Large-scale assembly tool rigidity and strength hierarchical checking method based on meshless simulation

Abstract

The invention provides a large-scale assembly tool rigidity and strength hierarchical checking method based on meshless simulation, which is based on a meshless simulation method, adopts an overall-to-local hierarchical calculation path, emphatically considers the strength checking of a bolt connecting piece and a welding seam, and provides a corresponding checking method. Through the method provided by the invention, a rigidity and strength checking system of the large-scale complex assembly tool is established, the comprehensiveness and accuracy of checking are improved, and more comprehensive guidance is provided for the design of the large-scale assembly tool.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of digital design of aviation manufacturing equipment, and particularly relates to a large assembly tool rigidity and strength hierarchical checking method based on meshless simulation. BACKGROUND

[0002] In the modern industrial manufacturing system, the aerospace industry has extremely strict requirements on product assembly quality. In this field, the overall structural rigidity and strength of the assembly tool and the local connection strength are one of the key elements that determine whether the product assembly quality can meet the standards. Rigidity and strength checking has become a "safety valve" and "optimization guide" in the design of assembly tools, on the one hand to ensure that the design meets safety standards, and on the other hand to provide direction for the improvement and perfection of the design, and its important value runs through the whole life cycle from the initial design stage to the operation stage. The rigidity and strength checking process is a systematic and rigorous process, and its core goal is to accurately evaluate the structural integrity and bearing capacity of the tool under the expected use conditions. However, with the continuous development of the equipment manufacturing industry towards high integration, the complexity of assembly tools is increasing, and the size is becoming increasingly large. This change makes it difficult for traditional experience-based checking methods to meet the rigidity and strength checking needs of large assembly tools.

[0003] Although the current finite element analysis technology has brought revolution to the rigidity and strength checking of assembly tools, changing it from the traditional mode of relying on "trial and error" to the scientific mode of "simulation-driven". However, when this technology is applied to complex assemblies, there is a problem of long pre-processing and calculation time. This drawback seriously restricts the iteration speed and flexibility of the design, resulting in low design efficiency. Therefore, designers usually simplify the complex assembly model significantly, which includes ignoring key connection parts such as bolts and welds, and then only simulating the rigidity and strength of the simplified overall structure. Given the high requirements of aircraft assembly tools on positioning accuracy and stability, bolts and welds as key connection parts are crucial to their quality and strength. If these connections have defects or insufficient strength, they are likely to fail prematurely during actual use. Once the connection part fails, it will directly affect the positioning accuracy of the assembly tool, and thus have a serious negative impact on the product assembly quality.

[0004] Therefore, while checking the overall structural rigidity and strength of large and complex assembly tools, detailed checking of key connection parts such as bolts and welds must also be carried out. In this way, the reliability, safety and economy of the entire assembly tool structure can be ensured, providing a solid guarantee for the high-quality assembly of aerospace products. SUMMARY

[0005] To solve the problem that the key connection position checking is neglected due to the comprehensive effect of factors such as technical limitations, unclear specifications, excessive reliance on experience and unreasonable resource allocation in the stiffness and strength checking process of a large assembly tooling, the present application provides a large assembly tooling stiffness and strength hierarchical checking method based on meshless simulation, which is a multi-dimensional checking method for the overall structural strength of the aircraft assembly tooling and the local bolt / weld joint. The method aims to establish a stiffness and strength checking system for large complex assembly tooling through meshless rapid simulation technology, improve the comprehensiveness and accuracy of the checking, and provide more comprehensive guidance for the design of large assembly tooling. The technical solution is as follows: A large assembly tooling stiffness and strength hierarchical checking method based on meshless simulation, which adopts a meshless method to calculate the stiffness and strength of the overall structure and the local key connection position of the large assembly tooling. The method comprises the following steps: Step one, material properties are given to the large assembly tooling numerical model, a binding contact relationship is established, boundary conditions are applied, external loads and tooling gravity loads are applied; Step two, the meshless method is used to calculate the stress field and deformation field of the overall structure of the large assembly tooling numerical model in step one; Step three, whether the overall structure of the large assembly tooling meets the stiffness and strength design requirements is judged based on the stress field and deformation field of the overall structure; Step four, when the overall structure of the large assembly tooling meets the stiffness and strength design requirements, the local key connection position with the maximum stress at the connection is identified based on the stress field of the overall structure; Step five, the counterforce of the associated components of the local key connection position in step four is extracted; Step six, only the associated components in step five are retained, and refined modeling is performed to obtain a local model, which needs to include bolted joints or welds; the cross section of the weld is a right triangle; Step seven, the counterforce in step five, the existing boundary conditions and the existing loads are applied to the same position of the local model in step six, the bolted joint and the associated component adopt friction contact, and then the stress field of the local model is calculated; Step eight, the strength of the bolted joint or the weld is obtained based on the stress field of the local model in step seven.

[0006] The above steps provide a complete checking method for the stiffness and strength checking of large complex assembly tooling, and improve the comprehensiveness of the checking.

[0007] Optionally, the large assembly tooling numerical model in step one does not include bolts and welds, and the large assembly tooling numerical model is used for mechanical calculation of the overall structure. In this way, the pre-processing and calculation time can be reduced.

[0008] In step one, the load coefficient when the external load is applied is taken as 1.5; the assembly gravity load is applied in combination with the gravity acceleration. The application considers the safety factor when the external load is applied; the assembly gravity load can ensure that the counterforce extracted conforms to the actual situation, and is a necessary condition for the strength checking of the bolted connection and the weld.

[0009] Optionally, in step three, based on the stress field and the deformation field of the overall structure, the maximum deformation criterion and the maximum Mises stress criterion are used to judge whether the overall structure of the large assembly tooling meets the rigidity and strength design requirements.

[0010] Optionally, in step five, the associated components need to include multiple parts connected by bolted connections or welds. In this way, the local model can be fully and accurately represented.

[0011] Optionally, in step six, the weld is a solid model, and single-sided welding or double-sided welding needs to be considered. The solid model is used to extract internal forces, and single-sided welding or double-sided welding makes the welding conform to the actual situation to ensure the accuracy of the internal forces.

[0012] Optionally, in step eight, the maximum Mises stress criterion is used for strength checking of the bolted connection; and the weld strength checking formula is used for strength checking of the weld, and the weld strength checking formula is and wherein, is the stress parallel to the hypotenuse on the weld cross section; is the stress perpendicular to the hypotenuse on the weld cross section; is the stress parallel to the welding direction on the weld hypotenuse; is the minimum ultimate strength of the weld plate; is the material coefficient, which is determined based on the steel type; is the partial coefficient, taken as 1.25.

[0013] Optionally, when performing weld strength checking, a local Cartesian coordinate system is established on the cross section where the maximum stress of the weld is located, one coordinate axis of the local Cartesian coordinate system is perpendicular to the hypotenuse of the cross section, and the other coordinate axis is parallel to the hypotenuse of the cross section, and then the values of , , are extracted based on the stress field of the local model. In this way, the values of , , can be directly obtained without complex coordinate conversion.

[0014] The beneficial effects of the application are as follows: This invention proposes a layered stiffness and strength verification method for large-scale assembly tooling based on meshless analysis. This method, from overall to local, encompasses verification methods for bolts and welds, establishing a stiffness and strength verification system for large and complex assembly tooling. This improves the comprehensiveness of the verification and provides more comprehensive guidance for the design of large-scale assembly tooling. Furthermore, this method, based on meshless analysis, can quickly obtain calculation results, reducing the simulation calculation time for large-scale assembly tooling from several days to minutes, ensuring the method's good feasibility. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of a large assembly tooling structure; Figure 2 This refers to the overall structural stress field and the local structure of bolted connections. Figure 3 This is a schematic diagram of reaction force extraction during bolt strength verification. Figure 4 This is a schematic diagram illustrating the reaction forces, loads, and boundary conditions during the bolt strength verification process. Figure 5 This is a partial structural diagram and its bolt stress contour plot; Figure 6 This refers to the stress field of the overall structure and the local structures of welded connections.

[0016] Figure 7 This is a schematic diagram of reaction force extraction during the weld strength verification process; Figure 8 Schematic diagrams of weld seams, single-sided welds, and double-sided welds; Figure 9 A schematic diagram illustrating the reactions, loads, and constraints during the weld strength verification process; Figure 10 For weld seam , , Schematic diagram of the stress field and its local coordinate system; Figure 11 for , , A schematic diagram of the weld; Figure 12 This is a schematic diagram of the method flow of the present invention. Detailed Implementation

[0017] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0018] The features and illustrative embodiments of various aspects of the present application will be described below in detail. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present application. However, it will be apparent to one of ordinary skill in the art that the present application can be practiced without some of these specific details. The description of the embodiments below is merely intended to provide a better understanding of the present application by showing examples of the present application. The present application is in no way limited to any specific settings and methods presented below, but covers any improvements, replacements and modifications of structures, methods and devices without departing from the spirit of the present application. In the drawings and the following description, well-known structures and technologies are not shown to avoid unnecessary obscuring of the present application.

[0019] It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict, and each embodiment can be referred to and cited by the other embodiments.

[0020] The present application will be described in detail below with reference to the drawings and specific embodiments.

[0021] Figure 1 A large assembly tool structure schematic diagram is shown. Referring to Figure 12 , the cgr format of the model is exported through Catia, and then imported into SimSolid. Since a large number of small connecting parts such as bolts and screws are included in the structure, a large number of bolts and screws will affect the efficiency, and in the overall structure stiffness calculation, they can be ignored, so all the bolts are deleted before exporting. After the preparation work of the three-dimensional model is completed, the following steps are performed: Step one: assign corresponding material properties, set binding contact, boundary conditions, gravitational acceleration and external load in SimSolid. The applied external load is 1.5 times the actual load.

[0022] Step two: perform mechanical calculation on the overall structure to obtain the stress field and deformation field of the overall structure.

[0023] Step three, based on the stress field and deformation field of the overall structure, the maximum deformation criterion and the maximum Mises stress criterion are used to judge whether the large assembly tool overall structure meets the stiffness design requirements.

[0024] Step four, when the overall structure of the large assembly tooling meets the requirements of the stiffness and strength design, further strength checking is performed on the bolted joints and welds based on the stress field of the overall structure, specifically: (1) Strength checking of bolted joints: The part with the maximum stress connected by the bolt is identified from the stress field of the overall structure, as shown in Figure 2 . This part may cause a large stress on the bolt, which has a risk of failure.

[0025] The counterforce of the identified part is extracted, as shown in Figure 3 .

[0026] The corresponding associated components are retained, and the bolted joint is added, and then the counterforce, boundary conditions, and loads are applied at the same positions of the associated components, as shown in Figure 4 . Since the bolt connection is adopted, the binding contact used to replace the bolt connection needs to be changed to friction contact when going from the overall structure to the local structure.

[0027] After the local structure is set, it is calculated to obtain the stress field of the bolt, as shown in Figure 5 . The maximum stress of the bolt at this part is 5 MPa, which is obviously lower than its yield strength of 353 MPa. Therefore, the bolt at this position is safe.

[0028] (2) Strength checking of welds: The part with the maximum stress connected by the weld is identified from the stress field of the overall structure, as shown in Figure 6 . This part may have stress concentration at the welding position, which may cause material failure.

[0029] The counterforce of the identified part is extracted, as shown in Figure 7 .

[0030] The corresponding associated components are retained, and the weld is modeled according to the actual situation. The square tube column is composed of four plates welded together, therefore, the last plate is welded on one side only, i.e. both single-sided and double-sided welding, as shown in Figure 8 .

[0031] The counterforce, boundary conditions, and loads are applied at the same positions, as shown in Figure 9 . Since the weld connection is adopted, the binding contact used to replace the weld connection needs to be changed to friction contact when going from the overall structure to the local structure.

[0032] After that, the simulation calculation is performed to obtain the stress field of the weld, and a local Cartesian coordinate system is established on the cross section where the maximum stress is located, one coordinate axis of which is perpendicular to the hypotenuse of the cross section, and the other coordinate axis is parallel to the hypotenuse of the cross section, as shown in Figure 10 . The local coordinate system is established to facilitate the direct extraction of ​​, , The numerical value of the stress is , , The representation on the model is shown in Figure 11 Since the stress in the weld is non-uniform, and it is difficult to calculate the average value of all points, the average value of the maximum and minimum values is taken.

[0033] In this embodiment, = 17.02 MPa, = 4.46 MPa, = 10 MPa, = 235 MPa, = 0.8, = 1.25. Therefore, we have:

[0034] And

[0035] It can be seen that the weld is also safe.

[0036] The above only expresses the embodiments of the present application, and the description is more specific and detailed, but it cannot be understood as a limitation on the scope of the patent. It should be noted that for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the scope of protection of the present application. In addition, the parts of the present application not described in detail are all conventional techniques.

Claims

1. A large assembly tool rigidity strength layered checking method based on meshless simulation, characterized in that, The method comprises the following steps: Step one, material properties are given to the large assembly tooling numerical model, a binding contact relationship is established, boundary conditions are applied, external loads and tooling gravity loads are applied; Step two, the stress field and deformation field of the large assembly tooling numerical model in step one are calculated by using the meshless method; Step three, whether the large assembly tooling structure meets the stiffness and strength design requirements is judged based on the stress field and deformation field of the overall structure; Step four, when the large assembly tooling structure meets the stiffness and strength design requirements, the local key connection position with the maximum stress is identified based on the stress field of the overall structure; Step five, the counterforce of the associated components of the local key connection position in step four is extracted; Step six, only the associated components in step five are retained, and fine modeling is performed to obtain a local model, which needs to include bolted joints or welds, and the cross section of the weld is a right triangle; Step seven, the counterforce in step five, the existing boundary conditions and the existing loads are applied to the same position of the local model in step six, the bolted joint and the associated component adopt frictional contact, and then the stress field of the local model is calculated; Step eight, the strength of the bolted joint or the weld is obtained based on the stress field of the local model in step seven.

2. The method of claim 1, wherein, The large assembly tooling numerical model in step one does not include bolts and welds, and the large assembly tooling numerical model is used for mechanical calculation of the overall structure.

3. The method of claim 1, wherein, In step one, the load coefficient when the external load is applied is 1.5; the tooling gravity load is applied in combination with the gravity acceleration.

4. The method of claim 1, wherein, In step three, whether the large assembly tooling structure meets the stiffness and strength design requirements is judged based on the stress field and deformation field of the overall structure by using the maximum deformation criterion and the maximum Mises stress criterion.

5. The method of claim 1, wherein, In step five, the associated components need to include multiple parts connected by bolted joints or welds.

6. The method of claim 1, wherein, In step six, the weld is a solid model, and single-sided welding or double-sided welding needs to be considered.

7. The method of claim 1, wherein, In step eight, the maximum Mises stress criterion is used for strength checking of the bolted connection; the weld strength checking formula is used for strength checking of the weld, and the weld strength checking formula is and wherein, is the stress parallel to the hypotenuse on the weld cross section; is the stress perpendicular to the hypotenuse on the weld cross section; is the stress parallel to the welding direction on the weld hypotenuse; is the minimum ultimate strength of the weld plate; is the material coefficient, determined based on the steel type; is the partial coefficient, taken as 1.

25.

8. The method of claim 7, wherein, When the weld strength is checked, a local Cartesian coordinate system is established on the cross section where the maximum stress of the weld is located. One coordinate axis of the local Cartesian coordinate system is perpendicular to the hypotenuse of the cross section, and the other coordinate axis is parallel to the hypotenuse of the cross section. Then the numerical values of the stress field based on the local model are extracted , , .

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