Trans. Nonferrous Met. Soc. China 24(2014) 2387−2392
A new hole-flanging method for thick plate by uptting process
Qi-quan LIN 1, Wen-zheng DONG 1, Zhi-gang WANG 2, Katsuyoshi HIRASAWA 2
1. School of Mechanical Engineering, Xiangtan University, Xiangtan 411105, China;
2. Department of Mechanical Systerms Engineering, Gifu University, Gifu 501-1193, Japan
Received 17 October 2013; accepted 29 April 2014
Abstract: Flange height and lip accuracy are generally restricted by the formability of sheet metals in the conventional hole-flanging operation. A new hole-flanging process, named uptting-flanging process, was propod to obtain a more substantial flange from thick plate. The finite element method (FEM) with DEFORM was utilized to simulate the novel upttin g−flanging process and the influence of geometric parameters on the flange height was studied in details. A ries of flanging experiments with A1050P-O were carried out to validate the FEM results, and the variations of Vicker hardness in the plate ction were discusd. The results showed that the newly upttin g−flanging process revealed higher flange height and better lip accuracy than the conventional hole-flanging process, and the results between FEM simulations and experiments showed good agreement. Besides, the hardness of the plate around the flange part increas due to the work hardening after the uptting-flanging process, which reveals better superiority in strength for the subquent machining or asmbling process.
Key words: uptting −flanging; flange height; FEM; thick plate; A1050 aluminum alloy; hardness
According to work of KACEM et al [7,8], the effect of the clearance-to-thickness ratio on the hole-flanging process was investigated to determine the occurrence of ironing. However, the izure defect cannot be avoided due to the high surface expansion and vere tribological conditions at the
contact between the punch and the inner wall during the hole-flanging process with ironing, as reported in previous studies [4,9,10]. Thus, other techniques should be propod to produce a long flange. On one hand, LIN et al [11,12] applied the cold extrusion to obtaining a more substantial flange with a lower diameter. In this ca, the flange was formed by exerting a punch force on the rim of a pre-holed cup-shaped workpiece at the same time as a clamping force was applied to suppressing dilation on the bottom of the cup. On the other hand, incremental forming had been adopted for a longer lip which was an emerging process with a high potential economic payoff for rapid prototyping and for small quantity production, as shown in the work of the previous literatures [13−16].
In the prent work, a novel hole-flanging process, named uptting-flanging process, was propod to obtain a more substantial flange from thick plate. The
1 Introduction
Hole-flanging is a process widely ud in press working of sheet metal. In conventional hole-flanging, a flat sheet with a pre-cut hole is formed as the punch moves down against a die so as to produce a smooth, round flanged lip with higher strength. However, flange height and lip thickness ar
e generally restricted by the formability of sheet metals in the conventi onal hole-flanging operation [1−3]. Especially for the thick plate, forming defects such as fracturing, thinning or shrinking can easily occur on the wall of resulting in workpiece unsuitable for machining or asmbling.
矛盾农村三部曲the flange, subquent Generally, when a longer flange or a better finished lip is needed, ironing is utilized. KUMA GA I et al [4,5] discusd the influence of the plate thickness on the punch load, the finished shape and the metal flow in the hole-flanging with the ironing of thick sheet metal. THIPPRAKMAS et al [6] performed the hole-flanging with ironing for thick sheet metal to study the effect of the quality of the initial hole on the flanged shape. Foundation item: Project (51175445) supported by the National Natural Science Foundation of China; Project (2010DFA52130) supported by the
International Cooperation Project of the Ministry of Science and Technology, China; Project (CX2013B277) supported by Hunan Provincial Innovation Foundation f or Postgraduate, China
Corresponding author: Qi-quanLIN;Tel:+86-139********;E-mail:**************DOI: 10.1016/S1003-6326(14)63361-6
2388 Qi-quan LIN, et al/Trans. Nonferrous Met. Soc. China 24(2014) 2387−2392
finite element method (FEM) with DEFORM was
utilized to simulate the novel uptting−flanging process
and the influence of geometric parameters on the flange
height was studied in details.
were taken into consideration, the pre-hole diameter, D,
and the width of shaping punch, L, which play an
important role in the flanging formability, as shown in
Fig. 2.
2 Uptting−flanging process
2.1 Principle of uptting−flanging process
To obtain a successful flange, the novel uptting−
flanging process will be distributed into three stages:
uptting, flanging and shaping, as shown in Fig. 1.
Firstly, the workpiece is held with the blank holder and
the uptting process is performed by lowering the
uptting punch, as shown in Fig. 1(a). An arresting ring
is positioned to prevent the material from flowing toward
the outer edge, and a taper is designed on the lower blank
holder to promote greater flow of material toward the
hole side. Figure 1(b) shows the flanging process
performed by pushing the flanging punch upwards.
Finally, the flange is shaped by pushing down the sleeve
punch, as shown in Fig. 1(c).
Fig. 2 FEM model of uptting−flanging process
Table 1 FEM simulation conditions
Name Analysis condition
Number of elements 30000 with the rectangular element
Processing speed 1 mm/s
Diameter: 100 mm; Pre-hole
diameter: 20 mm, 10 mm
Thickness: 5 mm
Object type: Elasto-plastic
Workpiece
Diameter: 26.4 mm;
Flanging profile radius: 30 mm
Flanging punch
Inner diameter: 31.4 mm;
Outer diameter: 35.4 mm
Shaping punch
Inner diameter: 36.4 mm;
Outer diameter: 45.2 mm
Uptting punch
Inner diameter: 27.4 mm;
Outer diameter: 120 mm
Die
Inner diameter: 46.2 mm;
Outer diameter: 120 mm
Blank holder
Taper angle 2°
Fig. 1 Principle of uptting−flanging process: (a) Uptting; (b)
Flanging; (c) Shaping Friction coefficient 0.1
The hot-rolled A1050P-O(JIS) aluminum sheet was
ud as the workpiece material, and its constitutive
equation was determined from the stress−strain curve
obtained by the tensile testing experiment, as shown in
Table 2. The tensile strength and strain hardening
exponent values were 77 MPa and 0.27, respectively.
2.2 FEM simulation tup
In this study, a commercial analytical code for
statistic implicit finite element method (DEFORM) was
ud as the FEM simulation tool. Due to symmetry, only
a quarter of the simulation model was ud to reduce the
calculated time, as shown in Fig. 2. The automatic
remeshing was t at every five steps to prevent a
divergence calculation. The blanked material was
assumed to be elasto-plastic type with the rectangular
element of approximately 30000 elements, and the tools
(die, punch and blank-holder) were modeled as rigid
ones, as shown in Table 1. Two geometric parameters
Table 2 Mechanical properties of hot-rolled A1050P-O(JIS)
aluminum sheet世界四大寓言
Plate Y ield Fracture Hardening
r
thickness/mm strength/MPa elongation/% exponent
5.0 35 55 0.73 0.27
ppt大小尺寸
Qi-quan LIN, et al/Trans. Nonferrous Met. Soc. China 24(2014) 2387−2392 2389 3 Results and discussion
3.1 Process parameters analysis
Figure 3 shows the relationships between the
uptting height (s), flange height (h), hole inside
diameter (d) and plate thickness around the hole (t). As
the uptting height increas, the thicker the plate is, the
smaller the hole diameter becomes, and the sheet
material around the hole is pushed upward as well. Thus,
during the uptting process, more sheet materials are
piled up for the following flange part. When the
uptting height exceeds 1.8 mm, both the hole diameter
and the plate thickness reveal a small change; however,
the flange height increas directly.
Fig. 4 V ariations in taper angle, flange height and the maximum
load after uptting−flanging process (s=2 mm, L=9.8 mm)
Fig. 3 V ariations in plate thickness, hole diameter and flange
height with uptting height Fig. 5 Relationship between flange height and hoop strain of
flange edge
In the upttin g−f langing process, a taper structure
is designed on the lower blank holder so as to promote a
greater flow of the material toward the hole side. Figure
4 illustrates the influence of taper angle on the flange
height and the maximum load after the up tting−
flanging process. Obviously, as the taper angle increas,
the compresd material flows into the flange more
easily, so that the maximum load greatly decreas.
Besides, the flange height gradually reduces becau the
workpiece volume decreas at the taper portion. To
obtain a higher flange under the lowest processing load,
an appropriate taper angle should be carefully designed.
And no cracks can be found during the flanging process
since the hoop strain exceeds no more than the fracture
limit. Moreover, under the same hoop strain, the flange
height increas as the uptting width increas, as
shown in Fig. 5.
3.3 Experimental verification
Bad on the FEM analysis, both the conventional
hole-flanging and the uptting−flanging die ts were
prepared under the same conditions with FEM
simulation. The thick paraffin petrolatum P460 was ud
as a lubricant and the diameter of the prepared hole for壬辰倭乱1592
the flanging process was 20 mm. All the experiments
were carried out on the 500 kN hydraulic oil press in our
laboratory.
Figure 6 shows a cross-ction of the flange after
the conventional flanging process with a 5 mm
aluminum plate. There are two kinds of shape defects in
the flange part. One is the insufficient flange height (e
Fig. 6(a)), and the other is the excessive thinning around
the tip part (e Fig. 6(b)). Besides, the quality defects
such as cracks on the flange edge (e Fig. 7(a)) and 3.2 Variations of hoop strain
To demonstrate the variations of hoop strain in
flanging process, four different flanging conditions are
investigated, as shown in Fig. 5. In the ca of the
conventional hole-flanging process (D=16 mm, L=0 mm),
the hoop strain exceeds 1.0 and cracks appear on the
flange’s edge. In the ca of the uptting−flanging
process, under all conditions, the hoop strain becomes
negative (which refers to compress stress) at first and
then changes to positive (which refers to tensile stress).
2390 Qi-quan LIN, et al/Trans. Nonferrous Met. Soc. China 24(2014) 2387−2392女生为什么会肾虚
shrinkage (e Fig. 7(b)) can easily occur after the
flanging process.
Fig. 6 Flange shape of conventional hole-flanging process: (a)
D=20 mm; (b) D=10 mm
Fig. 8 Flange shape of uptting−flanging process: (a) Front
side; (b) Rever side
Fig. 9 Distributions of V ickers hardness in plate ction (initial
hardness is HV34)
4 Conclusions
1) Considering the insufficient flange height and
quality defects in the conventional flanging process, a
novel flanging process, named uptting-flanging
process, was propod to obtain a more substantial flange
from thick plate and no crack occurs during the
uptting−flanging process beca u of the negative hoop
strain near the flange edge.
2) A taper structure designed on the lower
blank holder plays an important role during the
uptting−f langing process, and the larger the taper angel
is, the smaller the flange height and the maximum load
become.
3) The hardness of the plate around the flange part
increas due to the work hardening after the
uptting−fl anging process, which reveals better
鞘脂superiority in strength for the subquent machining or
asmbling process.
Fig. 7 Quality defects in conventional hole-flanging process:
(a) Edge cracks; (b) Shrinkage
However, as shown in Fig. 8, there are no
remarkable shape defects and quality defects in the
手工皂
uptting−fl anging process and its flange height is higher
than that in the conventional hole-flanging under the
same conditions. Moreover, the hardness of the plate
around the flange part increas due to the work
hardening after the uptting−flanging process (e
Fig. 9). As a result, the formed part reveals better
superiority in strength for the subquent machining or
asmbling process. Figure 10 shows the flange shape
after each forming stage in the uptting−flanging
process, and the characteristics of plate thickness and
flange height show good agreement between experiments
and FEM.
Qi-quan LIN, et al/Trans. Nonferrous Met. Soc. China 24(2014) 2387−2392 2391
Fig. 10 Flange shapes after each forming stage during uptting −flanging process: (a 1, b 1, c 1) Experimental results; (a 2, b 2, c 2) FEM results
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