Prediction method for limit flanging height of steel plate and flanging design method

Abstract

The invention discloses a method for predicting the limit flanging height of a steel plate and a flanging design method.In the curve flanging design process of the steel plate, the limit flanging height hmax is calculated according to the following formula: hmax = lambda * r1 / (1 + lambda) + (2-3.14 / 2) * r2; in the formula, hmax is the limit flanging height, mm; lambda is the hole expansion rate,% of the steel plate; r1 is the radius of a fillet between the heights of two adjacent flanges, mm; and r2 is the radius of the flanging fillet of the non-closed curve, mm. According to the method, the feasibility of die surface design and material selection is evaluated by utilizing a theoretical calculation method, the phenomenon of stamping cracking caused by too high flanging height of die surface design or wrong material selection is effectively avoided, simulation verification links are reduced, the die development period is shortened by more than 30%, material and working hour waste caused by die test failure is avoided, and the production efficiency is improved. The development cost is reduced, and the win-win situation of cost and efficiency is realized; the method has universality, the limit flanging height can be quickly predicted, and the development period is remarkably shortened.

Description

Technical Field

[0001] This invention relates to the field of metal sheet stamping technology, and in particular to a method for predicting the ultimate flange height of steel sheets and a flange design method. Background Technology

[0002] Lightweighting in the automotive industry is driving the development of automotive steel towards higher strength, better plasticity, and superior fracture toughness. Advanced high-strength or ultra-high-strength steels, with their high tensile strength and good toughness, are widely used in key load-bearing components such as front longitudinal beams, door sills, and top beams. When the tensile strength of a material exceeds 590 MPa, the stamping forming of parts generally involves a combination of processes such as drawing → trimming and flanging, and shaping, or blanking → flanging → punching and shaping.

[0003] The ease or difficulty of flanging a part depends not only on the mold design but also on the correct material selection. During the mold design phase, designers sometimes neglect formability issues in pursuit of a perfect shape or cost. In the mold development phase, most engineers currently rely on simulation forming software to verify the rationality of the mold shape and material selection. If formability requirements are not met, repeated communication with the mold design engineer is necessary to modify the mold or change the material, significantly increasing workload and extending the development cycle. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for predicting the limit flange height of steel plates; the present invention also provides a method for designing flanges of steel plates.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the prediction method of the present invention is as follows: In the process of designing the steel plate curved flange, the limit flange height h is calculated according to the following formula (Ⅰ). max ,

[0006] h max =λ×r1 / (1+λ)+(2-3.14 / 2)×r2 (Ⅰ);

[0007] Where: h max λ is the maximum flange height (mm); λ is the expansion rate of the steel plate (%); r1 is the fillet radius between two adjacent flange heights (mm); r2 is the fillet radius of the flange of a non-closed curve (mm).

[0008] Furthermore, in the design of the curved flange, the maximum safe flange height is 0.8 × h. max .

[0009] To solve the above technical problems, the technical solution adopted by the design method of the present invention includes the following steps: (1) Measure the part model to obtain the geometric feature parameters of the flange design, including the design value h1 of the flange height, the flange angle θ, the fillet radius r1 between two adjacent flange heights, and the fillet radius r2 of the flange of the non-closed curve.

[0010] (2) Measure the hole expansion ratio λ of the steel plate;

[0011] (3) Calculate the limit flange height h according to formula (1). max ;

[0012] (4) If the design value of the flange height h1 < 0.8 × h max If so, the design is feasible;

[0013] (5) If h1 ≥ 0.8 × h max If the design is not feasible, replace the steel plate material with one that has better flanging and hole-expanding performance or modify the mold surface design, and repeat steps (1)-(3) until h1 < 0.8 × h max .

[0014] Furthermore, the arc length L of the steel plate before flange turning is calculated using the following formula (II).

[0015] L=((180-θ) / 360)×2×3.14×(r1+r2-(h-r2)-(3.14 / 2)×r2) (II);

[0016] In the formula: L is the arc length of the material sheet, mm; θ is the flange angle, °; h is the final design value of the flange height, mm.

[0017] The beneficial effects of adopting the above technical solution are as follows: Based on the geometric characteristics of the part, such as the flange angle and fillet radius, and combined with the material's expansion rate, the present invention can quickly calculate the limit flange height of the material under ideal conditions, providing data support for the mold surface design of typical automotive parts and ensuring that the trial mold passes on the first attempt; in particular, by combining the safety margin to determine the optimal safe flange height, the trial mold passes on the first attempt even more effectively.

[0018] This invention utilizes theoretical calculations to evaluate the feasibility of mold surface design and material selection, effectively avoiding stamping cracks caused by excessively high flange heights in the mold surface design or incorrect material selection. It reduces simulation verification steps, shortens the mold development cycle by more than 30%, avoids material and time waste due to failed trial molding, reduces development costs, and achieves a win-win situation of cost and efficiency. This invention is universally applicable, can quickly predict the limit flange height, significantly shortens the development cycle, and is particularly suitable for high-strength steel plates with tensile strength ≥590MPa and thicknesses ranging from 0.8mm to 2.5mm, covering the needs of mainstream automotive parts. Attached Figure Description

[0019] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0020] Figure 1 This is a flowchart of the present invention;

[0021] Figure 2 This is a schematic diagram of the mold surface shape and key parameters of the part flange position in this invention;

[0022] Figure 3 This is a schematic diagram of the sheet metal shaping and key parameters of the present invention;

[0023] Figure 4 This is a comparison chart of the flanging test results in Example 1;

[0024] Figure 5 This is a comparison chart of the results of the edge-flipping experiment in Example 2. Detailed Implementation

[0025] Example 1: Figure 1 As shown, the prediction method and flanging design method for the ultimate flange height of this steel plate are described below.

[0026] (1) Figure 2 As shown, based on the mold surface shape of the part, the geometric characteristic parameters of the part are measured: the design value of the flange height h1 is 4.5mm, the flange angle θ is 90°, the fillet radius r1 between two adjacent flange heights is 35mm, and the fillet radius r2 of the flange of the non-closed curve is 3mm.

[0027] (2) The expansion rate λ of DP980-1.2mm material was measured to be 21% using GB / T 15825.4-2008 Metal Sheet Forming Properties and Test Methods Part 4: Hole Expansion Test;

[0028] (3) Calculate the limit flange height h max The calculation result is: h max =λ×r1 / (1+λ)+(2-3.14 / 2)×r2=0.21×35 / (1+0.21)+(2-3.14 / 2)×3=7.4mm;

[0029] (4) Considering the safety of the part forming process, the safety margin is set to 0.8. The calculated limit safety flange height is 0.8×h2=0.8×7.4=5.92mm. Therefore, the allowable flange height within the safety range is 5.92mm, which is greater than the design value of 4.5mm for the part flange height. That is, under this working condition, the limit safety flange height of this material is greater than the design value. The mold surface shape and material selection can meet the requirements of its flange forming performance.

[0030] (5) Figure 3 As shown, the arc length L of the material sheet is calculated using the formula L=((180-θ) / 360)×2×3.14×(r1+r2-(h-r2)-(3.14 / 2)×r2)=((180-90) / 360)×2×3.14×(35+3-(4.5-3)-(3.14 / 2)×3)=49.9mm. Therefore, the arc length L of the material sheet at the flanged part is 49.9mm.

[0031] (6) Verification of Predicted Results: The sheet metal was prepared according to the arc length calculated in step (5). Using a multi-functional flanging mold, appropriately sized inserts were selected so that the flanging angle θ was 90°, the fillet radius r1 between two adjacent flanging heights was 35mm, the fillet radius r2 of the non-closed curve was 3mm, and the flanging heights were 4.5mm, 5.5mm, and 6.6mm, respectively. Flanging experiments were conducted. The experimental results are as follows: Figure 4 As shown, when the flange height is 4.5mm, no flange cracking occurs; when the flange height is 5.5mm, there is slight, inconspicuous necking, but no obvious cracking occurs; when the flange height is 6.6mm, obvious cracking occurs.

[0032] Example 2: Figure 1 As shown, the prediction method and flanging design method for the ultimate flange height of this steel plate are described below.

[0033] (1) Figure 2 As shown, based on the mold surface shape of the part, the geometric characteristic parameters of typical parts are measured: the design value of the flange height h1 is 6mm, the flange angle θ is 90°, the fillet radius r1 between two adjacent flange heights is 35mm, and the fillet radius r2 of the flange of the non-closed curve is 3mm.

[0034] (2) The expansion rate λ of DP980-1.2mm material was measured to be 21% using GB / T 15825.4-2008 Metal Sheet Forming Properties and Test Methods Part 4: Hole Expansion Test;

[0035] (3) The limit flange height h is calculated using geometric relationships. max The calculation formula is: h max =λ×r1 / (1+λ)+(2-3.14 / 2)×r2=0.21×35 / (1+0.21)+(2-3.14 / 2)×3=7.4mm;

[0036] (4) Considering the safety of the part forming process, the safety margin is set to 0.8. The calculated limit safety flange height is 0.8×h2=0.8×7.4=5.92mm. Therefore, the limit flange height within the safety range is 5.92mm, which is less than the design value of 6mm for the flange height of the part. That is, under this working condition, the limit safety flange height of the material is less than the design value, and the scheme is not feasible.

[0037] (5) Figure 3 As shown, by changing the profile without changing the material, r2 is increased from 3mm to 5mm, and the maximum flange height h is... max =λ×r1 / (1+λ)+(2-3.14 / 2)×r2=0.21×35 / (1+0.21)+(2-3.14 / 2)×5=8.2mm;

[0038] (6) The limit safety flange height is calculated as 0.8×h2=0.8×8.2=6.56mm. Therefore, the allowable flange height within the safety range is 6.56mm, which is greater than the design value of 6mm for the part. The mold surface shape and material selection can meet the requirements of its flange forming performance.

[0039] (7) Calculate the arc length L of the material before flanging. The calculation formula is L=((180-θ) / 360)×2×3.14×(r1+r2-(h-r2)-(3.14 / 2)×r2)=((180-90) / 360)×2×3.14×(35+5-(4.5-5)-(3.14 / 2)×5)=45.4mm. Therefore, the arc length L of the flanging part is calculated to be 45.4mm.

[0040] (8) Verification of Predicted Results: The sheet metal was prepared according to the arc length calculated in step (7). Using a multi-functional flanging mold, appropriately sized inserts were selected so that the flanging angle θ was 90°, the fillet radius r1 between two adjacent flanging heights was 35mm, the flanging height h1 was 6mm, and the fillet radius r2 of the non-closed curve was distributed at 3mm and 5mm. Flanging experiments were then conducted. The experimental results are as follows: Figure 5 As shown, when the fillet radius r2 is 3mm, edge cracking occurs; when the fillet radius r2 is 5mm, no cracking occurs.

Claims

1. A method for predicting the ultimate flange height of steel plates, characterized in that: During the design of the steel plate curved flange, the limit flange height h is calculated according to the following formula (Ⅰ). max , h max =λ×r1 / (1+λ)+(2-3.14 / 2)×r2 (Ⅰ); Where: h max λ is the maximum flange height (mm); λ is the expansion rate of the steel plate (%); r1 is the fillet radius between two adjacent flange heights (mm); r2 is the fillet radius of the flange of a non-closed curve (mm).

2. The method for predicting the ultimate flange height of a steel plate according to claim 1, characterized in that: When designing the curved flange, the maximum safe flange height is 0.8 × h. max .

3. A method for designing steel plate flanges, comprising calculating the limit flange height using the method described in claim 1, characterized in that, The following steps are included: (1) Measure the part model to obtain the geometric feature parameters of the flange design, including the design value h1 of the flange height, the flange angle θ, the fillet radius r1 between two adjacent flange heights, and the fillet radius r2 of the flange of the non-closed curve. (2) Measure the hole expansion ratio λ of the steel plate; (3) Calculate the limit flange height h according to formula (1). max ; (4) If the design value of the flange height h1 < 0.8 × h max If so, the design is feasible; (5) If h1 ≥ 0.8 × h max If the design is not feasible, replace the steel plate material with one that has better flanging and hole-expanding performance or modify the mold surface design, and repeat steps (1)-(3) until h1 < 0.8 × h max .

4. The steel plate flanging design method according to claim 3, characterized in that: The arc length L of the steel plate before flange is calculated using the following formula (II). L=((180-θ) / 360)×2×3.14×(r1+r2-(h-r2)-(3.14 / 2)×r2) (II); In the formula: L is the arc length of the material sheet, mm; θ is the flange angle, °; h is the final design value of the flange height, mm.

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