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, msjoun@gnu.ac.kr.

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