Finite element analysis of multi-pass drawing under back
tension using a virtual state-variable body-force method
MinCheol Kim1), SeongWon Lee1), JaeGun Eom2), ManSoo Joun3)
1) School of Mechanical Engineering, Gyeongsang National University(GNU), Jinju / Korea
2) TIC of Gyeongsang National University, Sacheon / Korea
3) Corresponding author, School of Mechanical Engineering / Engineering Research Institute,
Gyeongsang National University/, Jinju / Korea, [email protected].
AFDEX
AFDEX, an Intelligent metal forming simulator
www.afdex.com MFRC
Applicability – Applications of the year 2008
Applicability – Applications of the year 2009
Accuracy – Tensile test
Engineering strain (mm/mm)
En
gin
ee
rin
gstr
ess
(MP
a)
0 0.1 0.2 0.3 0.40
200
400
600
800
1000
1200
Experiment (SCM435)
Analysis (SCM435)
Experiment (ESW95)
Analysis (ESW95)
Experiment (ESW105)
Analysis (ESW105)
Computational Material Science 2007 / Mechanics of Material 2008
A
C B
12.5slope
0.002
12.5slope
0.002
O
Elongation [mm]
Te
nsi
lelo
ad
[kN
]
0 1 2 3 4 5 6 7 8 90
2
4
6
8
10
12
ExperimentPrediction
A
C
B
O
B
C
O A B
Accuracy - Fracture prediction in tensile test
6
PredictionExperiment
SCM435 ESW105
Non-contacted Contacted Non-contacted Contacted
Accuracy - Extrusion test
7
Trans. ASME J. Eng. Mat. Tech. 1998 / Int. J. Mach Tools Manuf. 2000 / Trans. ASME J. Eng. Mat. Tech. 2007.
Metal flow and
temperature
Damage
Internal crack
Accuracy – Hot forging, bearing race
Accuracy - Cold forging, automobile part
9
Bend
ing p
rocess
Siz
ing p
rocess
Finite Element Ana. Des. 2009
Accuracy – Cold forging, rotor pole
KSPE Fall 2007
Accuracy – Enclosed die forging, bevel gear
Enclosed die forging Sizing
Accuracy - Hammer forging, ship engine part
12
2.0
2.0
2.0
2.0
1.15 1.15
Simulation failures (2009) Ours (2009)
Research background -Tube extrusion/drawing process
Previous studies on central bursting defects
C. Soyarslan et al.
ABAQUS/ Explicit
Elasto-plastic
K. Saanouni et al.
Forge
Elasto-plastic
H. Cho et al.
DEFORM
Labergeere et al.
ABAQUS/ Explicit
thermoelasto-viscoplastic
F. Ahmadi et al.
Rigid-plastic
McAllen et al.
ABAQUS
EXPERIMENTS
PREDICTIONS
Extrusion Drawing
cr
or100c
o
rr
r
81r
90r 78r 84r
72r 38r 67r 55r 60.0r 50r
83meanr
Chevron crack predictions
(a) Case 1 (b) Case 2 (c) Case 3 (d) Case 4
30, 18,
0.03
60, 18,
0.03
30, 30,
0.03
30, 18,
0.05 αº, R.A.%,
μ
82r 89r 68r 87r
82meanr
R = 0% R = 10% R = 20%
Effect of back tension – Central bursting defect
Swaging analysis – Motion of pusher
◎ Predictions with rigid mount
Spindle
Shoe
Cylinder roller
Workpiece
Die
◎ Experiments ◎ Modelling
◎ Predictions
with elastic mount
Artificial body force method
,
A R
ij j i i if f f
itS
ivS
V
Die itS
CSMaterial
Elastic
Plastic
itS
R
if
V
itS
CS
Elastic
Plastic
A
if
Artificial
body force
Actual
body force
ivS
○ Flow stress
ᆞ
○ Coefficient of Coulomb friction
ᆞ
○ Die velocity
ᆞ
○ Body force
ᆞ
○ Resultant force
ᆞ
0.2272.7 MPa
0.05
1.0mm/sv
Test Ex. 1 - Drawing process with back tension exerted
3000℃
2417℃
1834℃
1252℃
670℃
20℃
3.0mm
40
.0m
m
Artificial body force
13.2˚
Non-separable die
5.0
mm
C L
39.8912N/mm
1422N
Test Ex. 1 - Predictions
Metal flows and dimensions
C L
0.08
0.35
0.40
0.40
0.35
200
600
800
50
25
50
800
0.45
400
100
Effective strain
3.0mm
Puller die
2.54mm
2.54mm 2.54mm
3.0mm 3.0mm
Effective stress
1
2
3
4
5
6
7
8
9
10
Non-separable die Non-separable
die
Upper die
Lower die
1st upper
1st lower
(extrusion)
2nd upper
2nd lower (drawing)
2nd lower
3rd upper
3rd lower
3rd lower (flug)
3rd lower (drawing)
⊙ Tube extrusion and drawing process with back pressing
(a) Extrusion (b) Drawing (c) Drawing
1422N
Back pressing
force
Test Ex. 2 - Tube extrusion and drawing process
Stroke (mm)
Lo
ad
(10
kN
)
0 20 40 60 800
0.2
0.4
0.6
0.8
1
Upper_Die
Lower_Die
1422N
1422N
Input backpressing force=1422 N
First stage
Second stage
Third stage
KSTP 2009
Test Ex. 2 - Tube extrusion and drawing process
Application Ex. 1 – Six-pass rod drawing
CL
Die
btσ
2
α
l
ir
or
P
◎ Process information
Dimension\pass 1 2 3 4 5 6
[mm] 7.00 6.64 6.30 5.98 5.67 5.38
[mm] 6.64 6.30 5.98 5.67 5.38 5.10
[mm] 2.0 2.0 2.0 2.0 2.0 2.0
[º] 10.0 10.0 10.0 10.0 10.0 10.0
ir
or
l
Artificial body-force
specified region
r-axis
CL
Application Ex. 1 – Simulation information
◎ Material information -SWCH10A
- = 295 MPa Yσ
Elongation [mm]
Te
nsile
loa
d[k
N]
0 2 4 60
2
4
6
8
10
12
14
Measured
Prediction
True strain [mm/mm]
Tru
estr
ess
[MP
a]
0 0.2 0.4 0.6 0.8 10
100
200
300
400
500
600
◎ Flow stress
◎ Friction
-Coefficient of Coulomb friction: 0.02
◎ Back tensile stress
-R = 0% (Case 1)
-R = 10% (Case 2)
-R = 20%(Case 3) of Yσ
◎ For Case 2
Strain Damage Strain Damage Strain Damage Strain Damage Strain Damage Strain Damage
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
Pass 1
Pass 2
Pass 3
Pass 4
Pass 5
Pass 6
Application Ex. 1 – Predictions
Effect of back tension – strain and damage
Strain Damage Strain Damage Strain Damage
R = 0% R = 10% R = 20%
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Strain Damage
0.000
0.125
0.250
0.375
0.500
0.625
0.750
0.875
1.000
Back tensile stress = Initial yield stress multiplied by R
Radius [mm]
Da
ma
ge
0 1 2 3 4 5 60
0.2
0.4
0.6
0.8
1
0%
10%
20%
Effect of back tension – strain and damage
Back tensile stress = Initial yield stress multiplied by R
Stroke [mm]
Lo
ad
[kN
]
0 50 100 150 2000
4
8
12
16
20
0% Die & Pulling Tool
10% Die
10% Pulling Tool
20% Die
20% Pulling Tool
Drawing
force
[kN]
R = 10% R = 20%
Pass 1 4.4 8.8
Pass 2 4.0 7.9
Pass 3 3.6 7.2
Pass 4 3.2 6.4
Pass 5 2.9 5.8
Pass 6 2.6 5.2
Effect of back tension – Drawing force
0% 10% 20%
576.9
728.5
404.7
584.2
376.9
690.8
574.0
351.3
661.7
-300.0 -200.0 -100.0 0.0 100.0 200.0 300.0 400.0 500.0
Stress [MPa]
400 MPaσ
0 MPayyσ 29 MPa
yyσ 58 MPa
yyσ
64.5 MPayyσ 91.8 MPa
yyσ 118.9 MPa
yyσ
Hydrostatic
pressure
Normal
stress
max517.7MPap max
517.7MPap max520.5MPap
8800NP 12700NP 16500NP
Effect of back tension – Die pressure
R = 0% R = 10% R = 20%
R = 0% R = 10% R = 20%
Effect of back tension – Central bursting defect
Application Ex. 2 – Twenty-pass wiredrawing process
◎ A twenty-pass wiredrawing process was simulated
in a fully automatic manner by the presented approach.
-Radius of initial material is 7mm,
-Reduction of area per each pass is all 10%.
-Die land length is 2.0 mm.
-All die conical angles are 10º.
0.02
◎ Simulation information
-Flow stress: The same with Ex. 1
-Coefficient of Coulomb friction:
-Body force: 0%, 20%
1.0
1.5
2.0
2.5
Line legend
3.0Ø 4.13
Strain Damage
Ø 3.53
Ø 3.01
Ø 2.57
(a) Pass 11 (b) Pass 14 (c) Pass17 (d) Pass 20
1.0,
1.5,
2.0,
2.5
Variation of effective strain and damage
For the 20% back tension case
2.4
2.6
2.8
Line legend0%
`
20%
1.2
1.4
1.6
1.8
Line legend
2.0
0% 20%
1.2
1.4
1.6
1.8
2.0
2.4
2.6
2.8
0% back tension vs. 20% back tension
Strain Damage
◎ Artificial state-variable body-force method was presented to deal with
back tension or compression during drawing with higher accuracy and
generality.
-Some appropriate region of the material was considered as body-
force prescribed domain where the body-force was defined by a function
of an artificial state variable
-The artificial state-variable was treated as one of state variables in
remeshing with the result that the domain can be maintained during
remeshing, which increases the generality of the approach.
◎ The approach was successfully applied to fully automatic simulation of
two application examples including a six-pass rod drawing process and a
twenty-pass wiredrawing process.
-With the presented approach, the predictions with higher accuracy
could be obtained in terms of effect of back tension or compression.
-Generality of the approach is also noteworthy.
Conclusions
Research background – Forging defects
Hot shortness
Metal flow Buckling
Shape defect
Folding
Under-filling
Air-trapping
Piping
Ductile fracture
Bad spheroidizing
Chevron crack