Taiyuan University of Technology
Sheet Metal Forming
Processes and Die Design
冲压工艺及模具设计
College of Materials Science
and Engineering
Lecturer：CAO Xiao-qing（曹晓卿）
March,2009
Chapter 6 Buldging and Flanging
Main contents:
Flanging of a hole (dimpling)
 Flanging of outer edge;
 Bulging(expanding) and local forming
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Key points:
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Deformation feature of bulging and hole
flanging
New Words:
Flanging/dimpling（翻边）, buldging（胀形）,
press（压力机），formability（成形性）
ferrous metal（钢铁材料/黑色金属）
non-ferrous metal（有色金属）
non-metallic materials（非金属材料）
cutting process(分离工序）,
forming (plastic deformation)process（成形工序）
§6.1 Flanging
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Definition and classification
Flanging of a hole
Flanging of outer edge
Ironing flanging
1.Definition and classification
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definition: plane sheet(semi-product)
→vertical edge along certain straight
line or curve via flanging die
classification: flanging of a hole and
flanging of outer edge
2.Flanging of a hole
A hole is drilled or punched and the surrounding
metal is expanded into a flange.
2.1 Deformation feature
deformation zone: a ring of D-d
 ()    (),   (),   ()
risky section : edge fracture(βtype: local extension is not enough)
2.2 Deformation degree
flanging coefficient: m=d/D
limit flanging coefficient[m]: maximum deformation degree of no
fracture
2.Flanging of a hole
Phases in the procwss of flanging of a hole
2.Flanging of a hole
factors affecting [m]:
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material’s property;: ε↑[m]↓
relative thickness: d0 / t↓[m]↓
state of edge: smooth[m]<rough[m]
shape of flanging punch: flat[m]>spherical[m]
shape of hole: circular[m]>un-circular[m]
2.Flanging of a hole
2.3 Calculation of blank
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principle: neutral line length is constant.
punching hole in plane sheet:
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calculate the diameter of pre-punched hole from the size of
workpiece ,then check it with [m]
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calculate Hmax using [m],then compare with Hworkpiece
punching hole in the bottom of drawing work-piece
2.4 Flanging force
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estimate using empirical formula
2.Flanging of a hole
2.5 Determination of flanging die
2.Flanging of a hole
3.Convex-shrink flange
Shrinkage : wrinkle ,   (),   b /( R  b)
 Tension : edge fracture,   (),   b /( R  b)
 Blank calculating principle: constant
neutral line length
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4.Ironing flanging
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Blank calculating principle : constant
volume
Difference between general flanging and
ironing flanging
§6.2 Bulging and local forming
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Bulging
Local forming
1.Bulging
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1.1 Deformation feature
deformation region: stable (<d), double
axial tension stress, thickness of the
material thinner, unstable form is
fracture(αtype: strength is not enough)
1.2 Deformation degree
expressing index
affecting factors
2.Local forming
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Nosing: a die reduction method whereby the top of a
cup or a tubular shape may be closer or smaller in diameter
than its body.