1

Comparison between Experimental & Numerical Results for Single Point Diamond Turning (SPDT)

of silicon carbide (SiC)

John Patten, Director Manufacturing Research Center

Western Michigan University

NAMRC 35 May 22, 2007

2

Agenda

• Introduction to Silicon Carbide (SiC)• Background of HPPT Research• Background of ceramic simulations• 2-D orthogonal machining simulations

– Simulations of edge turning– Simulation of plunge cutting– Simulations of fly-cutting

• 3-D scratching simulations– Silicon Carbide

• Summary of results• Conclusions and future work

3

Silicon Carbide – Advanced Engineering Ceramic

• Types of SiC • Properties and applications of SiC• Problems in manufacturing

4

Research background – HPPT of ceramics

• Define HPPT• HPPT or amorphization of ceramics is responsible for the

ductile behavior of these brittle materials.• HPPT has been identified in Si and Ge, and other materials.• Ductile material removal has been achieved in SiC under

nanometer cutting conditions and phase transformation of chips has been recorded.

• Some factors contributing to ductile material removal at room temperature

– machining depth < tc

– negative rake angle tools with small clearance– sharp edge radius

5

Developments in simulations of ceramic machining

• Introduce AdvantEdge• Developments in AdvantEdge

– 2-D simulations of Silicon Carbide in the nanometer regime– 2-D simulations of Silicon Carbide using DP model– Newly developed 3-D scratching simulation capability

• Other developments outside AdvantEdge– FEA simulation of polycrystalline alpha-SiC– MD simulations of nanoindentation in SiC

6

2-D orthogonal machining simulations of SiC

• Three types of experiments were simulated– Edge turning of SiC– Plunge cutting of SiC– Fly-cutting of SiC

Visualization of 3-D turning operation in 2-D

7

Typical setup for 2-D orthogonal simulations

Parameters Geometry

Tool

Cutting edge radius, r

Rake angle, α

Clearance angle, β

Workp

iece

Workpiece length, l

Workpiece height, h

Pro

cess

Depth of Cut, feed

Length of Cut, loc

Cutting Speed, v

Width of cut

Coefficient of friction

8

Material model for simulations of SiC

0..3 12 IJ

The DP yield criterion is given by

κ is given by

ct

ct

..2

J2 is given by

213

232

2212 6

1 J

For a uniaxial state of stress

11 IThus J2 is given by

3

21

2

J

This gives κ of 16.25 GPa and α of -0.375 .

Here, σt = H/2.2 and σc = H

For H=26 GPa, κ becomes 16.25 GPa.

9

Simulations of edge turning

10

Edge turning simulations of SiC

Variable Definition Value Workpiece-Tool geometry

tool cutting edge radius 50 nm

tool rake angle 0º & -45º

tool clearance angle 5º & 50º

In-feed/uncut chip thickness(50, 100, 250, 300, 500)

nm

work piece velocity 0.05 m/s

Width of cut 250 µm

11

Simulation with achieved depth of approx. 220 nm

Note the deflection of workpiece material

12

Results from edge turning simulations, 0º rake, 5º clearance

0.45 0.30

1.001.25

3.65

6.00

0.00

2.00

4.00

6.00

100 300 500

Depth (nm)

Cu

ttin

g F

orc

e (N

)

Experiment Simulation

13

Results from edge turning simulations, 0º rake, 5º clearance

0.611.00

1.90

0.90

1.75

2.50

0.00

2.00

4.00

6.00

100 300 500

Depth (nm)

Th

rust

Fo

rce

(N)

Experiment Simulation

14

Results from edge turning simulations, -45º rake, 5º clearance

1.52.32.3

10.2

0.0

2.0

4.0

6.0

8.0

10.0

12.0

50 250

Depth (nm)

Cu

ttin

g F

orc

e (N

)

Experimental

Simulation

15

Results from edge turning simulations, -45º rake, 5º clearance

5.0

9.0

4.8

19.1

0.0

4.0

8.0

12.0

16.0

20.0

50 250

Depth (nm)

Th

rust

Fo

rce

(N)

Experimental

Simulation

16

Simulations of plunge cutting experiments

17

2-D plunge cutting simulations of SiC

• Using a flat nose tool, machining was performed across the wall thickness of a tube of polycrystalline SiC.

18

Parameters for plunge-cutting simulations of SiC

Parameters Value Unit Geometry

Tool

Cutting edge radius, r 50.0 nm

Rake angle, α -45.0 deg

Clearance angle, β 11 & 0 deg

Workp

iece

& P

roce

ss

Workpiece length, l 3.0 µm

Workpiece height, h 1.0 µm

(Actual ) Depth of Cut, doc

24.0 nm

Width of cut 3.0 mm

Length of Cut, loc 2.0 µm

Cutting Speed, v 5.0 m/s

coefficient of friction, COF 0.1 -

19

Simulation with achieved depth of 25 nm

Note the deflection of workpiece material

20

Results from simulations of SiC

21

Flycutting experiment

22

Flycutting experiment setup

23

Force results from flycutting of SiC

• 4 distinct cuts made• First cut overlapped 6 times• Significant noise generated towards end of the experiment

24

Results from flycutting of SiC

25

Results from cut 1, cut 2 & cut 3

26

Results from cut 4

27

Simulations of flycutting

28

Simulations of flycutting experiments

Parameters Value Unit Geometry

Tool

Cutting edge radius, r 40.0 nm

Rake angle, α -45.0 deg

Clearance angle, β 5 deg

Wo

rkpie

ce &

Pro

cess

Workpiece length, l 20.0 µm

Workpiece height, h 7.5 µm

In-Feed, feed 61 & 75 nm

Length of Cut, loc 15.0 µm

Cutting Speed, v 0.518 m/s

Friction factor 0.1 -

Method A

Method B

29

1.16E+11

1.02E+11

1.19E+11 1.17E+11

0.00E+00

2.00E+10

4.00E+10

6.00E+10

8.00E+10

1.00E+11

1.20E+11

1.40E+11

61 nm 75 nm

No

rmal

ized

fo

rce

(N/m

m^

2)

Experiment Simulation

Results of simulations, Method A

30

Results of simulations, Method B

1.162E+111.018E+11

2.47E+11

1.99E+11

0.000E+00

5.000E+10

1.000E+11

1.500E+11

2.000E+11

2.500E+11

3.000E+11

61 nm 75 nm

No

rmal

ized

fo

rce

(N/m

^2)

Experiment Simulation

31

3-D scratching simulations

32

3-D scratching simulations

33

Setup for 3-D scratching simulation of SiC

Parameters Value Unit Geometry

Programmed Depth (feed) 125 nm

Actual depth, doc 103 nm

Length of Cut, loc 10.0 µm

Cutting Speed, v 0.305 mm/s

Friction factor, µ 0.1, 0.26, 0.6 -

34

Scratching simulations of SiC

35

Results from simulation of SiC

36

Summary of results

• Summary of 2-D orthogonal machining simulations– Simulations agree with experiments for depths close to

100 nm and below.– Pressures at the tool-workpiece interface are greater

than the hardness of the material for these depths.– Workpiece deflection leads to actual depth being smaller

than the programmed depth.

• Summary of 3-D scratching simulations– SiC simulations show thrust forces in good agreement

with the experiment.– SiC simulations show cutting forces that are not in very

good agreement with the experiment.

37

Conclusions

• Two types of simulations have been presented: 2-D & 3-D

– 2-D orthogonal simulations of SiC produce useful results for depths at or below the DBT depth of the material.

– 2-D simulations create pressures at the tool-workpiece interface that are in agreement with what is expected from the experiments.

– 3-D scratching work shows encouraging results for initial attempts at simulations of ceramic materials for depths below the DBT depth of the materials.

38

Recent Related Work

• Validation of material models.• Development of analytical model to predict actual depth of

cut for a programmed depth of cut for each material• Predicting behavior of ceramic materials under the brittle

mode.• 2-D flycutting simulation using VAM.• Current effort: 3-D turning simulations using round nose

cutting tools.

39

Acknowledgements

• National Science Foundation for the research grant• Andy Grevstad and Third Wave Systems for software

support.• Jeremiah Couey and Dr Eric Marsh at Penn State University.• Dr Guichelaar for equipment at the Tribology lab.• Lei Dong at University of North Carolina at Charlotte.

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Questions and suggestions

41

42

Results from edge turning simulations, -45º rake, 50º clearance

1.71.45

1.23

2.30

0.91.25

3.65

6.00

0

2

4

6

50 100 300 500

Depth (nm)

Cu

ttin

g F

orc

e (N

)

Experiment

Simulation

43

Scratching simulation of Si

44

Results from scratching simulation of Si