Finite element simulation design method for interference assembly process of thin-walled part

Abstract

The invention provides a finite element simulation design method for an interference assembly process of a thin-wall part. The thin-wall part is composed of a thin-wall containing part and a contained part. And when the thin-wall containing part and the contained part are in interference assembly in a pressing machine, the thin-wall containing part and the contained part are assembled and combined through three-dimensional modeling, and finite element analysis software is imported. According to the method, the precision and reliability of the interference assembly process of the thin-wall part are effectively improved, a press-fitting machine model is simplified, the finite element analysis time is shortened, and the efficiency is improved; the product quality is stable and reliable, and the product yield is improved.

Description

Technical Field

[0001] The invention specifically relates to a finite element simulation design method for an interference assembly process of a thin-walled part. Background Art

[0002] Stainless steel is widely used in a variety of fields, including aerospace, automotive manufacturing, and precision instruments. Stainless steel has excellent mechanical properties and corrosion resistance, but its high hardness and large elastic modulus make it easy to generate large stresses and deformations during interference fit. Furthermore, the thermal expansion coefficient of stainless steel is relatively high, making dimensional changes during hot and cold fitting more significant and increasing the difficulty of assembly. Because the product requires thinner walls for stainless steel parts, they are prone to deformation when subjected to external forces. During interference fit, if the applied force is excessive or uneven, it can cause plastic deformation or even rupture of the part. Furthermore, due to the high precision requirements for the mating surfaces of thin-walled parts, any slight deformation or damage can affect the quality and performance of the assembly.

[0003] Currently, the assembly of interference-fit components primarily relies on presses, which have a relatively low degree of automation. The entire assembly process is essentially performed by on-site workers. During manual assembly, component quality is affected by subjective and objective factors such as the operator's mood and experience. This results in poor consistency in component assembly quality, low assembly pass rates, and significant waste of resources. To address this, the following technical solutions are proposed. Summary of the Invention

[0004] The technical problem solved by the present invention is to provide a finite element simulation design method for the interference assembly process of thin-walled parts, so as to solve the problem of how to improve the precision and reliability of the interference assembly process of thin-walled parts.

[0005] The technical solution adopted by the present invention is: a finite element simulation design method for the interference assembly process of thin-walled parts, wherein the thin-walled parts are composed of a thin-walled containing part and a contained part; when the thin-walled containing part and the contained part are interference assembled on a press, the thin-walled containing part and the contained part are assembled and combined through three-dimensional modeling and imported into finite element analysis software.

[0006] In the above technical solution, further: during the three-dimensional modeling, the press machine model is simplified;

[0007] The steps include:

[0008] Step 1: Remove features that have little impact on the overall mechanical behavior;

[0009] Step 2: Simplify the press-fitting mechanism components;

[0010] Step 3: Replace the mechanism processing process by applying force and position constraints through the contact surface.

[0011] In the above technical solution, further: the press model only retains the parts in contact with the thin-walled containing part and the contained part, and the other parts are constrained by position conditions. Among them, the press end in contact with the contained part limits the displacement and rotation in the X and Y directions and the rotation in the Z direction; the limiting tooling in direct contact with the thin-walled containing part completely fixes and limits the displacement and rotation in the X, Y, and Z directions.

[0012] In the above technical solution, further: it also includes a grid division step.

[0013] In the above technical solution, preferably: the thin-walled containing member is a stainless steel thin-walled cylinder; and the contained member is a ratchet end.

[0014] In the above technical solution, preferably, the thin-walled containing part and the contained part are made of AISI-304.

[0015] In the above technical solution, preferably: during the press-fitting process, the press head of the press-fitting machine applies a force of 300 to 450 N in the -Z direction to the contained part, the displacement distance is 1 mm, and the interference amount is 0.01 mm.

[0016] In the above technical solution, further: the interference fit end of the contained part is formed with a taper of 2°.

[0017] In the above technical solution, preferably: the friction type is small slip, penalty function-Coulomb friction, and the friction coefficient is 0.2.

[0018] In the above technical solution, preferably, the finite element analysis software is Huaxi A-CAE for CAXA 3D.

[0019] The advantages of the present invention compared with the prior art are:

[0020] 1. The introduction of the finite element analysis software of the present invention effectively improves the precision and reliability of the interference fit assembly process of thin-walled parts.

[0021] 2. The present invention simplifies the press model, reduces finite element analysis time, and improves efficiency.

[0022] 3. The setting of the press-fitting displacement distance and the interference amount of the present invention meets the interference assembly requirements of specific products, and the product quality is stable and reliable.

[0023] 4. The contained part of the present invention is tapered and can be approximately regarded as a guiding part, which can not only facilitate the automatic alignment of the ratchet end, but also delay the position of plastic deformation, thereby improving the product yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG1(a) is a front view of the interference fit of a thin-walled containing part and a contained part of a non-standard thin-walled part according to the present invention;

[0025] FIG1( b ) is a cross-sectional view taken along line AA of FIG1( a );

[0026] Figure 1(c) is a CC cross-sectional view of Figure 1(b);

[0027] Figure 2 It is a three-dimensional modeling diagram of the present invention;

[0028] Figure 3 Dividing a grid diagram for the position condition constraints of the present invention;

[0029] Figure 4 This is the pressure distribution diagram at the beginning of the press-fitting in the prior art;

[0030] Figure 5 The stress distribution diagram is completed by pressing the existing technology;

[0031] Figure 6 This is a diagram of the plastic deformation of the contact surface material during press-fitting in the prior art;

[0032] Figure 7 This is the state of the contact part cylinder after the prior art press-fitting is completed;

[0033] Figure 8 A simplified diagram of the taper optimization of the ratchet end of the contained member according to the present invention;

[0034] Figure 9 This is the pressure distribution diagram at the start of press-fitting after optimization of the present invention;

[0035] Figure 10 This is the stress distribution diagram after press-fitting after optimization of the present invention;

[0036] Figure 11 This is the plastic deformation diagram of the press-fit contact surface material after optimization of the present invention;

[0037] Figure 12 The state of the cylinder of the contact portion after the optimized press-fitting of the present invention is completed;

[0038] In the figure: 1-thin-wall containing part, 2-contained part, 3-pressing head of press fitting machine, 4-bottom support of press fitting machine. DETAILED DESCRIPTION

[0039] The following will be combined with Figures 1-3 of the embodiments of the present invention. Figure 8-12 And compared with the existing technology Figure 4-7 , the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0040] Based on the results of finite element analysis, the present invention remanufactured the part and then press-fitted it. After press-fitting, no curling marks were observed on the surface of the cylinder. Cylinders made of other materials were press-fitted using the above method, and similarly, no obvious defects were observed. By establishing a mechanical model and utilizing elastic-plastic finite element analysis, the press-fitting process was verified to be effective, and the uncertainty factors of some non-standard parts can be optimized, thereby improving the yield rate. All other embodiments obtained by persons of ordinary skill in the art without creative effort in the embodiments of the present invention are within the scope of protection of the present invention.

[0041] A finite element simulation design method for the interference fit process of a thin-walled part (as shown in Figure 1) is disclosed. The thin-walled part comprises a thin-walled containing part 1 and a contained part 2. During interference fit on a press, the thin-walled containing part 1 and the contained part 2 are assembled using three-dimensional modeling and then imported into finite element analysis software.

[0042] It should be noted that finite element analysis (FEA) software allows engineers to segment complex structures (such as thin-walled parts) into several small, simple units (i.e., finite elements) and analyze these units to simulate the mechanical behavior of the entire structure. FEA, based on the fundamental equations of continuum mechanics, can account for material and geometric nonlinearities, as well as the complexity of boundary conditions. Through fine meshing and precise calculation methods, FEA can predict stress, strain, displacement, and other parameters of a structure under various loading conditions. This is crucial for the interference fit assembly of thin-walled parts, as these parts are prone to deformation and stress concentration during assembly, requiring high-precision analysis to ensure assembly accuracy and reliability. The interference fit assembly of thin-walled parts may involve the interaction of multiple physical fields, such as temperature and stress fields. FEA software can easily handle these multi-physics coupling problems, establishing multi-physics coupled models to analyze the interactions and influences between different physical fields. This provides more comprehensive information for structural design and optimization, helping to ensure a smooth assembly process and improved assembly quality. FEA software often provides intuitive visualization tools that present FEA analysis results in the form of graphs or images. This helps engineers intuitively understand key information such as stress distribution and deformation during the assembly process, enabling them to promptly identify and resolve problems and improve product reliability and safety. Compared to traditional physical testing, finite element analysis can save significant time and money. It allows engineers to perform multiple simulations and optimizations during the design phase, reducing the number and cost of subsequent physical testing. This is particularly important for interference fit assembly processes of thin-walled parts, as physical testing can result in part damage and increased costs.

[0043] In the above embodiment, further: (see Figure 2) During 3D modeling, simplify the press model. After assembling the components in 3D modeling and importing them into the finite element analysis software, simplifying the press model during 3D modeling can reduce finite element analysis time and accurately reflect the stress distribution of the cylinder during the press-fitting process.

[0044] Specifically, the simplified press model includes the following steps:

[0045] Step 1: Remove features that have little impact on the overall mechanical behavior; generally such as small holes and chamfers.

[0046] Step 2: Simplify the press-fitting mechanism components, such as the driving cam, pressure rod, and working plane.

[0047] Step 3: Replace the mechanism processing process by applying force and position constraints on the contact surface;

[0048] It is assumed that the material is homogeneous and the forces acting in all directions are isotropic.

[0049] In the above embodiment, further: the press machine model only retains the portion in contact with the thin-walled containing part 1 and the contained part 2, and the other portions are constrained by position conditions.

[0050] Among them, the press head in contact with the contained part 2 limits the displacement and rotation in the X and Y directions and the rotation in the Z direction; the limiting tooling in direct contact with the thin-walled containing part 1 completely fixes and limits the displacement and rotation in the X, Y and Z directions.

[0051] It should be noted that finite element analysis typically requires significant computing resources, especially when the model is complex. By retaining only the contact areas between the press and the thin-walled containment part 1 and contained part 2, and constraining the positional conditions of other areas, the model's complexity and number of degrees of freedom can be significantly reduced, thereby reducing computational requirements and improving efficiency. This allows engineers to obtain analysis results in a shorter time, accelerating the design and optimization process. During the interference fit process, the stress, strain, and deformation in the contact area are of primary concern to engineers. By simplifying the press model to retain only the critical contact areas, the mechanical behavior of these critical areas can be more closely analyzed. This helps engineers more accurately assess potential assembly issues, such as stress concentration and excessive deformation, and implement appropriate optimization measures. Complex press models may contain numerous details and features that may not be essential for interference fit analysis. By simplifying the model to retain only those areas directly relevant to the assembly process, the model's complexity can be reduced, making the analysis process more concise and clear. This helps engineers better understand and analyze the assembly process, improving the accuracy and reliability of the analysis. During the design and optimization process, engineers may need to modify and analyze the model multiple times. By simplifying the press model and retaining only the critical contact areas, model modification and optimization can be performed more easily. This reduces the difficulty of modification and analysis, improving design efficiency. By retaining only the parts directly related to the assembly process and constraining the position conditions of other parts, this helps reduce redundant information and interference factors in the model. This ensures that the simulation results more accurately reflect the mechanical behavior during the assembly process, improving the accuracy and credibility of the simulation results.

[0052] In the above embodiment, further: a grid division step is also included.

[0053] It should be noted that in contact areas, where stresses, strains, and deformations are more complex, computational accuracy can be improved by refining the mesh. This helps more accurately capture the mechanical behavior of the contact area, resulting in more reliable analysis results. In non-contact areas, where their impact on the overall analysis is minimal, the mesh count can be appropriately reduced. This not only reduces computational cost but also avoids computational errors caused by excessive mesh counts. By retaining only critical contact areas and constraining other areas, the model's mesh count can be significantly reduced. This helps reduce computational requirements and improves efficiency, especially when working with large or complex models. Simplified models also facilitate parallel and distributed computing, further reducing computation time. This is particularly important when rapid analysis results are required for decision-making. When meshing, appropriate constraints and meshing strategies can be used to avoid mesh distortion and deformation. This improves mesh quality and results in more accurate analysis results. Simplified models also facilitate adaptive mesh adjustments. During simulation, mesh density and shape can be automatically adjusted based on analysis results to better capture changes in key parameters such as stress and strain. Simplified models are also easier to modify and optimize. During the design and optimization process, engineers can more quickly adjust model parameters and structures and re-mesh for analysis. By reducing model complexity and mesh size, analysis and optimization cycles can be shortened, improving design efficiency. This helps engineers develop products that meet requirements more quickly.

[0054] In the above embodiment, preferably, as a specific application of the present invention, the thin-walled containing member 1 is a stainless steel thin-walled cylinder; the contained member 2 is a ratchet end. In the above embodiment, preferably, the thin-walled containing member 1 and the contained member 2 are made of AISI-304.

[0055] It should be noted that AISI-304 stainless steel contains 18-20% chromium (Cr) and 8-10.5% nickel (Ni). These elements help form a dense passive film on its surface, which effectively resists corrosion from most oxidizing acids and bases, ensuring that the ratchet cylinder remains in good working condition in a variety of environments. AISI-304 stainless steel has excellent machinability. AISI-304 stainless steel is also excellently weldable and does not require preheating. AISI-304 stainless steel has high tensile and yield strengths, while also exhibiting good toughness. This allows the ratchet cylinder to withstand heavy loads and impacts during use without deforming or breaking, thus ensuring its reliability and durability. The smooth surface of AISI-304 stainless steel is less susceptible to dust and dirt accumulation, making the ratchet cylinder easy to clean and maintain during use. This helps extend the life of the ratchet cylinder and reduces failures and damage caused by improper cleaning and maintenance.

[0056] AISI-304 is a widely used austenitic stainless steel with a density of approximately 7.93 g / cm 3 Its tensile strength is 515-742MPa; its yield strength is between 200-300MPa; its elastic modulus is similar to other steels, but lower than carbon steel, about 193-200GPa.

[0057] In the above embodiment, preferably, during the press-fitting process, the press head 3 applies a force of 300 to 450 N in the -Z direction to the contained component, with a displacement distance of 1 mm and an interference amount of 0.01 mm.

[0058] It should be noted that the press can accurately control the force applied by the press head to the contained part within a range of 300 to 450N. This precise control helps ensure stability and consistency during the press-fitting process. At the same time, the press can also accurately control the displacement distance, such as 1mm, which helps to achieve precise assembly requirements. By precisely controlling force and displacement, the assembly process can be optimized, assembly errors can be reduced, and assembly accuracy and efficiency can be improved. Interference fit is an effective connection method. By forming a certain amount of interference (such as 0.01mm) between the contained part and the containing part, the tightness and strength of the connection can be enhanced.

[0059] In the above embodiment, the interference fit end of the contained member 2 is further tapered by 2°. The tapered contained member of the present invention can be roughly regarded as a guide portion, which not only facilitates the automatic alignment of the ratchet end, but also delays the position of plastic deformation, thereby improving the product yield.

[0060] from Figure 7 It can be seen from the figure that the ratchet end was chamfered in the original assembly process, but after press-fitting, the thin-walled part had obvious curling. In order to facilitate processing, the ratchet end was adjusted to have a 2° taper to play a guiding role. At the same time, during the actual press-fitting process, the material deformation was delayed and there was no obvious curling. The surface quality met the requirements. Figure 12 If the angle is too large, the contact area between the ratchet end and the thin-walled cylinder will be reduced, thereby reducing the assembly reliability.

[0061] In the above embodiment, preferably, the friction type is small slip and penalty function-Coulomb friction.

[0062] Small slip is applicable when the relative contact displacement between contact surfaces is much smaller than the size of the contact area, and when the contact area does not change much. Penalty functions are suitable for assembly models where the penetration of contact surfaces is small, such as in interference fits. In assembly models, the sliding friction of contact surfaces conforms to Coulomb's law. Therefore, small slip, penalty functions, and Coulomb friction are well-suited for thin-walled part assemblies.

[0063] In the above embodiment, a friction coefficient of 0.2 is preferred. In scenarios involving small slip and penalty-Coulomb friction, selecting a friction coefficient of 0.2 offers technical advantages such as improved convergence, reduced computational cost, adaptability to various operating conditions, and optimized contact behavior. These advantages make this setting highly valuable and practical in engineering analysis and numerical simulation.

[0064] In the above embodiment, preferably, the finite element analysis software is Huaxi A-CAE for CAXA 3D.

[0065] It should be noted that Huaxi A-CAE is an advanced multi-threaded CAE design software designed and developed specifically for CAE simulation in CAD environment.

[0066] It utilizes the unique Sefea™ (Strain-Enriched FEA) technology. Sefea is the latest enriched finite element method that improves upon the low-order elements commonly used in CAD simulations, enabling analysis to achieve the accuracy of second-order elements at the computational cost of first-order elements.

[0067] Huaxi A-CAE has the functions of fully coupling stress, thermal, electrical and fluid multi-physics fields, static / steady-state analysis, etc., and has high integration.

[0068] Huaxi A-CAE and CAXA3D offer seamless integration for product optimization. Users can perform a CAE analysis, copy it, and then optimize the CAD model based on the analysis results. After modifying the CAD model, users can synchronize and update the solution within seconds without having to re-set up CAE. This allows for faster and more convenient comparison of models.

[0069] In order to facilitate the comparison with the existing technology: when the ratchet end is subjected to the -Z direction force, stress concentration occurs on the contact surface between the ratchet end and the cylinder (see Figure 4 ); As the end is pressed in, plastic deformation occurs at the contact point between the ratchet end and the cylinder, and a slight curling occurs in the elastic area outside the cylinder (see Figure 5 , Figure 6 , Figure 7 ), this phenomenon is consistent with the deformation area and state described by the elastic-plastic theory; the stress in the deformation area is too large, the cylindrical state is unreliable during press fitting, and the surface quality is poor.

[0070] According to the above simulation results, the stress at the contact point between the ratchet end and the cylinder is too large, which causes the cylinder to undergo excessive plastic deformation. Therefore, the geometry of the ratchet end is changed (see Figure 8); The boss has a 2° taper and can be approximately regarded as a guiding part, which can not only facilitate the automatic alignment of the ratchet end, but also delay the position of plastic deformation, thereby improving the product yield.

[0071] Finite element analysis of the optimized model shows that when the ratchet end is subjected to -Z force, the contact surface between the ratchet end and the cylinder does not directly produce plastic deformation (see Figure 9 ); As the end is pressed in, the contact area between the ratchet end and the cylinder undergoes small plastic deformation, and the stress decreases (see Figure 10 , Figure 11 , Figure 12 ), the problem of excessive stress has been effectively improved and the surface quality is good.

[0072] Based on the finite element analysis results, the part was remanufactured and press-fitted, and no curling marks were observed on the cylinder surface after press-fitting. Cylinders made of other materials were press-fitted using the same method, and similarly no obvious defects were observed. By establishing a mechanical model and utilizing elastic-plastic finite element analysis, the press-fitting process was proven to be effective, optimizing the uncertainties of some non-standard parts and thus improving the yield rate.

[0073] The above description demonstrates that the advantages of the present press model, which restricts the contact between the thin-walled containment part 1 and the contained part 2 and constrains the remaining parts through positional constraints, are primarily reflected in improved computational efficiency, focus on key areas, reduced model complexity, ease of model modification and optimization, and improved accuracy of simulation results. These advantages help engineers more efficiently and accurately analyze and optimize interference fit processes, improving product quality and performance.

[0074] This invention, which employs reasonable constraints and meshing strategies during the meshing step, offers significant technical advantages for retaining only the contact portions of the press model with the thin-walled containment member 1 and the contained member 2. These advantages improve computational accuracy, optimize computational efficiency, enhance mesh quality, and facilitate model modification and optimization, thus enabling engineers to perform analysis and optimization more efficiently and accurately.

[0075] In summary, creating 3D models of the thin-walled enclosing part 1 and the enclosed part 2 during the interference fit process on the press and importing them into finite element analysis software offers technical advantages such as complex structural modeling capabilities, high-precision analysis, adaptability and flexibility, multi-physics field coupling analysis, excellent visualization, and high cost-effectiveness. These advantages help ensure the accuracy and reliability of the interference fit process for thin-walled parts, improving product quality and performance.

[0076] Each embodiment in this specification is described in a related manner. The same or similar parts between the embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments.

[0077] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications and equivalent replacements made within the spirit and principles of the present invention are included in the scope of protection of the present invention.

Claims

1. A finite element simulation design method for the interference fit assembly process of thin-walled parts, characterized by: The thin-walled part is composed of a thin-walled containing part (1) and a contained part (2); when the thin-walled containing part (1) and the contained part (2) are interference-fitted on a press, the thin-walled containing part (1) and the contained part (2) are assembled and combined through three-dimensional modeling and imported into finite element analysis software.

2. The finite element simulation design method for the interference fit process of thin-walled parts according to claim 1, characterized in that: When doing 3D modeling, simplify the press model; The steps include: Step 1: Remove features that have little impact on the overall mechanical behavior; Step 2: Simplify the press-fitting mechanism components; Step 3: Replace the mechanism processing process by applying force and position constraints through the contact surface.

3. The finite element simulation design method for the interference fit process of thin-walled parts according to claim 2, characterized in that: The press model only retains the parts in contact with the thin-walled containing part (1) and the contained part (2), and the other parts are constrained by position conditions; wherein the press end contacting the contained part (2) limits the displacement and rotation in the X and Y directions and the rotation in the Z direction; the limiting tooling in direct contact with the thin-walled containing part (1) completely fixes and limits the displacement and rotation in the X, Y and Z directions.

4. The finite element simulation design method for interference fit assembly of thin-walled parts according to claim 1, 2 or 3, characterized in that: A meshing step is also included.

5. The finite element simulation design method for the interference fit process of thin-walled parts according to claim 1, characterized in that: The thin-walled containing part (1) is a stainless steel thin-walled cylinder; the contained part (2) is a ratchet end.

6. The finite element simulation design method for interference fit process of thin-walled parts according to claim 1 or 5, characterized in that: The thin-walled containing part (1) and the contained part (2) are made of AISI-304.

7. The finite element simulation design method for the interference fit process of thin-walled parts according to claim 6, characterized in that: During the press-fitting process, the press head (3) of the press-fitting machine applies a force of 300 to 450 N in the -Z direction to the contained part, with a displacement distance of 1 mm and an interference amount of 0.01 mm.

8. The finite element simulation design method for the interference fit process of thin-walled parts according to claim 6, characterized in that: The interference fit end of the contained part (2) is formed with a taper of 2°.

9. The finite element simulation design method for the interference fit process of thin-walled parts according to claim 8, characterized in that: The friction type is small slip, penalty function-Coulomb friction, and the friction coefficient is 0.

2.

10. The finite element simulation design method for the interference fit process of thin-walled parts according to claim 1, characterized in that: The finite element analysis software is Huaxi A-CAE for CAXA 3D.

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