Quality control method for self-piercing riveting process

Abstract

To provide a quality control method for riveting process that can guarantee the riveting quality.SOLUTION: A control method for self-piercing riveting process comprises the steps of starting a self-piercing riveting device, acquiring operation parameters of the self-piercing riveting device, acquiring parameters of a to-be-riveted plate, calculating a deflection rate, calculating a rivet close defect rate and dynamically adjusting and controlling. According to the method, the influence relational expression of the deflection rate of the rivet and the close-fitting defect rate of the rivet is established, the riveting process is monitored in real time in combination with the detection technology, the specific influence of each influence parameter on the quality of the riveting process is analyzed according to the relational expression, the influence parameters are adjusted, self-adaptive optimization is achieved, and it is effectively guaranteed that the riveting quality meets the production requirement.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for controlling the process quality of riveting, and more particularly to a method for controlling the process quality of riveting using a self-piercing rivet (SPR). [Background technology]

[0002] Riveting using SPR (Self-piercing rivets) is an important joining technology that reduces automobile weight, energy consumption, and emissions, and increases the driving range of new energy vehicles. Self-piercing rivet joining is a riveting process in which an SPR rivet penetrates a plate under the action of an external force and then flows and expands within the underlying plate, forming interlocking plastic deformation. The resulting riveted joint has high tensile and shear strength, and self-piercing riveting technology solves the problem of aluminum spot welding not being able to meet joining performance requirements, overcoming issues such as insufficient fatigue strength and incompatibility between the rivet coating and the aluminum material.

[0003] The key control parameters for ensuring the quality of the riveting process are the distortion rate of the rivet and the degree of adhesion between the rivet and the plate materials being joined. In conventional riveting processes, the configuration parameters of the riveting process are generally determined by combining past work experience and the defect rate of the current riveting process, and the quality of the riveting process is monitored by visual identification or ultrasonic detection technology.

[0004] However, the configuration parameters in such processes, which are determined based on past riveting experience, have low accuracy, and the riveting parameters for one batch are fixed and cannot be changed. For parameters such as the punch rod punch force and belt movement tactile, the original parameter configuration cannot be self-adaptively optimized according to the monitoring results, making it difficult to guarantee the quality of riveting.

[0005] Therefore, it is necessary to design a process quality control method for self-piercing riveting to solve the above problems. Summary of the Invention [Problem to be solved by the invention]

[0006] SUMMARY OF THE INVENTION The present invention aims to provide a method for controlling the process quality of riveting using a self-piercing rivet, thereby solving the problems in the background art mentioned above. [Means for solving the problem]

[0007] To achieve the above objectives, the present invention provides the following technical solutions:

[0008] A process quality control method for self-piercing riveting, comprising the steps of:

[0009] Step S100: Activating the self-piercing riveting device The self-piercing riveting device includes a frame, a power mechanism, a transport mechanism, a feed mechanism, and a guide mechanism. The frame has a C-shaped structure, and the power mechanism is attached to the upper part of the open end of the frame. A die for attaching the workpiece to be riveted is provided at the lower part opposite the upper part. The output end of a planetary roller screw installed in the power mechanism is connected to a punch rod that penetrates through the feed mechanism, and a lateral passage is provided within the lower end of the feed mechanism. The output end of the transport mechanism attached to the frame passes a belt with rivets through a guide tube and through the lateral passage, and the end of the feed mechanism is connected to the guide mechanism. The guide mechanism includes a guide tube with a rivet feed nozzle installed inside, and a guide passage within the rivet feed nozzle for pushing out the rivet. The top end of the rivet feed nozzle protrudes from the top end of the guide tube and abuts against the end of the through-hole in the feed mechanism via a guide joint. A downward punch force F is applied by the action of the power mechanism, and the punch rod drives the rivet through the guide passage within the rivet feed nozzle into the die, completing the joining of the rivet with the workpieces to be riveted.

[0010] Step S200: Obtaining operating parameters of the self-piercing riveting device The operating parameters include the punch force F, the circumferential clamping stress σ of the rivet feed nozzle on the rivet, the belt movement t, the time T during which the punch force acts on the rivet, and the length L of the rivet.

[0011] Step S300: Obtaining parameters of plate materials to be riveted The parameters include the hardness B of the plate material to be riveted, its thickness H, and the ratio n of the rivet diameter to the rivet hole diameter.

[0012] Step S400: Calculation of distortion rate The distortion rate is calculated using the following formula:

[0013]

number

[0014] In the above formula, d, f, and g are adjustment coefficients, F is the punch force, B is the hardness of the plate material, H is the thickness of the plate to be riveted, σ is the circumferential clamping stress, and t is the belt movement tact.

[0015] Step S500: Calculation of rivet adhesion defect rate The rivet adhesion defect rate is calculated using the following formula.

[0016]

number

[0017] In the above formula, the values ​​of a, b, c, and k are adjustment coefficients, F is the punch force, L is the length of the rivet, n is the ratio of the rivet diameter to the rivet hole diameter, B is the hardness of the plates to be riveted, H is the thickness of the plates to be riveted, and T is the time the punch force acts on the rivet.

[0018] Step S600: Dynamic Adjustment and Control Based on whether the calculated distortion rate and rivet adhesion defect rate meet the production requirements, the relevant parameters are dynamically adjusted in steps S400 and S500, and the adjustment work is stopped when the adjusted distortion rate and rivet adhesion defect rate meet the requirements.

[0019] As a preferred technical solution of the present invention, the distortion in the calculation of the distortion rate specifically refers to the offset and inclination of the rivet head.

[0020] As a preferred technical solution of the present invention, the rivet adhesion defects used in calculating the rivet adhesion defect rate specifically refer to a depression in the countersunk head of the rivet, partial chipping of the peripheral edge of the countersunk head rivet, a protruding countersunk head, an incompletely round rivet head, a crushed peripheral edge of the rivet head, or insufficient adhesion between the peripheral edge of the rivet head and the edge of the object to be joined.

[0021] As a preferred technical solution of the present invention, a plurality of annular passages are provided outside the rivet feed nozzle, and each annular passage is provided with a flexible member, and the rivet feed nozzle is surrounded by two or three arc-shaped pieces to form a circumferential embrace around the rivet. [Effects of the Invention]

[0022] In summary, the advantageous effects of the present invention are as follows:

[0023] The present invention establishes an influence relationship between the distortion rate of the rivet and the adhesion defect rate between the rivet and the plate material to be riveted, and based on the relationship, analyzes the specific impact of each influence parameter on the quality of the riveting process. It then combines this with detection technology to perform real-time monitoring of the riveting process, and based on the monitoring results, adjusts one or more influence parameters in a timely manner, thereby more accurately predicting and adjusting various factors in the riveting process, thereby achieving self-adaptive optimization.

[0024] For example, if the distortion rate of the rivet is too large or the adhesion is insufficient, parameters such as the punch force of the punch rod and the belt movement tact can be adjusted in real time to optimize the rivet joining effect.

[0025] In other words, it eliminates the drawback of the traditional riveting process, in which the riveting parameters for a batch are fixed and cannot be changed, reduces the reliance on experience that is present in the traditional riveting process, and enables workers with different skill levels to produce high-quality riveted products. This significantly improves the stability of riveted quality, reduces quality variations and unnecessary rework and adjustments due to insufficient riveted quality, and increases the reliability and safety of products. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a flow chart of a method for controlling the process quality of self-piercing riveting according to the present invention. [Figure 2] 1 is a schematic diagram of the structure of a self-piercing rivet fastening device according to the present invention; [Figure 3] 1 is a schematic diagram of a structure of a guide mechanism according to the present invention; [Figure 4] 1 is a graph showing a numerical curve fitting curve of an asymptotic function model regression analysis according to an embodiment of the present invention. [Figure 5] 1 is a graph showing a numerical curve fitting curve of a DoseResp model regression analysis according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0027] Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely for illustrative purposes and are not intended to limit the present invention. In order to facilitate a full understanding of the present invention, many specific details will be described in the following description. However, the present invention may have other embodiments and modifications thereof. Therefore, it should be noted that the scope of protection of the present invention is not limited to the specific examples disclosed below.

[0028] As shown in FIGS. 1 to 3, the process quality control method for self-piercing riveting provided by the present invention includes the following steps:

[0029] Step S100: Activating the self-piercing riveting device The self-piercing riveting device includes a frame 100 , a power mechanism 300 , a transport mechanism 200 , a feed mechanism 400 , and a guide mechanism 500 .

[0030] The frame 100 has a C-shaped structure, and the power mechanism 300 is attached to the upper part of the open end of the frame 100, and a die for attaching the material to be riveted is provided at the lower part opposite to the upper part.

[0031] The output end of the planetary roller screw installed in the power mechanism 300 is connected to a punch rod that penetrates through the feed mechanism 400, and a lateral passage is provided in the lower end of the feed mechanism 400. The output end of the conveying mechanism 200 attached to the frame 100 passes a riveted belt 401 through a guide tube and passes through the lateral passage, and the end of the feed mechanism 200 is connected to the guide mechanism 500.

[0032] Guide mechanism 500 includes a guide tube 502 with a rivet feed nozzle 501 installed inside. Rivet feed nozzle 501 has a guide passage inside it that pushes out the rivet. The top end of rivet feed nozzle 501 protrudes from the top end of guide tube 502 and abuts against the end of the through hole in feed mechanism 400 via a guide joint. A downward punch force F is applied by the action of power mechanism 300, and the punch rod drives the rivet through the guide passage in rivet feed nozzle 501 into the die, completing the joining of the rivet with the workpieces to be riveted.

[0033] Step S200: Obtaining operating parameters of the self-piercing riveting device The operating parameters include the punch force F, the circumferential clamping stress σ of the rivet feed nozzle 501 on the rivet, the movement t of the belt 401, the time T during which the punch force acts on the rivet, and the length L of the rivet.

[0034] Step S300: Obtaining parameters of plate materials to be riveted The parameters include the hardness B of the plate material to be riveted, its thickness H, and the ratio n of the rivet diameter to the rivet hole diameter.

[0035] Considering the current processing level and experience of aluminum alloy sheets for automobile bodies, as well as the current riveting process requirements, the punch force of the riveting equipment punch rod is typically set to 60 kN or 80 kN, the punch force application time is 1 to 3 seconds, the circumferential clamping stress generated by the rivet feed nozzle 501 is 10 MPa or more, increasing at a gradient of 5 MPa, the rivet diameter is 0.2 mm smaller than the rivet hole diameter, i.e., the ratio of the rivet diameter to the rivet hole diameter is 0.97 or less, the movement tact time of the belt 401 is typically 1 to 3.5 seconds, and the aluminum alloy sheets for automobile bodies to be riveted have a hardness in the range of 60 to 150 HB and a thickness in the range of 0.5 to 6 mm.

[0036] Step S400: Calculation of distortion rate The distortion rate is calculated using the following formula:

[0037]

number

[0038] In the above formula, the values ​​d, f, and g are adjustment coefficients, F is the punch force, B is the hardness of the plate material, H is the thickness of the plate to be riveted, σ is the circumferential clamping stress, and t is the movement tact of the belt 401.

[0039] Taking the riveting of two layers of aluminum alloy body plate material, each 3 mm thick and 120HB hardness, as an example, the punch force of the punch rod of the SPR self-piercing riveting device was set to 60 kN, the circumferential clamping stress was set to 10 MPa, and the movement tact of each rivet on the belt 401 was adjusted. The strain rate of multiple sets was obtained and the collected data is shown in Table 1 below.

[0040] [Table 1]

[0041] Combined with the corresponding data in the table above and performing a regression analysis using the asymptotic function model, we obtain the complete control equation as follows:

[0042]

number

[0043] The curve fitting analysis results are shown in Figure 4. The coefficient of determination was 0.98434, which is very close to 1. This indicates that the resulting control equation can explain the variation in the data. As can be seen, when the punch rod force of the self-piercing riveting equipment is set to 60 kN and the circumferential clamping stress is set to 10 MPa to rivet two layers of aluminum alloy body sheet material that is 3 mm thick and has a hardness of 120HB, the belt movement tact and strain rate can be controlled using the above equation. The belt movement tact corresponding to the strain rate required for production can be accurately calculated using the formula, and the belt movement tact in the self-piercing riveting equipment can be adjusted to achieve the control objective.

[0044] Step S500: Calculation of rivet adhesion defect rate The rivet adhesion defect rate is calculated using the following formula.

[0045]

number

[0046] In the above formula, the values ​​of a, b, c, and k are adjustment coefficients, F is the punch force, L is the length of the rivet, n is the ratio of the rivet diameter to the rivet hole diameter, B is the hardness of the plates to be riveted, H is the thickness of the plates to be riveted, and T is the time the punch force acts on the rivet.

[0047] Taking the riveting of two layers of 3mm thick, 120HB hardness aluminum alloy body sheet material as an example, the punch force of the punch rod of the self-piercing riveting device was set to 60kN, the rivet length was set to 7.2mm, the ratio of the rivet diameter to the rivet hole diameter was set to 0.97, and the punch force application time T of the punch rod was adjusted. The rivet adhesion defect rate for multiple sets was obtained and the collected data is shown in Table 2 below.

[0048] [Table 2]

[0049] Combined with the corresponding data in the table above, and performing a regression analysis using the DoseResp model, we obtain the complete control equation:

[0050]

number

[0051] The results of the curve fitting analysis are shown in Figure 5. The coefficient of determination was 0.98973, which is very close to 1, indicating that the obtained control equation can explain the variability of the data.

[0052] As can be seen from this, when the punch force of the punch rod of the self-piercing riveting device is set to 60 kN, the rivet length is set to 7.2 mm, the ratio of rivet diameter to rivet hole diameter is set to 0.97, the hardness of the plates to be riveted is set to 120 HB, and the thickness of the plates to be riveted is set to 3 mm, the punch force application time of the punch rod and the rivet adhesion defect rate can be controlled using the above formula, thereby obtaining a rivet adhesion defect rate that meets the requirements, and ultimately achieving the control objective.

[0053] Step S600: Dynamic Adjustment and Control Based on whether the calculated distortion rate and rivet adhesion defect rate meet the production requirements, the relevant parameters are dynamically adjusted in steps S400 and S500, and the adjustment work is stopped when the adjusted distortion rate and rivet adhesion defect rate meet the requirements.

[0054] The distortion in the above distortion rate specifically refers to the offset of the head and the inclination of the rivet head.

[0055] Rivet adhesion defects in the above rivet adhesion defect rates specifically refer to depressions in the countersunk head of the rivet, partial chipping of the periphery of the countersunk head rivet, protrusions of the countersunk head, incomplete circularity of the rivet head, crushing of the periphery of the rivet head, or insufficient adhesion between the periphery of the rivet head and the edge of the object to be joined.

[0056] Furthermore, as shown in FIG. 3, a plurality of annular passages 503 are provided outside the rivet feed nozzle 501, and a flexible member 504 is provided in each annular passage 503, and the rivet feed nozzle 501 is surrounded by two or three arc-shaped pieces, forming a circumferential embrace around the rivet.

[0057] When designing the number of arc-shaped pieces in the rivet feed nozzle 501, taking into account actual production errors, it is difficult for the inner surfaces of the arc-shaped pieces of the rivet feed nozzle 501 to make even contact with the outer surface of the rivet head, and during the actual riveting process there are only a few contact points between each arc-shaped piece and the rivet, which causes uneven circumferential clamping stress on the rivet. When the rivet feed nozzle 501 has two arc-shaped pieces, the rivet is subjected to two coaxial, different-direction side pressures generated by the arc-shaped pieces, and this makes it easy for the rivet to shift or vibrate in a plane perpendicular to the rivet feed nozzle 501.

[0058] When the rivet feed nozzle 501 has three arc-shaped pieces, the rivet receives the same amount of lateral pressure in the three central directions generated by the arc-shaped pieces, and the rivet can maintain better stability and balance in the guide passage according to the principle of triangular stability, and the circumferential clamping stress received by the outer periphery of the rivet head is more evenly distributed. For this reason, in a specific implementation of this embodiment, a rivet feed nozzle 501 consisting of three arc-shaped pieces is preferred.

[0059] It should be understood that the above-described embodiments are one or more embodiments of the present invention, and there are many other embodiments and variations thereof based on the present invention. Any variations and modifications made by those skilled in the art according to the present invention without pioneering innovation fall within the scope of protection of the present invention. [Industrial Applicability]

[0060] The present invention can be advantageously used as a method for process quality control of self-piercing riveting. [Explanation of symbols]

[0061] 100 frames 200 Transport mechanism 300 Power mechanism 400 Feeding mechanism 401 Belt 500 Guide mechanism 501 Rivet feed nozzle 502 Guide tube 503 Ring Road 504 Flexible Member 600 Dies

Claims

1. 1. A method for process quality control of self-piercing riveting, comprising: Step S100 includes a step of starting up the self-piercing rivet fastening device, The self-piercing riveting device includes a frame, a power mechanism, a transport mechanism, a feed mechanism, and a guide mechanism; The frame has a C-shaped structure, the power mechanism is attached to an upper portion of the open end of the frame, and a die for attaching a riveted material is provided at a lower portion opposite to the upper portion, The output end of the planetary roller screw installed in the power mechanism is connected to a punch rod that penetrates through the feed mechanism, a lateral passage is provided in the lower end of the feed mechanism, the output end of the conveying mechanism attached to the frame passes a riveted belt through a guide tube and passes through the lateral passage, and the end of the feed mechanism is connected to the guide mechanism, The guide mechanism includes a guide tube in which a rivet feed nozzle is installed, and the inside of the rivet feed nozzle is a guide passage for pushing out the rivet, and the top end of the rivet feed nozzle protrudes from the top end of the guide tube and abuts against the end of the through hole in the feed mechanism via a guide joint, and a downward punch force F is applied by the action of the power mechanism, and a punch rod drives the rivet through the guide passage in the rivet feed nozzle to the die, completing the joining of the rivet with the material to be joined, Step S200 includes a step of acquiring operating parameters of the self-piercing rivet fastening device, The operating parameters include punch force F, circumferential clamping stress σ of the rivet feed nozzle on the rivet, belt movement t, time T during which the punch force acts on the rivet, and rivet length L, Step S300 includes a step of acquiring parameters of a plate material to be riveted, The parameters of the riveted plate material include hardness B, thickness H, and ratio n of the rivet diameter to the rivet hole diameter of the riveted plate material, Step S400 includes a step of calculating a distortion rate, The distortion rate is calculated by the following formula: [Equation 1] In the above formula, d, f, and g are adjustment coefficients, F is the punch force, B is the hardness of the plate material, H is the thickness of the plate to be riveted, σ is the circumferential clamping stress, and t is the belt movement tact. Step S500 includes a step of calculating a rivet adhesion defect rate, The rivet adhesion defect rate is calculated by the following formula: [Equation 2] In the above formula, the values ​​of a, b, c, and k are adjustment coefficients, F is the punch force, L is the length of the rivet, n is the ratio of the rivet diameter to the rivet hole diameter, B is the hardness of the plate material to be riveted, H is the thickness of the plate material to be riveted, T is the time during which the punch force acts on the rivet, and Step S600 includes a step of performing dynamic adjustment and control; In step S600, the relevant parameters are dynamically adjusted in steps S400 and S500 based on whether the calculated distortion rate and rivet adhesion defect rate meet the production requirements, and the adjustment work is stopped when the adjusted distortion rate and rivet adhesion defect rate meet the requirements.

2. 2. The method for controlling process quality of self-piercing riveting as claimed in claim 1, wherein the distortion in calculating the distortion rate refers to the offset and inclination of the rivet head.

3. The method for controlling process quality of self-piercing rivets as set forth in claim 1, wherein the rivet adhesion defects used in calculating the rivet adhesion defect rate are a depression in the countersunk head of the rivet, partial chipping of the peripheral edge of the countersunk head rivet, a protrusion of the countersunk head, an incompletely circular rivet head, a crushed peripheral edge of the rivet head, or insufficient adhesion between the peripheral edge of the rivet head and the edge of the object to be joined.

4. 2. The method for controlling the process quality of self-piercing riveting as claimed in claim 1, wherein the rivet feed nozzle has a plurality of annular passages outside thereof, each annular passage having a flexible member, and the rivet feed nozzle is surrounded by two or three arc-shaped pieces to form a circumferential embrace around the rivet.

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