Yong_IAB

8/13/2019 Yong_IAB

1/20

Predictive Modeling of Tool Wearin Hard Turning

Yong Huang

Advisor: Prof. Steven Y. Liang

The G. W. W. School of Mechanical Engineering

Georgia Institute of Technology

Atlanta, Georgia

8/13/2019 Yong_IAB

2/20

Introduction and motivation Hard turning process is defined as single point turning of

materials harder than 50HRc and differs from

conventional turning in: Workpiece material property

Chip formation mechanism

Cutting tool required

Cutting condition applied

It offers possible benefits over grinding process:

Lower equipment costs Shorter setup time

Reduced process steps

High material removal rate

Better surface integrity

Elimination of cutting fluid

8/13/2019 Yong_IAB

3/20

Challenging issues in hard

turning technology The top issues to be solved in hard turning process:

Tool wearTool wear Form accuracy

Surface integrity

Economic consideration

Why tool wear: High cost of CBN cutting tool, which is generally applied in hard turning

Cost of down-time for tool changing affects the economic justification ofhard turning

What to do about tool wear: To find a relationship defining tool wear rate as the function of cutting

condition and tool geometry for a given tool/work combination in hardturning

8/13/2019 Yong_IAB

4/20

Factors influencing wear rate

Tool materials composition CBN particle size and CBN content Binder materials

Applied coating material and coating thickness

Cutting condition Feedrate

Depth of cut

Cutting speed

Tool geometry Rake angle for up-sharp tool

Chamfer length and angle, rake angle for chamfered tool

Hone radius, rake angle for honed tool

Tool nose radius

8/13/2019 Yong_IAB

5/20

Tool wear in hard turning Wear patterns in metal cutting

Crater wear

Flank wear Depth of cut notching

Thermal shock crack

Nose wear

Chipping Tool breakage

Built-up edge

Wear mechanisms in metal cutting

Abrasion Adhesion

Attrition

Fatigue

Dissolution/diffusion Tribochemical process

Wear pattern in metal cutting

8/13/2019 Yong_IAB

6/20

Tool wear in hard turning (contd)

Main wear patterns in hard turning

Crater wear

Flank wear

Chipping: happens in aggressive cutting conditions

Flank wear and crater wear are our interests in this studyFlank wear and crater wear are our interests in this study

Main wear mechanisms in hard turning Abrasion: due to cementite and CBN particle (if have in high CBN

tool) (Narutaki, et al., 1979; Davies et al., 1996)

Adhesion: due to high temperature/stress along the tool/chip andtool/workpiece interfaces (Hooper, et al., 1988; Chou, 1994; Davies

et al., 1996) Diffusion: binder material is not stable with iron due to high

temperature (Narutaki, et al., 1979; Konig, et al., 1993)

Tribochemical process: no convincible evidence yet

Abrasion, adhesion, and diffusion are considered as basicAbrasion, adhesion, and diffusion are considered as basic

mechanisms heremechanisms here

8/13/2019 Yong_IAB

7/20

Objective of this researchCrater wear

Flank wear

To develop a scientific, systematic, and reliable methodology to

predict the tool flank/crater wear ratestool flank/crater wear rates based on cutting conditioncutting condition

and tool geometrytool geometry for given tool and workpiece material properties.

8/13/2019 Yong_IAB

8/20

Modeling of flank wear rate

2l

R

R

R

VBVBVB +

A

OB F

G

C

E

1l

Worn flank face

Flank face

P

P

Cutting

velocity

P-P view

Worn flank face

Flank face

Tool chamfer

area

1l

2

l

3

2

1

VB

( )[ ]

++

+

= +

273

1

tan

)tan(cotT

K

cdiffc

aT

adhesioncn

t

n

aabrasion

Q

eVBVKVeKVBVP

PKK

VBRVB

R

dt

dVB

Abrasion Adhesion Diffusion

8/13/2019 Yong_IAB

9/20

Modeling of flank wear rate (contd)

Process

modeling

(Huang &

Liang,

2002a) Temperature

model(Huang &

Liang,

2002b)

Update

mechanism

Flank

wear

rate

model

Stress model

(Huang &

Liang, 2001)

dt

dVB

T

Material properties

of workpiece &

tool

Cutting condition

Tool geometry

Process

info.

Updated VB

Other process

constants andcalibrated

wear

coefficients

8/13/2019 Yong_IAB

10/20

Modeling of crater wear rate

maxt

Interested

rectangular zone

x

feedf/2

oomaxt

dw

Previous

location of toolnose center

Longest contact

length due to

maxt

Interested

rectangular zone

x

feedf/2

oomaxt

dw

Previous


x

feedf/2

oomaxt

dw

Previous


Longest contact

length due to

x

xxxxVeKxxVeK

hxxV

xP

xPKK

dt

xdKchip

xT

K

diffchip

xaT

adhesionchipn

t

n

a

abrasionT

Q

+

++

= +

)()()()(

1)()(

)(

)()( 273)()(1

Abrasion Adhesion Diffusion

8/13/2019 Yong_IAB

11/20

Modeling of crater wear rate (contd)

maxt

Process

modeling

(Huang &

Liang, 2002a)

along the

interested zone

Chip velocity

model Update

mechanism

Craterwear

rate

model

dtdKT

Material propertiesof workpiece & tool

Cutting

condition

Tool

geometry

Temperature,

stress, and

chip velocitydistributions

New

crater

profile

Other process

constants and

calibrated

wear

coefficients

Max. chip

thickness

model

Normalstress

model

(Li,

1997)

8/13/2019 Yong_IAB

12/20

Calibration & validation of wear rate models

Calibration of wear rate model

Qdiffadhesionabrasion

KKaKK,

,,, need to be calibrated

Those coefficients depend on tool/workpiece combination.

Calibration stepsCalibration steps Optimize the coefficients of wear rate model by minimizing the least

square error between predicted and measured flank wear rates for threecutting conditions (v=1.520m/s, f=.0760mm/rev, doc=.203mm;v=2.29m/s, f=.168mm/rev, doc=.203mm; v=1.520m/s, f=.0760mm/rev,doc=.102mm; ) (Huang and Liang, 2002c)

Validation stepsValidation steps Validate the flank wear rate model based on seven cutting conditions

(Huang and Liang, 2002c)

Validate the crater wear rate model based on three cutting conditions(Huang and Liang, 2002d)

8/13/2019 Yong_IAB

13/20

Calibrated wear rate models Tool material: Kennametal KD050

Workpiece material: hardened 52100, 62HRC

( )[ ]

++

+

=

+

273

20460

6100313.914

1

107204.5104761.10295.0

tan

)tan(cot

4

Tcc

Tcn

t

n

a eVBVVeVBVPPK

VBRVB

R

dt

dVB

xxxxxVe

xxVh

e

xxV

xP

xPK

dt

xdK

chipT

chip

T

chipnt

n

aT

++

+

=

+

)()(107204.5

)()(1

104761.1

)()(

)(

)(0295.0

)(

273204606

100313.914

1

4

8/13/2019 Yong_IAB

14/20

Validation of flank wear rate model

0 1 2 3 40

50

100

150

0 20 40 60 8020

40

60

80

0 10 20 30 400

50

100

150

200

0 50 100 1500

5

10

15

20

1 2 3 440

60

80

100

40 50 60 70 8010

15

20

25

Wear rate (m/min)

0 5 10 150

50

100

150

Time (min)

Flank wear length (m)

0 50 100 1505

10

15

20


(1) (1)

(2) (2)

(3) (3)

(4)

(4)

0 1 2 3 40

50

100

150

0 20 40 60 8020

40

60

80

0 10 20 30 400

50

100

150

200

0 50 100 1500

5

10

15

20

1 2 3 440

60

80

100

40 50 60 70 8010

15

20

25

Wear rate (m/min)

0 5 10 150

50

100

150

Time (min)


0 50 100 1505

10

15

20


(1) (1)

(2) (2)

(3) (3)

(4)

(4)

0 5 10 1540

60

80

100

120

40 60 80 1000

5

10

15

0 20 40 600

50

100

150

200

0 50 100 150 2000

5

10

15

0 20 40 60 800

100

200

300

Time (min)


0 50 100 150 2000

5

10

15


Wear rate (m/min)

(8)

(B)

(10)

(10)

(8)

(B)

0 5 10 1540

60

80

100

120

40 60 80 1000

5

10

15

0 20 40 600

50

100

150

200

0 50 100 150 2000

5

10

15

0 20 40 60 800

100

200

300

Time (min)


0 50 100 150 2000

5

10

15


Wear rate (m/min)

0 5 10 1540

60

80

100

120

40 60 80 1000

5

10

15

0 20 40 600

50

100

150

200

0 50 100 150 2000

5

10

15

0 20 40 60 800

100

200

300

Time (min)


0 50 100 150 2000

5

10

15


Wear rate (m/min)

(8)

(B)

(10)

(10)

(8)

(B)

Solid line: predictions

Triangular: measurements

Flank wear progression

8/13/2019 Yong_IAB

15/20

Validation of crater wear rate model

0 0.05 0.10

0.2

0.4

0.6

0.8

Distance from tool tip (mm)

Chipvelocity

0 0.05 0.10

500

1000

1500


Normalstress(Mpa

)

0 0.05 0.1-0.2

-0.15

-0.1

-0.05

0


Crater

wearrate(um/min)

0 0.05 0.1360

380

400

420

440

460


Temp

erature(um/min)

0 0.05 0.1

-6

-4

-2

0

2


Craterweardepth(u

m)

Time elapsed: 22.0 min

0 0.05 0.1

-15

-10

-5

0

5


Craterweardepth(u

m)


0 0.05 0.1-15

-10

-5

0

5


Crater

weardepth(um)


0 0.05 0.1-20

-15

-10

-5

0

5


Crater

weardepth(um)


Cutting conditions:

cutting speed: 1.52 m/s, feedrate: 0.076 mm/rev, depth of cut: 0.102 mm

Solid line: predictions; dash line: measurements

Crater wear progressionProcess information & crater wear rate

8/13/2019 Yong_IAB

16/20

Summary:

Abrasion, adhesion, and diffusion in hard turning areconsidered as the main wear mechanisms for theprogressive tool wear. The total tool wear rate iscontributed from abrasion, adhesion, and diffusionmechanisms.

The progressive tool flank/crater wear can be modeledas the function of cutting condition and tool geometry fora given tool/workpiece combination in a reasonableaccuracy in hard turning.

8/13/2019 Yong_IAB

17/20

8/13/2019 Yong_IAB

18/20

0 10 20 30 40 50 600

20

40

60

80

100

Time (min)

Percentageofea

chmechanism Abrasion

Adhesion

Diffusion

0 2 4 6 8 100

10

20

30

40

50

60

70

80

90

Time (min)

Abrasion

Adhesion

Diffusion

General cutting condition (#10) Aggressive cutting condition (#4)

8/13/2019 Yong_IAB

19/20

8/13/2019 Yong_IAB

20/20

Hardened 52100

steel washerDynamometer

CBN tool insert

Pin-on-diskGoal: to identify the wearcoefficients under semi-sliding conditions without

the effect of diffusionwear.

Yong_IAB

Documents