the large opening structure, carry out deformation simulation analysis of the large opening structure under the shape-preserving state, compare the surface variance of the opening frame in the large opening structure with and without the shape-preserving tooling, and verify the degree to which the shape-preserving tooling can suppress the warping deformation of the easily deformed opening frame in the large opening cabin structure.

[0085] 3. After the reconstruction design of the conformal tooling structure is completed, in order to address the unclear relationship between the adjustment force of the adjustable tooling and the deformation of the conformal structure, the end of the conformal structure positioning support is selected as the force control axis, and a simulation is designed to obtain the data on the contact force of the force control axis and the deformation of the conformal point under working conditions such as lifting and transportation, and a mathematical model between the two is established.

[0086] 3.1 According to the reconstructed shape-keeping tooling, the positioning support end of the shape-keeping tooling is designed as an adjustable mechanism, and the force control axis is selected at the end of the positioning support point.

[0087] 3.2 Based on the tooling designed above, in order to realize the automatic adjustment of the positioning support end face of the conformal tooling with the force control axis, an orthogonal simulation is designed to carry out the deformation simulation of the opening frame in the large opening cabin structure under different loads, obtain the contact force between the positioning support end face and the opening frame and the deformation of the positioning support end face, and calculate the surface variance of the positioning support end face of the conformal tooling.

[0088] 3.3 Based on the acquired data, the least squares regression method is used to establish a mathematical model with the surface variance of the positioning support end face as the independent variable and the contact force between the positioning support structure and the opening frame as the dependent variable.

[0089] 4. During the on-site conformal process, a laser tracker is used to measure the position error of the positioning support end of the conformal tooling to evaluate its degree of deformation. The mathematical model established in the previous section is used to calculate the adjustment force of the corresponding adjustable positioning support end to achieve deformation control of the large opening structure.

[0090] 4.1 The handheld instrument performs an all-round scan of the large opening structure and conformal tooling to be measured, and switches between multiple scanning modes to scan different areas to obtain the three-dimensional point cloud data of the structure. The scanned point cloud data is reconstructed in three dimensions using the adaptation software to obtain the scanned three-dimensional model of the large opening cabin structure and conformal tooling.

[0091] 4.2 Import the three-dimensional digital model of the structure into the measurement software, match the coordinate system between the three-dimensional digital model and the three-dimensional model obtained by scanning after loading, analyze the deviation between the two, and use this as the position error of the positioning support end of the conformal tooling, so as to calculate the surface variance of the area.

[0092] 4.3 Based on the mathematical model between the surface variance of the positioning support end of the conformal tooling and the contact force between it and the conformable structure established in the previous section, the surface variance obtained by scanning calculation is used as input to calculate the force required for the conformal adjustment of the adjustable end of the conformal tooling. By manually or automatically adjusting the adjustable end, the contact force between the positioning support end face of the conformal tooling and the conformal surface of the large opening cabin structure meets the requirements.

[0093] 4.4 After the conformal tooling is adjusted, the laser tracker is used again to measure the large opening cabin structure and the conformal tooling, analyze the deformation state, and perform multiple feedback adjustments until the deformation of the conformal surface of the large opening cabin structure is reduced by 30% compared to before adjustment, completing the forward design of the adjustable tooling.

[0094] Example

[0095] 1. Reasonably simplify the asymmetric large opening structure and establish a high-fidelity finite element simulation model to simulate the deformation of the large opening structure under actual working conditions, extract the deformation results, evaluate the elastic deformation degree of the opening frame based on the surface variance calculation, and select the larger deformation area as the positioning support point of the shape-preserving tooling.

[0096] 1.1 According to the actual large opening structure produced, a typical asymmetric large opening structure with a length of 6000mm, a width of 2000mm and a height of 3000mm is designed, in which the opening diameter of the left frame is 1400mm and the opening diameter of the right frame is 1600mm. Figure 2 As shown in the figure, CATIA software is used to model the structure and obtain the digital model.

[0097] 1.2 According to the requirements of mesh division, the large opening model is appropriately simplified, non-main components such as bolts and skins are removed, and the main load-bearing components are retained. The simplified structure is imported into ABAQUS software and assembled to obtain the finite element model of the large opening structure. The material is 6061T6 aluminum alloy, and the material parameters are shown in Table 1.

[0098] Table 1 6061T6 aluminum alloy material parameters

[0099]

[0100] Note: E is elastic modulus, v is Poisson's ratio, σ s is the yield strength, X t For tensile strength.

[0101] 1.3 The large opening structure adopts the tetrahedral unit C3D6. In the contact module, binding constraints are applied to different components to simulate the fixed relationship between the components.

[0102] 1.4 In the load and boundary module, according to the actual working conditions, the five degrees of freedom of the hanging point of the large opening structure except the movement in the z direction are restricted, the motion coupling reference point of the hanging point area is established, a tensile displacement of 100 mm is applied along the z direction, and the gravity field of the overall structure is applied in the LOAD module.

[0103] 1.5 Perform finite element simulation, read the three-dimensional finite element simulation results of the large opening structure, select the large opening frame according to the square area with a length and width of 100 mm, extract the displacement U of all nodes in the area, calculate the surface variance of different areas according to the concept of surface variance, and use multiple symmetrical areas with large surface variance as shape-preserving points. Finally, the shape-preserving points of the large opening frame are selected as follows: Figure 3 As shown, the surface variance of this area is shown in Table 2 below.

[0104] Table 2 Surface shape variance in the conformal area

[0105]

[0106]

[0107] 2. Comprehensively consider the surface variance of the opening frame conformal area and the volume factor of the conformal tooling calculated in the previous section, and carry out the topological optimization design of the conformal tooling with the surface variance and volume of the conformal area as constraints. The design process is as follows: Figure 4 shown.

[0108] 2.1 Based on the conformal points determined in the previous section, an optimization model considering local displacement constraints is designed. The structural design domain is a cuboid of 3800×1300×1200 mm, and the non-design domain is the corresponding conformal positioning support structure.

[0109] 2.2 Use Python language to write structural topology optimization with the minimum strain energy of the structure as the optimization goal, and the surface variance and volume of the conformal area within a certain range of constraints. The upper limits of the surface variance of conformal points 1-8 are 50%, and the volume is 10%. Import the optimization results into Abaqus software for dynamic and static mechanical simulation, extract the surface variance and volume results, and iterate to obtain the final optimized structure.

[0110] 2.2 Taking the strain energy of the structure as the optimization target, considering the deformation and quality requirements, the surface variance and volume constraint upper limits of the conformal area are imposed to perform structural topology optimization, so that the optimized conformal tooling can control the material usage and the warping deformation of the conformal area within a certain range, seek the optimal distribution of materials, and achieve the minimization of structural flexibility under given boundary conditions and external forces.

[0111] 2.3 After the optimization is completed, the tooling optimization model is exported and reconstructed based on the results and empirical methods. First, the topology optimization results are sliced ​​to obtain the cross-sectional curve, which is fitted using a straight line. Then, considering the manufacturability of the structure, some components are appropriately modified to obtain preliminary reconstruction results, such as Figure 6 shown.

[0112] 2.4 The above reconstructed model is imported into Abaqus software. The structure adopts tetrahedral element C3D6 and the material is 6061T6 aluminum alloy. The material parameters are shown in Table 1. Then, in the load and boundary condition module, the support points are fixed, gravity is applied, and static analysis of the structure is carried out. No large stress concentration occurs in the structure, and it can be considered that the static strength meets the requirements.

[0113] 2.5 The above-mentioned conformal tooling model is assembled into the large opening structure model in Abaqus software, and the deformation simulation analysis of the large opening structure under the conformal state is carried out. The surface shape variance of the conformal area under the conformal state is shown in Table 3. The conformal tooling has a significant inhibitory effect on the warping deformation of the conformal area.

[0114] Table 3 Surface shape variance of the conformal area under conformal state

[0115]

[0116] 3. After the structural reconstruction design of the conformal tooling is completed, in order to address the problem of flexible tooling, a force control axis is selected at the end of the support point, and a simulation is designed to obtain the data on the contact force of the force control axis and the deformation of the conformal positioning support end under conditions such as lifting and transportation, and a mathematical model between the two is established.

[0117] 3.1 According to the reconstructed shape-keeping tooling, the shape-keeping positioning support end is designed as an adjustable mechanism in actual manufacturing, and the force control axis is selected at the end of the positioning support.

[0118] 3.2 Design an orthogonal simulation. In the load module, apply equidistant vertical loads of 0-100N along the 45°, 135°, 225° and 315° directions of the left and right opening frames, respectively. Perform deformation simulation of the opening frame under different loads, extract the contact force between the supporting structure and the conformal frame structure and the deformation of the supporting points, and calculate the sum of the surface variances of the eight supporting points, as shown in Table 4 below.

[0119] Table 4 Contact force increment and deformation of support point under different loads

[0120]

[0121] 3.3 Based on the data in the above table, the least squares regression method is used to establish a mathematical model with the surface variance of the positioning support end face as the independent variable and the contact force between the positioning support structure and the conformable structure as the dependent variable. The mathematical model curve is as follows: Figure 6 shown.

[0122] 4. Use a laser tracker to measure the position error of the end face of the positioning support of the conformal tooling, evaluate its surface variance, and calculate the adjustment force of the corresponding adjustable clamping end using the mathematical model established in the previous section to achieve deformation control of the large opening structure.

[0123] 4.1 The handheld instrument performs an all-round scan on the manufactured large opening structure and conformal tooling to obtain the three-dimensional point cloud data of the structure. The scanned point cloud data is reconstructed in three dimensions using software adapted to the laser scanner to obtain a scanned three-dimensional model of the large opening structure and conformal tooling.

[0124] 4.2 Import the three-dimensional digital model of the structure into the measurement software, match the coordinate system between the three-dimensional digital model and the scanned three-dimensional model, analyze the deviation between the two, and use this as the position error of the positioning support end face of the conformal tooling. Calculate the surface variance of the area as shown in Table 5.

[0125] 4.3 The above mathematical model is imported into the control system of the on-site tooling, the surface variance is input into the control panel, and the adjustable end is automatically adjusted to achieve automatic adjustment and control of deformation. Finally, the surface variance of the area is shown in Table 5. The deformation of the shape-preserving area is reduced by 41%, which meets the design requirements.

[0126] Table 5 Surface shape variance of the shape-preserving area before and after automatic adjustment

[0127]

[0128] It should be noted that, in this article, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element. In addition, it should be pointed out that the scope of the method and device in the embodiment of the present invention is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in reverse order according to the functions involved, for example, the described method may be performed in an order different from that described, and various steps may also be added, omitted, or combined. In addition, the features described with reference to certain examples may be combined in other examples.

[0129] Through the description of the above implementation modes, those skilled in the art can clearly understand that the above implementation modes can be implemented by means of software plus a necessary general hardware platform, and of course by means of hardware, but in many cases the former is a better implementation mode. The above describes the embodiments of the present invention in conjunction with the accompanying drawings, but the present invention is not limited to the above specific implementation modes, which are merely illustrative and not restrictive. Under the enlightenment of the present invention, those skilled in the art can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are within the protection of the present invention.

Claims

1. A simulation-based forward design method for a large opening structure on-site shape preservation scheme, characterized by: Here are the steps: Step 1: Simplify the large opening structure and establish a high-fidelity finite element simulation model; simulate the deformation of the large opening structure under actual working conditions, evaluate the elastic deformation degree of the large opening structure based on the surface variance calculation, and select the support points of the shape-preserving tooling according to the elastic deformation degree; Step 2: According to the support points of the shape-conserving tooling, the shape-conserving tooling model is designed and optimized by considering the deformation factor of the large opening structure and the volume factor of the shape-conserving tooling; Step 3: Install the shape-preserving tooling model into the high-fidelity finite element simulation model, carry out deformation simulation analysis of the large opening structure under the shape-preserving state, and calculate the surface shape variance under the shape-preserving state; Step 4: Select the end of the conformal structure positioning support as the force control axis, design simulation to obtain the data of the contact force of the force control axis and the deformation of the conformal point under working conditions such as lifting and transportation, and establish a mathematical model between the two; Step 5: During the on-site conformal process, a laser tracker is used to measure the position error of the positioning support end of the conformal tooling to evaluate its degree of deformation. The mathematical model established in the previous section is used to calculate the adjustment force of the corresponding adjustable positioning support end to achieve deformation control of the large opening structure.

2. The method according to claim 1, characterized in that: In step one, the specific process is as follows: 1.

1. Extract the large opening structure based on the actual large opening cabin 3D model, remove the parts that have no effect on the structural simulation analysis results in the large opening cabin model, simplify the tiny features, and complete the establishment of a high-fidelity finite element simulation model of the large opening structure; 1.2, according to the actual working conditions of the large opening structure, set different analysis steps to simulate the assembly process of the large opening structure, divide the grid, set the load and boundary conditions in turn, and perform finite element simulation analysis and calculation of the large opening structure after completing the model condition setting; 1.

3. After the simulation is completed, the deformation and stress distribution data of the opening frame are extracted, and the surface variance R of the contact end surface with the conformal tooling is calculated. 2 , the expression is as follows; Where {Δu i }={u′ i }-{u i },{u′ i } is the displacement of node i, {u i } is the rigid body displacement of node i, N is the number of control nodes corresponding to the local area; in the calculation, the actual displacement of node i {u′ i } is obtained through finite element analysis, the rigid body displacement {u i }It is obtained by solving and calculating its translation and rotation; 1.4, select the horizontal right side as the 0° direction, divide the opening frame into regions along the directions of 45°, 135°, 225° and 315°, calculate the surface variance of the divided local areas respectively, so as to quantitatively characterize the degree of elastic deformation under actual working conditions, compare the deformation results of the local areas equidistant in the four directions, and select the local area with the largest surface variance as the positioning support position of the shape-preserving tooling.

3. The method according to claim 2, characterized in that: In step 2, the specific process is as follows: 2.

1. Establish an optimizable finite element analysis model of the conformal fixture, analyze the design domain and non-design domain of the structure, take the positioning support end of the conformal fixture for the large opening cabin structure as the non-design domain, and the main structure as the design domain, and define the boundary conditions and external loads; 2.2, taking the strain energy of the structure as the optimization target, considering the deformation and quality requirements, imposing the upper limit of the surface variance and volume constraints in the conformal area, and using the solid isotropic material penalty method to perform structural topology optimization; 2.

3. After the optimization is completed, the tooling optimization model is exported. First, the topology optimization results are sliced ​​to obtain the cross-sectional curve, which is then fitted using a straight line. Then, considering the manufacturability of the structure, the hollow truss structure is selected to fit the tooling shape to obtain the preliminary reconstruction result. 2.

4. After the reconstruction is completed, the model is imported, meshed, materials, sections, specified sections, boundary conditions and loads are defined in sequence. The reconstructed model is statically analyzed using Abaqus software to verify the static strength of the conformal tooling.

4. The method according to claim 3, characterized in that: in step 4, the specific process is as follows: 4.1, the positioning support end of the reconstructed shape-keeping tooling is designed as an adjustable mechanism, and the force control axis is selected at the end of the support point; 4.

2. Design orthogonal simulation to simulate the deformation of the opening frame in the large opening cabin structure under different loads, obtain the contact force between the positioning support end face and the opening frame and the deformation of the positioning support end face, and calculate the surface variance of the positioning support end face of the conformal tooling; 4.3, based on the acquired data, a mathematical model is established using the least squares regression method with the surface variance of the positioning support end face as the independent variable and the contact force between the positioning support structure and the opening frame as the dependent variable.

5. The method according to claim 4, characterized in that: in step 5, the process is as follows: 5.

1. Use the instrument to perform an all-round scan of the large opening structure and conformal tooling to be measured, and switch multiple scanning modes to scan different areas to obtain the three-dimensional point cloud data of the structure. Use the adaptation software to perform three-dimensional reconstruction of the scanned point cloud data to obtain the scanned three-dimensional model of the large opening structure and conformal tooling; 5.

2. Import the 3D digital model of the structure into the measurement software, match the coordinate system between the 3D digital model and the 3D model obtained by scanning after loading, analyze the deviation between the two, and use it as the position error of the positioning support end of the conformal tooling, so as to calculate the surface variance of the area; 5.

3. Based on the mathematical model between the surface variance of the positioning support end of the conformal tooling and the contact force between it and the conformable structure, the surface variance obtained by scanning calculation is used as input to calculate the force required for the conformal adjustment of the adjustable end of the conformal tooling. By manually or automatically adjusting the adjustable end, the contact force between the positioning support end surface of the conformal tooling and the conformal surface of the large opening cabin structure meets the requirements; 5.

4. After the conformal tooling is adjusted, repeat steps 5.1-5.3 and perform multiple feedback adjustments until the deformation of the conformal surface of the large opening cabin structure is reduced by 30% compared to before adjustment.

6. The method according to claim 5, characterized in that: The mathematical model of the solid isotropic material penalty method is as follows: Where i is the unit number, ρ is the design variable, K, U, F are the overall stiffness matrix, displacement vector and external force vector respectively, u and k are the stiffness matrix and displacement vector of a single unit respectively, C represents the total strain energy of the structure, v i Represents the volume of the corresponding unit, V0 is the design volume of the total volume, R 2 represents the surface variance of the local area, Represents the local area surface variance before optimization.

7. The method according to claim 6, characterized in that: In 1.1, the parts that are not affected include: bolts and skin.

8. The method according to claim 7, characterized in that: In 1.1, small features include: chamfers and holes.

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