Assembly accuracy analysis method for thin-walled closed structures

Abstract

This invention discloses a method for analyzing the assembly accuracy of a thin-walled closed structure. The method includes: analyzing the deviation transmission law during the assembly process of the wall panel (11), and solving for the cumulative deviation of each wall panel assembly before closure; extracting key deviation parameters of the thin-walled closed structure (1), and deriving the coordinates of the torsion center of the thin-walled closed structure with deviations based on the definition of the torsion center; solving for the equivalent load of the torsion center of the thin-walled closed structure based on the cumulative deviation of each wall panel assembly and static equilibrium conditions; establishing a constrained torsion differential equation of the thin-walled closed structure expressed in terms of torsion rate based on the properties of the torsion center; solving the constrained torsion differential equation, deriving the warping deformation of the end face nodes of the thin-walled closed structure based on the torsion center, superimposing the warping deformation data of the end face nodes with the cumulative deviation of each wall panel assembly before closure, and calculating the geometric accuracy index of the thin-walled closed structure to achieve the analysis and prediction of the assembly accuracy of the thin-walled closed structure.

Description

Technical Field

[0001] This invention relates to a method for analyzing the geometric accuracy of flexible structure assembly, and more particularly to a method for analyzing the assembly accuracy of thin-walled closed structures. Background Technology

[0002] Closed thin-walled structures are important components of aerospace structures such as rocket fuel tanks. They bear huge static and dynamic loads during product service. The assembly precision of high-load closed thin-walled structures directly determines the service performance of aerospace products.

[0003] The closed thin-walled structure is assembled from multiple welded panels. Due to initial deviations and assembly deformations, cumulative deviations exist before final closure. During closure assembly, these cumulative deviations cause deformation of the closed structure. The weak rigidity of the thin-walled structure leads to a redistribution of displacements at various points after closure, ultimately resulting in assembly deviations. Simultaneously, the geometric accuracy feature centers of the panel components, such as the perpendicularity of the assembly edges, are located on the panel boundaries. After closure assembly, the location of these feature centers shifts from the panel boundaries to the structural center of the closed loop segment, such as roundness and cylindricity. The shift in geometric accuracy evaluation indicators and their feature centers makes it difficult to establish a correlation between the geometric accuracy of components and the geometric accuracy of the closed structure, making the analysis and control of closed assembly accuracy challenging.

[0004] However, current assembly deviation transmission and geometric accuracy analysis methods, such as the deviation flow method and the state space method, are all focused on the continuous assembly process of multiple parts. They cannot consider the overall coordinated deformation and geometric accuracy feature center transfer problem when the assembly is closed, and are therefore difficult to apply to the deviation transmission analysis of the entire assembly process from open wall panels to closed loop segments. Summary of the Invention

[0005] The purpose of this invention is to provide a method for analyzing the assembly accuracy of thin-walled closed structures, which can analyze and predict the assembly accuracy of thin-walled closed structures.

[0006] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution:

[0007] A method for analyzing the assembly accuracy of a thin-walled closed structure, wherein the thin-walled closed structure is a closed ring structure formed by the connection and enclosure of wall panels;

[0008] The assembly accuracy analysis method includes:

[0009] S1, analyze the deviation transmission law in the wall panel assembly process, solve the cumulative deviation of each wall panel assembly before the closed assembly, and use it as input data for the closed assembly accuracy analysis;

[0010] S2. Based on the results of the previous deviation analysis, the key deviation parameters of the thin-walled closed structure are extracted, and the coordinates of the torsion center of the thin-walled closed structure with deviation are derived according to the definition of the torsion center of the thin-walled closed structure.

[0011] S3, solve for the equivalent load at the torsional center of the thin-walled closed structure by the cumulative assembly deviation of each panel and the static equilibrium condition; based on the properties of the torsional center of the thin-walled closed structure, establish the constrained torsional differential equation of the thin-walled closed structure in terms of torsion rate;

[0012] S4. Solve the constraint torsion differential equation, derive the end face node warping deformation of the thin-walled closed structure based on the torsion center, superimpose the end face node warping deformation data with the cumulative deviation of each wall panel assembly before closure, and calculate the geometric accuracy index of the thin-walled closed structure to realize the analysis and prediction of the assembly accuracy of the thin-walled closed structure.

[0013] Furthermore, the method for analyzing the deviation transmission law in the wall panel assembly process and solving the cumulative deviation of each wall panel assembly before closed assembly includes: establishing a unified characterization method for dimensional deviation and assembly deformation based on the geometric characteristics of the wall panel, establishing an assembly deviation transmission chain based on the wall panel assembly sequence, and solving the cumulative deviation at the end of continuous wall panel assembly.

[0014] Furthermore, the specific method for deriving the torsional center coordinates of the deviated thin-walled closed structure includes:

[0015] S21, arbitrarily select a pole A′ on the end face of the thin-walled closed structure. The coordinates of pole A′ are (x... a′ ,y a′ Take any starting point on the end face of the thin-walled closed structure, and then calculate the sector coordinates ω′ with A′ as the pole and the sector inertial product I. ω′x and I ω′y :

[0016]

[0017]

[0018]

[0019] In the formula, ψ is the torsion function, h′ is the distance from the tangent at any point on the end face of the thin-walled closed structure to the pole A′, and t is the thickness of the thin-walled closed structure;

[0020] S22, Establish the pole A′ and the torsion center A(x) a ,y a Geometric relationship:

[0021] h=h′+(x a′ -x a sinα-(ya′ -y a cosα

[0022] in, Therefore, the above formula can be written as:

[0023] hds=h′ds+(x a′ -x a )dy-(y a′ -y a )dx

[0024] Integrating both sides, we get:

[0025] ω=ω′+(x a′ -x a )y-(y a′ -y a )x+C

[0026] When a thin-walled closed structure is subjected only to torsion, the fan-shaped normal stress on the end face will not generate moments about the x and y axes. Therefore:

[0027]

[0028] Represented using sector coordinates:

[0029]

[0030] S23, Combining the above equations, the coordinates of the torsion center of the closed end face can be expressed by the coordinates of the pole A′ as follows:

[0031]

[0032] Furthermore, the specific method for establishing the constrained torsional differential equation of the thin-walled closed structure expressed in terms of torsion includes:

[0033] S31, derive the sector stress and moment under constrained torsion, characterize the internal torque of constrained torsion with torsion ratio and warping function, and establish the basic equation of constrained torsion of closed loop segment;

[0034] S32. Based on the properties of the torsion center, namely that the moment of shear stress about the torsion center is equal to the total torque, the relationship between the warping function and the torsion rate is derived, and the basic equation of closed-loop constrained torsion is constructed using the single parameter torsion rate.

[0035] S33. Based on the external load on the thin-walled closed structure, take the structural micro-element, derive the relationship between the external torque and the end face torque from the static equilibrium condition, differentiate the basic equation of the constrained torsion of the closed loop segment, and establish the constrained torsion differential equation.

[0036] Furthermore, the specific methods for analyzing and predicting the assembly accuracy of the thin-walled closed structure include:

[0037] S41, the closed assembly of the ring segment goes through the stage of correction-springback. The cumulative deviation correction at the end of the assembly of the preceding parts generates corresponding forces and moments. Based on the deformation coordination and static equilibrium conditions during the springback process, the load of the closed assembly is equivalent to the torsion center, and the external moment on the torsion center is solved.

[0038] S42, based on the constraint torsion differential equation and the external torque on the torsion center, solve for the end face torsion angle after springback; based on the warping deformation relationship between the torsion center and the end face node, solve for the warping deformation of the node on the end face that is a distance h from the torsion center.

[0039] S43, the cumulative deviation of the closed warping deformation and deviation transmission model is superimposed to obtain the overall deviation of the closed assembly of the thin-walled closed structure. Based on the geometric characteristics of the thin-walled closed structure, the accuracy index is established and solved to realize the prediction and analysis of the assembly accuracy of the thin-walled closed structure.

[0040] Furthermore, the assembly accuracy indicators of the thin-walled closed structure include end face roundness, cylindricity, and / or axis perpendicularity.

[0041] The assembly accuracy analysis method of the present invention has the following advantages over the prior art:

[0042] The assembly accuracy analysis method of this invention is a torsional center mapping method for assembly deviations under coordinated deformation of a closed structure. It solves for the torsional center of the end face of the closed structure containing deviations, derives the differential equations of torsional center load and constraint torsion for the closed assembly of a thin-walled closed structure, and constructs a mapping model between the cumulative deviation of part assembly and the geometric accuracy of the closed assembly. This forms a geometric accuracy analysis method where the characteristic center of the closed assembly process of a thin-walled closed structure is transferred from the part boundary to the assembly center, enabling the prediction and deviation analysis of the geometric accuracy of the closed thin-walled structure assembly. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the thin-walled closed structure involved in the assembly accuracy analysis method of the thin-walled closed structure of the present invention;

[0044] Figure 2 This is a schematic diagram illustrating the conceptual principle of the assembly accuracy analysis method of the present invention.

[0045] Figure 3 This is a schematic diagram of the torsion center of a thin-walled closed structure based on an embodiment of the present invention;

[0046] Figure 4 This is a schematic diagram of the torsion center of a thin-walled closed structure with deviation in one embodiment of the present invention;

[0047] Figure 5 This is a schematic diagram of a closed assembly process based on an embodiment of the present invention. Detailed Implementation

[0048] The present invention will be further illustrated below with specific embodiments:

[0049] This embodiment provides a method for analyzing the assembly accuracy of a thin-walled closed structure, which can analyze and predict the assembly accuracy of the thin-walled closed structure 1.

[0050] See Figure 1 It should be noted that the thin-walled closed structure 1 mentioned in this embodiment is a closed ring structure formed by several wall panels 11 being connected together in sequence.

[0051] It should be noted that the end face of the thin-walled closed structure 1 mentioned in this article refers to the plane containing the enclosing edge of the entire thin-walled closed structure 1. The "enclosing edge" is as follows: Figure 1 The edge indicated by the middle arrow A1.

[0052] See Figure 2 The assembly accuracy analysis method of this embodiment mainly includes the following steps S1 to S4.

[0053] S1, analyze the deviation transmission law in the assembly process of wall panel 11, and solve the cumulative deviation of each wall panel 11 before the closed assembly, which serves as the input data for the closed assembly accuracy analysis.

[0054] Specifically, step S1 is implemented by the following methods:

[0055] Based on the geometric characteristics of panel 11, a unified characterization method for dimensional deviation and assembly deformation is established. Based on the assembly sequence of panel 11, an assembly deviation transmission chain is established to solve the cumulative deviation at the end of continuous assembly of panel 11.

[0056] It should be noted that,

[0057] The dimensional deviations include the circumferential dimensional tolerances of the wall panel 11 and the perpendicularity tolerances of the assembly edges;

[0058] The assembly deformation refers to the deformation caused by welding assembly between the wall panels 11. The unified characterization method for dimensional deviation and assembly deformation includes, but is not limited to, the small displacement spin method.

[0059] S2, based on the results of the previous deviation analysis, that is, the cumulative deviation of each wall panel 11 before the closed assembly obtained in step S1, extract the key deviation parameters of the thin-walled closed structure 1, and derive the coordinates of the torsion center of the thin-walled closed structure 1 with deviation according to the definition of the torsion center of the thin-walled closed structure 1.

[0060] The specific process of deriving the torsion center coordinates of the deviated thin-walled closed structure 1 includes steps S21 to S23.

[0061] S21, arbitrarily select a pole on the end face of the thin-walled closed structure 1, denoted by A′, and the coordinates of this pole A′ are (x... a′ ,y a′ Take any starting point on the end face of the thin-walled closed structure 1, and then calculate the sector coordinates ω′ with A′ as the pole and the sector inertial product I. ω′x and I ω′y :

[0062]

[0063]

[0064]

[0065] In the formula, ψ is the torsion function, h′ is the distance from the tangent at any point on the end face of the thin-walled closed structure 1 to the pole A′, and t is the thickness of the thin-walled closed structure 1.

[0066] S22, Establish the pole A′ and the torsion center A(x) a ,y a Geometric relationship:

[0067] h=h′+(x a′ -x a sinα-(y a′ -y a cosα

[0068] in, Therefore, the above formula can be written as:

[0069] hds=h′ds+(x a′ -x a )dy-(y a′ -y a )dx

[0070] Integrating both sides, we get:

[0071] ω=ω′+(x a′ -x a )y-(y a′ -y a )x+C

[0072] When the thin-walled closed structure 1 is subjected to torsion only by torque, the fan-shaped normal stress on the end face will not generate moments about the x-axis and y-axis, therefore:

[0073]

[0074] Represented using sector coordinates:

[0075]

[0076] S23, combining the above equation (i.e., the sector coordinate ω and sector inertia product I in step S22) ωx The coordinates of the torsion center of the closed end face can be expressed by the coordinates of the pole A′ as follows:

[0077]

[0078] Thus, the coordinates of the torsion center of the thin-walled closed structure 1 with deviation are derived.

[0079] S3. Based on the "deformation coordination" theory, the equivalent load at the torsional center of the thin-walled closed structure 1 is solved by the cumulative assembly deviation of each wall panel 11 and the static equilibrium condition. Based on the torsional center properties of the thin-walled closed structure 1, the constrained torsional differential equation of the thin-walled closed structure 1 expressed in terms of torsion rate is established.

[0080] It should be noted that the "deformation coordination" theory is an existing theory.

[0081] The specific implementation method for establishing the constrained torsional differential equation of the thin-walled closed structure 1 expressed in terms of torsion includes steps S31 to S33.

[0082] S31, when the thin-walled closed structure 1 is subjected to constrained torsional deformation, its end face cannot warp freely, and there is normal stress inside, which causes the structure to bend, further generating bending shear stress and forming an additional torque, namely the secondary torque. The internal torque of the thin-walled closed structure 1 under constrained torsion is obtained by superimposing the free torsional torque and the secondary torque. Based on this, the sector stress and moment under constrained torsion are derived, and the internal torque under constrained torsion is characterized by the torsional rate and warping function, establishing the basic equation for constrained torsion of the closed loop segment.

[0083] S32, the basic equation for constrained torsion contains two parameters: warping function and torsion rate. Based on the properties of the torsion center, i.e., the moment of shear stress about the torsion center is equal to the total torque, the relationship between the warping function and the torsion rate is derived. The basic equation for constrained torsion of a closed loop is constructed using the single parameter torsion rate.

[0084] S33. Based on the external load on the thin-walled closed structure 1, take a structural element and derive the relationship between the external torque and the end face torque from the static equilibrium condition. Differentiate the basic equation of the constrained torsion of the closed loop segment and establish the constrained torsion differential equation.

[0085] S4. Solve the constraint torsion differential equation for the thin-walled closed structure 1 established in step S3. Derive the warping deformation of the end face nodes of the thin-walled closed structure 1 based on the torsion center. Superimpose the warping deformation data of the end face nodes with the cumulative assembly deviation of each wall panel 11 before closure and calculate the geometric accuracy index of the thin-walled closed structure 1 to realize the analysis and prediction of the assembly accuracy of the thin-walled closed structure 1.

[0086] The analysis and prediction of the assembly accuracy of the thin-walled closed structure 1 is specifically implemented by steps S41 to S43.

[0087] S41, the closed-loop assembly undergoes a shaping-springback stage. The cumulative deviation at the end of the preceding parts assembly generates corresponding forces and moments. Based on the deformation coordination and static equilibrium conditions during the springback process, the load on the closed assembly is equivalent to the torsion center, and the external moment acting on the torsion center is solved.

[0088] S42, based on the constrained torsion differential equation constructed in step S3, and the external torque on the torsion center obtained in step S41, solve for the end face torsion angle after springback. Based on the relationship between the torsion center and the warping deformation of the end face nodes, solve for the warping deformation of the nodes on the end face that are a distance h from the torsion center.

[0089] S43, the cumulative deviation of the closed warping deformation and deviation transmission model is superimposed to obtain the overall deviation of the closed assembly of the thin-walled closed structure 1. Based on the geometric characteristics of the thin-walled closed structure 1, the accuracy index is established and solved to realize the prediction and analysis of the assembly accuracy of the thin-walled closed structure 1.

[0090] It should be noted that the assembly accuracy indicators of the thin-walled closed structure 1 include, but are not limited to, the end face roundness, cylindricity, and axis perpendicularity of the closed ring segment.

[0091] The assembly accuracy analysis method of this embodiment has the following advantages:

[0092] The assembly accuracy analysis method in this embodiment is a torsional center mapping method for assembly deviations under coordinated deformation of a closed structure. It solves for the torsional center of the end face of the closed structure containing deviations, derives the differential equations of torsional center load and constraint torsion for the closed assembly of the thin-walled closed structure 1, and constructs a mapping model between the cumulative deviation of part assembly and the geometric accuracy of the closed assembly. This forms a geometric accuracy analysis method where the characteristic center of the closed assembly process of the thin-walled closed structure 1 is transferred from the part boundary to the assembly center, realizing the prediction and deviation analysis of the geometric accuracy of the closed thin-walled structure assembly, and providing a theoretical basis for further control of the assembly accuracy of the thin-walled closed structure 1.

[0093] The following is a specific implementation example to illustrate the concept of the invention. Please refer to [link / reference]. Figures 3 to 5 .

[0094] (Corresponding to step S1) Analyze the deviation transmission law in the wall panel assembly process, solve the cumulative deviation of each wall panel assembly before the closed assembly, and use it as the input for the closed assembly accuracy analysis.

[0095] Based on the geometric characteristics of the panel, a unified characterization method for dimensional deviations and assembly deformation is established. An assembly deviation transmission chain is established based on the panel assembly sequence to solve for the cumulative deviation at the end of continuous panel assembly. In this embodiment, dimensional deviations include circumferential dimensional tolerances of the panel and perpendicularity tolerances of the assembly edges. Assembly deformation refers to the deformation caused by welding between panel members. The unified characterization method for deviations and deformations is the small displacement screw method. The input parameters for closed assembly accuracy analysis are the three translational components and three rotational components [uv wαβγ] of the cumulative deviation at the assembly end. T .

[0096] (Corresponding to step S2) Based on the previous deviation analysis, extract the key deviation parameters of the thin-walled closed structure, and derive the coordinates of the torsion center of the thin-walled closed structure with deviation according to the definition of the torsion center of the closed structure.

[0097] The steps for solving the torsional center coordinates of a thin-walled closed structure with deviations include:

[0098] (Corresponding to step S21) as follows Figure 4 As shown, the curvature of each panel remains constant, and the center and central angle have initial deviations. A coordinate system for the deviated closed structure end face is established with the center of the standard end face as the origin and the line connecting the starting end of panel 1 and the center as the y-axis. Taking the end face of panel 1 of the thin-walled closed structure assembled from the six panels shown in the figure as an example, the initial deviation of the panel is represented by the center coordinate (x...). o1 ,y o1 ), central angle α1, and the angle α between the line connecting the starting point and the center of the circle and the y-axis in the global coordinate system. 01 This indicates that the parameters are related to the characteristic deviations solved during the panel assembly process; therefore, using the circumferential s-coordinate, it can be expressed as:

[0099]

[0100] In the formula, r is the radius of the arc on the end face of the wall panel. Similarly, the coordinates of each center are denoted as (x... oi ,y oi The central angle is α. i The angle between the line connecting the starting point and the center of the circle and the y-axis is α. 0i Where i = 1, 2, ..., 6, the other five wall panels are represented using s-coordinates as follows:

[0101]

[0102] (Corresponding to step S22) Taking the origin of the coordinate system as the pole A′ and the left end of the wall panel 1 as the starting point, the distance h′ from the top of the wall panel to the pole is expressed in s-coordinates as:

[0103]

[0104] Therefore, the end face has:

[0105]

[0106] Where s0 = 0.

[0107] (Corresponding to step S23) The area of ​​the closed structure formed by the line connecting the centerline of the end face of wall panel 1 and the origin of the coordinate system can be written as:

[0108]

[0109] Therefore, the area of ​​the closed structure enclosed by the centerlines of the six wall panels for:

[0110]

[0111] The torsion function is then:

[0112]

[0113] therefore:

[0114]

[0115] The sector coordinates of the end face with pole A′ are:

[0116]

[0117] By combining the above equations, the torsion center of the end face of the ring segment with deviation can be determined.

[0118] (Corresponding to step S3) Based on the deformation coordination process of the closed assembly, the equivalent load at the torsion center is solved by the cumulative deviation and static equilibrium conditions; based on the properties of the torsion center, the constraint torsion differential equation of the thin-walled closed structure expressed in terms of torsion rate is established.

[0119] The derivation of the constrained torsion differential equation for a thin-walled closed structure includes the following steps:

[0120] (Corresponding to step S31) The internal torque of a thin-walled closed structure under constrained torsion can be written as:

[0121] M z =M f +M ω

[0122] Where M f For free torsional torque, and M ω To constrain the secondary torque generated by torsion.

[0123] For a thin-walled closed structure constrained torsion, the warping formula can be written as:

[0124] w=-θ(z)ω(s)

[0125] Where θ(z) is the warping function.

[0126] Therefore, the axial strain of the thin-walled closed structure can be obtained as:

[0127]

[0128] The axial normal stress is then:

[0129] σ z =Eε z =-Eθ′ω

[0130] Therefore, the sector normal stress is:

[0131] σ ω =-Eθ′ω

[0132] In constrained torsion, sectorary normal stresses will generate corresponding internal forces, i.e., two moments, which can be written as:

[0133]

[0134] in For the end face sectoral moment of inertia.

[0135] Therefore, the secondary torque can be written as:

[0136]

[0137] The fundamental equation for the constrained torsion of a thin-walled closed structure can then be written as:

[0138]

[0139] (Corresponding to step S32) Derivation of total shear stress under constrained torsion. The relationship with θ. From the warping formula, the shear strain under constrained torsion is:

[0140]

[0141] Therefore, the total shear stress is:

[0142]

[0143] Will Substituting into the above equation, we can obtain the total shear stress as:

[0144]

[0145] Due to the properties of the torsional center, the moment of the shear stress about the torsional center is equal to the total torque M. z ,therefore:

[0146]

[0147] Let the polar moment of inertia of the end face at the center of torsion be... And there are and therefore:

[0148]

[0149] remember Then the warping function θ can be derived from the rotation angle. Represented as:

[0150]

[0151] (Corresponding to step S33) When a thin-walled closed structure is subjected to an external load, taking a small element with high dz, the relationship between the external torque and the end face torque can be written as follows based on the static equilibrium condition:

[0152]

[0153] Therefore, differentiating the fundamental equation for constrained torsion of a thin-walled closed structure yields:

[0154]

[0155] Substituting into the expression for θ, we get:

[0156]

[0157] This is the constrained torsional differential equation for a thin-walled closed structure.

[0158] (Corresponding to step S4) Solve the constraint torsion differential equation of the thin-walled closed structure, derive the warping deformation of the end face nodes based on the torsion center, superimpose it with the deviation before closure, and calculate the geometric accuracy index of the thin-walled closed structure to realize the assembly accuracy analysis of the thin-walled closed structure.

[0159] The steps for analyzing the assembly accuracy of thin-walled closed structures include:

[0160] (Corresponding to step S41) Based on the cumulative deviation and structural stiffness before closure, we can obtain:

[0161] F1=K1V1

[0162] M1 = K2V2

[0163] In the formula, V1 = [uvw] T For the translational component of the deviation, V2=[αβγ] T For the rotational component of the deviation, K1 and K2 are the stiffness matrices corresponding to the translational and rotational degrees of freedom, respectively. After springback, the springback force / torque, which are of the same magnitude but opposite in direction, can be obtained from the deformation compatibility condition, as follows: Figure 5 As shown, the deformation compatibility condition is therefore written as:

[0164] F1 = F2

[0165] M1 = M2

[0166] Since the rebound load acts on the boundary of the thin-walled closed structure, a new moment M is generated after the static equilibrium condition is equivalently converted to the torsional center. e2 ,in:

[0167] M e2i =M 2i +F 2i h i (i = α, β, γ).

[0168] (Corresponding to step S42) The thin-walled closed structure is subjected to an external torque M e2 The twist angle can be obtained by solving the differential equation through the boundary conditions of the loop segments. Furthermore, the warping deformation of the node on the end face at a distance h from the torsion center is solved using the torsion center and warping formula. Let h be the distance h from the torsion center of the i-th node. i Warped and deformed into w i Then the deformation after the point is closed and coordinated is:

[0169]

[0170] (Corresponding to step S43) Based on the cumulative deviation before closure, calculate the deviation after coordinated deformation of the closed assembly by superimposing the node deviations, i.e.:

[0171]

[0172] Where [v] xi v yi v zi ] T The cumulative deviation is solved by the node assembly deviation transfer model. Based on this, geometric accuracy indicators such as end face roundness, cylindricity, and axis perpendicularity of the thin-walled closed structure are obtained through fitting, realizing the transfer of the deviation characteristic center from the boundary to the closed center.

[0173] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for analyzing the assembly accuracy of a thin-walled closed structure, wherein the thin-walled closed structure (1) is a closed ring structure formed by the enclosure and connection of wall panels (11); Its features are: The assembly accuracy analysis method includes: S1, analyze the deviation transmission law of the wall panel (11) assembly process, solve the cumulative deviation of each wall panel (11) before the closed assembly, and use it as input data for the closed assembly accuracy analysis. S2, based on the results of the previous deviation analysis, extract the key deviation parameters of the thin-walled closed structure (1), and derive the coordinates of the torsion center of the thin-walled closed structure (1) with deviation according to the definition of the torsion center of the thin-walled closed structure (1); S3, solve the equivalent load at the torsional center of the thin-walled closed structure (1) by the cumulative assembly deviation of each wall panel (11) and the static equilibrium condition; based on the torsional center properties of the thin-walled closed structure (1), establish the constraint torsional differential equation of the thin-walled closed structure (1) in terms of torsion rate; S4, solve the constraint torsion differential equation, derive the end face node warping deformation of the thin-walled closed structure (1) based on the torsion center, superimpose the end face node warping deformation data with the cumulative assembly deviation of each wall plate (11) before closure and calculate the geometric accuracy index of the thin-walled closed structure (1), and realize the analysis and prediction of the assembly accuracy of the thin-walled closed structure (1).

2. The method for analyzing the assembly accuracy of a thin-walled closed structure according to claim 1, characterized in that: The method for analyzing the deviation transmission law of the wall panel (11) assembly process and solving the cumulative deviation of each wall panel (11) before closed assembly includes: establishing a unified characterization method of dimensional deviation and assembly deformation based on the geometric characteristics of the wall panel (11), establishing an assembly deviation transmission chain based on the assembly sequence of the wall panel (11), and solving the cumulative deviation at the end of continuous assembly of the wall panel (11).

3. The method for analyzing the assembly accuracy of a thin-walled closed structure according to claim 1, characterized in that: The specific method for deriving the torsional center coordinates of the deviated thin-walled closed structure (1) includes: S21, take any pole A′ on the end face of the thin-walled closed structure (1), and the coordinates of the pole A′ are (x a′ ,y a′ Take any starting point on the end face of the thin-walled closed structure (1), and then calculate the sector coordinates ω′ with A′ as the pole and the sector inertial product I. ω′x and I ω′y : In the formula, ψ is the torsion function, h′ is the distance from the tangent at any point on the end face of the thin-walled closed structure (1) to the pole A′, and t is the thickness of the thin-walled closed structure (1); S22, Establish the pole A′ and the torsion center A(x) a ,y a Geometric relationship: h=h′+(x a′ -x a )sinα-(y a′ -y a )cosα in, Therefore, the above formula can be written as: hds=h′ds+(x a′ -x a )dy-(y a′ -y a )dx Integrating both sides, we get: ω=ω′+(x a′ -x a )y-(y a′ -y a )x+C When the thin-walled closed structure (1) is subjected to torsion only by torque, the fan-shaped normal stress on the end face will not generate moments about the x-axis and y-axis, therefore: Represented using sector coordinates: S23, Combining the above equations, the coordinates of the torsion center of the closed end face can be expressed by the coordinates of the pole A′ as follows:

4. The method for analyzing the assembly accuracy of a thin-walled closed structure according to claim 1, characterized in that: The specific implementation method for establishing the constrained torsional differential equation of the thin-walled closed structure (1) expressed in terms of torsion includes: S31, derive the sector stress and moment under constrained torsion, characterize the internal torque of constrained torsion with torsion ratio and warping function, and establish the basic equation of constrained torsion of closed loop segment; S32. Based on the properties of the torsion center, namely that the moment of shear stress about the torsion center is equal to the total torque, the relationship between the warping function and the torsion rate is derived, and the basic equation of closed-loop constrained torsion is constructed using the single parameter torsion rate. S33. Based on the external load on the thin-walled closed structure (1), take the structural micro-element, derive the relationship between the external torque and the end face torque from the static equilibrium condition, differentiate the basic equation of the closed loop segment constraint torsion, and establish the constraint torsion differential equation.

5. The method for analyzing the assembly accuracy of a thin-walled closed structure according to claim 1, characterized in that: The specific methods for analyzing and predicting the assembly accuracy of the thin-walled closed structure (1) include: S41, the closed assembly of the ring segment goes through the stage of correction-springback. The cumulative deviation correction at the end of the assembly of the preceding parts generates corresponding forces and moments. Based on the deformation coordination and static equilibrium conditions during the springback process, the load of the closed assembly is equivalent to the torsion center, and the external moment on the torsion center is solved. S42, based on the constraint torsion differential equation and the external torque on the torsion center, solve for the end face torsion angle after springback; based on the warping deformation relationship between the torsion center and the end face node, solve for the warping deformation of the node on the end face that is a distance h from the torsion center. S43, superimpose the cumulative deviation of the closed warping deformation and deviation transmission model to obtain the overall deviation of the closed assembly of the thin-walled closed structure (1), establish and solve the accuracy index based on the geometric characteristics of the thin-walled closed structure (1), and realize the prediction and analysis of the assembly accuracy of the thin-walled closed structure (1).

6. The method for analyzing the assembly accuracy of a thin-walled closed structure according to claim 5, characterized in that: The assembly accuracy indicators of the thin-walled closed structure (1) include end face roundness, cylindricity and / or axis perpendicularity.

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