A method for predicting riveting deformation of thin-walled parts

Abstract

This invention discloses a method for predicting riveting deformation of thin-walled parts, specifically including the following steps: S1, constructing a single-nail riveting mechanical model; S2, constructing a riveting interference model; S3, constructing a prediction model. This invention relates to the technical field of riveting deformation prediction for thin-walled parts. This method calculates the maximum riveting force required for forming a standard-sized upsetting head using a mechanical model, coupled with a riveting interference model. After obtaining the dimensions of the upsetting head, rivet diameter, rivet hole diameter, thickness of the thin-walled part, and riveting pressure, it can effectively predict the deformation thickness of the thin-walled part, providing theoretical support for process optimization and quality control.

Description

Technical Field

[0001] This invention relates to the field of riveting deformation prediction technology for thin-walled parts, specifically to a method for predicting riveting deformation of thin-walled parts. Background Technology

[0002] Thin-walled parts are widely used in aerospace, automotive manufacturing, and other fields, and riveting is a common connection method. However, thin-walled parts are prone to deformation during riveting, which directly affects the workpiece's accuracy and performance. Ensuring controllable deformation during riveting is crucial for the high-performance use of thin-walled parts after riveting. To address this, a method for predicting riveting deformation of thin-walled parts is proposed. A mechanical model is built to calculate the maximum riveting force required for forming a standard-sized upset head. A riveting interference model is coupled, and after obtaining the dimensions of the upset head, rivet diameter, rivet hole diameter, thickness of the thin-walled part, and riveting pressure, the deformation thickness of the thin-walled part can be effectively predicted. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a method for predicting riveting deformation of thin-walled parts, thus solving the problems mentioned in the background section.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a method for predicting riveting deformation of thin-walled parts, specifically comprising the following steps:

[0005] S1. Construction of the mechanical model for single-nail riveting: Based on the mechanical behavior of the rivet during the riveting process, the mechanical equations of the riveting process are derived.

[0006] Among them, mechanical behavior includes the stress distribution and deformation characteristics of the rivet;

[0007] S2. Construction of Riveting Interference Model: Based on the size of the waist-shaped upsetting head, the diameter of the rivet rod, the diameter of the rivet hole, the thickness of the thin-walled part, and the riveting pressure, establish the mathematical relationship between the interference and the deformation of the thin-walled part;

[0008] S3. Prediction Model Construction: Couple the single-nail riveting mechanical model with the riveting interference model to form a prediction model for riveting deformation of thin-walled parts.

[0009] The present invention is further configured such that: the mechanical equations derived in S1 during the riveting process, when the drum-shaped pier head undergoes uniform deformation, include:

[0010] A1. Set the center position of the rivet's drum-shaped upsetting head as the origin O of the coordinate system, and define the direction of the rivet shank as the Z-axis. (Cylindrical coordinate system) ,in It is radial distance. Z is the azimuth, and Z is the altitude.

[0011] A set of equilibrium differential equations in the constructed cylindrical coordinate system:

[0012]

[0013] In the formula, The radial stress experienced by the rivet. The circumferential stress experienced by the rivet. and This represents the shear stress experienced by the rivet.

[0014] A2. The formula for calculating the riveting force during the forming of a waist-drum shaped upsetting head is as follows:

[0015]

[0016] In the formula, The riveting force is given by h1, where h1 is the height of the drum-shaped upsetting head, and R1 is the radius of the drum-shaped upsetting head. For riveting strain; The yield strength of the rivet.

[0017] The present invention is further configured such that: the mechanical equations derived in S1 during the riveting process, when the drum-shaped pier head undergoes uneven deformation, include:

[0018] B1. The formula for calculating the riveting force during the forming of the waist-drum shaped upsetting head is revised as follows:

[0019]

[0020] In the formula, de is the equivalent diameter of the waist drum-shaped upset head;

[0021] B2. Express the contour curve of the waist-drum shaped upsetting head using a function. The function expression is as follows:

[0022]

[0023] In the formula, , , The bottom diameter of the upsetting head is The maximum diameter of the upsetting head is The diameter of the upper end face of the upsetting head is , where x is the contour point function value of the drum-shaped upset head;

[0024] B3. After riveting is completed, calculate the equivalent diameter of the drum-shaped upsetting head. The calculation formula is as follows:

[0025] ;

[0026] B4. Obtain the maximum riveting force required to form a standard-sized pier head by combining the standard pier head dimensions, where the standard pier head dimensions are:

[0027]

[0028] In the formula, d is the diameter of the rivet.

[0029] The present invention is further configured such that: before forming the waist-drum shaped upsetting head, the waist-drum shaped upsetting head is divided into contact friction stress zones, wherein the contact friction stress zones include, from the outside to the inside, a constant friction coefficient zone and a friction stress decreasing zone, and the constant friction coefficient zone and the friction stress decreasing zone are coaxially arranged;

[0030] The diameter of the friction stress reduction zone is twice the height of the drum-shaped upsetting head, and the origin O of the coordinate system is located on the axis of the friction stress reduction zone.

[0031] The present invention is further configured such that: the method for establishing the mathematical relationship between the interference amount and the deformation of the thin-walled component in S2 includes:

[0032] C1. Using rivets to fix the upper and lower thin-walled parts, the upper thin-walled part deforms during the forming of the waist-drum shaped upsetting head. The calculation of the deformation thickness of the upper thin-walled part is as follows:

[0033]

[0034] In the formula, H1 is the deformation thickness of the upper thin-walled component, H1 is the sum of the minimum thicknesses of the upper and lower thin-walled components, t1 is the thickness of the upper thin-walled component, and t2 is the thickness of the lower thin-walled component.

[0035] Further information:

[0036] ;

[0037] Δ = (d1 - d0) ÷ d0 × 100%;

[0038] In the formula, d0 is the diameter of the rivet when the rivet hole is filled, d1 is the diameter of the rivet hole when the rivet shank material expands the rivet hole, h0 is the height of the rivet shank outside the rivet hole when the rivet shank material fills the rivet hole, and △ is the relative interference of the riveting.

[0039] C2. When the rivet contacts the hole wall, the volume of the rivet shank outside the rivet hole is equal to the volume of the upset head after it is formed. Since the rivet is uniformly upset during the deformation stage before contacting the rivet hole wall, according to the principle that the volume of the rivet shank material remains constant:

[0040]

[0041] In the formula, h is the rivet shank length and d is the rivet diameter;

[0042] C3. Combining C1 and C2, we can easily obtain:

[0043] .

[0044] This invention provides a method for predicting riveting deformation of thin-walled parts. It has the following beneficial effects:

[0045] This invention calculates the maximum riveting force required to form a standard-sized upsetting head using a mechanical model, and couples it with a riveting interference model. After obtaining the dimensions of the drum-shaped upsetting head, the diameter of the rivet rod, the diameter of the rivet hole, the thickness of the thin-walled part, and the riveting pressure, it can effectively predict the deformation thickness of the thin-walled part, providing theoretical support for process optimization and quality control. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the process of the present invention;

[0047] Figure 2 This is a schematic diagram of the cylindrical coordinate system in this invention;

[0048] Figure 3 This is a schematic diagram of the friction stress region distribution in this invention;

[0049] Figure 4 This is a schematic diagram showing the dimensions and outline of the rivet upsetting head in this invention;

[0050] Figure 5 This is a schematic diagram showing the dimensions of the rivet when the rivet hole is filled in this invention;

[0051] Figure 6 This is a schematic diagram of the rivet dimensions during the forming of the waist drum-shaped upsetting head in this invention. Detailed Implementation

[0052] The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention.

[0053] Please see Figure 1-6 The present invention provides the following technical solution: a method for predicting riveting deformation of thin-walled parts, specifically including the following steps:

[0054] S1. Construction of the mechanical model for single-nail riveting: Based on the mechanical behavior of the rivet during the riveting process, the mechanical equations of the riveting process are derived, where the mechanical behavior includes the stress distribution and deformation characteristics of the rivet.

[0055] The riveting process is essentially the process where the rivet is subjected to an impact load applied by a punch, forcing the rivet to deform. During riveting assembly, the riveting force is the primary external force, applied to the rivet by the punch. By analyzing the riveting force and deriving the relationship between the riveting force and the deformation of the rivet's upsetting head during the riveting process, a model relating the riveting force to the upsetting head dimensions is constructed. Since the rivet shank is a metal cylinder, the forming problem of the rivet's upsetting head can be solved as a local upsetting problem of a metal cylinder.

[0056] The uniform deformation of the waist-drum shaped abutment head includes:

[0057] A1. Set the center position of the rivet's drum-shaped upsetting head as the origin O of the coordinate system, as shown in the attached diagram. Figure 2 As shown, the direction of the rivet shank is defined as the Z-axis, and a cylindrical coordinate system is used. ,in It is radial distance. Z is the azimuth, and Z is the altitude.

[0058] A set of equilibrium differential equations in the constructed cylindrical coordinate system:

[0059]

[0060] In the formula, The radial stress experienced by the rivet. The circumferential stress experienced by the rivet. and This represents the shear stress experienced by the rivet.

[0061] A2, as attached Figure 3 As shown, before forming the drum-shaped upsetting head, the contact friction stress zone is divided into two parts. The contact friction stress zone includes a constant friction coefficient zone and a friction stress decreasing zone from the outside to the inside. The constant friction coefficient zone and the friction stress decreasing zone are set coaxially. The diameter of the friction stress decreasing zone is twice the height of the drum-shaped upsetting head, and the origin O of the coordinate system is located on the axis of the friction stress decreasing zone.

[0062] The formula for calculating the riveting force when forming a waist-drum shaped upsetting head is:

[0063]

[0064] In the formula, The riveting force is given by h1, where h1 is the height of the drum-shaped upsetting head, and R1 is the radius of the drum-shaped upsetting head. For riveting strain; The yield strength of the rivet.

[0065] When the drum-shaped abutment head deforms unevenly, it includes:

[0066] B1. The formula for calculating the riveting force during the forming of the waist-drum shaped upsetting head is revised as follows:

[0067]

[0068] In the formula, de is the equivalent diameter of the waist drum-shaped upset head;

[0069] B2. Because the upsetting head is shaped like a waist drum, its outline can be approximated as a parabola, as shown in the attached figure. Figure 4 As shown, the contour curve of the drum-shaped upsetting head is expressed by a function, and the function expression is:

[0070]

[0071] In the formula, , , The bottom diameter of the upsetting head is The maximum diameter of the upsetting head is The diameter of the upper end face of the upsetting head is , where x is the contour point function value of the drum-shaped upset head;

[0072] B3. After riveting is completed, calculate the equivalent diameter of the drum-shaped upsetting head. The calculation formula is as follows:

[0073] ;

[0074] B4. Obtain the maximum riveting force required to form a standard-sized pier head by combining the standard pier head dimensions, where the standard pier head dimensions are:

[0075]

[0076] In the formula, d is the diameter of the rivet.

[0077] S2. Construction of Riveting Interference Model: Based on the dimensions of the drum-shaped upsetting head, the diameter of the rivet shank, the diameter of the rivet hole, the thickness of the thin-walled part, and the riveting pressure, a mathematical relationship between the interference and the deformation of the thin-walled part is established. Once the rivet shank material fills the rivet hole, it can be assumed that no more rivet material will flow into the rivet hole during subsequent riveting processes. When the gap between the rivet shank and the rivet hole is filled with rivet shank material, the rivet dimensions are as shown in the attached figure. Figure 5 As shown, the mathematical relationships specifically include:

[0078] C1. Using rivets to fix the upper and lower thin-walled parts, the upper thin-walled part deforms during the forming of the waist-drum shaped upsetting head. The calculation of the deformation thickness of the upper thin-walled part is as follows:

[0079]

[0080] In the formula, H1 is the deformation thickness of the upper thin-walled component, H1 is the sum of the minimum thicknesses of the upper and lower thin-walled components, t1 is the thickness of the upper thin-walled component, and t2 is the thickness of the lower thin-walled component.

[0081] Although the strength of thin-walled parts is greater than that of rivet materials, under the riveting force applied by the punch, the thin-walled parts will undergo axial deformation, resulting in indentation of the material around the rivet hole in the upper thin-walled part, as shown in the attached figure. Figure 6 As shown, it is assumed that the compression of the thin-walled part in the upsetting head coverage area causes the material of the thin-walled part to expand radially, and the thickness of the thin-walled part in the uncovered area does not change;

[0082] Further information:

[0083] ;

[0084] Δ = (d1 - d0) ÷ d0 × 100%;

[0085] In the formula, d0 is the diameter of the rivet when the rivet hole is filled, d1 is the diameter of the rivet hole when the rivet shank material expands the rivet hole, h0 is the height of the rivet shank outside the rivet hole when the rivet shank material fills the rivet hole, and △ is the relative interference of the riveting.

[0086] C2. When the rivet contacts the hole wall, the volume of the rivet shank outside the rivet hole is equal to the volume of the upset head after it is formed. Since the rivet is uniformly upset during the deformation stage before contacting the rivet hole wall, according to the principle that the volume of the rivet shank material remains constant:

[0087]

[0088] In the formula, h is the rivet shank length and d is the rivet diameter;

[0089] C3. Combining C1 and C2, we can easily obtain:

[0090]

[0091] It is evident that the relative interference after riveting is completed is related to the size of the drum-shaped upsetting head, the diameter of the rivet hole, the diameter of the rivet rod, and the thickness of the thin-walled part.

[0092] S3. Prediction Model Construction: Couple the single-nail riveting mechanical model with the riveting interference model to form a prediction model for riveting deformation of thin-walled parts.

[0093] Based on the prediction model, combined with the known dimensions of the waist-shaped upsetting head, the diameter of the rivet rod, the diameter of the rivet hole, the thickness of the thin-walled part, and the riveting pressure, the deformation thickness of the thin-walled part can be calculated. This provides accurate and reliable data support for the deformation analysis of thin-walled parts during riveting.

[0094] In summary, the riveting deformation prediction method for thin-walled parts provided by this invention can effectively predict deformation during the riveting process, providing theoretical support for process optimization and quality control.

[0095] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0096] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for predicting riveting deformation of thin-walled parts, characterized in that: Specifically, the following steps are included: S1. Construction of the mechanical model for single-nail riveting: Based on the mechanical behavior of the rivet during the riveting process, the mechanical equations of the riveting process are derived. Among them, mechanical behavior includes the stress distribution and deformation characteristics of the rivet; S2. Construction of Riveting Interference Model: Based on the size of the waist-shaped upsetting head, the diameter of the rivet rod, the diameter of the rivet hole, the thickness of the thin-walled part, and the riveting pressure, establish the mathematical relationship between the interference and the deformation of the thin-walled part; S3. Prediction Model Construction: Couple the single-nail riveting mechanical model with the riveting interference model to form a prediction model for riveting deformation of thin-walled parts; The mechanical equations derived in S1 during the riveting process, when the drum-shaped abutment head undergoes uniform deformation, include: A1. Set the center position of the rivet's drum-shaped upsetting head as the origin O, and set the rivet shank direction as the Z-axis. Use a cylindrical coordinate system (ρ, θ, Z), where ρ is the radial distance, θ is the azimuth angle, and Z is the height. A set of equilibrium differential equations in the constructed cylindrical coordinate system: Where σ ρ σ is the radial stress on the rivet. θ τ is the circumferential stress on the rivet. zρ and τ θρ This represents the shear stress experienced by the rivet. A2. The formula for calculating the riveting force during the forming of a waist-drum shaped upsetting head is as follows: In the formula, F sq The riveting force is given by h1, the height of the drum-shaped upsetting head is given by R1, and the riveting strain is given by μ1. s The yield strength of the rivet; The mechanical equations derived in S1 for the riveting process, when the drum-shaped abutment head undergoes uneven deformation, include: B1. The formula for calculating the riveting force during the forming of the waist-drum shaped upsetting head is revised as follows: In the formula, de is the equivalent diameter of the waist drum-shaped upset head; B2. Express the contour curve of the drum-shaped upsetting head using a function. The function expression is as follows: f(x)=Ax 2 +Bx+C; In the formula, The bottom diameter of the upsetting head is d l The maximum diameter of the upsetting head is d m The diameter of the upper end face of the upsetting head is d u , where x is the contour point function value of the drum-shaped upset head; B3. After riveting is completed, calculate the equivalent diameter of the drum-shaped upsetting head. The calculation formula is as follows: B4. Obtain the maximum riveting force required to form a standard-sized pier head by combining the standard pier head dimensions, where the standard pier head dimensions are: In the formula, d is the diameter of the rivet.

2. The method for predicting riveting deformation of thin-walled parts according to claim 1, characterized in that: Before forming the waist-drum shaped upsetting head, the waist-drum shaped upsetting head is divided into contact friction stress zones. The contact friction stress zones include a constant friction coefficient zone and a friction stress decreasing zone from the outside to the inside. The constant friction coefficient zone and the friction stress decreasing zone are coaxially arranged. The diameter of the friction stress reduction zone is twice the height of the drum-shaped upsetting head, and the origin O of the coordinate system is located on the axis of the friction stress reduction zone.

3. The method for predicting riveting deformation of thin-walled parts according to claim 2, characterized in that: The methods for establishing the mathematical relationship between the interference amount and the deformation of the thin-walled component in S2 include: C1. Using rivets to fix the upper and lower thin-walled parts, the upper thin-walled part deforms during the forming of the waist-drum shaped upsetting head. The calculation of the deformation thickness of the upper thin-walled part is as follows: H1 + ΔH = t1 + t2; In the formula, ΔH is the deformation thickness of the upper thin-walled component, H1 is the sum of the minimum thicknesses of the upper and lower thin-walled components, t1 is the thickness of the upper thin-walled component, and t2 is the thickness of the lower thin-walled component. Further information: In the formula, d0 is the diameter of the rivet when the rivet hole is filled, d1 is the diameter of the rivet hole when the rivet shank material expands the rivet hole, h0 is the height of the rivet shank outside the rivet hole when the rivet shank material fills the rivet hole, and △ is the relative interference of the riveting. C2. When the rivet contacts the hole wall, the volume of the rivet shank outside the rivet hole is equal to the volume of the upset head after it is formed. Since the rivet is uniformly upset during the deformation stage before contacting the rivet hole wall, according to the principle that the volume of the rivet shank material remains constant: In the formula, h is the rivet shank length and d is the rivet diameter; C3. Combining C1 and C2, we can easily obtain:

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