1 Introduction
Parameter | Yield strength ↑ | Young’s modulus ↑ | Bending radius ↑ | Sheet thickness ↑ | Forming strategy |
---|---|---|---|---|---|
Amount of springback | ↑ | ↓ | ↑ | ↓ | To be investigated |
2 State of the art roll forming of tubes
3 FE-Simulation of the roll forming process
Yield strength Rp0,2 (MPa) | Tensile strength Rm (MPa) | Young’s Modulus E (GPa) | Elongation at fracture A (%) | Density ρ (g/cm3) | Sheet thickness s0 (mm) | Sheet width b0 (mm) |
---|---|---|---|---|---|---|
505 | 567 | 72 | 11 | 2.81 | 1.5 | 168 |
3.1 FE-Model for the roll forming process
3.1.1 Initial situation
3.1.2 Double radius forming
3.1.3 W-forming strategies
3.1.4 Summary of the strategies
Pass | 2R | W1 | W2 | |||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
a1 (mm) | r1 (mm) | a2 (mm) | r2 (mm) | a1 (mm) | r1 (mm) | a2 (mm) | r2 (mm) | a1 (mm) | r1 (mm) | a2 (mm) | r2 (mm) | |
1 | 22.3 | 30 | 61.7 | 250 | 22.3 | 30 | 61.7 | − 250 | 34.4 | 26 | 49.6 | − 200 |
2 | 22.3 | 30 | 61.7 | 150 | 22.3 | 30 | 61.7 | 150 | 34.4 | 26 | 49.6 | 200 |
3 | 23.6 | 28 | 60.4 | 119 | 23.6 | 28 | 60.4 | 119 | 34.4 | 26 | 49.6 | 100 |
4 | 23.6 | 28 | 60.4 | 91 | 23.6 | 28 | 60.4 | 91 | 34.4 | 26 | 49.6 | 65 |
5 | 25.7 | 26 | 58.3 | 75 | 25.7 | 26 | 58.3 | 75 | 34.4 | 26 | 49.6 | 45 |
6 | 25.7 | 26 | 58.3 | 60 | 25.7 | 26 | 58.3 | 60 | 34.4 | 26 | 49.6 | 35 |
7 | 28.1 | 26 | 55.9 | 50 | 28.1 | 26 | 55.9 | 50 | 34.4 | 26 | 49.6 | 30.8 |
8 | 30.7 | 26 | 53.3 | 41 | 30.7 | 26 | 53.3 | 41 | 36.6 | 26 | 47.4 | 29.4 |
9 | 30.7 | 26 | 53.3 | 35 | 30.7 | 26 | 53.3 | 35 | 38.4 | 26 | 45.6 | 28.3 |
10 | 34.4 | 26 | 49.6 | 30.8 | 34.4 | 26 | 49.6 | 30.8 | 40.2 | 26 | 43.8 | 27.1 |
11 | 36.6 | 26 | 47.4 | 29.4 | 36.6 | 26 | 47.4 | 29.4 | 42 | 26 | 42 | 26 |
12 | 38.4 | 26 | 45.6 | 28.3 | 38.4 | 26 | 45.6 | 28.3 | ||||
13 | 40.2 | 26 | 43.8 | 27.1 | 40.2 | 26 | 43.8 | 27.1 | ||||
14 | 42 | 26 | 42 | 26 | 42 | 26 | 42 | 26 |
3.2 Discussion of the FE-results
3.2.1 Buckling limit strain
3.2.2 Geometry and bending radius
3.2.3 Welding of the tube
3.2.4 Recommendations for the choice of the forming strategy
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W-forming is recommended. The compression of the band edge after pass 1 leads to a lower plastic elongation of the band edge and thus to a reduced buckling tendency of the band edge.
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The use of a downhill strategy reduces the elongation of the band edge, especially in the first passes.
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Appropriate roll design regarding the use of the type of rolls. The use of side rolls is not recommended in the first passes as they cause a high elongation of the band edge.
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The combination of forming the target radius in the band edge area (high elongation of the band edge) in combination with the downhill strategy (reduced elongation of the band edge) leads to high efficiency thanks to the large forming operation at the beginning of the process.
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For a high process efficiency, it is recommended to keep the maximum longitudinal strain as equal as possible in each pass.