Method for optimizing clamping machining with temporary fastener distribution controlling the interlaminar structure gap

Abstract

The application belongs to the field of aerospace, automobile and ship component assembly and processing, and discloses a temporary fastener distribution optimization clamping processing method for controlling the gap of a laminated structure. The method comprises the following steps: a multi-physical field coupling simulation model of the laminated structure and the temporary fastener is established to accurately simulate the interlayer gap distribution in the pre-tightening force loading and drilling process; then, an intelligent optimization algorithm is used to iteratively optimize the installation position, quantity and pre-tightening force of the temporary fastener, and a closed-loop optimization mechanism of "simulation-computation-verification" is formed. Through multiple rounds of optimization iteration, the temporary fastener distribution scheme that can simultaneously meet the following two optimization objectives is finally obtained: (1) the maximum interlayer gap in the initial state and the processing process is controlled below the corresponding threshold value, and damage-free processing is ensured; (2) on the premise of meeting the quality requirements, the temporary fastener distribution scheme with the least time is optimized, and the processing efficiency is maximized.

Description

Technical Field

[0001] This invention belongs to the field of aerospace, automotive, and ship component assembly and processing, and particularly relates to a method for optimizing the distribution and clamping of temporary fasteners to control the gaps in laminated structures. Background Technology

[0002] In the aerospace, automotive, and shipbuilding industries, laminated structures are widely used in critical structural components due to their excellent high specific strength and high specific stiffness. These structures are typically composed of stacked composite / composite, composite / metal, or metal / metal materials, connected by bolts or rivets. To ensure assembly accuracy, the connecting holes of the laminated structure need to be integrally drilled. However, due to the large size of the components and variations in forming accuracy, initial interlayer gaps often exist during workpiece assembly. Under the axial force of drilling, these gaps widen further, causing chips to intrude into the interlayers, leading to scratches, burrs, and other quality problems. Furthermore, cleaning interlayer chips reduces production efficiency. To address these issues, temporary fasteners such as through-hole clamps and blind rivets are used before drilling to clamp the laminated structure, reducing interlayer gaps and thus suppressing drilling damage. However, the mechanism by which parameters such as the installation location, quantity, and preload of temporary fasteners affect interlayer gaps is still unclear, and there is a lack of scientific distribution theory to guide the process. While using a large number of temporary fasteners can suppress interlayer gaps, their installation and removal are time-consuming and labor-intensive, seriously affecting production efficiency. Using traditional experience-based distribution methods, drilling still frequently results in damage, leading to forced assembly or situations where assembly is impossible. This seriously affects the connection quality and stability of the structure, and in more serious cases, may cause the workpiece to be scrapped, significantly impacting the assembly accuracy and production efficiency of components.

[0003] To effectively suppress damage caused by interlayer gaps during the drilling process of laminated structures and improve processing quality and assembly accuracy, scholars have conducted relevant research and achieved certain results. Shangao Automation Engineering (Shanghai) Co., Ltd. invented a patent for "A Temporary Fastener for Aircraft Assembly" (patent publication number CN201620893015.X). This temporary fastener uses a hand tool to rotate a hexagonal screw, causing the clamping jaws to move axially and open, thus contacting the aircraft structural components. A pre-tightening is achieved by applying a set torque value, thus pre-tightening and fixing two aircraft structural components. This patent optimizes the structural design and usage method of the temporary fastener, but does not address the optimization of the distribution of temporary fasteners. Shanghai Aircraft Manufacturing Co., Ltd. invented a patent for "A Verification Device for Temporary Fasteners of Composite Materials and Its Usage Method" (patent publication number CN202010842265.1). This device uses an air gun to install temporary fasteners onto composite material plates. Through torque and pressure sensors, the torque and pre-tightening force during the tightening process are detected, achieving precise installation control of individual temporary fasteners. However, this invention is only applicable to the installation verification of a single temporary fastener and cannot guide the overall layout optimization of multiple temporary fasteners. Li Xueting et al. from Nanjing University of Aeronautics and Astronautics invented a patent for "A Method for Optimizing the Layout of Temporary Fasteners in the Pre-connection Stage of Composite Wing Boxes" (patent number CN202110536485.6). This patent, through the establishment of a finite element model and genetic algorithm, aims to reduce chatter amplitude, burr height, and chip ingress, optimizing the layout scheme within a given range of temporary fastener quantities, thereby improving drilling accuracy and assembly quality. However, this invention only optimizes the number and position of temporary fasteners, without considering the influence of initial clearance before processing and the pre-tightening force of temporary fasteners, and is only applicable to composite laminate structures; its versatility needs improvement.

[0004] In summary, existing research has made some progress in the structural design and single-piece installation control of temporary fasteners, but there are still shortcomings in the overall distribution optimization method of multiple temporary fasteners. Further research is needed on temporary fastener layout strategies that take into account both processing quality and efficiency. Summary of the Invention

[0005] To overcome the problems existing in the above-mentioned prior art, the present invention proposes an optimized clamping machining method for the distribution of temporary fasteners to control the gap of the laminated structure, and realizes the scientific optimization of the layout of temporary fasteners by combining mechanical simulation with intelligent algorithms. This method first establishes a multi-physics coupling simulation model of the laminated structure and temporary fasteners, and accurately simulates the interlayer gap distribution during preloading and drilling machining; then uses an intelligent optimization algorithm to iteratively optimize the installation position, quantity and preloading force of the temporary fasteners, forming a closed-loop optimization mechanism of "simulation - calculation - verification". Through multiple rounds of optimization iteration, a distribution plan of temporary fasteners that can simultaneously meet the following two optimization goals is finally obtained: (1) Control the maximum interlayer gap in the initial state and during the machining process below the corresponding threshold to ensure damage-free machining; (2) On the premise of meeting the quality requirements, optimize the distribution plan of temporary fasteners with the least time consumption to maximize the machining efficiency. The present invention breaks through the limitations of the traditional empirical distribution method, and significantly improves the process reliability and machining efficiency of the laminated structure assembly through quantitative analysis and intelligent optimization. Moreover, this method is applicable to laminated structures of various structures and material combinations, providing scientific and reliable process guidance for the assembly machining of laminated structure parts.

[0006] To achieve the above-mentioned invention purpose, the technical solution of the present invention is as follows:

[0007] An optimized clamping machining method for the distribution of temporary fasteners to control the gap of the laminated structure, comprising the following steps:

[0008] In the first step, clarify the parameters of the laminated structure parts, including material properties, structure, geometric dimensions, initial interlayer gap size, boundary constraint conditions and load conditions, and judge whether there is an initial interlayer gap; if there is an initial interlayer gap, sequentially execute the second, third and fourth steps; if there is no initial interlayer gap, sequentially execute the third and fourth steps;

[0009] In the second step, with the goal of suppressing the initial interlayer gap, determine the distribution plan of the temporary fasteners: establish a set i of all candidate distribution plans of the temporary fasteners, i = 1, 2,..., n; n ≥ 1, input the parameters of the laminated structure parts and the distribution plan of the temporary fasteners into the preloading deformation simulation model, simulate the initial interlayer gap distribution of the laminated structure parts under the preloading force of the temporary fasteners, output the maximum interlayer gap value a, compare a with the threshold a' through an intelligent optimization algorithm, retain the distribution plan of the temporary fasteners that satisfies a < a', discard other non-conforming distribution plans of the temporary fasteners through the intelligent optimization algorithm, and at the same time select a new distribution plan of the temporary fasteners and perform iterative optimization until all the distribution plans of the temporary fasteners that can suppress the initial interlayer gap are screened out;

[0010] Step 3: With the goal of suppressing the interlayer gap during the machining process, determine the distribution plan of the temporary fasteners: If Step 2 is executed, use the distribution plan of the temporary fasteners obtained in Step 2 as the current candidate plan set k, where k = 1, 2, …, m; m ≤ n; if Step 2 is not executed, use the set i of all candidate temporary fastener distribution plans as the current candidate plan set k, where k = 1, 2, …, m; m = n, and simulate the interlayer gap situation during the drilling process for the candidate temporary fastener distribution plans through the drilling deformation simulation model, and output the maximum interlayer gap value b; compare b with the threshold b′ through the intelligent optimization algorithm, retain the candidate temporary fastener distribution plans that meet b < b′, discard other non-conforming temporary fastener distribution plans, and select a new temporary fastener distribution plan for iterative optimization to obtain the distribution plan of the temporary fasteners that suppress the interlayer gap during the machining process;

[0011] Step 4: With the goal of maximizing the machining efficiency, determine the distribution plan of the temporary fasteners: Use the set j of the distribution plans of the temporary fasteners obtained in Step 3 as candidates, where j = 1, 2, …, s; s ≤ m, calculate the total machining time T of each temporary fastener distribution plan, including the installation and disassembly time of the temporary fasteners and the drilling time of the laminated structural parts, screen the optimal temporary fastener distribution plan with the goal of minimizing the total machining time T, and use this to guide the installation of the temporary fasteners and the drilling of the laminated structure.

[0012] Furthermore, the intelligent optimization algorithm judges the feasibility of the current temporary fastener distribution plan by comparing the maximum interlayer gap value output by the simulation model with the threshold; and through similarity analysis, excludes the temporary fastener distribution plans similar to the current infeasible temporary fastener distribution plans to narrow the search scope; selects a new temporary fastener distribution plan based on the genetic algorithm or particle swarm algorithm, and iteratively optimizes until the evaluation of all temporary fastener distribution plans is completed.

[0013] Furthermore, the deformation simulation model includes a pre-tightening deformation simulation model and a drilling deformation simulation model, which respectively simulate the change of the interlayer gap during the pre-tightening force loading process and the drilling process. Its input parameters at least include the material properties, geometric dimensions, distribution plan of the temporary fasteners, boundary constraint conditions and load conditions of the laminated structural parts, and the output parameter is the maximum interlayer gap value a or b; the deformation simulation model is a finite element model, a multi-body dynamics model or a data-driven surrogate model.

[0014] Furthermore, the threshold a′ in Step 2 is set according to the initial interlayer gap tolerance, and the threshold b′ in Step 3 is set according to the critical conditions for chip intrusion and interlayer burr generation.

[0015] Furthermore, the laminated structural components include laminates of composite materials and composite materials, laminates of composite materials and metals, or laminates of metals, and the temporary fasteners include bolts, temporary rivets, or through-hole clamps.

[0016] The beneficial effects of this invention are as follows: This invention provides a method for optimizing the distribution and clamping of temporary fasteners in laminated structures. By establishing a closed-loop optimization process of "simulation-optimization-verification," it combines a mechanical simulation model with intelligent algorithms to accurately simulate the gap changes under the action of preload and drilling force. This intelligently adjusts the distribution of temporary fasteners, thereby controlling the initial interlayer gap and the processing interlayer gap below the corresponding gap thresholds. With the goal of minimizing total processing time, it selects the optimal temporary fastener distribution scheme, achieving scientific optimization of the temporary fastener layout. This method overcomes the limitations of traditional empirical distribution methods, effectively suppressing interlayer gaps and avoiding quality problems such as interlayer scratches and burrs, significantly improving assembly accuracy. Simultaneously, while ensuring processing quality, this method minimizes the installation, disassembly, and processing time of temporary fasteners, greatly improving component production efficiency. This method is applicable to laminated structures of various structures and material combinations, providing scientific and reliable process guidance for the assembly and processing of laminated structural components. Attached Figure Description

[0017] Figure 1 This is a flowchart of a method for optimizing the distribution and clamping of temporary fasteners to control the gaps in a laminated structure.

[0018] Figure 2 This is an example of an optimized clamping process method using temporary fastener distribution that controls the gaps between stacked structures.

[0019] Figure 3 These are two typical temporary fastener structures: through-hole clamp (a) and pop rivet (b).

[0020] In the diagram: 1. Lower workpiece; 2. Upper workpiece; 3. Drill template; 4. Temporary fastener. Detailed Implementation

[0021] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings and technical solutions.

[0022] This embodiment discloses a method for optimizing the distribution and clamping of temporary fasteners to control the gaps in a laminated structure, referring to... Figure 1 and Figure 2 The method combines a mechanical simulation model with an intelligent algorithm to intelligently adjust the distribution of temporary fasteners, thereby achieving scientific optimization of the temporary fastener layout.

[0023] The first step is to clarify the relevant parameters and drilling conditions of the laminated structural components:

[0024] S1.1 Figure 2 The lower layer workpiece 1 is a titanium alloy I-beam type workpiece with a thickness of 4mm, and the upper layer workpiece 2 is a composite material plate with a thickness of 2mm. The drilling template 3 has holes arranged on it for installing temporary fasteners 4 or for drilling. The temporary fasteners 4 are nut-type through-clamps. The lower layer workpiece 1, the upper layer workpiece 2 and the drilling template 3 are stacked and assembled, and are temporarily fastened together by the temporary fasteners 4. During drilling, the entire stacked component is fixed through the bottom of the lower layer workpiece 1. The drill bit drills through the holes on the drilling template 3 to drill through the stacked structure of the upper and lower workpieces. For ease of calculation, the axial force of the drilling is equivalent to a concentrated load acting at the drilling position.

[0025] S1.2 Determine whether the stacked structure has an initial interlayer gap. If it does, proceed to step two; otherwise, proceed to step three. In this embodiment, an initial gap is preset, so step two is executed.

[0026] The second step is to optimize the distribution scheme of temporary fasteners with the goal of suppressing the initial interlayer gap:

[0027] S2.1 Define the set of all candidate temporary fastener distribution schemes i (i = 1, 2, 3, ..., n; n ≥ 1);

[0028] S2.2 Input the workpiece parameters and the distribution scheme of temporary fasteners into the pre-tightening deformation simulation model. In this embodiment, the finite element simulation model is used to accurately simulate the interlayer gap distribution during the pre-tightening force loading process.

[0029] S2.3 uses a pre-tightening deformation simulation model to output the maximum interlayer gap 'a' during the pre-tightening force loading process of temporary fasteners;

[0030] S2.4 Input the maximum interlayer gap 'a' into the intelligent optimization algorithm and determine whether 'a' is less than the given threshold 'a'. If it is, it means that the distribution scheme of the temporary fastener can suppress the initial interlayer gap, so the distribution scheme of the temporary fastener is retained. Otherwise, the distribution scheme of the temporary fastener is discarded. At the same time, according to the intelligent optimization algorithm, other similar non-compliant temporary fastener distribution schemes are discarded, and a new temporary fastener distribution scheme is selected and re-input into the pre-tightening deformation simulation model for calculation.

[0031] S2.5 optimizes the distribution scheme of temporary fasteners that can suppress the initial interlayer gaps through multiple rounds of iteration.

[0032] The third step is to optimize the distribution scheme of temporary fasteners, with the goal of suppressing interlayer gaps during processing:

[0033] S3.1 The distribution scheme of the temporary fasteners selected in the second step is taken as the current candidate distribution scheme set k (k=1,2,3,…,m; m≥1), and the total number of schemes k is less than or equal to scheme i, that is, m≤n;

[0034] S3.2 Input the workpiece parameters and the distribution scheme of temporary fasteners into the drilling deformation simulation model to accurately simulate the interlayer gap distribution during the drilling process;

[0035] S3.3 outputs the maximum interlayer gap b during the drilling process using a drilling deformation simulation model;

[0036] S3.4 Input the maximum interlayer gap b into the intelligent optimization algorithm and determine whether b is less than the threshold b'. If it is, it means that the distribution scheme of the temporary fastener can suppress the interlayer gap during the processing, so the distribution scheme of the temporary fastener is retained. Otherwise, the distribution scheme of the temporary fastener is discarded. At the same time, according to the intelligent optimization algorithm, other similar substandard temporary fastener distribution schemes are discarded, and a new temporary fastener distribution scheme is selected and re-input into the drilling deformation simulation model for calculation.

[0037] S3.5 optimizes the distribution scheme of temporary fasteners that can suppress interlayer gaps during processing through multiple rounds of iteration.

[0038] The fourth step is to optimize the distribution scheme of temporary fasteners with the goal of maximizing processing efficiency:

[0039] S4.1 The distribution scheme of the temporary fasteners obtained in the third step is taken as the current candidate distribution scheme set j (j=1,2,3,…,s; s≥1), and the total number of schemes j is less than or equal to the number of schemes k, i.e. s≤m;

[0040] S4.2 Calculate the total time T for each of the distribution schemes j of temporary fasteners, where T = installation time of temporary fasteners + disassembly time + drilling time;

[0041] S4.3 With the goal of minimizing the total time T, compare all distribution schemes of temporary fasteners in the distribution scheme set j and discard the distribution schemes of temporary fasteners that do not meet the requirements.

[0042] S4.4 Through multiple rounds of comparison and optimization, the optimal distribution scheme of temporary fasteners is obtained;

[0043] S4.5 Install temporary fasteners according to the optimal distribution scheme of temporary fasteners, and complete the drilling of the holes to be processed and the reaming of the temporary fastener mounting holes, thereby suppressing the initial interlayer gap and the processing interlayer gap, and significantly improving production efficiency while ensuring processing quality, so as to achieve high-quality and high-efficiency drilling processing of laminated structural parts.

[0044] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for optimizing the distribution and clamping of temporary fasteners to control the gaps in a laminated structure, characterized in that, The steps include the following: The first step is to clarify the parameters of the laminated structure, including material properties, structure, geometric dimensions, initial interlayer gap size, boundary constraint conditions, and load conditions, and determine whether there is an initial interlayer gap; if there is an initial interlayer gap, then steps two, three, and four are executed in sequence; if there is no initial interlayer gap, then steps three and four are executed in sequence; The second step is to determine the distribution plan of the temporary fasteners with the goal of suppressing the initial interlayer gap: establish a set i of all candidate temporary fastener distribution plans, where i = 1, 2, …, n; n≥1. Input the parameters of the laminated structure and the distribution plan of the temporary fasteners into the pre-tightening deformation simulation model, simulate the initial interlayer gap distribution of the laminated structure under the pre-tightening force loading of the temporary fasteners, output the maximum interlayer gap value a, compare a with the threshold a′ through the intelligent optimization algorithm, retain the distribution plans of the temporary fasteners that satisfy a < a′, discard other non-conforming distribution plans of the temporary fasteners through the intelligent optimization algorithm, and at the same time select new distribution plans of the temporary fasteners and iterate and optimize until all distribution plans of the temporary fasteners that can suppress the initial interlayer gap are screened out; The third step is to determine the distribution plan of the temporary fasteners with the goal of suppressing the interlayer gap during the processing: if the second step is executed, use the distribution plan of the temporary fasteners obtained in the second step as the current candidate plan set k, where k = 1, 2, …, m; m≤n; if the second step is not executed, use the set i of all candidate temporary fastener distribution plans as the current candidate plan set k, where k = 1, 2, …, m; m = n, and simulate the interlayer gap situation of the candidate temporary fastener distribution plan during the drilling process through the drilling deformation simulation model, and output the maximum interlayer gap value b; compare b with the threshold b′ through the intelligent optimization algorithm, retain the candidate temporary fastener distribution plans that satisfy b < b′, discard other non-conforming distribution plans of the temporary fasteners, and select new distribution plans of the temporary fasteners for iterative optimization to obtain the distribution plan of the temporary fasteners that suppress the interlayer gap during the processing; The fourth step is to determine the distribution plan of the temporary fasteners with the goal of maximizing the processing efficiency: take the set j of the distribution plans of the temporary fasteners obtained in the third step as candidates, where j = 1, 2, …, s; s≤m, calculate the total processing time T of each distribution plan of the temporary fasteners, including the installation and disassembly time of the temporary fasteners and the drilling time of the laminated structure, screen the optimal distribution plan of the temporary fasteners with the goal of minimizing the total processing time T, and use this to guide the installation of the temporary fasteners and the drilling process of the laminated structure.

2. The temporary fastener distribution optimization clamping processing method for controlling the gap of the stacked structure according to claim 1, characterized in that, The intelligent optimization algorithm judges the feasibility of the current distribution plan of the temporary fasteners by comparing the maximum interlayer gap value output by the simulation model with the threshold; and through similarity analysis, excludes the distribution plans of the temporary fasteners that are similar to the current infeasible distribution plans of the temporary fasteners to narrow the search range; selects new distribution plans of the temporary fasteners based on the genetic algorithm or the particle swarm algorithm, and iteratively optimizes until the evaluation of all distribution plans of the temporary fasteners is completed.

3. The temporary fastener distribution optimization clamping processing method for controlling the gap of the laminated structure according to claim 1, characterized in that, The deformation simulation model includes a preload deformation simulation model and a drilling deformation simulation model, which respectively simulate the changes in interlayer gap during the preload loading process and the drilling process. Its input parameters include at least the material properties, geometric dimensions, distribution scheme of temporary fasteners, boundary constraints and load conditions of the laminated structure, and the output parameter is the maximum interlayer gap value a or b. The deformation simulation model is a finite element model, a multibody dynamics model or a data-driven proxy model.

4. The temporary fastener distribution optimization clamping processing method for controlling the gap of the stacked structure according to claim 1, characterized in that, The threshold a′ in the second step is set according to the initial interlayer gap tolerance, and the threshold b′ in the third step is set according to the critical conditions of chip intrusion and interlayer burr generation.

5. The temporary fastener distribution optimization clamping processing method for controlling the gap of the stacked structure according to claim 1, characterized in that, The laminated structural components include laminates of composite materials and composite materials, laminates of composite materials and metals, or laminates of metals and metals. Temporary fasteners include bolts, temporary rivets, or through-hole clamps.

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