Method for analyzing assembly precision of thin-wall closed structure

Abstract

The invention discloses a thin-wall closed structure assembly precision analysis method. The assembly precision analysis method comprises the following steps: analyzing a deviation transfer rule in the assembly process of wallboards (11), and solving the assembly accumulated deviation of each wallboard before closed assembly; key deviation parameters of the thin-wall closed structure (1) are extracted, and the torsion center coordinates of the thin-wall closed structure with deviation are deduced according to the torsion center definition of the thin-wall closed structure; solving the equivalent load of the torsion center of the thin-wall closed structure according to the assembly accumulated deviation of each wall plate and the static balance condition; based on the torsion center property of the thin-wall closed structure, establishing a constrained torsion differential equation of the thin-wall closed structure expressed by a torsion rate; solving the constraint torsion differential equation, deducing the end face node buckling deformation of the thin-wall closed structure according to the torsion center, superposing the end face node buckling deformation data with the assembly accumulated deviation of each wallboard before closing, and calculating the geometric accuracy index of the thin-wall closed structure, thereby achieving the analysis and prediction of the assembly accuracy of the thin-wall closed structure.

Description

Technical Field

[0001] The invention relates to a flexible structure assembly geometric accuracy analysis method, in particular to a thin-wall closed structure assembly accuracy analysis method. Background Art

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

[0003] The closed thin-walled structure is assembled by welding multiple wall panels. Affected by the initial deviation and assembly deformation, there are cumulative deviations before the final closed assembly. During the closed assembly, the accumulated deviation of the assembly causes the deformation of the closed structure. The weak rigidity of the thin-walled structure leads to the redistribution of the displacement of each point after closure, which eventually forms the assembly deviation of the closed structure. At the same time, the center of the geometric accuracy feature of the wall panel parts is on the boundary of the wall panel, such as the verticality of the assembly edge. After the closed assembly, the position of the center of the geometric accuracy feature is transferred from the boundary of the wall panel to the structural center of the closed loop segment, such as roundness and cylindricity. The transfer of geometric accuracy evaluation indicators and their characteristic centers makes it difficult to establish the correlation between the geometric accuracy of components and the geometric accuracy of the closed structure, and the closed assembly accuracy is difficult to analyze and control.

[0004] However, current assembly deviation transfer and geometric accuracy analysis methods, such as the deviation flow method and the state space method, all focus on the continuous assembly process of multiple parts. They are unable to consider the overall coordinated deformation and geometric accuracy feature center transfer problems during closed assembly, and are difficult to apply to the deviation transfer analysis of the entire assembly process from open wall panels to closed ring segments. Summary of the invention

[0005] The purpose of the present invention is to provide a method for analyzing the assembly accuracy of a thin-walled closed structure, which can realize the analysis and prediction of the assembly accuracy of the thin-walled closed structure.

[0006] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

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

[0008] The assembly accuracy analysis method comprises:

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

[0010] S2, based on the previous deviation analysis results, extract the key deviation parameters of the thin-walled closed structure, and derive the torsion center coordinates of the thin-walled closed structure with deviation according to the definition of the torsion center of the thin-walled closed structure;

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

[0012] S4, solve the constrained torsion differential equation, derive the warping deformation of the end face node of the thin-walled closed structure according to the torsion center, superimpose the warping deformation data of the end face node with the cumulative deviation of each wall panel assembly before closure, and calculate the geometric accuracy index of the thin-walled closed structure to achieve analytical prediction of the assembly accuracy of the thin-walled closed structure.

[0013] Furthermore, the deviation transmission law of the wall panel assembly process is analyzed to solve the cumulative deviation of each wall panel assembly before closed assembly. The specific implementation method includes: establishing a unified characterization method for dimensional deviation and assembly deformation according to 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 method for deriving the torsion center coordinates of the thin-walled closed structure with deviation includes:

[0015] S21, select a point A' at random on the end surface of the thin-walled closed structure. The coordinates of the point A' are (x a′ ,y a′ ), select a starting point at any point on the end surface of the thin-walled closed structure, and then calculate the sector coordinates ω′ and the sector inertia product I with A′ as the pole ω′x and I ω′y :

[0016]

[0017]

[0018]

[0019] Where ψ is the torsion function, h′ is the distance from the tangent line at any point on the end surface 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 )’s geometric relationship:

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

[0022] in, In this way, 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 gives:

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

[0026] When the thin-walled closed structure is only torsionally twisted by torque, the end face fan normal stress will not form a moment on the x-axis and y-axis, so:

[0027]

[0028] The fan coordinates are expressed as:

[0029]

[0030] S23, based on the above formula, 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 constrained torsion differential equation of the thin-walled closed structure expressed by torsion is established, and its specific implementation method includes:

[0033] S31, derive the fan stress and moment during constrained torsion, characterize the internal torque of constrained torsion with torsion rate and warping function, and establish the basic equation of constrained torsion in closed loop segment;

[0034] S32, based on the properties of the torsion center, that is, 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 for constrained torsion of the closed loop segment is constructed using a single parameter torsion rate;

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

[0036] Furthermore, the analysis and prediction of the assembly accuracy of the thin-walled closed structure is specifically implemented by:

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

[0038] S42, according to the constrained torsion differential equation and the external torque on the torsion center, solve the end face torsion angle after springback, and according to the relationship between the torsion center and the end face node warping deformation, solve the node on the end face that is at a distance h from the torsion center;

[0039] S43, superimposes the closed warping deformation and the cumulative deviation solved by the deviation transfer model to obtain the overall deviation of the closed assembly of the thin-walled closed structure, establishes and solves the accuracy index according to the geometric characteristics of the thin-walled closed structure, and realizes the prediction and analysis of the assembly accuracy of the thin-walled closed structure.

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

[0041] Compared with the prior art, the assembly accuracy analysis method of the present invention has the following beneficial effects:

[0042] The assembly accuracy analysis method of the present invention is a torsion center mapping method of assembly deviation under coordinated deformation of closed structures, which solves the torsion center of the end face of the closed structure with deviation, derives the torsion center load and constraint torsion differential equation of the closed assembly of the thin-walled closed structure, and constructs a mapping model between the accumulated deviation of the part assembly and the geometric accuracy of the closed assembly. A geometric accuracy analysis method is formed under which the characteristic center of the closed assembly process of the thin-walled closed structure is transferred from the part boundary to the assembly center, and the geometric accuracy prediction and deviation analysis of the closed thin-walled structure assembly are realized. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0044] Figure 2 The schematic diagram of the assembly accuracy analysis method of the present invention is shown in FIG.

[0045] Figure 3 A schematic diagram of a torsion center of a thin-walled closed structure in an embodiment of the present invention;

[0046] Figure 4 A schematic diagram of a torsion center of a thin-walled closed structure with deviation in an implementation case of the present invention;

[0047] Figure 5 It is a schematic diagram of a closed assembly process in an implementation case of the present invention. DETAILED DESCRIPTION

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

[0049] This embodiment provides a method for analyzing the assembly accuracy of a thin-walled closed structure. The method for analyzing the assembly accuracy can realize the analysis and prediction of the assembly accuracy of a thin-walled closed structure 1 .

[0050] See also Figure 1 It should be noted that the thin-walled closed structure 1 mentioned in the present embodiment is a closed ring segment structure formed by a plurality of wall panels 11 being enclosed and 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 where an enclosed closed edge of the entire thin-walled closed structure 1 is located. Figure 1 The edge indicated by arrow A1.

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

[0053] S1, analyzing the deviation transmission law of the wall panel 11 assembly process, solving the cumulative deviation of each wall panel 11 before closed assembly, and using it as input data for closed assembly accuracy analysis.

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

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

[0056] It should be noted that

[0057] The dimensional deviation includes the circumferential dimensional tolerance of the wall panel 11 and the verticality tolerance of the assembly edge;

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

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

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

[0061] S21, select a point on the end surface of the thin-walled closed structure 1, represented by A', the coordinates of the point A' are (x a′ ,y a′ ), select any starting point on the end surface of the thin-walled closed structure 1, and then calculate the fan coordinates ω′ and the fan inertia product I with A′ as the pole ω′x and I ω′y :

[0062]

[0063]

[0064]

[0065] Wherein, ψ is the torsion function, h′ is the distance from the tangent line of any point on the end surface 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 )’s geometric relationship:

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

[0068] in, In this way, 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 gives:

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

[0072] When the thin-walled closed structure 1 is only twisted by torque, the end face fan-shaped normal stress will not form a moment on the x-axis and y-axis, so:

[0073]

[0074] The fan coordinates are expressed as:

[0075]

[0076] S23, combining the above formula (i.e., the sector coordinate ω and the 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 torsion center coordinates of the thin-walled closed structure 1 with deviation are derived.

[0079] S3, according to the "deformation coordination" theory, the equivalent load of the torsion 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 torsion center properties of the thin-walled closed structure 1, the constrained torsion differential equation of the thin-walled closed structure 1 expressed in torsion is established.

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

[0081] The method for establishing the constrained torsion differential equation of the thin-walled closed structure 1 expressed by torsion specifically includes steps S31 to S33.

[0082] S31, when the thin-walled closed structure 1 is subjected to constrained torsion deformation, the end face cannot bend freely, and there is positive stress inside, which causes the structure to bend, further generating bending shear stress, forming additional torque, i.e., secondary torque. When the thin-walled closed structure 1 is constrained to torsion, the internal torque is obtained by superimposing the free torsion torque and the secondary torque. Based on this, the fan-shaped stress and moment during constrained torsion are derived, and the internal torque of constrained torsion is characterized by torsion rate and warping function, and the basic equation of closed segment constrained torsion is established.

[0083] S32, there are two parameters in the basic equation of constrained torsion, namely the warping function and the torsion rate. According to the property of the torsion center, that is, 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 constrained torsion in a closed loop segment is constructed using a single parameter, the torsion rate.

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

[0085] S4, solving the constrained torsion differential equation of the thin-walled closed structure 1 established in step S3, deriving the warping deformation of the end face nodes of the thin-walled closed structure 1 according to the torsion center, superimposing the end face node warping deformation data with the cumulative assembly deviation of each wall panel 11 before closing and calculating the geometric accuracy index of the thin-walled closed structure 1, so as 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 a method comprising steps S41 to S43.

[0087] S41, the closed assembly of the ring segment goes through the stage of shape correction-springback, and the cumulative deviation shape correction of the previous parts at the end of the assembly generates corresponding forces and moments. According to the deformation coordination and static equilibrium conditions of the springback process, the closed assembly load is equivalent to the torsion center, and the external moment of the torsion center is solved.

[0088] S42, according to the constrained torsion differential equation constructed in the previous step S3 and the external torque on the torsion center obtained by solving the step S41, the end face torsion angle after springback is solved. According to the relationship between the torsion center and the warping deformation of the end face node, the warping deformation of the node on the end face that is at a distance h from the torsion center is solved.

[0089] S43, superimposing the closed warping deformation and the accumulated deviation solved by the deviation transfer model, obtaining the overall deviation of the closed assembly of the thin-walled closed structure 1, establishing and solving the accuracy index according to the geometric characteristics of the thin-walled closed structure 1, and realizing the prediction and analysis of the assembly accuracy of the thin-walled closed structure 1.

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

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

[0092] The assembly accuracy analysis method of this embodiment is a torsion center mapping method of assembly deviation under coordinated deformation of closed structures. It solves the torsion center of the end face of the closed structure with deviation, derives the torsion center load and constraint torsion differential equation of the closed assembly of the thin-walled closed structure 1, and constructs a mapping model between the cumulative deviation of the part assembly and the geometric accuracy of the closed assembly. A geometric accuracy analysis method is formed under which 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, and the geometric accuracy prediction and deviation analysis of the closed thin-walled structure assembly are realized, which provides 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 present invention. Figures 3 to 5 .

[0094] (Corresponding to step S1) analyzing the deviation transmission law of the wall panel assembly process, solving the cumulative deviation of each wall panel assembly before closed assembly, as the input of closed assembly accuracy analysis;

[0095] According to the geometric characteristics of the wall panels, a unified characterization method for dimensional deviation and assembly deformation is established, and an assembly deviation transmission chain is established based on the wall panel assembly sequence to solve the cumulative deviation at the end of the continuous assembly of the wall panels. The dimensional deviation in this embodiment includes the circumferential dimension tolerance of the wall panels and the verticality tolerance of the assembly edge. The assembly deformation is the deformation caused by the welding assembly between the wall panels. The unified characterization method for the deviation and deformation is the small displacement screw method. The input parameters for the closed assembly accuracy analysis are the three translation components and three rotation components of the cumulative deviation at the end of the assembly [uv wαβγ] T .

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

[0097] The solution of the torsion center coordinates of a thin-walled closed structure with deviation includes the following steps:

[0098] (corresponding to step S21) Figure 4 As shown in the figure, the curvature of each wall panel remains unchanged, the center of the circle and the center angle have initial deviations, and the center of the standard end face is used as the coordinate origin, and the line connecting the starting end of wall panel 1 and the center of the circle is used as the y-axis to establish a closed structure end face coordinate system with deviations. Taking the end face of wall panel 1 of the thin-walled closed structure assembled by 6 wall panels as an example, the initial deviation of the wall panel is calculated using the center coordinate (x o1 ,y o1 ), the center angle α1, the angle α between the starting point and the center of the circle and the y-axis in the global coordinate system 01 It indicates that each parameter is related to the characteristic deviation solved during the panel assembly process, so it can be expressed as follows using the circumferential s coordinate:

[0099]

[0100] Where r is the radius of the arc on the end face of the wall panel. Similarly, the coordinates of the center of each circle are recorded as (x oi ,y oi ), the central angle is α i , the angle between the starting point and the center of the circle and the y-axis is α 0i , where i = 1, 2, ..., 6, then the other five panels are expressed in s coordinates as follows:

[0101]

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

[0103]

[0104] Therefore, the end faces have:

[0105]

[0106] Where s0=0.

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

[0108]

[0109] Therefore, the closed structural area enclosed by the center lines of the six wall panels is for:

[0110]

[0111] The torsion function is:

[0112]

[0113] therefore:

[0114]

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

[0116]

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

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

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

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

[0121] M z =M f +M ω

[0122] Among them, M f is the free torsion torque, and M ω The secondary torque generated by the constrained torsion.

[0123] For a thin-walled closed structure with 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:

[0129] σ z =Eε z =-Eθ′ω

[0130] Therefore, the fan normal stress is:

[0131] σ ω =-Eθ′ω

[0132] The fan-shaped normal stress in the constrained torsion will produce corresponding internal forces, namely double moments, which can be written as:

[0133]

[0134] in is the end face sector moment of inertia.

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

[0136]

[0137] Then the basic equation of constrained torsion of thin-walled closed structure can be written as:

[0138]

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

[0140]

[0141] The total shear stress is therefore:

[0142]

[0143] Will Substituting the above formula, the total shear stress can be obtained as:

[0144]

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

[0146]

[0147] Note the polar moment of inertia of the end face about the torsion center And there is and therefore:

[0148]

[0149] remember Then the warping function θ can be expressed by the rotation angle It is expressed as:

[0150]

[0151] (Corresponding to step S33) When the thin-walled closed structure is subjected to external load, the microelement of height dz is taken. According to the static equilibrium condition, the relationship between the external torque and the end torque can be written as:

[0152]

[0153] Therefore, the basic equation of constrained torsion of thin-walled closed structures can be differentiated as follows:

[0154]

[0155] Substituting into the θ expression we get:

[0156]

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

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

[0159] The steps of thin-walled closed structure assembly accuracy analysis include:

[0160] (Corresponding to step S41) According to the cumulative deviation and structural stiffness before closure, it can be obtained:

[0161] F1=K1V1

[0162] M1=K2V2

[0163] Where V1 = [uvw] T is the deviation translation component, V2=[αβγ] T is the deviation rotation component, K1 and K2 are the stiffness matrices corresponding to the translational and rotational degrees of freedom, respectively. After rebound, the deformation coordination condition can be used to obtain the rebound force / torque with the same magnitude and opposite direction, such as Figure 5 As shown, the deformation coordination condition is 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 formed after the static equilibrium condition is equivalent to the torsion 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 torsion angle can be obtained by solving the differential equation through the ring segment constraint boundary conditions , and further solve the warping deformation of the node on the end face with a distance h from the torsion center according to the torsion center and warping formula. Let the distance h from the i-th node to the torsion center be i , the warping deformation is w i , then the deformation of the point after closed coordination is:

[0169]

[0170] (Corresponding to step S43) According to the node deviation and the accumulated deviation before closing, the deviation after the closed assembly coordinated deformation is solved, that is:

[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, the geometric accuracy indicators such as the end face roundness, cylindricity and axis perpendicularity of the thin-walled closed structure are obtained through fitting, and the deviation feature center is transferred from the boundary to the closed center.

[0173] The above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope 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 segment structure formed by enclosing and connecting wall panels (11); Features: The assembly accuracy analysis method comprises: S1, analyzing the deviation transmission law of the wall panel (11) assembly process, solving the cumulative assembly deviation of each wall panel (11) before closed assembly, and using it as input data for closed assembly accuracy analysis; S2, based on the previous deviation analysis results, 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) containing the deviation according to the definition of the torsion center of the thin-walled closed structure (1); S3, solving the equivalent load of the torsion center of the thin-walled closed structure (1) based on the cumulative deviation of the assembly of each wall panel (11) and the static equilibrium condition; based on the torsion center property of the thin-walled closed structure (1), establishing the constrained torsion differential equation of the thin-walled closed structure (1) expressed by the torsion rate; S4, solving the constrained torsion differential equation, deriving the warping deformation of the end face node of the thin-walled closed structure (1) according to the torsion center, superimposing the warping deformation data of the end face node with the cumulative assembly deviation of each wall panel (11) before closure, and calculating the geometric accuracy index of the thin-walled closed structure (1), so as to 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 of 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 for 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 the 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 method for deriving the torsion center coordinates of the thin-walled closed structure (1) containing deviations comprises: S21, select any pole A' on the end surface of the thin-walled closed structure (1), the coordinates of the pole A' are (x a′ ,y a′ ), select any starting point on the end surface of the thin-walled closed structure (1), and then calculate the sector coordinates ω′ and the sector inertia product I with A′ as the pole ω′x and I ω′y : Where ψ is the torsion function, h′ is the distance from the tangent line at any point on the end surface 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 )’s geometric relationship: h=h′+(x a′ -x a )sinα-(y a′ -y a )cosα in, In this way, the above formula can be written as: hds=h′ds+(x a′ -x a )dy-(y a′ -y a )dx Integrating both sides gives: ω=ω′+(x a′ -x a )y-(y a′ -y a )x+C When the thin-walled closed structure (1) is only subjected to torque, the end face fan-shaped normal stress will not form a moment on the x-axis and y-axis, so: The fan coordinates are expressed as: S23, based on the above formula, 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 method for establishing the constrained torsion differential equation of the thin-walled closed structure (1) expressed by torsion includes: S31, derive the fan stress and moment during constrained torsion, characterize the internal torque of constrained torsion with torsion rate and warping function, and establish the basic equation of constrained torsion in closed loop segment; S32, based on the properties of the torsion center, that is, 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 for constrained torsion of the closed loop segment is constructed using a single parameter torsion rate; S33, according to the external load on the thin-walled closed structure (1), take the structural microelement, derive the relationship between the external torque and the end torque from the static equilibrium condition, differentiate the basic equation of constrained torsion of the closed loop segment, and establish the constrained 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 analysis and prediction of the assembly accuracy of the thin-walled closed structure (1) is specifically implemented by: S41, the closed assembly of the ring segment goes through the stage of shape correction-springback. The cumulative deviation shape correction of the previous parts at the end of the assembly generates corresponding forces and moments. According to the deformation coordination and static equilibrium conditions of the springback process, the closed assembly load is equivalent to the torsion center, and the external moment of the torsion center is solved; S42, according to the constrained torsion differential equation and the external torque on the torsion center, solve the end face torsion angle after springback, and according to the relationship between the torsion center and the end face node warping deformation, solve the node on the end face that is at a distance h from the torsion center; S43, superimposing the closed warping deformation and the accumulated deviation solved by the deviation transfer model, obtaining the overall deviation of the closed assembly of the thin-walled closed structure (1), establishing and solving the accuracy index according to the geometric characteristics of the thin-walled closed structure (1), and realizing 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 indexes of the thin-walled closed structure (1) include end face roundness, cylindricity and / or axis verticality.

Images