TPT November 2009

FEA simulation: the roll forming of small diameter thick-wall ERW tube By Jiying Liu, Guoxian Niu and Zhengqing Ai, North China University of Technology, Beijing, China

Abstract Using the method of elastic-plastic finite element analysis, nonlinear finite element software Msc.Marc is used for simulating the small- diameter thick-walled tube in the roll-forming process. During the analysis the roundness error is analysed and the polynomial equation is summed up according to the same diameter and the same wall thickness. The tube wall thickness change is stated after roll-forming, and the peak point of the changing error is given a new concept for modifying the roller gap contour because the wall thickness change is disclosed. To obtain uniform thickness of tube, the modified and fitted spline contour should be used for roll gap design. The conclusions can be used in the high-precision welded tube roll forming process. Foreword Small diameter thick-wall electric resistance welded (ERW) tubes have been widely used in the automobile industry. This is because the thick-wall tube can be prevented from suffering leakage and penetration, in addition to resisting various impacts and fluctuations in temperature. This research looks at the roll-forming technological process of the small diameter thick-wall welded tube with OD≤20mm, and thickness/diameter ratio of more than 5%. Its small diameter and thick walls cause various difficulties during roll forming. Roll forming in engineering often depends on experience and trial- and-error, which results in a long development cycle and high cost. The nonlinear finite element software called Msc.Marc is used for simulation of the roll-forming technological process of the small diameter thick-wall welded tube. It helps by summarising the changing rule of welded tube wall thick- ness from results of numerical simulation. It also carries out roundness error analysis to the inside diameter of the welded tube in results of simulation with Matlab, which provides the basis for designing a method of efficiently forming small diameter thick-wall ERW tubes. 1 Object researched and process planning 1.1 Determining object researched According to the dimensions of ERW steel tube, specifications of small diameter thick-wall tubes defined in the topic are chosen for researching. So various thickness/diameter ratios are chosen for simulation as Table 1 shows.

Thickness/diameter ratio (t/D) x 100%

Outside diameter x thickness / (mm x mm)

15% 20% 25% 30%

8 x 1.2, 10 x 1.5, 12 x 1.8, 20 x 3

8 x 1.6, 10 x 2, 14 x 2.8, 15 x 3, 16 x 3.2

8 x 2, 10 x 2.5, 12 x 3, 14 x 3.5

10 x 3  Table 1 : Specifications of ERW tube

 Figure 1 : The specifications of ERW tube used for simulation

1.2 Roll tooling design All roll tooling is designed using the double radius forming method by the soft- ware COPRA. Refer to Table 2 for the forming angle before final pass, and refer to Fig. 2 for Arc 1 and Arc 2 of double radius.

 Figure 2 : The forming Arc 1 & Arc 2

Station No.

Arc 1

Arc 2

1 2 3 4 5 6 7 8

65° 65° 65° 65° 65° 65° 65° 65°

-15°

0°

15° 30° 45° 60° 75° 90°

 Table 2 : Setting angle of forming arc

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N ovember 2009

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