A method for fast predicting the transfer of a material across a deformation zone under isothermal local loading of a web

Abstract

The application discloses a method for rapidly predicting the transfer of materials across the deformation zone of a local loading area of a web part, and comprises the following steps: first, a partition mode on the rib is adopted to extract the geometric structure of the local loading transition area, and a final forging die of the geometric structure of the transition area is modeled based on a three-dimensional modeling software; a constant-thickness blank is designed, a finite element model of the local loading transition area is created, and the transfer characteristics of the materials across the deformation zone are analyzed; according to the material flow across the deformation zone and the simulated shunt layer position at the web, the loading area is divided into three regions; stress analysis is performed on the base elements of the three regions to obtain a prediction model of the finite element shunt layer position and the volume of the material transfer across the deformation zone; and the finite element results are compared with the prediction model results to verify the effectiveness of the prediction model. The application can efficiently predict the shunt layer position across the deformation zone in a short time, and obtain the volume of the material flowing to the non-loading area per unit time, thereby providing theoretical guidance for avoiding folding defects and regulating uneven deformation.

Description

Technical Field

[0001] This invention relates to the field of large stiffened plate components in aerospace manufacturing, and particularly to a method for rapidly predicting material transfer across deformation zones in stiffened plate components under isothermal local loading. Background Technology

[0002] With the continuous development of high-tech industries such as aerospace, the demand for large, integral, lightweight, and thin-walled complex components with longitudinal and transverse multi-ribbed structures has increased significantly to meet their high reliability and efficient structural and functional requirements. Due to their geometric characteristics, the traditional integral forging process for these components places stringent requirements on the maximum tonnage of the equipment, limiting their forming capacity. Simply increasing the tonnage of the equipment to address the shortcomings in forming tonnage and forming capacity is insufficient to obtain large and complex forgings and meet the ever-increasing demands for forming loads.

[0003] Isothermal local loading combines the advantages of both isothermal forging and local loading forming processes. While significantly reducing material deformation resistance and improving material plasticity, it effectively reduces the forming load on large, multi-ribbed components, providing an effective approach for integrated forming and manufacturing of such components. This allows for "small equipment doing big work," and is of great significance for achieving high-performance, low-cost manufacturing of large aerospace stiffened components. However, during isothermal local loading of multi-ribbed components, there is an inherent material transfer phenomenon across deformation zones, which can easily lead to defects such as folding and severe uneven deformation, limiting the application of isothermal local loading forming technology. Therefore, this invention proposes a method for rapidly predicting material transfer volume. It analyzes the material flow and stress state across zones during isothermal local loading of multi-ribbed components, obtaining a predictive model for the location of the flow divider layer and the material transfer volume. This provides guidance for rapidly predicting material transfer across deformation zones, thereby avoiding folding defects and improving uneven deformation. Summary of the Invention

[0004] The purpose of this invention is to solve the technical problems existing in the prior art and to provide a method for rapidly predicting the material transfer across the deformation zone under isothermal local loading in stiffened components.

[0005] To achieve the above objectives, the technical solution provided by this invention is: a method for rapidly predicting material transfer across deformation zones under isothermal local loading in stiffened members, comprising the following steps:

[0006] (1) For ribbed parts, the rib-on-partition method is adopted to extract the geometric structure of the local loading transition zone with ribs and web (the area between two ribs). The final forging die of the transition zone geometry is modeled based on 3D modeling software to identify the geometric position of the first loading zone and the second loading zone of the first loading step.

[0007] (2) Design a simple, uniformly thick billet and create a finite element model of the first and second loading steps of the local loading transition zone. Based on the simulation results of the two loading steps, analyze the back-and-forth flow of the material in the first and second loading zones. This flow is the material transfer characteristic across the deformation zone.

[0008] (3) Based on the material flow characteristics across the deformation zone observed in the simulation results and the location of the simulated flow split layer at the web, the pre-loaded zone is divided into three regions: a) the region between the flow split layer and the partition rib is I; b) the region between the flow split layer and the adjacent rib on the other side is II; c) the region of the rib groove on the other side is III.

[0009] (4) Perform stress analysis on the basic elements in the three regions divided in step (3), and obtain a rapid prediction model of the location of the finite element diversion layer and the cross-regional transfer volume of the material by comprehensively solving the stress balance equation, the Tresga yield equation and the boundary conditions.

[0010] (5) Compare the finite element results with the prediction model results to verify the effectiveness of the prediction model.

[0011] Preferably, the stiffener has a plane of symmetry, the stiffener is vertically symmetrical about the plane of symmetry, and the material flow characteristics of the stiffener are consistent vertically along the plane of symmetry.

[0012] Preferably, the final forging die in step (1) includes an upper die and a lower die assembly, which form a cavity for placing the blank.

[0013] Preferably, the lower mold assembly includes a first lower mold and a second lower mold, and a pad is provided below the first lower mold.

[0014] Beneficial effects of this invention:

[0015] This invention aims to predict the material transfer volume during isothermal local loading of multi-ribbed components. It obtains a predictive model for the location of the flow divider and the material transfer volume, which can efficiently predict the location of the flow divider in a short time and obtain the volume of material flowing to the unloaded area per unit time. This provides theoretical guidance for avoiding folding defects, offers new ideas for coordinating uneven deformation, improving forming limits and accuracy, and solves some of the shortcomings of material flow control in the labor-saving near-net-shape forming of high-performance lightweight large components for aerospace. Thus, it enriches the isothermal local loading process methods for large, complex, multi-ribbed, thin-webbed load-bearing components used in the aerospace field. Attached Figure Description

[0016] The accompanying drawings, which are provided to further illustrate the invention and constitute a part of this invention, are illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention.

[0017] Figure 1 This is a schematic diagram of the geometric structure of the local loading transition region of the present invention;

[0018] Figure 2 This is a schematic diagram of the final forging die geometry of the local loading transition zone in an example of the present invention;

[0019] Figure 3 This is a schematic diagram showing the simulation prediction and experimental verification results of the folding defects in the geometry of the local loading transition zone of this invention;

[0020] Figure 4 This is a schematic diagram of the force analysis of the basic elements in different regions within the loading area of ​​this invention;

[0021] Figure 5 This is a flowchart of the method for rapidly predicting material transfer across the deformation zone under isothermal local loading in stiffened components according to the present invention;

[0022] Figure 6 This is a schematic diagram illustrating the mathematical expressions established for each primitive element in this invention;

[0023] Figure 7 This is a schematic diagram illustrating the comprehensive solution of the simultaneous equations of this invention.

[0024] Attached image captions:

[0025] 1-Left web plate 2-Parting line 3-Right web plate 4-Symmetrical plane 5-Left side rib 6-Middle rib 7-Right rib 8-Equal thickness blank 9-Padded block 10-First lower mold 11-Second lower mold 12-Upper mold 13-Deformed blank 14-Folding defect Detailed Implementation

[0026] This section will describe in detail specific embodiments of the present invention. Preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the drawings is to supplement the textual description with graphics, so that people can intuitively and vividly understand each technical feature and overall technical solution of the present invention, but they should not be construed as limiting the scope of protection of the present invention.

[0027] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0028] In the description of this invention, "several" means one or more, "more than" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0029] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0030] Reference Figures 1-7 A preferred embodiment of the present invention provides a method for rapidly predicting material transfer across deformation zones under isothermal local loading in stiffened members, comprising the following steps:

[0031] (1) For ribbed parts, the rib-on-partition method is adopted to extract the geometric structure of the local loading transition zone with ribs and web (the area between two ribs). The final forging die of the transition zone geometry is modeled based on 3D modeling software to identify the geometric position of the first loading zone and the second loading zone of the first loading step.

[0032] (2) Design a simple, uniformly thick billet and create a finite element model of the first and second loading steps of the local loading transition zone. Based on the simulation results of the two loading steps, analyze the back-and-forth flow of the material in the first and second loading zones. This flow is the material transfer characteristic across the deformation zone.

[0033] (3) Based on the material flow characteristics across the deformation zone observed in the simulation results and the location of the simulated flow split layer at the web, the pre-loaded zone is divided into three regions: a) the region between the flow split layer and the partition rib is I; b) the region between the flow split layer and the adjacent rib on the other side is II; c) the region of the rib groove on the other side is III.

[0034] (4) Perform stress analysis on the basic elements in the three regions divided in step (3), and obtain a rapid prediction model of the location of the finite element diversion layer and the cross-regional transfer volume of the material by comprehensively solving the stress balance equation, the Tresga yield equation and the boundary conditions.

[0035] (5) Compare the finite element results with the prediction model results to verify the effectiveness of the prediction model.

[0036] As a preferred embodiment of the present invention, it may also have the following additional technical features:

[0037] In this embodiment, the transition zone geometry in step (1) includes a left web 1 and a right web 3, and a parting line 2 is formed at the connection between the left web 1 and the right web 3.

[0038] In this embodiment, the stiffener has a symmetry plane 4, the stiffener is symmetrical about the symmetry plane 4, and the material flow characteristics of the stiffener are consistent along the symmetry plane.

[0039] In this embodiment, the final forging die in step (1) includes an upper die 12 and a lower die assembly, which form a mold cavity for placing the blank 13.

[0040] In this embodiment, the lower mold assembly includes a first lower mold 10 and a second lower mold 11, and a pad 9 is provided below the first lower mold 10.

[0041] This invention addresses the inherent material transfer phenomenon across regions during isothermal local loading of multi-ribbed components by obtaining a finite element prediction model for the location of the flow divider layer and the volume of material transfer. Through the finite element prediction model for the location of the flow divider layer and the volume of material transfer, it is found that as the downward pressure increases, the amount of material transferred across regions gradually increases, and the contact area with the unloaded mold gradually increases, resulting in an increase in the local stress generated on the workpiece. This causes the finite element flow divider layer to gradually approach the parting line 2, resulting in a reduction in the volume of material flowing to the unloaded area per unit time.

[0042] Preferred embodiment

[0043] In the isothermal local loading simulation prediction process, this invention designs a simple, uniformly thick billet 8 as an example of the billet for a method to rapidly predict the material transfer volume during isothermal local loading of multi-ribbed components; the geometric parameters of the transition zone during the isothermal local loading process are shown in Table 1 below.

[0044] Table 1 Geometric parameters of the deformation zone

[0045]

[0046] Includes the following steps:

[0047] (1) Geometric Extraction and Modeling of the Local Loading Transition Zone: Based on the requirements, the structural parameters of the geometric structure of the local loading transition zone of the forging are designed, and the solid sample of the transition zone is drawn and extracted to create a finite element model. The embodiment mainly uses the finite element model of the transition zone geometry. The calculation process can be performed directly using the built-in measurement tools in 3D modeling software such as UG. Specifically, based on the geometric structural parameters in Table 1, the structures described by web thickness, rib height, rib width, and web length and width are constructed respectively. The actual transition zone structure is as follows: Figure 1As shown, based on the created transition zone geometry, a three-dimensional finite element model of the forging die is established, i.e., the die geometry of the locally loaded transition zone is as follows. Figure 2 As shown; during the structural construction process, it is also necessary to consider the functional structure of actual large multi-ribbed thin-web components;

[0048] (2) Blank design for the geometry of the local loading transition zone: For the component in this embodiment, the specific dimensions are based on a simple equal-thickness blank 8;

[0049] (3) Rules for dividing the deformation zone: Refer to Appendix Figure 4 The given embodiment load zone division diagram is based on the finite element simulation analysis of the simple shape and thickness billet 8 described above. The material flow during the local loading process is quantitatively characterized. Based on the material flow across the deformation zone and the simulated flow divider position at the web, the loading deformation area is divided into three regions: a) the region between the flow divider and the partition rib is region I; b) the region between the flow divider and the adjacent rib on the other side is region II; c) the rib groove region on the other side is region III.

[0050] (4)Reference Figures 5-7 In the flowchart of the prediction model solution, mathematical expressions are established for each basic element, and a prediction model for the location of the flow divider and the volume of material transfer is established. Since the material transfer behavior across the deformation zone is similar in the left web region 1 and the right web region 3 during the flow process, and the stress state of these two regions is the same, this paper mainly takes the material transfer process of the left web region 1 as an example to establish the force balance equation. According to the appendix... Figure 2 During the first loading step, as the upper mold 12 is pressed down, the material in the left web region can be considered to be in an upsetting deformation state, therefore stress only exists in the z and x directions. Furthermore, when the material between the left side reinforcement 5 and the middle partition reinforcement 6 reaches equilibrium along the transverse stress, i.e. The flow divider layer begins to form between the left-side rib 5 and the middle partition rib 6. This occurs when the material between the right-side rib 7 and the middle partition rib 6 reaches equilibrium along the transverse stress. The diversion layer begins to form between the right-side rib 7 and the middle partition rib 6, therefore... This is considered as the equilibrium condition for the formation of the flow divider. This paper simplifies the loading process between the left-side rib 5 and the middle partition rib 6 of the workpiece into a plane stress problem, and satisfies the following basic assumptions to simplify the calculation:

[0051] The mold is considered as an ideal rigid body, and the deformed blank 13 is considered as a rigid-plastic body, and the stress is uniform.

[0052] In the isothermal forming process of titanium alloys at high temperature and low strain rate, the effect of temperature is ignored, and the flow stress in the deformation zone is regarded as constant;

[0053] Satisfies the Tresga yield equation:

[0054]

[0055] In the formula, σ max σ min For the maximum and minimum principal stresses, K and τ max This represents the maximum shear stress at which the material yields.

[0056] The friction between the workpiece and the mold is considered as shear friction.

[0057] The calculation is divided into three regions. Using boundary conditions as a premise, simultaneous equations are established based on stress equilibrium conditions and the Tresgaard yield criterion. The solutions for each of the three regions are then analyzed. For example:

[0058] Depend on Figure 4 The forces acting on the elementary elements are analyzed, and the force equilibrium equations are established based on the stress equilibrium conditions. The equilibrium equations are then solved simultaneously with the Tresga yield equation.

[0059] σ x H-(σ x +dσ x )H+2mτdx=0 (2)

[0060] In the formula, σ x σ z These represent the stresses in the x and z directions of the basic element, respectively; m is the friction factor between the mold and the blank; and H is the instantaneous height of the blank when it is subjected to loading.

[0061] Since material deformation follows the Tresgaard yield criterion, the following formula can be obtained:

[0062]

[0063] σ x σ z These are the stresses in the x and z directions of the basic element, respectively, and τ is the maximum shear stress at which the material yields.

[0064]

[0065] Solving the indefinite integral of equation (4) yields the following formula:

[0066]

[0067] In equation (5), C1 is a constant coefficient.

[0068] When the reduction s≈0, i.e. z≈H, the stress in the z-direction of the material in region I is... Therefore, the boundary conditions are:

[0069]

[0070] Combining boundary condition equations (6), (3), and (5), we obtain equation (7):

[0071]

[0072] In the formula, σ x σ z These represent the stresses in the x and z directions of the basic element, respectively. and They are respectively Figure 4 The stress magnitudes in zones I, II, and III; m is the friction factor between the mold and the blank; H is the instantaneous height of the blank under load.

[0073] Similarly, it can be deduced that:

[0074]

[0075]

[0076] In equation (8), b1 is the rib width W1 on the left side of the first loading zone; in equation (9), t is the stress at the interface between zone II and zone III; L 12 The spacing D between the left-side reinforcement and the middle partition reinforcement. 12 .

[0077] Reference Figures 6-7 Solve the system of equations simultaneously, based on the fact that the stresses on both sides of the flow divider are equal, i.e. Therefore, solving equations (7), (8), and (9) simultaneously yields:

[0078]

[0079] Therefore, the volume of material transferred is:

[0080] When the reduction is s, the billet thickness is H'

[0081] H'=Hs (11)

[0082] According to equation (11), the location of the flow layer x can be determined. l

[0083]

[0084]

[0085] D is the billet width; s is the reduction amount; V is the volume of material transferred when the reduction amount is s; b is the rib width.

[0086] (5) Compare the finite element results with the prediction model results:

[0087] Model calculations revealed that as the reduction increases, the amount of material transferred across zones gradually increases, and the contact area with the unloaded mold zone gradually increases. This leads to an increase in local stress on the workpiece, causing the flow layer to gradually approach the parting line 2. (Refer to...) Figure 1 This results in a reduction in the volume of material flowing into the unloaded area per unit time.

[0088] The maximum error between the predicted and simulated results of the material transfer model was 5.23% in the first loading step and 7.1% in the second loading step, with average errors of 1.83% and 2.29%, respectively. This indicates that the proposed rapid prediction method for local loading material transfer is reliable and effective, and provides a theoretical basis for avoiding folding defects during material transfer across deformation zones.

[0089] The specific data of the prediction model and finite element simulation results for the location of the diversion layer and the material transfer volume in the first and second loading steps are shown in Tables 2 and 3 below.

[0090] Table 2. Prediction Model and Finite Element Simulation Results of Displacement Layer Location and Material Transfer Rate (First Loading Step)

[0091]

[0092]

[0093] Table 3. Prediction Model and Finite Element Simulation Results of Distributor Location and Material Transfer Rate (Second Loading Step)

[0094]

[0095] Without causing conflict, those skilled in the art can freely combine and use the above-mentioned additional technical features.

[0096] The above description is only a preferred embodiment of the present invention. Any technical solution that achieves the purpose of the present invention by essentially the same means is within the protection scope of the present invention.

Claims

1. A method for rapid prediction of the transfer of a sheet of material subjected to isothermal local loading across a deformation zone, characterized in that: Includes the following steps: (1) For ribbed parts, the rib-on-partition method is adopted to extract the geometric structure of the local loading transition zone with ribs and web (the area between two ribs). The final forging die of the transition zone geometry is modeled based on 3D modeling software to identify the geometric position of the first loading zone and the second loading zone of the first loading step. (2) Design a simple, uniformly thick billet and create a finite element model of the first and second loading steps of the local loading transition zone. Based on the simulation results of the two loading steps, analyze the back-and-forth flow of the material in the first and second loading zones. This flow is the material transfer characteristic across the deformation zone. (3) Based on the material flow characteristics across the deformation zone observed in the simulation results and the location of the simulated flow split layer at the web, the pre-loaded zone is divided into three regions: a) the region between the flow split layer and the partition rib is I; b) the region between the flow split layer and the adjacent rib on the other side is II; c) the region of the rib groove on the other side is III. (4) Perform stress analysis on the basic elements in the three regions divided in step (3), and obtain a rapid prediction model of the location of the finite element diversion layer and the cross-regional transfer volume of the material by comprehensively solving the stress balance equation, the Tresga yield equation and the boundary conditions. (5) Compare the finite element results with the prediction model results to verify the effectiveness of the prediction model.

2. The method for rapidly predicting material transfer across deformation zones under isothermal local loading in stiffened members according to claim 1, characterized in that: The transition zone geometry in step (1) includes a left web and a right web. There are partition ribs at the connection between the left web and the right web, and parting lines are formed on the ribs.

3. The method of claim 1, wherein the method is a rapid prediction of the transfer of the material across the deformation zone of the locally loaded material of the web member at the isothermal condition. The stiffener has a plane of symmetry, and the stiffener is symmetrical about the plane of symmetry. The material flow characteristics of the stiffener are consistent along the plane of symmetry.

4. The method for rapidly predicting material transfer across deformation zones under isothermal local loading in stiffened members according to claim 1, characterized in that: The final forging die in step (1) includes an upper die and a lower die assembly, which form a cavity for placing the blank.

5. A method for rapid prediction of the transfer of a locally loaded material across a deformation zone in a web member according to claim 4, wherein: The lower mold assembly includes a first lower mold and a second lower mold, with a pad block disposed below the first lower mold.

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