Method for predicting riveting deformation of thin-wall part

Abstract

The invention discloses a thin-wall part riveting deformation prediction method. The method specifically comprises the following steps: S1, constructing a single-nail riveting mechanical model; s2, constructing a riveting interference amount model; s3, constructing a prediction model; the invention relates to the technical field of thin-wall part riveting deformation prediction. According to the thin-wall part riveting deformation prediction method, the maximum riveting force value required for forming an upset head with the standard size is calculated through a mechanical model, a riveting interference amount model is coupled, and after the size of the waist-drum-shaped upset head, the diameter of a rivet rod, the diameter of a rivet hole, the thickness of the thin-wall part and riveting pressure are obtained, the deformation thickness of the thin-wall part can be effectively predicted; and theoretical support is provided for process optimization and quality control.

Description

Technical Field

[0001] The present invention relates to the technical field of thin-walled component riveting deformation prediction, and in particular to a thin-walled component riveting deformation prediction method. Background Art

[0002] Thin-walled parts are widely used in aerospace, automobile manufacturing and other fields, and riveting is a common connection method. However, thin-walled parts are prone to deformation during riveting, which will directly affect the accuracy and performance of the workpiece. How to ensure that the deformation during riveting is controllable is of great value for the high-performance use of thin-walled parts after riveting. To this end, a method for predicting the riveting deformation of thin-walled parts is proposed. A mechanical model is built to calculate the maximum riveting force required to form a standard size nut. The riveting interference model is coupled. After obtaining the size of the drum-shaped nut, the diameter of the nail 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 effectively predicted. Summary of the invention

[0003] In view of the deficiencies in the prior art, the present invention provides a method for predicting riveting deformation of thin-walled parts, which solves the problems raised in the above-mentioned background technology.

[0004] To achieve the above objectives, the present invention is implemented through the following technical solutions: A method for predicting riveting deformation of thin-walled parts, specifically comprising the following steps: S1. Construction of single-nail riveting mechanical model: Based on the mechanical behavior of the rivet during the riveting process, the mechanical equations in the riveting process are derived; Among them, the mechanical behavior includes the stress distribution and deformation characteristics of the rivet; S2. Construction of riveting interference model: According to the size of the waist drum-shaped heading, the diameter of the nail rod, the diameter of the rivet hole, the thickness of the thin-walled part and the riveting pressure, the mathematical relationship between the interference and the deformation of the thin-walled part is established; S3. Prediction model construction: The single-nail riveting mechanical model is coupled with the riveting interference model as a prediction model for riveting deformation of thin-walled parts.

[0005] The present invention is further configured as follows: the mechanical equation derived in the riveting process in S1 includes the following when the waist drum-shaped pier head is uniformly deformed: A1. Set the center position of the rivet waist drum-shaped head as the coordinate origin O, set the direction of the rivet rod as the Z axis, and the cylindrical coordinate system ,in is the radial distance, is the azimuth and Z is the altitude.

[0006] Construct a set of balanced differential equations in cylindrical coordinates:

[0007] In the formula, is the radial stress on the rivet, is the hoop stress on the rivet, and is the shear stress on the rivet; A2. The calculation formula of riveting force when waist drum-shaped upsetting head is:

[0008] In the formula, is the riveting force, h 1 is the waist drum head height, R 1 is the radius of the waist drum pier head, is the riveting strain; is the yield strength of the rivet.

[0009] The present invention is further configured as follows: the mechanical equation derived in the riveting process in S1 includes the following when the waist drum-shaped pier head is unevenly deformed: B1. The calculation formula for the riveting force during the forming of the waist drum-shaped heading is modified to:

[0010] Where de is the equivalent diameter of the waist drum-shaped heading; B2. The contour curve of the waist drum-shaped heading is expressed as follows:

[0011] In the formula, , , , the bottom diameter of the upsetting head is , the maximum diameter of the upsetting head is The upper end diameter of the upsetting head is , x is the contour point function value of the waist drum-shaped heading; B3. After riveting is completed, the equivalent diameter of the waist drum-shaped heading is calculated using the following formula: ; B4. Combine the standard pier head size to obtain the maximum riveting force required to form the standard pier head size, where the standard pier head size is:

[0012] Where d is the diameter of the rivet.

[0013] The present invention is further configured as follows: before the waist-drum-shaped heading is formed, the waist-drum-shaped heading is divided into contact friction stress zones, wherein the contact friction stress zones sequentially include a constant friction coefficient zone and a friction stress decreasing zone from the outside to the inside, and the constant friction coefficient zone and the friction stress decreasing zone are coaxially arranged; The diameter of the friction stress decreasing zone is twice the height of the waist drum-shaped upsetting head, and the coordinate origin O is located on the axis of the friction stress decreasing zone.

[0014] The present invention is further configured as follows: the method of establishing the mathematical relationship between the interference amount and the deformation of the thin-walled part in S2 includes: C1. Use rivets to fix the upper and lower thin-walled parts. When the waist drum-shaped heading is formed, the upper thin-walled part is deformed. The calculation of the deformation thickness of the upper thin-walled part is:

[0015] In the formula, is the deformation thickness of the upper thin-walled part, H 1 is the sum of the minimum thickness of the upper thin-walled part and the lower thin-walled part, t 1 is the thickness of the upper thin-walled part, t 2 is the thickness of the lower thin-walled part; Further information: ; Δ = (d 1 -d 0 )÷d 0 ×100%; Where, d 0 is the diameter of the rivet when the hole is filled, d 1 h is the diameter of the rivet hole when the rivet hole is expanded by the shank material. 0 is the height of the nail rod outside the rivet hole when the rivet hole is filled with nail rod material, △ is the relative interference of riveting; C2. When the rivet is in contact with the hole wall, the volume of the rivet rod outside the rivet hole is equal to the volume of the upsetting head after the upsetting head is formed. The rivet is uniformly upset in the deformation stage when it does not contact the rivet hole wall. According to the principle that the volume of the rivet rod material remains unchanged, it can be obtained that:

[0016] Where h is the length of the rivet shank and d is the diameter of the rivet. C3, combined with C1 and C2, it is easy to get: .

[0017] The present invention provides a method for predicting riveting deformation of thin-walled parts. It has the following beneficial effects: The present invention calculates the maximum riveting force required for forming a standard-sized nut through a mechanical model, and couples the riveting interference model to obtain the size of the waist-drum-shaped nut, the diameter of the nail 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 effectively predicted, providing theoretical support for process optimization and quality control. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the process of the present invention; Figure 2 It is a schematic diagram of a cylindrical coordinate system in the present invention; Figure 3 It is a schematic diagram of the regional distribution of friction stress in the present invention; Figure 4 It is a schematic diagram of the size and outline of the rivet head in the present invention; Figure 5 A schematic diagram of the rivet size when the nail hole is filled in the present invention; Figure 6 It is a schematic diagram of the rivet size when the waist drum type heading is formed in the present invention. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0020] See also Figure 1-6 The embodiment of the present invention provides the following technical solution: a method for predicting riveting deformation of thin-walled parts, specifically comprising the following steps: S1. Construction of single-nail riveting mechanical model: 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.

[0021] The riveting process is actually the process in which the rivet is subjected to the impact load applied by the punch, which then forces the rivet to deform. In the riveting assembly process, the riveting force is the main external force, which is applied to the rivet by the punch. The riveting force is calculated analytically, and the relationship between the riveting force and the deformation of the rivet waist drum-shaped upsetting head during the riveting process is deduced. A relationship model between the riveting force and the upsetting head size is constructed. Since the shape of the rivet shank is a metal cylinder, the forming problem of the rivet waist drum-shaped upsetting head can be solved as a local upsetting problem of the metal cylinder.

[0022] When the waist drum pier head is uniformly deformed, it includes: A1. Set the center position of the rivet waist drum-shaped heading as the coordinate origin O. Figure 2 As shown, the rivet rod direction is set as the Z axis, cylindrical coordinate system ,in is the radial distance, is the azimuth and Z is the altitude.

[0023] Construct a set of balanced differential equations in cylindrical coordinates:

[0024] In the formula, is the radial stress on the rivet, is the hoop stress on the rivet, and is the shear stress on the rivet; A2, as attached Figure 3 As shown, before the waist-drum-shaped heading is formed, the contact friction stress zone of the waist-drum-shaped heading is divided, and 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 coaxially arranged, the diameter of the friction stress decreasing zone is twice the height of the waist-drum-shaped heading, and the coordinate origin O is located on the axis of the friction stress decreasing zone; The calculation formula of riveting force during waist drum-shaped upsetting is:

[0025] In the formula, is the riveting force, h 1 is the waist drum head height, R 1 is the radius of the waist drum pier head, is the riveting strain; is the yield strength of the rivet.

[0026] When the waist drum pier head is unevenly deformed, it includes: B1. The calculation formula for the riveting force during the forming of the waist drum-shaped heading is modified to:

[0027] Where de is the equivalent diameter of the waist drum-shaped heading; B2. Since the shape of the upsetting head is waist drum-shaped, its outline can be approximated as a parabola. Figure 4 As shown in the figure, the contour curve of the waist drum-shaped heading is expressed by function, and the function expression is:

[0028] In the formula, , , , the bottom diameter of the upsetting head is , the maximum diameter of the upsetting head is The upper end diameter of the upsetting head is , x is the contour point function value of the waist drum-shaped heading; B3. After riveting is completed, the equivalent diameter of the waist drum-shaped heading is calculated using the following formula: ; B4. Combine the standard pier head size to obtain the maximum riveting force required to form the standard pier head size, where the standard pier head size is:

[0029] Where d is the diameter of the rivet.

[0030] S2. Construction of riveting interference model: According to the size of the waist drum-shaped heading, the diameter of the nail rod, the diameter of the rivet hole, the thickness of the thin-walled part and the riveting pressure, the mathematical relationship between the interference and the deformation of the thin-walled part is established. When the nail rod material fills the rivet hole, it can be assumed that no more rivet material will flow into the rivet hole during the subsequent riveting process. When the gap between the rivet rod and the rivet hole is filled with the nail rod material, the rivet size is as shown in the attached figure. Figure 5 As shown, the mathematical relationship specifically includes: C1. Use rivets to fix the upper and lower thin-walled parts. When the waist drum-shaped heading is formed, the upper thin-walled part is deformed. The calculation of the deformation thickness of the upper thin-walled part is:

[0031] In the formula, is the deformation thickness of the upper thin-walled part, H 1 is the sum of the minimum thickness of the upper thin-walled part and the lower thin-walled part, t 1 is the thickness of the upper thin-walled part, t 2 is the thickness of the lower thin-walled part; Although the strength of the thin-walled part material is greater than that of the rivet material, the thin-walled part will deform in the axial direction under the riveting force applied by the punch, which will cause the material around the riveting hole of the upper thin-walled part to dent. Figure 6 As shown, it is assumed that the compression of the upper thin-walled part in the area covered by the heading 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; Further information: ; Δ = (d 1 -d 0 )÷d 0 ×100%; Where, d 0 is the diameter of the rivet when the hole is filled, d 1 h is the diameter of the rivet hole when the rivet hole is expanded by the shank material. 0 is the height of the nail rod outside the rivet hole when the rivet hole is filled with nail rod material, △ is the relative interference of riveting; C2. When the rivet is in contact with the hole wall, the volume of the rivet rod outside the rivet hole is equal to the volume of the upsetting head after the upsetting head is formed. The rivet is uniformly upset in the deformation stage when it does not contact the rivet hole wall. According to the principle that the volume of the rivet rod material remains unchanged, it can be obtained that:

[0032] Where h is the length of the rivet shank and d is the diameter of the rivet. C3, combined with C1 and C2, it is easy to get:

[0033] It can be seen that the relative interference amount of riveting after riveting is completed is related to the size of the waist drum-shaped heading, the diameter of the rivet hole, the diameter of the rivet rod and the thickness of the thin-walled part.

[0034] S3. Prediction model construction: The single-nail riveting mechanical model is coupled with the riveting interference model as a prediction model for riveting deformation of thin-walled parts.

[0035] According to the prediction model, combined with the known waist drum-shaped heading size, nail rod diameter, rivet hole diameter, thin-walled part thickness and riveting pressure, the deformation thickness of the thin-walled part can be calculated, which provides accurate and reliable data support for the deformation analysis of thin-walled parts during riveting.

[0036] In summary, the method for predicting riveting deformation of thin-walled parts provided by the present invention can effectively predict the deformation during the riveting process and provide theoretical support for process optimization and quality control.

[0037] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0038] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for predicting riveting deformation of thin-walled parts, characterized in that: The specific steps include: S1. Construction of single-nail riveting mechanical model: Based on the mechanical behavior of the rivet during the riveting process, the mechanical equations in the riveting process are derived; Among them, the mechanical behavior includes the stress distribution and deformation characteristics of the rivet; S2. Construction of riveting interference model: According to the size of the waist drum-shaped heading, the diameter of the nail rod, the diameter of the rivet hole, the thickness of the thin-walled part and the riveting pressure, the mathematical relationship between the interference and the deformation of the thin-walled part is established; S3. Prediction model construction: The single-nail riveting mechanical model is coupled with the riveting interference model as a prediction model for riveting deformation of thin-walled parts.

2. A method for predicting riveting deformation of thin-walled parts according to claim 1, characterized in that: The mechanical equations derived in S1 during the riveting process include: A1. Set the center position of the rivet waist drum-shaped head as the coordinate origin O, set the direction of the rivet rod as the Z axis, and the cylindrical coordinate system ,in is the radial distance, is the azimuth, Z is the altitude; Construct a set of balanced differential equations in cylindrical coordinates: ； In the formula, is the radial stress on the rivet, is the hoop stress on the rivet, and is the shear stress on the rivet; A2. The calculation formula of riveting force when waist drum-shaped upsetting head is: ； In the formula, is the riveting force, h1 is the height of the waist drum-shaped header, R1 is the radius of the waist drum-shaped header, is the riveting strain; is the yield strength of the rivet.

3. A method for predicting riveting deformation of thin-walled parts according to claim 2, characterized in that: The mechanical equations derived in the riveting process in S1 include: B1. The calculation formula for the riveting force during the forming of the waist drum-shaped heading is modified to: ； Where de is the equivalent diameter of the waist drum-shaped heading; B2. The contour curve of the waist drum-shaped heading is expressed as follows: ； In the formula, , , , the bottom diameter of the upsetting head is , the maximum diameter of the upsetting head is The upper end diameter of the upsetting head is , x is the contour point function value of the waist drum-shaped heading; B3. After riveting is completed, the equivalent diameter of the waist drum-shaped heading is calculated using the following formula: ； B4. Combine the standard pier head size to obtain the maximum riveting force required to form the standard pier head size, where the standard pier head size is: ； Where d is the diameter of the rivet.

4. A method for predicting riveting deformation of thin-walled parts according to claim 3, characterized in that: The waist drum-shaped heading is divided into contact friction stress zones before the waist drum-shaped heading is formed, wherein the contact friction stress zones include a constant friction coefficient zone and a friction stress decreasing zone from the outside to the inside, and the constant friction coefficient zone and the friction stress decreasing zone are coaxially arranged; The diameter of the friction stress decreasing zone is twice the height of the waist drum-shaped upsetting head, and the coordinate origin O is located on the axis of the friction stress decreasing zone.

5. A method for predicting riveting deformation of thin-walled parts according to claim 4, characterized in that: The method of establishing the mathematical relationship between the interference amount and the deformation of the thin-walled part in S2 includes: C1. Use rivets to fix the upper and lower thin-walled parts. When the waist drum-shaped heading is formed, the upper thin-walled part is deformed. The calculation of the deformation thickness of the upper thin-walled part is: ； In the formula, is the deformation thickness of the upper thin-walled part, H1 is the sum of the minimum thicknesses of the upper thin-walled part and the lower thin-walled part, t1 is the thickness of the upper thin-walled part, and t2 is the thickness of the lower thin-walled part; Further information: ;Δ=(d1-d0)÷d0×100%; Where, d0 is the diameter of the rivet when the hole is filled, d1 is the diameter of the rivet hole when the rivet hole is expanded by the rivet rod material, h0 is the height of the rivet rod outside the rivet hole when the rivet hole is filled by the rivet rod material, and △ is the relative interference of the riveting; C2. When the rivet is in contact with the hole wall, the volume of the rivet rod outside the rivet hole is equal to the volume of the upsetting head after the upsetting head is formed. The rivet is uniformly upset in the deformation stage when it does not contact the rivet hole wall. According to the principle that the volume of the rivet rod material remains unchanged, it can be obtained that: ； Where h is the length of the rivet shank and d is the diameter of the rivet. C3, combined with C1 and C2, it is easy to get: 。

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