Personal backgroundYear Company Position 2008-2009 Offshore Geo Survey Sdn. Bhd. Engineer 2011-2013...

Name : Muhammad Hasnulhadi Bin Mohammad Jaafar

Age : 31 Nationality : Malaysian

Educational background

Year Institution Qualification

2004-2008 International Islamic

University Malaysia Bachelor of Engineering

2010-2011 Universiti Putra Malaysia Master of Manufacturing

Systems Engineering

Working experiences

Year Company Position

2008-2009 Offshore Geo Survey Sdn. Bhd. Engineer

2011-2013 Universiti Malaysia Perlis Junior lecturer

2013-present Toyohashi University of Technology Doctoral student

Personal background

1

Punching and Trimming of Die-Quenched Steel

Parts and Ultra-High Strength Steel Sheets

Chapter Contents

1 Introduction

2 Small clearance punching of die-quenched steel sheets by

punch having small round edge

3 Automatic centring in small clearance punching of die-

quenched steel sheets

4 Repeated small clearance punching of die-quenched steel

sheets

5 Reduction of flying speed of scrap and noise in trimming of

ultra-high strength steel sheets

6 Prevention of chipping and edge fracture in trimming of ultra-

high strength steel sheets having curved shape

7 Future perspectives 2

Introduction:

Lightweight automobiles for reduction of CO2 emission

• Improve fuel consumption

• Reduce CO2 emission

Reduction of vehicle weight:

Lightweight materials

Al, Mg, Ti alloys, High strength

steel sheets (car body - cheaper)

Hybrid, Plug-in hybrid

electric vehicle,

• High initial cost

• Heavy battery

• Less charging station

Hot stamping of quenchable steel sheets

• Springback reduce

• Tensile strength of die-quenched - 1.5 GPa

AlSi-coated

22MnB5

Laser

Cutting and trimming

(finishing operation)

Hold at bottom dead centre:

5-10 s (martensite)

<5 s

Transfer

Hot stamping Furnace heating:

3-5 minutes (austenite)

Advantageous

950 °C

• Formability due to in ductility

• Forming load due to in flow stress

Quenchable

steel sheet

3

Problem of laser cutting of die-quenched steel parts

and cold stamping of high strength steel sheets

Die-quenched steel parts

Finishing

process

• Large process time - low

production rate

• Microstructure changes at

heat affected zones (HAZ)

• Expensive equipment and

installation cost

• Not easily available for small

-middle size companies

Disadvantageous of laser cutting

High strength steel sheets

• Springback, wrinkle, crack,

fracture, large forming load

High

strength

Laser

cutting

Laser

trimming

Wrinkling

Fracture Crack Crack

980

Mild steel 590

Springback

4



Chapter Contents

1 Introduction






sheets






Small clearance punching of die-quenched steel

sheets by punch having small round edge

To improve sheared edge quality of die-quenched steel sheet by

small clearance punching using punch having small round edge

Die

Punch Clearance ratio:

10-15%

Rollover

Burnished

Fracture

Burr

Punching of ultra-high strength steel sheet:

Small burnished, large fracture

Sharp

edge Tensile

stress: Small

c Small clearance

Small round edge

Relieve stress

concentration

Shearing

zone

No crack

Conventional punching

6

Sheet

Die

Punch

Die

Punch

Tools dimensions, punching conditions and

material properties

Corner radius,

R= 0.15, 0.3, 0.5

f 10

Sheet

holder

Die-quenched sheet

Die holder

Small corner round edge Lower die plate

Die (SKD11)

TiAlN-coated punch (SKH51)

Clearance, c=0.8, 10

Punching speed,

v = 0.03-75 mm/s

Material Thickness

[mm]

Tensile strength

[MPa]

Hardness

[HV20]

Elongation

[%]

Al-Si coated

22MnB5 1.2 1504 504 5.0

7

Punching load-stroke curve

Pu

nch

ing l

oad

[k

N]

1 2

50

40

30

20

10

0

Punch stroke s [mm]

R=0.5

R=0.3

R=0.15

8

Sheared edge surface for clearance: c=0.8 vs 10%

Burnished

Burnished

Fracture

Burnished

Fracture

Secondary

burnished

Fracture

Secondary

fracture

R=0.50 mm

R=0.30 mm

R=0.15 mm

c=10%

Burnished

Fracture

Burnished

Fracture

Fracture

Secondary

fracture

Secondary

burnished

Burnished

R=0.50 mm

R=0.30 mm

R=0.15 mm

c=0.8%

9

Depth percentages of sheared edge surface for

different punching speed for R=0.3 mm

Dep

th p

erce

nta

ge

[%]

-20

Punching speed v [mm/s]

Fracture surface

unevenly distributed

100

80

60

40

20

0

Rollover

Fracture

Burnished

Burr

Fracture

scatter on

sheared edge

10

Delayed fracture times around sheared edge

for different clearance and punch radius

0

2

4

6

8

24

c =0.8%

c =10%

Del

ayed

fra

cture

tim

e [h

]

Crack

No crack

0.2 0.4 0.6

Punch corner radius R [mm]

35 % Hydro chloride

solution,

room temperature

Delayed fracture time

= time from immerse

of sheet in the 35%

concentration hydro-

chloric acid to visual

observation of cracks

11

Conclusions

• Too small round edge radius i.e. 0.15mm initiates the

onset of cracks from the edge of punch.

• The high punching speed produces a large burnished

surface on the sheared edge surface of die-quenched

steel sheets.

• The small clearance prevents the delayed fracture at the

sheared edge of die-quenched steel sheets.

12



Chapter Contents

1 Introduction






sheets






Automatic centering for slight clearance

punching of die-quenched steel sheets

To develop automatic centring in small clearance punching

process in order to eliminate eccentricity between punch and die

Problem of eccentricity

Chipping Wear

Small clearance punching

Punch

Die

Small

clearance

• Difficult tools setting

• Punch and die eccentric

Eccentric

14

Approach of automatic centring

Die holder

CL

Punch holder

CR

Gap

Die-quenched

sheet

Punch

Eccentric

CL > CR

fd

fm

Moving

die fm< fd

15

Punch holder


16


17


18


19


20


FR FL

FR > FL

Imbalanced

force

21


22


23


24


25

CL = CR


CL CR

Concentric

26

Tools dimensions and punching conditions

Eccentricity in x- and y-

directions ex= -7, ey= 7 µm

y

x

Die holder

TiCN-coated punch (SKH51)

Sheet

holder Sheet

Moving die

(SKD11)

t

Clearance 0.8

f 10.02

Gap

30

µm

f 10

Oil

f 19.94 f 20 30µm

v=75mm/s

27

Finite element simulation of punching without

centering using fixed die

750

500

250

0

-250

-500

-1000

-750

-1250

Normal stress (MPa)

ex=7µm

28

Flow stress

[Mpa] σ = 2430 0.13

Coefficient of

friction [µ] 0.1

Eccentricity in x-

direction, ex [µm] 3, 7, 10

Punching speed

[mm/s] 75

750

500

250

0

-250

-500

-1000

-750

-1250

29

Finite element simulation of punching without

centering using fixed die

Normal stress (MPa)

Relationship between imbalanced force calculated

by FEM and punch strokes

ΔF = FR - FL

FL FR

θ

Fixed

die

1000

750

500

250

0

Imb

alan

ced f

orc

e Δ

F [

N]

0.2 0.4 0.6 Punch strokes [mm]

ex = -10 µm

ex = -7 µm

ex = -3 µm

30

Small clearance punching without and

with automatic centring

Sheet

Punch holder

Punch

Sheet

holder

Fixed

die

Sheet

Punch holder

Punch

Sheet

holder

Moving

die

(a) Without centring

(using fixed die)

(b) With automatic centring

(using moving die)

31

Surface of sheared edge for punching

without and with automatic centring

Burnished

θ = 0° 90° 180° 270° 0°

n = 1 Fracture

n = 5 Fracture Burnished

*n is number of strikes

Without centring

Fracture

θ = 0° 90° 180° 270° 0°

n = 1 Burnished

n = 5 Burnished Fracture

With automatic centring

32

Fatigue strength and delayed fracture time of sheets:

without centering vs automatic centering

Nu

mber

of

cycl

es t

o f

ailu

re [

× 1

04]

50

40

30

20

10

0

60

Automatic

centering

Without

centering

θ=0° 45°

Crack

Fracture

surface

23

4

3

2

1

0

Del

ayed

fra

ctu

re t

ime

[h]

24

90

°

No crack

θ = 45°

Cracks

90

°

θ = 45°

Automatic

centering

Without

centering

Fatigue strength Delayed fracture (Fatigue bending test) (Immerse in 35% HCl)

33

Conclusions

• The moving die is shifted by the imbalanced force, and

thus becomes concentric with the punch after several

strikes.

• As the punch and moving die concentric, the quality of

sheared edge surface is improved.

• The uniform burnished surface on the sheared edge

increase the fatigue strength of the sheet and prevent the

occurrence of delayed fracture.

34



Chapter Contents

1 Introduction






sheets






Repeated small clearance punching of die-quenched

steel sheets

Car body part:

Multiple holes: joining,

attaching, painting, etc.

To investigate effects of repeated small clearance punching of

die-quenched steel sheet

Die-quenched

steel sheet

Punch

Automatic feeder

Guide rail

Sheet holder

Automatic feeder

stroke per minute

Punching

speed

Clearance

ratio

20 SPM 75 mm/s 0.8 %

For industrial

application: process

must be stable

36

Automatic feeding

machine

Die-quenched sheet

Punch

Sheet

holder

SPM=20

Repeated small clearance punching of die-quenched

steel sheets

37

Punch broken:

Fracture part

stuck in the hole

(a) TiN-coated punch

After n = 11

1mm

(b) TiAlN-coated punch

After n = 32

1mm

n = number of strikes

Broken of punch in repeated small clearance

punching using fixed die

38

**Low number

of successful

strikes

Depth percentage of die-quenched steel sheet for

repeated punching with automatic centring for n=500

-20

100

80

60

40

20

0 100 200 300 400 500

Number of strikes n

Dep

th p

erce

nta

ge

[/%

]

Secondary

burnished

Secondary

fracture

Rollover

Burr

Fracture

Burnished

39 **High number of successful strikes

Fracture

Punch surface for repeated punching of die-quenched

steel sheet after n=500

As received

1 mm

After n=500

Galling

1 mm

40

Gradual increase punching speed in initial

strikes and lubrication of punch

Dep

th p

erce

nta

ge

[%]

100

80

60

40

20

0 1 2 3 4 5

Number of strikes n

15 30 45

60 75 Gradual increase punching speed

Sheet holder

Punch Sponge with

lubricant

Die

holder

Container

Lubrication of punch

41

Sheared edge of die-quenched steel sheet for

gradual increase in speed and lubricated punch

n

0° 90° 180° 180° 270° 0°

250

500

1mm

42

1mm

θ = 0° 90° 180° 270° 0°

θ = 0° 90° 180° 270° 0°

1mm

(a) Punch without lubricant

(b) Punch with lubricant

Punch surface after repeated small clearance punching

43

Conclusions

• The number of successful strikes is low for repeated punching

with the fixed die and the punch was broken because of

occurrence of eccentricity.

• The number of successful strikes is high for repeated small

clearance punching with automatic centring.

• Galling at the punch surface is increases with the increases of

number of strikes, and thus deteriorate the quality of the

sheared edge surface.

• The gradual increase of punching speeds in the initial strikes

and lubricating the punch are effective to improve the quality

of sheared edge and reduce galling at the punch surface.

44



Chapter Contents

1 Introduction






sheets






Reductions of flying speed of scrap and noise in

trimming of ultra-high strength steel sheets

Trimming – remove scrap

• High flying speed of scrap

• Scrap jump out of container

• Collision with die wall

• High sound level – noisy, increase

risk of hearing problem

• Tolerable noise levels in industrial

plants < 100 dB

Die

Car body

panel Scrap

Punch Sheet

holder

Stamped centre pillar

Trimming

Trimming zone

To reduce flying speed of scrap and noise level in trimming of

ultra-high strength steel parts

Problem in trimming of ultra-high

strength steel parts

Container Die

46

Tools dimensions, trimming conditions and

material properties

Die

Sheet holder

Sheet

Flat punch

1.0×103

18

0

Scrap

Scrap length

L=20mm

Punch speed, 48 mm/s

1.2

8

12 Sound

meter

Material Thickness [mm] Tensile strength [MPa] Elongation [%]

JSC1180YN 1.2 1242 8.1

JSC980YN 1.2 1004 12.6

JSC780YN 1.2 813 17.3

High speed camera

Microphone

47

Clearance, c = 5-15%

Flying behaviour of scrap JSC980YN for trimming

with flat punch for c=10%

Flat punch

Sheet

Die

Frame

rate:

800fps

48

Relationship between flying speed of scrap and

clearance ratio

Clearance to thickness ratio c [%] 5 10 15 0

1000

2000

3000

Free fall

Fly

ing

sp

eed o

f sc

rap [

mm

/s]

JSC780YN

JSC980YN

JSC1180YN

Flat punch

49

Relationship between noise level of scrap and

maximum trimming load for c=10%

40

Maximum trimming load [kN]

60

10

80

90

100

110

120

0

Max

imu

m s

oun

d l

evel

[d

B]

80 20

Sound

meter

JSC780YN

JSC980YN

JSC1180YN

Sound level of

press machine

50

Flying behaviour of scrap JSC980YN for trimming

with bevel punch for c=10%

Bevel punch

Die

Sheet

Frame

rate:

800fps

51

Trimming load-punch stroke curves for different

punch shapes

0 2

20

10

4 6

30

40

60

70

50

Flat punch

8 10 12 14 Punch stroke s [mm]

Tri

mm

ing l

oad

[k

N] Inclined angle, θ = 1°,5°,10°

Die

110 80

Bevel punch

Bevel α =1°

Bevel α =5° Bevel α =10°

52

θ

Flying speed of scrap for trimming with different

punch shapes F

lyin

g s

pee

d o

f sc

rap

[m

m/s

] 2500

0

1000

2000

1500

500

Tensile strength of sheet [MPa]

Flat punch

980 1180 780

Bevel, θ =1°

Bevel, θ =5°

Bevel, θ =10°

53

Noise level of trimming with different punch shapes

Tensile strength of sheet [MPa]

0

110

80

100

Max

imum

sou

nd

lev

el [

dB

]

90

10

980 1180 780

Bevel, θ =1°

Bevel, θ =5°

Bevel, θ =10°

Flat punch

54

Conclusions

• The flying speed of scrap and noise level are increased

with increase of sheet strength and trimming load.

• The sheet is gradually trimmed by the bevel punch, and

thus reduce the trimming load, flying speed of scrap,

and noise level.

• The bevel punch with inclined angle of 5°is the best

for the reduction of flying speed of scrap and noise

level.

55



Chapter Contents

1 Introduction






sheets






Prevention of chipping and edge fracture in trimming of

ultra-high strength steel sheets having curved shaped

Flat, inclined and curvature

surfaces

Chipping, edge fracture

Defect of product - reduce production

rate, increase operation cost

Car body panel

Chipping

Fracture

To prevent chipping and edge fracture in trimming of ultra-high

strength steel sheets having curved shape

Trimming of ultra-high strength

steel sheets having curved shape

57

Tools dimensions, trimming conditions and

material properties

40

Corner radius, R=1 mm

Die

Sheet holder

120° 10

Flat punch

t

L-shaped sheet

Cle

aran

ce 1

0%

Die

L-shaped

sheet

55

Flat punch

Material Thickness [mm] Tensile strength [MPa] Elongation [%]

JSC1180YN 1.2 1242 8.1

JSC980YN 1.2 1004 12.6

JSC780YN 1.2 813 17.3

JSC590YN 1.2 629 26.2

Punching speed, 4 mm/s

58

Trimming of L-shaped JSC1180YN sheet with

flat punch

Flat punch

Die

Sheet holder

L-shape sheet

Frame rate: 2000fps

59

Percentage of chipping for trimming with

flat punch for number of trimming n=10

Chipping

No chipping JSC1180YN

Nu

mb

er o

f tr

imm

ing

n

2

4

8

6

10

1

3

7

5

9

Chipping

zones Chip

60

Percentage of chipping in trimming of JSC1180YN

with L-shaped punch for n=10

Chipping

No chipping

20

40

80

60

100

Per

centa

ge

of

chip

pin

g [

%]

Die

Sheet holder

Inclined angle,

θ= 0, 1, 3, 5, 10

L-shaped punch

L-shaped punch to

prevent chipping

and edge fracture 61

Quality of L-shaped blank after trimming with

flat and L-shaped punches

Trimming with flat punch

Blank

after

trimming

Bend

Blank

after

trimming

Trimming with L-shaped punch

Straight

No

fracture

Fracture

62

Load-stroke curves for trimming with flat and

L-shaped punch for different inclined angle

10

20

30

40

50

L-shaped, θ=1°

L-shaped, θ=3°

L-shaped, θ=5° L-shaped, θ=10°

Tri

mm

ing

lo

ad [

kN

]

60

4 6 8 2 10 12

Punch stroke [mm]

0

L-shaped θ=0°

Flat

63

Conclusions

• The possibility of chipping and fracture is increase with the

increase of steel sheet strength.

• The scrap was bent and twisted towards the die, and thus

caused the edge fracture in trimming with the flat punch.

• Chipping, edge fracture, and bending of the sheet was

prevented by trimming with the L-shaped punch.

64



Chapter Contents

1 Introduction






sheets






Future perspectives

Application of die-quenched steel and ultra-high strength steel

sheets for car body panels and parts increase

Tools problems: wear,

broken, short tool life

New tool and coating

material

Tools material

Coating Sheet

θr

Die

Punch

Trimming of ultra-high

strength steel parts

Relief angle θr - reduce

contact between punch

and scrap surface

Car body panel: many

holes on single part

Multiple holes in

single stroke

66

Moving

die

Publications

1) Hasnulhadi Jaafar, Ken-ichiro Mori, Yohei Abe, Keishiro Nakanishi, Automatic

centring with moving die for cold small clearance punching of die-quenched steel

sheets, Journal of Materials Processing Technology, 227 (2016), pp. 190–199.

2) 安部洋平, 岡本泰尚, 森謙一郎, Hasnulhadi Jaafar, “超高張力鋼板のトリミングにおける変形挙動とスクラップ速度の低減”, 塑性と加工, 57-661 (2016), pp. 146-

152.

Conferences

1) Hasnulhadi Jaafar, Ken-ichiro Mori, Yohei Abe, Correction of eccentricity

between punch and die in slight clearance punching of ultra-high strength steel

sheets, 11th International Conference on Technology of Plasticity, Nagoya, Japan,

19-24 October 2014.

2) Hasnulhadi Jaafar, Ken-ichiro Mori, Yohei Abe, Keishiro Nakanishi, Cold

punching of high strength die-quenched steel sheets, JSTP 7th International

Seminar on Precision Forging, Nagoya, Japan, 9-12 March 2015.

List of publications

67

Personal backgroundYear Company Position 2008-2009 Offshore Geo Survey Sdn. Bhd. Engineer 2011-2013...

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