Method for designing head body parameters of multi-point stretch-bending forming die

Abstract

According to the method for designing the parameters of the head body of the multi-point stretch-bending forming die, the influence of the contact area and the deformation step difference is fully considered, the relation between the radius of the head body and the forming radius of a profile, the relation between the radius of the head body and the width of the head body is established on the basis of the fitting hypothesis and the deformation step difference hypothesis, and the design accuracy is improved. And the relationship among the fitting chord length, the forming radius, the fitting gap and the deformation order difference is determined. According to the method, a definite theoretical basis is provided for the radius and the arrangement distance of the head body of the multi-point flexible profile stretch-bending die. Furthermore, under the condition that rigidity and strength checking is considered, a specific design scheme of parameters of the fan-type multipoint stretch-bending forming die head body is further provided. The method provided by the invention comprises a complete theoretical basis and a specific design method, and provides a reliable design method for the quantitative design of the parameters of the fan-shaped multi-point stretch-bending forming die head body.

Description

Technical Field

[0001] This invention belongs to the field of profile forming technology, specifically relating to a design method for the head body parameters of a multi-point stretch bending forming mold. Background Technology

[0002] Sheet metal forming technology plays a vital role in modern manufacturing, with widespread applications in aerospace, automotive, high-speed rail, and many other fields. Among these, stretch bending, a key sheet metal processing technique, is primarily used to manufacture parts with complex curved surfaces and high precision requirements. In stretch bending, the design of the stretch bending die is a crucial factor influencing the forming quality.

[0003] Traditional bending dies use a full-contact forming method, which has two prominent problems: First, a single die can only be used for a single forming surface, leading to high remanufacturing costs. Second, the design of the forming surface relies heavily on the designer's experience to determine the surface parameters, requiring repeated trials and modifications to achieve the desired forming effect. An unreasonable surface design not only increases the die's scrap rate but also wastes time and resources.

[0004] In contrast, multi-point stretch bending forming dies utilize a multi-point contact method for forming, exhibiting significant advantages. This design offers greater flexibility, allowing a single die to meet the processing needs of various forming surface specifications. Regarding springback design, multi-point stretch bending forming dies can effectively control springback by repeatedly adjusting forming surface parameters, thus avoiding the problems associated with traditional stretch bending dies. This not only reduces die manufacturing costs but also improves production efficiency.

[0005] However, multi-point stretch bending forming dies also face new challenges in practical applications. Due to the effects of stress concentration and localized plastic deformation, if the contact surface design or head spacing of the die contact head is unreasonable, creases can easily form on the profile surface, directly affecting the manufacturing accuracy of the parts. Therefore, how to design scientific and reasonable head parameters has become a key technology in the design of multi-point stretch bending forming dies. Summary of the Invention

[0006] To address the lack of scientifically sound design basis for head body parameters in current multi-point stretch bending forming die designs, this invention provides a design method for head body parameters in multi-point stretch bending forming dies. Based on the fit assumption and deformation step assumption, this method establishes the relationships between the head body radius and the profile forming radius, fit gap, and head body width, as well as the relationships between the fit chord length, forming radius, fit gap, and deformation step. This provides a clear theoretical basis for the head body radius and arrangement spacing of multi-point flexible profile stretch bending dies. The technical solution is as follows: A method for designing the head body parameters of a multi-point stretch bending forming die is disclosed. The multi-point stretch bending forming die employs multiple discrete head bodies arranged in a ring array to form a fan shape. The head body has a cylindrical shape. Based on this arrangement, a first relationship is established between the head body radius and the profile forming radius, the fitting gap, and the head body width using a fitting assumption. A second relationship is established between the fitting chord length, the forming radius, the fitting gap, and the deformation step using both the fitting assumption and the deformation step assumption. The head body parameters are obtained based on the first and second relationships. This invention provides a clear design basis for the head body radius and arrangement spacing of multi-point flexible profile stretch bending dies.

[0007] When using the fit assumption, if the gap between the profile and the head body is within the range of 0-0.3 mm, it is determined that the head body and the profile are fitted, and the gap is the distance along the radius of the forming surface between the forming surface of the profile and the contact surface of the head body. Determining that the head body and the profile are fitted facilitates obtaining the range of values ​​for the head body radius.

[0008] When the deformation step assumption is adopted, the maximum distance between the theoretical forming surface and the actual forming surface is less than the permissible deformation step difference. This provides a design basis for how the head body is arranged to obtain acceptable forming quality.

[0009] Optionally, a permissible deformation step of 0.5 mm can be used to ensure the forming quality of the profile.

[0010] Optionally, for a single forming condition, the process of establishing the first and second relationships includes: Step 1: Obtain the geometric relationship of the head-body fan-shaped arrangement:

[0011]

[0012] in, r The radius of the head and body; R Δ is the profile forming radius; Δ is the fitting gap; D The width of the head and body; h The chord height corresponding to the width of the head-body fit; Step Two: When establishing the first relationship, based on the fit assumption and the geometric relationship of the head-body fan-shaped arrangement, the range of values ​​for the head-body radius is obtained given the profile forming radius and head-body width:

[0013] in, The critical radius of the head and body; Head-body critical chord height; Δ c Allowable fitting gap; D c This is the critical fit width between the head and body.D c = D The subscript 'c' indicates the allowable fitting gap Δ c The corresponding relevant parameters; Step 3: When establishing the second relationship, based on the fitting assumption, establish the relationship between the fitting chord length, forming radius, fitting gap, and deformation step:

[0014] in, l To fit the chord length; δ The deformation step difference represents the maximum distance between the theoretical forming surface and the actual forming surface; The deformation step assumption requires that the deformation step difference must be less than the permissible deformation step difference. Based on the deformation step difference assumption, we obtain:

[0015]

[0016] in, δ c To allow for deformation step difference, l max To satisfy the maximum fitting chord length under the deformation step assumption, l max Actually, it's about R , D , r The function is represented as l max ( R , D , r ), at a given profile forming radius R and head and body width D In this case, l max ( R , D , r Degenerate into l max ( r ).

[0017] To reduce the manufacturing cost of bending dies and improve production efficiency, the ball head size should be suitable for multiple forming conditions. For multiple forming conditions, the method further includes: Step 4: For multi-specification forming radii R ∈[ R 1, R 2], given an initial ball head width D c Under the given conditions, we obtain:

[0018]

[0019] in, R 1 represents the lower limit of the forming radius for multiple specifications. R 2 represents the upper limit of the forming radius for multiple specifications. r c1 for R The critical radius of the head and body corresponding to 1. r c2 for R The critical radius of the head body corresponding to 2. Then, taking the intersection of the above two inequalities, we obtain the applicable forming radius in [ R 1, R 2] The range of values ​​for the sphere's head radius in the interval: .

[0020] Furthermore, if the rigidity of the head body does not meet the usage requirements, the obtained head body parameters are iteratively optimized based on the rigidity check. This creates a closed loop in the head body parameter design process, ensuring both high forming quality of the profile and high safety of the head body.

[0021] Optionally, the obtained head-body parameters are iteratively optimized based on the stiffness check, including: Step 1: Calculate the head-body radius, based on R upper limit R 1 and lower limit R 2. D Δ c , δ c ,calculate r c1 and r c2 The range of values ​​for the head-body radius is obtained. And select one r The value is used as the head-body radius; Step 2: Arrange the constraint heads by... r Value Calculation l max ( r ),ensure l ≤ l max The head and body are arranged without interference. Step 3: Perform a rigidity check on the entire mold. If the rigidity meets the usage requirements, the head body parameter design is complete. If the rigidity does not meet the requirements, the head body width needs to be increased for iterative optimization design. Optionally, by increasing the width of the head and body, Repeating steps one through three changes the range of values ​​for the head-body radius, which may in turn change the value of the head-body radius. or, With the current r The value is input, and its corresponding value is calculated. D c ,if r = R ,but D c = D Then according to D and D c Calculation of size relationship l max :if D ≤ D c ,but l max = l max ( D c , r );if D > D c ,but l max = l max ( D , r This keeps the radius of the head body constant.

[0022] The beneficial effects of this invention are as follows: To address the lack of scientifically sound design basis for head body parameters in multi-point stretch bending forming die design, this invention proposes a design method for the head body parameters of a fan-shaped multi-point stretch bending forming die. This method fully considers the contact area and deformation step difference, geometrically establishing the relationship between the head body radius and the profile forming radius, the fitting gap, and the head body width, as well as the relationship between the fitting chord length and the forming radius, the fitting gap, and the deformation step difference. The proposed method provides a theoretical basis for the quantitative design of key parameters of the fan-shaped multi-point stretch bending forming die head body. Furthermore, considering rigidity and strength verification, a specific design process for the head body parameters of the fan-shaped multi-point stretch bending forming die is provided. In summary, the method proposed in this invention, from theoretical basis to specific design process, provides reliable design criteria for the quantitative design of the head body parameters of a fan-shaped multi-point stretch bending forming die. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the geometric analysis of the present invention; Figure 2 This is a schematic diagram illustrating the design process of the head body parameters of the present invention; Figure 3 This is a schematic diagram of the head body model and the arrangement of different forming radii according to an embodiment of the present invention; Figure 4 A mold model for full contact; Figure 5 Forming radius R Mises stress contour plot and plastic deformation contour plot for 1=1200 mm; Figure 6 Forming radius R Mises stress contour plot and plastic deformation contour plot for 2 = 3887.5 mm. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] The features and illustrative embodiments of various aspects of the present invention will now be described in detail. Numerous specific details are set forth in the following detailed description to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced without requiring some of these specific details. The following description of embodiments is merely intended to provide a better understanding of the invention by illustrating examples of the invention. The invention is by no means limited to any specific setups and methods set forth below, but covers any improvements, substitutions, and modifications to structures, methods, and devices without departing from the spirit of the invention. Well-known structures and techniques are not shown in the drawings and the following description to avoid unnecessarily obscuring the invention.

[0026] It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other, and the various embodiments can be referenced and cited from each other.

[0027] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0028] See Figure 1 For a single forming condition, where one type of head body is only suitable for one forming radius, firstly, through geometric analysis of the fan-shaped arrangement of the head bodies, the relationship between the head body radius and the profile forming radius, the fitting gap, and the head body width can be established:

[0029]

[0030] in, r The radius of the head and body; R Δ is the profile forming radius; Δ is the fitting gap; D The width of the head and body; h The chord height corresponds to the width of the head-body fit.

[0031] Next, assuming the gap between the head and the profile is within a certain range, the head and profile are fitted together. Based on this fitting assumption (0≤Δ≤Δ...), c , where Δ c To determine the allowable fitting gap, the range of values ​​for the head body radius is obtained given the profile forming radius and head body width:

[0032] in, The critical radius of the head and body; Head-body critical chord height; D c This is the critical fit width between the head and body. D c = D The symbols with the subscript 'c' in the text indicate that the gap is equal to the allowable fitting gap (Δ=Δ). c The relevant parameters under the given conditions are: The above formula clarifies the design basis for the head body radius given the head body width and forming radius.

[0033] Then, based on the fit assumption, the relationship between the fit chord length, forming radius, fit gap, and deformation step is established:

[0034] in, l To fit the chord length; δ The deformation step difference represents the maximum distance between the theoretical forming surface and the actual forming surface.

[0035] Subsequently, since the deformation step difference assumption requires that the deformation step difference must be less than the permissible deformation step difference, based on this deformation step difference assumption, we obtain:

[0036]

[0037] in, δ c To allow for deformation step difference, l max To satisfy the deformation step assumption, the maximum fitting chord length. l max Actually, it's about R , D , rThe function is represented as l max ( R , D , r ). At a given profile forming radius R and head and body width D In this case, l max ( R , D , r Degenerate into l max ( r ).

[0038] Based on the above, for multi-forming conditions, i.e., when one head body is suitable for multiple forming radii, let's assume the forming radius... R ∈[ R 1, R 2], given an initial ball head width D c Under the given conditions, we obtain:

[0039]

[0040] The two formulas above respectively give the lower limit of the forming range. R 1 and upper limit R The range of values ​​for the ball head radius corresponding to 2 is then taken, and their intersection is used to obtain the value applicable to the forming radius in [ ]. R 1, R 2] The range of values ​​for the sphere's head radius in the interval:

[0041] See Figure 2 If the rigidity of the head body does not meet the usage requirements, this invention can iteratively optimize the obtained head body parameters based on the rigidity check. The main steps include: Step 1: Calculate the head-body radius. Input R Upper and lower limits R 1 and R 2. D Δ c , δ c ,calculate r c1 and r c2 The range of values ​​for the head-body radius is obtained. And select one r The value is used as the head-body radius.

[0042] Step Two: Constrain the head body arrangement. (From...) rValue Calculation l max ( r ),ensure l ≤ l max The head and body are arranged without interference.

[0043] Step 3: Rigidity Check. Perform a rigidity check on the entire mold. If the rigidity meets the usage requirements, the design of the key head body parameters is complete. If the rigidity does not meet the requirements, the head body width needs to be increased.

[0044] Optionally, increase the width and thickness of the head body, repeating steps one through three. This design approach may result in a lower head body radius. r Changes occur during iterative design.

[0045] Optionally, increase the width and thickness of the head body to match the current... r The value is input, and its corresponding value is calculated. D c It is important to note that if r = R If it cannot be solved, then take D c = D Then according to D and D c Calculation of size relationship .if D ≤ D c ,but l max = l max ( D c , r );if D > D c ,but l max = l max ( D , r This design concept maintains the head-to-body radius. r It remains unchanged during iterative design.

[0046] This embodiment takes a forming radius in the range of [1200 mm, 3887.5 mm] as an example, and uses the method proposed in this invention to determine the head body radius. The upper and lower limits of the forming radius are used as examples to illustrate the head body layout design process. The specific implementation steps are as follows: Step 1: Take R ∈[1200 mm, 3887.5 mm]、D c =60 mm, Δ c =0.3 mm δ c =0.5 mm.

[0047] Step 2: Calculation r c1 ≈667 mm r c2 ≈1083 mm, therefore the range of the head-body radius is [1083 mm, 1200 mm]. In this embodiment, we take... r =1200 mm.

[0048] Step 3: Assume the initial state D c =60 mm cannot meet the stiffness and strength requirements, D c Increased to 80 mm. Step 4: Targeting R =1200 mm and r For the 1200 mm working condition, calculate its corresponding... D c ,because r = R ,Pick D c = D =80mm; for R =3887.5 mm and r For the 1200 mm working condition, calculate its corresponding... D c ≈65 mm.

[0049] Step 4: Calculate the length of the maximum fitting chord that satisfies the deformation step assumption. l max ( r ).for R For the working condition of 1=1200 mm, because D ≤ D c ,so l max = l max ( D c , r )≈69 mm; for R For the working condition of 2=3887.5 mm, because D > D c ,so l max = lmax ( D , r )≈35 mm.

[0050] Figure 3 The image shows the final head model and a schematic diagram of the arrangement of different forming radii.

[0051] Finally, to illustrate the effectiveness of the fan-shaped multi-point contact forming in the embodiments of the present invention, the fan-shaped multi-point contact forming and full contact forming of T-profiles were compared using the finite element method. Figure 4 The image shown is a full-contact mold model. Figure 5 and Figure 6 The figures shown are forming radii. R 1 = 1200 mm and R Mises stress and plastic deformation cloud diagrams for 2=3887.5 mm. Finite element simulation results of the T-section show that the fan-shaped multi-point stretch bending forming die designed based on the method proposed in this invention exhibits no obvious wrinkles in its forming effect, approaching the forming effect of full contact. This demonstrates the feasibility and effectiveness of the design method for the head body parameters of the fan-shaped multi-point stretch bending forming die proposed in this invention.

[0052] The above description merely illustrates embodiments of the present invention and is quite specific and detailed; however, it should not be construed as limiting the scope of the patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Furthermore, any parts of the present invention not described in detail are conventional techniques.

Claims

1. A method for designing the parameters of a multi-point stretch bending forming die head, characterized in that, The multi-point bending forming die adopts multiple discrete heads, and the heads are arranged in a ring array to form a fan shape. The head shape is a cylindrical surface. Based on this arrangement feature, the first relationship between the head radius and the profile forming radius, the fitting gap, and the head width is established using the fitting assumption. The second relationship between the fitting chord length, the forming radius, the fitting gap, and the deformation step is established using the fitting assumption and the deformation step assumption. The head parameters are obtained based on the first and second relationships.

2. The method according to claim 1, characterized in that, When the fit assumption is adopted, if the gap between the profile and the head body is in the range of 0-0.3 mm, it is determined that the head body and the profile are fitted. The gap is the distance between the profile forming surface and the head body contact surface along the radial direction of the forming surface.

3. The method according to claim 1, characterized in that, When the deformation step assumption is adopted, the maximum distance between the theoretical forming surface and the actual forming surface is less than the allowable deformation step.

4. The method according to claim 3, characterized in that, The permissible deformation step is 0.5 mm.

5. The method according to claim 1, characterized in that, For a single forming condition, the process of establishing the first and second relationships includes: Step 1: Obtain the geometric relationship of the head-body fan-shaped arrangement: in, r The radius of the head and body; R Δ is the profile forming radius; Δ is the fitting gap; D The width of the head and body; h The chord height corresponding to the width of the head-body fit; Step Two: When establishing the first relationship, based on the fit assumption and the geometric relationship of the head-body fan-shaped arrangement, the range of values ​​for the head-body radius is obtained given the profile forming radius and head-body width: in, The critical radius of the head and body; Head-body critical chord height; Δ c Allowable fitting gap; D c This is the critical fit width between the head and body. D c = D The subscript 'c' indicates the allowable fitting gap Δ c The corresponding relevant parameters; Step 3: When establishing the second relationship, based on the fitting assumption, establish the relationship between the fitting chord length, forming radius, fitting gap, and deformation step: in, l To fit the chord length, it represents the distance between the nearest contact points of two adjacent head bodies; δ The deformation step difference represents the maximum distance between the theoretical forming surface and the actual forming surface; The deformation step assumption requires that the deformation step difference must be less than the permissible deformation step difference. Based on the deformation step difference assumption, we obtain: in, δ c To allow for deformation step difference, l max To satisfy the maximum fitting chord length under the deformation step assumption, l max Actually, it's about R , D , r The function is represented as l max ( R , D , r ), at a given profile forming radius R and head and body width D In this case, l max ( R , D , r Degenerate into l max ( r ).

6. The method according to claim 5, characterized in that, For multi-forming conditions, the method further includes: Step 4: For multi-specification forming radii R ∈[ R 1, R 2], given an initial ball head width D c Under the given conditions, we obtain: in, R 1 represents the lower limit of the forming radius for multiple specifications. R 2 represents the upper limit of the forming radius for multiple specifications. r c1 for R The critical radius of the head and body corresponding to 1. r c2 for R 2 corresponds to the critical radius of the head and body; Then, taking the intersection of the two inequalities above yields the result applicable to forming radii in [ R 1, R 2] The range of values ​​for the sphere's head radius in the interval: 。 7. The method according to claim 6, characterized in that, If the rigidity of the head body does not meet the usage requirements, the obtained head body parameters are iteratively optimized based on the rigidity check.

8. The method according to claim 7, characterized in that, The obtained head-body parameters are iteratively optimized based on the stiffness and strength check, including: Step 1: Calculate the head-body radius, based on R upper limit R 1 and lower limit R 2. D Δ c , δ c ,calculate r c1 and r c2 The range of values ​​for the head-body radius is obtained. And select one r The value is used as the head-body radius; Step 2: Arrange the constraint heads by... r Value Calculation l max ( r ),ensure l ≤ l max The head and body are arranged without interference. Step 3: Check the rigidity of the entire mold. If the rigidity meets the requirements, the design of the head body parameters is complete. If the rigidity does not meet the requirements, the head body width needs to be increased for iterative optimization design.

9. The method according to claim 8, characterized in that, After increasing the width of the head and body, Repeat steps one through three, or... With the current r The value is input, and its corresponding value is calculated. D c ,if r = R ,but D c = D Then according to D and D c Calculation of size relationship :if D ≤ D c ,but l max = l max ( D c , r );if D > D c ,but l max = l max ( D , r ).

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