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124
N
ovember
2009
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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%
8 x 1.2, 10 x 1.5, 12 x 1.8, 20 x 3
20%
8 x 1.6, 10 x 2, 14 x 2.8, 15 x 3, 16 x 3.2
25%
8 x 2, 10 x 2.5, 12 x 3, 14 x 3.5
30%
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.
Station No.
Arc 1
Arc 2
1
65°
-15°
2
65°
0°
3
65°
15°
4
65°
30°
5
65°
45°
6
65°
60°
7
65°
75°
8
65°
90°
Table 2
:
Setting angle of forming arc
Figure 2
:
The forming Arc 1 & Arc 2