Improved adhesive rivet composite connection process and optimization method

Abstract

An improved adhesive rivet composite connection process increases an annular gasket sleeved on a rivet between two adhesive substrates, the inner diameter size D2 of the annular gasket is the same as the diameter D3 of the rivet, the design tolerance ensures that the rivet passes through smoothly, and the area of the annular gasket is 1.5-2.0 times the cross-sectional area of the rivet. The composite connection process optimization method comprises designing and manufacturing an adhesive rivet joint, performing a quasi-static tensile test on the adhesive rivet joint, determining an optimized design scheme, and optimizing the design variables of the gasket height h1 and the rivet diameter D3. The present application establishes an adhesive rivet joint peak load optimization method, which optimizes the adhesive layer peak load and the rivet peak load by selecting key geometric design variables of the adhesive rivet joint, and finally realizes the coincidence of the adhesive layer peak load position and the rivet peak load position, so that the adhesive layer and the rivet fail at the same time, thereby achieving the goal of improving the load capacity and impact resistance of the adhesive rivet joint.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of automobile material connection, more specifically to an improved adhesive-riveted composite connection process and optimization method. BACKGROUND

[0002] Further realizing automobile light weight is an effective way to reduce vehicle energy consumption, which puts forward higher requirements for automobile materials and structures. At present, the diversification of automobile materials has become an inevitable trend, and the connection problem of multiple dissimilar materials has gradually become a research hotspot.

[0003] The adhesive connection technology has the advantages of uniform stress distribution, good appearance quality, etc. Since the adhesive connection technology does not have the problems of hole deformation and thermal deformation, it also has good fatigue resistance. However, since the adhesive used for the body structure is mostly thin, its damage energy absorption effect may be slightly insufficient under certain special working conditions. In addition, the adhesive is prone to aging, which reduces the connection reliability. Compared with adhesive connection, the riveted connection technology has good energy absorption effect when damaged and is not prone to aging, and has high reliability. However, when the riveted connection technology is used alone, there may be a possibility of electrochemical corrosion due to the direct contact between the rivet and the metal material of the vehicle body. Therefore, a new connection method combining adhesive connection and riveted connection can effectively avoid the shortcomings of pure adhesive connection and riveted connection, and is a feasible solution.

[0004] One technical difficulty of using adhesive-riveted connection technology is how to accurately quantify and control the thickness of the adhesive layer. Most of the previous process methods are to select appropriate glass beads or copper wire diameters and uniformly arrange them in the adhesive area to achieve the effect of controlling the thickness of the adhesive layer. However, using the above method will cause the adhesive to adhere to the rivet during the curing stage, which is not conducive to the subsequent optimization process.

[0005] In addition, research shows that the adhesive-riveted joint often has two failure processes when it breaks. The first segment is the failure of the adhesive layer, at which time the failure strength is high and the failure displacement is short. After the failure of the adhesive layer, the rivet fails immediately. The strength of a single rivet is much lower than that of the adhesive layer, but the failure displacement is longer and the energy absorption effect is good. Currently, one of the reasons limiting the widespread application of adhesive-riveted joints is that after the adhesive layer fails, the adhesive-riveted joint basically loses its carrying capacity, and the rivet has little strength contribution to the joint strength. Therefore, if the rivet strength can be "added" to the adhesive layer strength through some method, the functions of both can be utilized, greatly improving the mechanical properties of the adhesive-riveted joint. SUMMARY

[0006] The present application provides an improved adhesive-riveted composite connection process and optimization method to obtain higher connection strength for the adherend and achieve the purpose of simultaneous failure of the adhesive layer and the rivet of the adhesive-riveted joint.

[0007] The present invention adopts the following technical solutions:

[0008] An improved adhesive-riveting composite connection process adds an annular gasket that fits over the rivet between the two bonded substrates. The inner diameter D2 of the annular gasket is the same as the rivet diameter D3. The design tolerance ensures smooth passage of the rivet. The area of ​​the annular gasket is 1.5-2.0 times the cross-sectional area of ​​the rivet. The rivet diameter D3 and the gasket thickness h1 are used as design variables. The gasket thickness h1 is used to control the thickness of the adhesive layer to obtain optimal connection strength.

[0009] The present invention also provides an improved method for optimizing the bonding and riveting composite connection process, comprising the following steps:

[0010] Step 1: Design and make the adhesive riveted joint: Select an appropriate annular gasket to control the thickness of the adhesive layer, then use a glue gun to evenly apply the automotive adhesive to the bonding surface of the two substrates. Place the bonding specimen on the designed special fixture to complete the overlap assembly. Finally, use a rivet gun to assemble a rivet with a diameter of D3 into the bonding specimen and cure it as required to complete the production of the adhesive riveted joint.

[0011] Step 2: Perform a quasi-static tensile test on the riveted joint: Place the riveted joint on a tensile testing machine. After the tensile test is completed, obtain the general load-displacement curve of the riveted joint through the host computer. The adhesive layer and the rivet break at displacements a1 and a2, respectively. The load-displacement curve has two peaks, and the peak load is optimized.

[0012] Step 3. Determine the optimization scheme: Initially select the gasket height h1, gasket inner diameter D2, rivet height h2, rivet diameter D3, and substrate aperture D1 as design variables. Apply a range to the gasket height h1 and rivet diameter D3, aiming to minimize the distance TPD between the two peaks. The optimization model used is as follows:

[0013] find DV=(DV1,DV2,...,DV5) T

[0014]

[0015] Step 4. Optimize the design variables gasket height h1 and rivet diameter D3: Develop an experimental design (DOE) plan, select gasket heights h1 and rivet diameters D3 of different sizes, make adhesive riveted joints in sequence and perform tensile shear tests, obtain load-displacement curves, determine the distance TPD between the peak value of the adhesive layer fracture and the peak value of the rivet failure, and find the gasket height h1 and rivet diameter D3 corresponding to TPD = 0 as the optimized design variables.

[0016] In a preferred embodiment, in the above step 1, a hole with a diameter D1 is respectively opened in the center of the bonding area of ​​the two substrates to accommodate the rivet.

[0017] In a preferred embodiment, the thickness of the adhesive layer in the above step 1 is controlled by the height h1 of the annular gasket, the inner and outer diameters of the gasket are D2 and D6, and the inner diameter of the gasket is aligned with the apertures of the two substrates.

[0018] In a preferred embodiment, the surfaces of the two substrates in the above step 1 need to be processed before bonding, including sandblasting, wiping and sun exposure.

[0019] In a preferred embodiment, the above step 4 searches for the gasket height and rivet diameter corresponding to TPD=0, and the specific process is as follows:

[0020] (1) First experimental design plan: 5 design variables are selected, each variable has n levels, and the full factorial method is selected as the experimental design method;

[0021] (2) Verify the results of the first experimental design: Make n 2 The quasi-static tensile shear tests were performed on the group of adhesive riveted joints in sequence. The load-displacement curves of each group of adhesive riveted joints were obtained, and the distance TPD between the peak value of the adhesive layer fracture and the peak value of the rivet failure was calculated. The correlation between the gasket height h1, the rivet diameter D3, and TPD was analyzed to find the gasket height and rivet diameter that minimized the TPD distance in the preliminary test plan, which were recorded as h1_opt1 and D3_opt1. The initially selected design variable interval was divided in half using the dichotomy method to determine the interval range of h1_opt1 and D3_opt1.

[0022] (3) Formulate the experimental design plan for the second time: formulate the experimental design plan for the second time based on the new interval range, and make the corresponding size of the riveted joint for tensile shear test, find the gasket height and rivet diameter that minimize the TPD distance in the second experimental plan, and record them as h1_opt2 and D3_opt2; continue to use the dichotomy method to divide the design variable interval selected for the second time in half, and confirm the interval range of h1_opt2 and D3_opt2;

[0023] (4) Formulate the test design plan for the mth time: formulate the test design plan for the mth time based on the new interval range, and make the corresponding size of the riveted joint for tensile shear test, and find the corresponding gasket height and rivet diameter that minimizes the TPD distance in the mth test plan, which is recorded as h1_opt m and D3_opt m ; It has been verified that when the gasket height is h1_opt m and the rivet diameter is D3_opt m The optimization target TPD=0 can be achieved, and the peak value of adhesive layer fracture coincides with the peak value of rivet failure.

[0024] It can be seen from the above description of the present invention that, compared with the prior art, the present invention has the following advantages:

[0025] 1. The present invention adds an annular gasket between the two base materials, which can effectively adjust the thickness of the adhesive layer and ensure sufficient riveting force, thereby obtaining higher connection strength.

[0026] 2. The present invention establishes a peak load optimization method for adhesive riveted joints. By selecting key geometric design variables of adhesive riveted joints, the peak load of the adhesive layer and the peak load of the rivet are optimized, and finally the peak load position of the adhesive layer and the peak load position of the rivet are coincident, so that the adhesive layer and the rivet fail at the same time, thereby achieving the goal of improving the load-bearing capacity and impact resistance of the adhesive riveted joint. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a top view of the assembly of the riveted joint of the present invention.

[0028] Figure 2 This is the assembly front view of the riveted joint of the present invention.

[0029] Figure 3 1 is a top view of the substrate of the present invention.

[0030] Figure 4 It is a front view of the substrate of the present invention.

[0031] Figure 5 It is a front view of the rivet of the present invention.

[0032] Figure 6 It is a top view of the annular gasket of the present invention.

[0033] Figure 7 It is a front view of the annular gasket of the present invention.

[0034] Figure 8 This is a general load-displacement curve diagram of the riveted joint of the present invention.

[0035] Figure 9 Comparison of load-displacement curves of riveted joints before and after optimization of the present invention.

[0036] Figure 10 This is a general load-displacement curve diagram of a riveted joint according to an embodiment of the present invention.

[0037] Figure 11 This is a comparison diagram of the load-displacement curves of the riveted joint before and after optimization of Example 1 of the present invention.

[0038] Figure 12 This is a performance comparison chart of the three types of connectors after optimization according to Example 1 of the present invention. DETAILED DESCRIPTION

[0039] The following describes specific embodiments of the present invention with reference to the accompanying drawings. Numerous details are provided below to provide a comprehensive understanding of the present invention, but those skilled in the art will appreciate that the present invention can be practiced without these details. Well-known components, methods, and processes are not described in detail below.

[0040] The present invention proposes an improved adhesive riveting composite connection process and provides a method for optimizing key geometric parameters and material parameters of an adhesive riveting joint.

[0041] Reference Figures 1 to 7 An improved adhesive-riveting composite joining process incorporates an annular gasket 3, which fits over a rivet 2, between the two bonded substrates 1. The gasket's inner diameter D2 is the same as the rivet's diameter D3, designed within a tolerance designed to ensure smooth passage of the rivet 2. The gasket's area is 1.5-2.0 times the cross-sectional area of ​​the rivet 2. The rivet diameter D3 and gasket thickness h1 are used as design variables, with the latter controlling the thickness of the adhesive layer 4. Optimizing the rivet diameter and gasket thickness to achieve optimal joint strength, while maintaining the same bonding area for each rivet 2, is crucial.

[0042] The present invention also provides an improved method for optimizing the bonding and riveting composite connection process, comprising the following steps:

[0043] Design and manufacture riveted joints. Figures 1 to 7 , a hole 10 with a diameter of D1 is opened in the center of the bonding area of ​​the two substrates 1 to accommodate the rivet 2. First, the surface of the substrate is processed according to the bonding technical requirements, including sandblasting, wiping with acetone, and sun exposure. In order to determine the thickness of the adhesive layer, a ring gasket 3 with an inner and outer diameter of D2 and D6 and a height of h1 is selected. After wiping with acetone, it is aligned with the hole diameter of the substrate 1. Then use a glue gun to evenly apply the automotive adhesive on the bonding surface, and place the bonding specimen on the designed special fixture to complete the overlap assembly. Finally, use a rivet gun to assemble the blind rivet 2 with a diameter of D3 in the bonding specimen, and cure the bonding joint according to the curing instructions of the adhesive to complete the production of the riveted joint.

[0044] Perform a quasi-static tensile test on the riveted joint. Place the riveted joint on the tensile testing machine. Be careful to place gaskets at both ends of the riveted joint to avoid bending moments. After the tensile test is completed, obtain the general load-displacement curve of the riveted joint through the host computer. Figure 8 The adhesive layer and rivet break at displacements a1 and a2, respectively. The load-displacement curve has two peaks, and the peak load needs to be optimized.

[0045] Optimization design is determined. Design variables are selected according to the following principles: (1) have a significant effect on the strain of the adhesive layer along the direction of external force; (2) have a significant effect on the rivet strength. It is preliminarily determined that the gasket height h1 and the inner diameter D2, the rivet height h2 and the diameter D3, and the base material hole diameter D1 are used to control the size of the adhesive layer, which belong to the key geometric design variables. The base material height H and length L3 belong to irrelevant variables, and similarly, L1 and L2 used to control the size of the bonding area have a significant effect on the strength of the adhesive-bonded joint, but their changes will not affect the strain of the adhesive layer, which is determined by the definition of strain (the ratio of the change length of the adhesive layer to the original length). Therefore, L1 and L2 also belong to irrelevant variables. The constraint condition is to apply a range to the gasket height h1 and the rivet diameter D3, and the latter rivet diameter D3 is selected according to the mechanical design manual to select several values. The optimization goal is to minimize the distance between the two peaks (The peak distance, TPD). Thus, the final optimization model is as follows:

[0046] find DV=(DV1, DV2,..., DV5) T

[0047]

[0048] Firstly, a test design (DOE1) scheme is formulated. The selected design variables are 5 in total, and each variable takes n levels, and the value conditions are shown in Table 1. The test design method is selected as the full factorial method, although there are 5 design variables, only 2 variables are independent of each other, and finally the design scheme has n 2 schemes.

[0049] Table 1 Value level of adhesive-bonded joint design variable (DOE1)

[0050]

[0051] The results of the first test design (DOE1) scheme are verified. According to the formulated test design scheme, n 2 groups of adhesive-bonded joints are made, and then they are subjected to quasi-static tensile shear tests in turn, the load displacement curves of each group of adhesive-bonded joints are obtained, and the distance TPD between the adhesive layer fracture peak value and the rivet failure peak value is calculated. The correlation analysis is carried out among the gasket height h1, the rivet diameter D3 and the TPD. The gasket height and the rivet diameter corresponding to the minimum TPD distance in the preliminary test scheme are found out, which are denoted as h1_opt1 and D3_opt1. The bisection method is used to divide the selected design variable interval in half, and the interval range where h1_opt1 and D3_opt1 are located is confirmed.

[0052] The second experimental design (DOE2) plan is formulated. Assume that the interval ranges of h1_opt1 and D3_opt1 are both in the upper half of the interval, that is, Based on the new range, a second design of experiment (DOE2) was developed, as shown in Table 2. Riveted joints of the corresponding dimensions were fabricated and subjected to tensile shear testing. The corresponding gasket height and rivet diameter that minimized the TPD distance in the second experimental plan were identified, denoted as h1_opt2 and D3_opt2. The second selected design variable range was then divided in half using the bisection method to confirm the range within which h1_opt2 and D3_opt2 fell.

[0053] Table 2 Design variable value levels of the second riveted joint (DOE2)

[0054]

[0055] Formulate the experimental design (DOEm) plan for the mth time. Assume h1_opt1, h1_opt2, ..., h1_opt m-1 , and D3_opt1, D3_opt2,...,D3_opt m-1 The interval range is in the upper half of the interval, that is, According to the new interval range, the experimental design (DOEm) scheme is formulated for the mth time, as shown in Table 3, and the corresponding size of the riveted joint is made for tensile shear test. The corresponding gasket height and rivet diameter that minimize the TPD distance in the mth experimental scheme are found and recorded as h1_opt. m and D3_opt m It has been verified that when the spacer height is h1_opt m and the rivet diameter is D3_opt m When TPD=0, the optimization target can be achieved, and the peak value of the adhesive layer fracture coincides with the peak value of the rivet failure. The schematic diagrams before and after optimization are shown as follows: Figure 9 shown.

[0056] Table 3 Design variable value levels of the mth riveted joint (DOEm)

[0057]

[0058]

[0059] The following is a specific experimental example of the "an improved adhesive riveting composite connection process optimization method" of the present invention.

[0060] Example 1

[0061] An improved method for optimizing a bonding and riveting composite connection process comprises the following steps:

[0062] First step, design and make the adhesive-riveted joint. Two pieces of substrate in the center of the bonding area with a diameter of D1 = 5 mm hole to accommodate rivets. First, according to the technical requirements of the surface of the substrate treatment, including sandblasting, wiping with acetone, and other processes. In order to determine the thickness of the adhesive layer, select the inner diameter D2 = 5 mm, outer diameter D6 = 6 mm, height h1 = 0.2 mm ring gasket, acetone wipe and substrate hole diameter alignment. Then use the glue gun evenly coated on the bonding surface, the adhesive test specimen placed in the designed special fixture to complete the lap assembly. Finally, the rivet gun with a diameter of D3 = 5 mm core-pulling rivet assembly in the adhesive joint, and according to the curing instructions of the adhesive curing of the adhesive joint, complete the adhesive-riveted joint production.

[0063] Second step, the adhesive-riveted joint for quasi-static tensile test. The adhesive-riveted joint placed on the tensile testing machine, pay attention to the two ends of the adhesive-riveted joint placed gasket, to avoid the bending moment. After the tensile test by the host computer to obtain the general load displacement curve of the adhesive-riveted joint, see Figure 5 . The adhesive layer and rivet respectively at displacement 0.4 mm and 1.63 mm fracture, load displacement curve has two peaks, the need to optimize the peak load.

[0064] Third step, determine the optimization design. Preliminary determination is used to control the size of the gasket height h1 and inner diameter D2, rivet height h2 and diameter D3, substrate hole diameter D1, these belong to the key geometric design variables. The constraint condition is to impose a range on the gasket height h1 and rivet diameter D3, the latter rivet diameter D3 according to the mechanical design manual to select several values. Optimization goal is the minimum distance between the two peaks (The peak distance, TPD). Thus the final optimization model is as follows:

[0065] find DV = (DV1, DV2,..., DV5) T

[0066]

[0067] Fourth step, the first formulation of the test design (DOE1) scheme. The selected design variables are 5, each variable takes 3 levels, the value is shown in Table 4. The test design method selected is the full permutation method, although there are 5 design variables, but only two variables are independent of each other, the final design scheme has 9 kinds of scheme.

[0068] Table 4 adhesive-riveted joint design variable value level (DOE1)

[0069]

[0070] The fifth step is to verify the result of the first test design (DOE1) scheme. According to the prepared test design scheme, 9 groups of adhesive riveted joints are prepared, and then the quasi-static tensile shear test is carried out on the adhesive riveted joints, the load displacement curve of each group of adhesive riveted joints is obtained, and the distance TPD between the peak value of the adhesive layer fracture and the rivet failure peak value is calculated. It is found that when h1=0.1 and D3=1.5, the TPD distance is the smallest, and TPD=0.31. The bisection method is continued to divide the preliminary selected design variable interval in half, that is

[0071] The sixth step is to prepare the second test design (DOE2) scheme. According to the new interval range, the second test design (DOE2) scheme is prepared, as shown in Table 2, and the corresponding size of the adhesive riveted joint is prepared for tensile shear test, and the corresponding gasket height and rivet diameter are found when the TPD distance is the smallest in the second test scheme. When h1=0.2 and D3=1.5, TPD=0. Thus, when the gasket height is 0.2 mm and the rivet diameter is 1.5 mm, the load displacement curve of the adhesive riveted joint obtained can achieve the effect of the coincidence of the adhesive fracture peak value and the rivet failure peak value.

[0072] Table 5: Value level of adhesive riveted joint design variable (DOE2)

[0073]

[0074] The seventh step is to verify the optimization result. The comparison of the load displacement curves of the adhesive riveted joints before and after optimization is shown in Figure 6 As shown in the figure, the rivet load peak value and the adhesive layer load peak value are coincided after optimization, and the strength is improved by about 20% than before optimization. Similarly, in order to further verify the accuracy of the optimization result, the riveted joint and the adhesive joint are also prepared respectively according to the optimized result, and the performance comparison of the three kinds of joints is shown in Figure 7 As shown in the figure, the strength of the riveted joint is less than 2000N, the strength of the adhesive joint is about 7000N, and the strength of the adhesive riveted joint combined with the two is close to 10000N, and the impact resistance is also greatly improved, which shows that the optimization result is effective and has application value.

[0075] The above is only a specific embodiment of the present application, but the design concept of the present application is not limited thereto, and any non-essential modification of the present application using this concept shall be regarded as an infringement of the protection scope of the present application.

Claims

1. An improved method for optimizing the bonding and riveting composite connection process, characterized in that: The adhesive-riveting composite joining process includes: adding an annular gasket that fits over the rivet between the two bonded substrates. The inner diameter D2 of the annular gasket is the same as the rivet diameter D3. The design tolerance ensures that the rivet can pass through the annular gasket smoothly. The annular gasket area is 1.5-2.0 times the cross-sectional area of ​​the rivet. The rivet diameter D3 and the gasket thickness h1 are used as design variables. The gasket thickness h1 is used to control the thickness of the adhesive layer, and the gasket height h1 and the rivet diameter D3 are optimized. The optimization method of the adhesive riveting composite connection process includes the following steps: Step 1: Design and make the adhesive riveted joint: Select an appropriate annular gasket to control the thickness of the adhesive layer, then use a glue gun to evenly apply the automotive adhesive to the bonding surface of the two substrates. Place the bonding specimen on the designed special fixture to complete the overlap assembly. Finally, use a rivet gun to assemble a rivet with a diameter of D3 into the bonding specimen and cure it as required to complete the production of the adhesive riveted joint. Step 2: Perform a quasi-static tensile test on the riveted joint: Place the riveted joint on a tensile testing machine. After the tensile test is completed, obtain the general load-displacement curve of the riveted joint through the host computer. The adhesive layer and rivet break at displacements a1 and a2, respectively. The load-displacement curve has two peaks, corresponding to the adhesive layer fracture peak and the rivet failure peak, respectively. Optimize the peak load. Step 3: Determine the optimization solution: Initially select the gasket height h1, gasket inner diameter D2, rivet height h2, rivet diameter D3, and substrate aperture D1 as design variables, and impose a range on the gasket height h1 and rivet diameter D3, with the goal of minimizing the distance TPD between the two peaks; Step 4. Optimize the design variables gasket height h1 and rivet diameter D3: Develop an experimental design (DOE) plan, select gasket heights h1 and rivet diameters D3 of different sizes, make adhesive riveted joints in sequence and perform tensile shear tests, obtain load-displacement curves, determine the distance TPD between the peak value of the adhesive layer fracture and the peak value of the rivet failure, and find the gasket height h1 and rivet diameter D3 corresponding to TPD = 0 as the optimized design variables.

2. The improved method for optimizing the bonding and riveting composite connection process according to claim 1, characterized in that: In the step 1, a hole with a diameter D1 is respectively opened in the center of the bonding area of ​​the two substrates to accommodate the rivet.

3. The improved method for optimizing the bonding and riveting composite connection process according to claim 2, characterized in that: The thickness of the adhesive layer in step 1 is controlled by the height h1 of the annular gasket, the inner and outer diameters of the gasket are D2 and D6, and the inner diameter of the gasket is aligned with the apertures of the two substrates.

4. The improved method for optimizing the bonding and riveting composite connection process according to claim 1, wherein: In step 1, the surfaces of the two substrates need to be processed before bonding, including sandblasting, wiping and sun exposure.

5. The improved adhesive riveting composite connection process optimization method according to claim 1, characterized in that: The step 4 is to find the gasket height and rivet diameter corresponding to TPD=0. The specific process is as follows: (1) The first experimental design plan was formulated: a total of 5 design variables were selected, each variable had n levels, and the full factorial method was selected as the experimental design method; (2) Verify the results of the first experimental design: Make the test plan according to the established experimental design The quasi-static tensile shear tests were performed on the group of adhesive riveted joints in sequence. The load-displacement curves of each group of adhesive riveted joints were obtained, and the distance TPD between the peak value of the adhesive layer fracture and the peak value of the rivet failure was calculated. The correlation between the gasket height h1, the rivet diameter D3, and TPD was analyzed to find the gasket height and rivet diameter that minimized the TPD distance in the preliminary test plan, which were recorded as h1_opt1 and D3_opt1. The initially selected design variable interval was divided in half using the dichotomy method to determine the interval range of h1_opt1 and D3_opt1. (3) Formulate the experimental design plan for the second time: formulate the experimental design plan for the second time based on the new interval range, and make the corresponding size of the riveted joint for tensile shear test, find the gasket height and rivet diameter that minimize the TPD distance in the second experimental plan, and record them as h1_opt2 and D3_opt2; continue to use the dichotomy method to divide the design variable interval selected for the second time in half, and confirm the interval range of h1_opt2 and D3_opt2; (4) Formulate the test design plan for the mth time: Based on the interval range divided by the dichotomy in the test design plan formulated for the m-1th time, formulate the mth test plan, and make the corresponding size of the riveted joint for tensile shear test, and find the corresponding gasket height and rivet diameter that minimizes the TPD distance in the mth test plan, which is recorded as h1_opt m and D3_opt m ; When TPD=0, the peak value of adhesive layer fracture and rivet failure coincide. and as the optimized design variables.

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