Presentation At Vjti Mumbai

Walchand College of Engineering Sangli Characteristics of Machined Surfaces on Al/SiCp Metal Matrix Composites Prof. Dr. Uday A. Dabade Assistant Professor Department of Mechanical Engineering Date: 19th February 2009

Overview 

Introduction



Conclusions from Literature Review



Objectives and Scope of Research Work



Experimental Details



Mechanics of Surface Generation



Analytical Model to Predict the Machining Force Components



Surface Integrity analysis ( Residual stress & micro-hardness)



Conclusions 2

Introduction Why Study of Machining of MMCs 

MMCs replacing conventional materials in engineering and industrial applications



Higher strength to weight ratio and wear resistance.



MMCs properties can be tailored for specific applications.



The primary use was for aerospace but recently used for automobile, electronic and recreation industries.



Excessive wear of cutting tools and fracturing of the reinforcement particles adversely affect the machined surface quality/integrity.

Structure of space shuttle

Hubble Space Telescope

Cast Grp/Al components

Al/SiCp electronic Cylinder Block of package a 2-wheeler 3

Conclusions from Literature Machining of MMCs Past work details

Extent of work

References

Tool wear and Tool-life estimation

30 – 35 Papers

Brun and lee (1985), Tomac and Tonnessen (1992), Monaghan and O’Reilly (1992), Joshi et al.(1999), Davim and Baptista (2000), Quan Yanming (2000), etc.

Mechanics of machining (chip formation and cutting force analysis)

10 – 15 papers

Chambers(1990), Monahan et al.(1994), Lin (1998), Iuliano (1998), Gallab and Sklad (1998), Joshi et al. (1999, 2001), Yusuf Ozcatalbas (2003), Cheung and Chan (2003), Manna and Bhattacharya (2003)

Surface topography (surface roughness) analysis

15 – 20 papers

Looney et al. (1992), Monaghan (1994), Arola (1997), Sahin (2002), Tosun (2004), Kilickap (2005), Ramulu and Pederson (2006), Palanikumar(2007)

Surface and sub-surface integrity analysis (residual stresses and microhardness)

3 – 4 papers

Quigley and Monaghan(1994), Chan et al. (2001), Quan and Ye (2003), Gallab and Sklad (2004), Kannan and Kishawy (2006)

This area was considered for research work

4

Conclusions from Literature Review Gaps in literature (machined surface characteristics) 

Effect of a change in cutting tool geometry on machined surface characteristics has not been analysed adequately.



Change in size and volume fraction of reinforcement on surface integrity has not been analysed.



Limited efforts to improve the surface integrity using alternative methods like machining process optimization, hot machining, etc.

5

Objectives of Research Work 

To analyse the mechanics of surface generation in turning of Al/SiCp composites.



To asses and model surface topography and sub-surface integrity by incorporating the effect of change in tool type, geometry as well as size and volume fraction of reinforcement.



To develop an analytical model to predict cutting forces in machining of MMCs.



To optimize and improve the machined surface quality as well as integrity using some alternative methods. 6

Theme of Experimental Work

Surface roughness

Work related parameters Tool related parameters Process related parameters

Surface damage Mechanics of machining

Micro-hardness Residual stresses

SURFACE INTEGRITY

7

Cause and Effect Diagram

8

Theme of Experimental Work Selection of Work related parameters Size of reinforcement

15 µm

Easy to machine

65 µm

Difficult to machine

Al/SiCp 20 %

Vol. of reinforcement 30 %

Volume >10% significantly affect the behavior of Al-matrix in AMCs

Designation of material for experimentation : 1. 2. 3. 4.

Al/SiC/20p/600 = 20% SiCp and 15 µm reinforcement size Al/SiC/30p/600 = 30% SiCp and 15 µm reinforcement size Al/SiC/20p/220 = 20% SiCp and 65 µm reinforcement size Al/SiC/30p/220 = 30% SiCp and 65 µm reinforcement size 9

Theme of Experimental Work Selection of tool geometry related parameters 1.

Geometry of cutting edge : Wiper and wiper less cutting edge geometry with varying chamfer angle It influence the surface topography and integrity by wiping action of wiper inserts

2.

Tool nose radius : 0.4 and 0.8 mm It affects surface topography, surface damage and residual stresses

10

Theme of Experimental Work Insert type and geometries

(a) W1 – Type insert

(b) W2 – Type insert

(c) Wiper insert geometry

(a) NW – Type insert geometry

(b) Conventional insert geometry 11

Theme of Experimental Work Selection of Process related parameters Feed rate (mm/rev) 0.05 0.1 0.2 Cutting speed (m/min) 40 80 120 Depth of cut (mm) 0.2 0.6 1.0

It influence the rate of deformation and affect the surface topography and integrity

Surface integrity influenced by change in speed and composition of composites

It influence plastic deformation and vary the thermal and mechanical stresses

12

Experimental Design, Set-up and Procedure Experimental Design Taguchi Method L-27 Orthogonal array Dependent parameters: 1. 2. 3. 4. 5.

Chip formation mechanism Machining force components Surface roughness Surface residual stresses Micro-hardness beneath the machined surface 13

Experimental Design, Set-up and Procedure Experimental Set-up

Tool holder : Rake angle = – 6°, Inclination angle = 6°, Approach angle = 95° CNC Turning lathe (EMCO/PCTURN Modell345-II) 14

Experimental Design, Set-up and Procedure Experimental Set-up Kistler dynamometer

CNC Turret

PC Monitor

Tool holder fixture

CNC chuck Workpiece

Charge amplifier Cutting tool

Data acquisition system

15

Experimental Design, Set-up and Procedure Experimental Procedure 

Turning experiments using CBN inserts



Work piece diameter = 16 mm



Length of machining for each run = 7 mm



In process measurement of machining force components



Collection of chips during individual experimental run

Total experiments = 108 (27 each on 4 types of composite material) 

16

Experimental Design, Set-up and Procedure Specimen preparation

Specimens for micro-hardness measurement, residual stress and SEM analysis

Photographs of machined specimens (Al/SiC/30p/220)

Specimens for microhardness measurement

17

Experimental Design, Set-up and Procedure Assessment of response variables Response Variables

Equipment Used

Force Components

Kistler 3-component force dynamometer (Model 9257 A)

Chip form and size

FEI Quanta 200 HV SEM Tester and Nikon measurescope MM-22 (made in Japan)

Surface Finish

Portable surface roughness measurement equipment (Mahr Perthometer Model M2)

Surface damage

SEM Make: FEI Quanta 200 HV SEM Tester

Residual stress

XRD, non destructive technique. PHILIPS make PANLYTICAL residual stress analyzer

Micro-hardness

Shimadzu HMV-2 with Vickers Pyramid indenter

18

Experimental Results and Discussions

It involves analysis of 1. 2. 3. 4. 5. 6.

Chip formation mechanism Machining force components Analytical model to predict the force components Surface roughness Micro-hardness beneath the machined surface Surface residual stresses

19

Chip Formation Mechanism 20p/600

30p/600

spring type

Tubular helix type

20p/220

30p/220

Observation of chip formed at 0.2 mm/rev feed rate Coarser reinforcement – small segmented , needle type chips Finer reinforcement – C-type, continuous and tubular type chips.

Increase in cutting speed

120 m min -1

½ circle Small segmented segmented type

80 m min -1

Connected C-type chips

Small radii C-type

40 m min -1

Segmented chips

20

Chip Formation Mechanism Observation of chip formed An increase in volume fraction of reinforcement shows highly strained chips Free surface of chip

Highly strained chips

Inner surface of chip

Al/SiC/20p/600

Al/SiC/30p/600 21

Chip Formation Mechanism Identification of favorable parameters and composition favoring chip breaking Chip condition

Favorable chips

Nonfavorable chips

Array Process parameters number

Cutting force (N)

Surface roughness (µmRa)

FR

CS

DOC

20p/ 220

30p/ 220

20p/ 600

30p 600

20p/ 220

30p/ 220

20p/ 600

30p/ 600

22

0.05

40

1

121.3

117.5

123.4

108.8

0.85

0.7

0.34

0.18

10

0.05

80

1

116.1

117.3

107.7

93.9

0.87

0.67

0.24

0.14

7

0.05

120

1

128.8

124.2

109.7

100.5

1.13

1.14

0.68

0.35

27

0.2

40

1

261.9

266.3

271.5

270.3

1.84

2.06

1.41

1.29

15

0.2

80

1

269

271.2

296.5

277.9

1.82

1.65

1.1

0.78

3

0.2

120

1

284.3

282.2

316.7

313.5

1.91

1.99

1.75

1.29

Favorable chips Expt # 7

Non-favorable chips Expt # 3

22

Analysis of Cutting Force Components Minitab-14 software was used for statistical analysis of experimental data. ANOVA and AOM were performed to identify the significant effect of each process parameter on the response variables. Feed rate and depth of cut are the significant parameters influencing the machining force components. 23

Analysis of Cutting Force Components Effect of feed rate Very little dependence of cutting force on composition of composites. Radial forces are sensitive to change in composition and more sensitive to size than volume fraction of reinforcement. Al/SiC/20p/600

200

Al/SiC/30p/220

Al/SiC/30p/600

180

180

AOM value of radial force (N)

AOM value of cutting force (N)

200

Al/SiC/20p/220

160 140 120 100 80 60

100 80 60

20

Cutting force Vs. FR

Al/SiC/30p/600

120

20 0.2

Al/SiC/30p/220

140

40

0.1 Feed rate (mm/rev.)

Al/SiC/20p/600

160

40 0.05

Al/SiC/20p/220

0.05

0.1 Feed rate (mm/rev.) Radial force Vs. FR

0.2

24

Analysis of Cutting Force Components Effect of depth of cut Al/SiC/20p/600

200

Al/SiC/20p/220

Al/SiC/20p/600

Al/SiC/30p/220

Al/SiC/30p/600

180

Al/SiC/30p/220

Al/SiC/30p/600

AOM value of radial force (N)

AOM value of cutting force (N)

200

Al/SiC/20p/220

180 160 140 120 100 80 60 40

160 140 120 100 80 60 40 20

20 0.2

0.6 Depth of cut (mm)

1

0.2

0.6 Depth of cut (mm)

1

Radial force Vs. DOC

Cutting force Vs. DOC An increase in depth of cut reduces the chip flow angle and causes the

chips to flow close to the machined surfaces resulting higher radial force

tan η =

sin ( K r avg + Cb ) 2d + cos ( K r avg + Cb ) f sin K r avg

DOC, d (mm)

Chip flow angle, η (º)

0.2

13.32

0.6

5.21

1.0

3.27

25

Analysis of Cutting Force Components Effect of tool nose radius Change in tool nose radius does not have significant influence on the cutting and feed forces. Radial forces are influenced by TNR and sensitive to size than volume fraction of reinforcement. Radial forces increases with tool nose radius.

100 80 60

Al/SiC/20p/220

Al/SiC/20p/600

Al/SiC/30p/220

Al/SiC/30p/600

40

Al/SiC/20p/600

Al/SiC/30p/220

Al/SiC/30p/600

100 80 60 40

0.4 0.8 Tool nose radius (mm) Cutting force Vs. TNR

Al/SiC/20p/220

Al/SiC/20p/600

Al/SiC/30p/220

Al/SiC/30p/600

100 80 60 40 20

20

20

120 AOM value of radial force (N)

120 AOM value of feed force (N)

AOM value of cutting force (N)

120

Al/SiC/20p/220

0.4 0.8 Tool nose radius (mm) Feed force Vs. TNR

0.4 0.8 Tool nose radius (mm) Radial force Vs TNR

26

Analysis of Cutting Force Components Effect of tool nose radius Radial forces increases with tool nose radius. radial force

Lc (0.4)

Depth of cut 0.4 TNR

Lc (0.8)

rake face

Depth of cut 0.8TNR TNR: 0.4 mm TNR: 0.8 mm

Lc (0.8) > Lc (0.4) Lc= length of contact (TNR)

Effect of tool nose radius on contact length along radial direction

27

Analytical Model: Machining Force Components

28

Analytical Model: Machining Force Components Assumptions 





 

Reinforcement particles are uniformly distributed and have a spherical shape. All the SiC particles within the contact area equally share the total normal load. Sticking zone at secondary deformation zone (SDZ) is assumed approximately equal to un-deformed chip thickness. Effect of BUE has not been considered. The friction at tool-chip and tool-work interfaces is considered to involve 2-body as well as 3-body abrasion.

29

Analytical Model: Machining Force Components Oblique 3-D force components [122,129]

k a b [cos ( β − α e ) cos λ + sin β sin λ tanη ] Fz = sin φe cos (φe + β −α e )

(1)

'

FY ' =

k a b sin ( β − α e ) sin φe cos (φe + β −α e )

(2)

(3)

k a b [cos ( β − α e ) sin λ − sin β cos λ tanη ] FX = sin φe cos (φe + β −α e ) '

Flow stress ‘k’ of the material has been calculated using Johnson–Cook Equation [131].

(4)

•  k =  A + B ⋅ ε  1+ C ⋅ ln ε  1− T *m   n

30

Analytical Model: Machining Force Components

(5)

Effective temperature is evaluated using Kronenberg Equation [142]

Co ksV 0.44 A0.22 Te = W 0.44 h0.56 cot φn + tan( φn − αn) cosη s

Shear strain is given by [122,132]

ε=

Dimensionless strain rate is given by [133]

2.59 *Vs ε= depth of cut

(6)

•

(7)

Material Properties and constants for J-C Equation [131] A (MPa)

B (MPa)

n

C

m

Tm (°C)

265

426

0.34

0.15

1

635 31

Analytical Model: Machining Force Components (8) Friction at Tool-Chip Interface

Ff = FN µ Chip

Rake face

SDZ: tool-chip interface Chip

Work-piece

Negative rake tool

Tool SiC particles responsible for two-body abrasion SiC particles responsible for three-body abrasion

(9)

Total normal force at tool-chip interface (FN) is given by Equation (9) [137]

FN = FN 1× N P × Probability of particles involved in abr asion 32

Analytical Model: Machining Force Components Normal force on Individual Abrasive Particle

P

r R

N

S

δPo

Cutting tool rake face

δY0

2r Q

θp O

δs max. upto radius of reinforcement Reinforcement particle

(10 ) Normal force acting on single abrasive particle is given by [137]: FN1 = 2.9×π× R×σ y tool×δ ( ) P0

(11)

2

2  9π  σ y (tool ) δPO =    R *  4 E    

1 (1 − v1 ) 2 (1 − v2 ) 2 = + * E E1 E2

(12)

33

Analytical Model: Machining Force Components (13 ) Total number of Abrasive Particle at Tool-Chip interface

NP =

VR × f × d π× R 2

(14 )

Estimation of Frictional Force (FF)

FF = FP 2 + FR 3 FP2 is frictional force due to two-body (ploughing), and FR3 is frictional force due to three-body (rolling). Ploughing component of friction force, FP2 [137], due to two-body (15) abrasion wear can be given by :

FP 2 = N P Ai 3 σ y × Probability of particles involved in tw o-body abrasion (16) Ai =

R2  π  2 ×θ p ) − Sin ( 2 ×θ p )  (  2  180 

34

Analytical Model: Machining Force Components Frictional force due to three-body (rolling) FR 3 =

k(tool )  2 R  πΗ t  rgroove

  

2

(17) 1

2    r  2   groove 1 − 1 −     × FN    2 R   

Finally the Coefficient of Friction (µ ) is given by:   R2  π  2θ p ) − sin ( 2θ p )  × H t × Probability of particles  (  Np ×  2  180       involved in abrasion    1 2   2 2    k(tool )  2 R     r groove       +    × FN    1 − 1 −      πΗ t  rgroove     2 R     FF     µ= = FN    9π 2  σ y ( tool ) 2    V × f × d    2.9 × π × R × σ y ( tool ) ×     R   × P   × * 2     4 E π× R            Probability of particles involved in abrasion  

(18)

35

Analytical Model: Machining Force Components Consideration to Forces on Wiper Cutting Edge Feed motion

FNV’ FNF’ FNV’’

FFF’

FFV’

FFV’’ Major cutting edge

Rake face

Minor cutting edge

36

Analytical Model: Machining Force Components (19) The total cutting force is given by:

FZ = FZ '+ FFV '+ FFV '' The total radial force is given by:

FY = FY '+ FNV '+ FNF '

(20)

(21)

The total feed force is given by:

FX = FX '+ FFF '+ FNV ''

37

Model Validation: Machining Force Components 300

Experimental

350

Predicted

200 150 100

210 140 70

50 0

0 1

3

5

7

9

11

13

15

17

19

21

23

25

27

1

3

5

7

9

Orthogonal array number

200

Experimental

160

Predicted

160

11 13 15 17 19 Orthogonal array number

Experimental

21

23

25

27

23

25

27

Predicted

120 Radial force (N)

Radial force (N)

Predicted

280 Cutting force (N)

Cutting force (N)

250

Experimental

120 80

80

40

40

0

0 1

3

5

7

9

11 13 15 17 19 Orthogonal array number

21

23

Al/SiC/30p/220

25

27

1

3

5

7

9

11 13 15 17 19 Orthogonal array number

21

Al/SiC/30p/600

38

Model Validation: Machining Force Components 300

Experimental

Predicted

300

Predicted

250

200

Cutting force (N)

Cutting force (N)

250

Experimental

150 100 50

200 150 100 50

0 1

3

5

7

9

11

13

15

17

19

21

23

25

27

Orthogonal array number

0 1

3

5

7

9

11

13

15

17

19

21

23

25

27

Orthogonal array number 200

Experimental

200

Predicted

Predicted

160 Radial force (N)

Radial force (N)

160

Experimental

120 80 40

120 80 40

0 1

3

5

7

9

11 13 15 17 19 Orthogonal array number

21

23

25

27

0 1

Al/SiC/30p/220 (40% debonding)

3

5

7

9

11 13 15 17 19 Orthogonal array number

21

Al/SiC/30p/220 (60% debonding)

23

25

27

39

Analysis of Surface Roughness Both Ra and Rt values show identical trend. Therefore in statistical analysis Ra values have been analysed.

surface roughness (µmRa)

surface roughness (µmRt)

40

Analysis of Surface Roughness Effect of Feed rate

AOM value of S.R.(µm)

2.5

Al/SiC/20p/220

Al/SiC/20p/600

Al/SiC/30p/220

Al/SiC/30p/600

SiCp reinforcement

2

radial force

1.5 1 feed force

machined surface

0.5

end cutting edge depth of cut

transient surface

0 0.05

0.1 Feed rate (mm/rev.)

0.2

feed rate

cutting direction rake face

Surface roughness Vs. FR

Surface roughness increases with feed rate.

Surface roughness is sensitive to change in composition of composites. Increase in feed rate increases the friction at the end cutting edge. It increases the debonding/pull-out tendency of SiC particles 41

Analysis of Surface Roughness Effect of work material Surface roughness of coarser reinforcement is higher due to larger size cavities formed.

Composites of fine and higher volume fraction reinforcement generates surfaces free from cavities and cracks. 42

Analysis of Surface Roughness 2.5

Effect of Tool nose radius

Increase in TNR radius reduces surface roughness.

Ra = f

2

32r

Al/SiC/20p/600

Al/SiC/30p/220

Al/SiC/30p/600

2 AOM value of S.R.(µm)

Surface roughness is influenced by TNR and sensitive to size than volume fraction.

Al/SiC/20p/220

1.5 1

0.5 0 0.4 0.8 Tool nose radius (mm) Surface roughness Vs. TNR

43

Analysis of Surface Roughness Effect of insert geometry Surface roughness significantly influenced by change in insert geometry Surface roughness is sensitive to size than volume fraction of reinforcement. Wiper type insert geometry improves surface roughness. 2.5

Al/SiC/20p/220

Al/SiC/20p/600

Al/SiC/30p/220

Al/SiC/30p/600

AOM value of S.R.(µm)

2 1.5 1 0.5 0 W1

W2 Insert geometry

NW

44

Analysis of Surface Roughness Effect of insert geometry Surface roughness with wiper (W1 & W2) type inserts is lower than conventional (NW) type inserts Insert=W1, TNR=0.4mm, Feed rate=0.2mm/rev, Cutting speed=120m/min, DOC=1mm (Ra=1.9μm)

Insert=NW, TNR=0.4mm, Feed rate=0.2mm/rev, Cutting speed=80m/min, DOC=0.6mm (Ra=2.56μm)

Effect of work material Tendency of SiC fracture/crushing and debonding is more with coarser particles. Al/SiC/30p/220 (Ra=0.56μm)

Al/SiC/30p/600 (Ra=0.16μm)

(Insert=W1,TNR=0.8mm, Feed rate=0.05mm/rev, Cutting speed=120m/min, DOC=0.6mm)

45

Analysis of Micro-hardness 0

0.150 µm 0.240 µm

6 .0

0µ

m

Vickers microindentation at 0.120 µm

0.030µm

bulk micro-hardness

m achined edge

0.180 µm 0.0

90

µm

all dimensions are in µm

Line diagram and photograph of indented specimen

Microhardness higher at close to machined surfaces and decreases to the bulk material hardness at a certain distance. The region from the machined surface till the position at which it reaches the bulk hardness is called as an altered material zone (AMZ). 46

Bulk hardness

120

120

Analysis of Micro-hardness

AMZ ~180μm

110

110

100

Identification of AMZ 170

Microhardness (VHN)

160 150 140 130

Test 2 Test 4 Test 6 Test 8 Test 10 Test 12 Test 14 Test 16 Test 18 Test 20 Test 22 Test 24 Test 26

150 170 140 160 130 150 120 140 110 130

80 100

60

90 120 150 180 210 Distance beneath the machined surface (μm)

240

270

30 30

60 60

Material

rohardness (VHN)

140 130

Al/SiC/30p/220

120

Al/SiC/30p/600

Test 2 Test 4 Test 6 Test 8 Test 10 Test 12 Test 14 Test 16 Test 18 Test 20 Test 22 Test 24 Test 26

160

150 140 130 120 110 100 90 80

90 120 150 180 210 90 120 the150 210 Distance beneath machined180 surface (μm) Distance beneath the machined surface (μm)

240 240

270 270

Test 1 Test 3 Test 5 Test 7 Test 9 Test 11 Test 13 Test 15 Test 17 Test 19 Test 21 Test 23 Test 25

Test 2 Test 4 Test 6 Test 8 Test 10 Test 12 Test 14 Test 16 Test 18 Test 20 Test 22 Test 24 Test 26

Effect of size and vol(µm) ume fraction of rei Bulk hardness (VHN) AMZ 150 altered material z 140 range of130119 - 122 ~ 180 – 210 rohardness (VHN)

150

Test 1 Test 3 Test 5 Test 7 Test 9 Test 11 Test 13 Test 15 Test 17 Test 19 Test 21 Test 23 Test 25

160

Al/SiC/30p/600 Al/SiC/20p/220

Al/SiC/30p/220 160

Test Test22 Test Test44 Test Test66 Test 8 Test 8 Test 10 Test 10 Test 12 Test 12 Test 14 Test 14 Test 16 Test 16 Test 18 Test 18 Test 20 Test 20 Test 22 Test24 22 Test Test 24 Test 26 Test 26

AMZ ~ 120μm Bulk hardness AMZ ~ 150μm

90 110

100 30

270

Bulk hardness

100 120

AMZ ~180μm

110

240

Test Test 11 Test Test 33 Test Test 55 Test 7 Test 7 Test 9 Test 9 Test 11 Test 11 Test 13 Test 13 Test 15 Test 15 Test 17 Test 17 Test 19 Test 19 Test 21 Test 23 21 Test Test 23 Test 25 Test 27 25 Test Test 27

160 180

Bulk hardness

120

90 120 150 180 210 Distance beneath the machined surface (μm)

Microhardness (VHN)

Test 1 Test 3 Test 5 Test 7 Test 9 Test 11 Test 13 Test 15 Test 17 Test 19 Test 21 Test 23 Test 25 Test 27

60

Al/SiC/30p/220

Microhardness Microhardness(VHN) (VHN)

180

100 30

range of12099 –102

~ 120 –150

47

Analysis of Residual Stresses and Micro-hardness

Feed rate (mm/rev.)

0 0.05

0.1

0.2

-20 -40 -60 -80 -100 -120 Al/SiC/20p/220

Al/SiC/20p/600

Al/SiC/30p/220

Al/SiC/30p/600

Mean of microhardness at 30μm(VHN)

Residual stress( MPa)

20

180

Al/SiC/20p/220

Al/SiC/20p/600

Al/SiC/30p/220

Al/SiC/30p/600

170 160 150 140 130 120 0.05

0.1 Feed rate (mm/rev)

0.2

Mean average tool temperature (ºC)

Effect of feed rate 500

Al/SiC/20p/220 Al/SiC/30p/220

Al/SiC/20p/600 Al/SiC/30p/600

460 420 380 340 300 260 0.05

0.1 Feed rate (mm/rev.)

0.2

Increase in FR change stresses from higher compressive to lower compressive or tensile, and micro-hardness reduces. Compressive stresses at lowest FR but at higher FR, increased deformation rate and MRR increases deformation temperature and heat generation. Increase in heat generation at higher feed and size of reinforcement increases residual stresses.

48

Analysis of Residual Stresses and Micro-hardness Vickers micro-hardness indenter

higher resistance by surface to indentation

lower resistance by surface to indentation machined surfacetensile stresses

machined surfacecompressive stresses depth beneath the machined surface (a)

(b)

Compressive stresses offer more resistance to penetration of indenter. At lower feed rate, residual stresses are compressive, the micro-hardness is higher. Increase in feed rate deteriorates quality of machined surface (more boundary defects) Pit holes, cavities releases the stresses resulting tensile or lower compressive stresses and reduces the micro-hardness. 49

Analysis of Residual Stresses and Micro-hardness Effect of depth of cut 180

0 Residual stress (MPa)

0.2

0.6

1

-20 -40 -60 -80

-100 -120

Al/SiC/20p/220

Al/SiC/20p/600

Al/SiC/30p/220

Al/SiC/30p/600

170

Al/SiC/20p/220

Al/SiC/20p/600

Al/SiC/30p/220

Al/SiC/30p/600

160 150 140 130

540 Mean average tool tempertaure (ºC)

Depth of cut (mm) Mean of microhardness at 30μm (VHN)

20

120

Al/SiC/20p/220

Al/SiC/20p/600

Al/SiC/30p/220

Al/SiC/30p/600

500 460 420 380 340 300 260

0.2

0.6 Depth of cut (mm)

TNR

Increase in DOC changes the stresses from higher compressive to lower compressive or tensile, and the micro-hardness reduces.

Feed rate 0.05

0.4

a − r 1 − cos ( kr )   −1  f   l = r  kr + sin    + sin ( kr )  2r   

1

0.1

0.2

0.2

0.6 Depth of cut (mm)

1

DOC

Length of contact

% increase

0.2

0.45

-----

0.6

0.85

88.76

1.0

1.25

47.02

0.2

0.47

-----

0.6

0.87

84.11

1.0

1.28

45.68

0.2

0.52

----

0.6

0.93

76.14

1.0

1.33

43.22

50

Analysis of Residual Stresses and Micro-hardness Effect of cutting speed 40

80

120

Residual stress (MPa)

-20 -40 -60 -80 -100 -120

Al/SiC/20p/220

Al/SiC/20p/600

Al/SiC/30p/220

Al/SiC/30p/600

Mean of microhardness at 30μm (VHN)

Cutting speed (m/min.)

0

180

Al/SiC/20p/220

Al/SiC/20p/600

Al/SiC/30p/220

Al/SiC/30p/600

170 160 150 140 130 120 40

80 Cutting speed (m/min)

120

At 40 m/min, higher compressive stresses. Since higher machining forces required due to lower heat generation. At 80 m/min, increases the deformation rate and work temperature. At 120 m/min, strain rate increases, material difficult to deform and work hardened. Reduces friction, more heat carried away by chip. Mechanical stresses prominent than thermal stresses.

51

Analysis of Residual Stresses and Micro-hardness Effect of tool nose radius 0

Tool nose radius (mm) 0.4

0.8

Residual stress (MPa)

-20 -40 -60 -80 -100 -120

0.4 mm tool nose radius

Al/SiC/20p/220

Al/SiC/20p/600

Al/SiC/30p/220

Al/SiC/30p/600

0.8 mm tool nose radius



Increase in TNR increases passive (ploughing) force.



It is resolved into radial and feed force and increases the tensile stresses behind the cutting edge.



Thus higher compressive stresses on the machined surfaces

52

Analysis of Residual Stress and Micro-hardness Effect of insert geometry Negative rake angle Chip

Chamfer 30º×100

Negative rake angle Chamfer 20º×100

Chip

20º

30º

Machined surface

Machined surface Direction of pressure applied (in material to be removed)

Direction of pressure applied (in work material) Work material

W2 type insert geometry

Work material

W1 type insert geometry

W2 type inserts induces higher compressive stresses than W1 and NW type inserts. Increased chamfer angle directs the load to work material resulting higher tensile stresses behind the cutting edge. It introduces higher compressive stresses on the machined surfaces.

53

Analysis of Residual Stress and Micro-hardness Effect of insert geometry

During machining with W2 type insert the machined surface passing through the extended cutting edge behaves as an extruded material. The extended cutting edge apply excessive load on the machined surface resulting higher compressive stresses in the machined surface. Simultaneously the work hardening occurs and micro-hardness increases. 54

Optimization of Turning Process on Al/SiCp Composites Grey relational Analysis Material

Al/SiC/20p/220

Al/SiC/30p/220

Al/SiC/20p/600

Al/SiC/30p/600

Best machining conditions

r1-I1-f1-V1-d1

r1-I1-f1-V1-d1

r1-I1-f1-V1-d1

r2-I3-f1-V2-d1

Worst machining conditions

r1-I3-f3-V2-d2

r1-I1-f3-V3-d3

r1-I1-f3-V3-d3

r1-I1-f3-V3-d3

Overall best machining conditions: r2-I2-f1-V1-d1 Use of 0.8 mm tool nose radius, W2 type insert geometry, 0.05 mm/rev feed rate, 40 m/min cutting speed and 0.2 mm depth of cut. (In case of Al/SiC/20p/600 use of W1 type insert geometry is beneficial). 55

Optimization of Turning Process on Al/SiCp Composites Response variable

Al/SiC/20p/220

Al/SiC/30p/220

Al/SiC/20p/600

Al/SiC/30p/600

Best

Worst

Best

worst

Best

worst

Best

worst

Cutting force (N)

28.2

192.1

40.8

266.3

23.9

316.7

25.2

313.5

Radial force (N)

31.3

115.9

44

164

13.4

122

39.3

104.6

Feed force (N)

6.6

60

5.9

77.1

8.4

104

4.1

86.5

Sur. roughness (µ mRa)

1.21

2.56

1.26

2.06

0.26

1.75

0.21

1.29

Residual stress

– 148.4

145.4

– 133.6

80

– 93.9

2.4

– 187.3

29.4

Micro-hardness

130

166

145

172

119

149

127

150

SEM Photographs

best

best

worst

best

worst

best

worst

worst

56

Hot Machining on Al/SiCp composites Material

Al/SiC/30p/220 Al/SiC/30p/600

Insert type

W2 type insert geometry

TNR (mm)

0.8

Feed rate (mm/rev)

0.1

Depth of cut (mm)

0.6

Cutting speed (m/min) Work Temp (°C)

Heating Coil: Canthol Wire 0.3 mm dia. Thermocouple: Chromel - Alumel

40, 80 and 120 Room temp(25°C), 60°C, 90°C and 120°C

Experimental Set-up

57

Hot Machining on Al/SiCp composites Cutting force analysis 100

Cutting speed, 40m/min

Cutting speed, 80m/min

100

Cutting speed, 120m/min

Cutting speed, 80m/min

Cutting speed, 120m/min

80

80 Cutting force (N)

Cutting force (N)

Cutting speed, 40m/min

60

40

20

60

40

20

0 Room temperature

60°C

90°C

120°C

Work temperature (°C)

0 Room temp erature

60°C

90°C

120°C

Work temperature (°C)

Al/SiC/30p/220

Al/SiC/30p/600

Coarser reinforcement - cutting forces reduces (~15 to 45 %) at 60°C. However, effect of further increase in work temperature is non-significant. Finer reinforcement - upto 60°C cutting forces are non-significant. But further increase in temperature increases cutting forces. 58

Hot Machining on Al/SiCp composites

2

Cutting speed 40 m/min

Cutting speed 80 m/min

Cutting speed 120 m/min

Surface roughness (µmRa)

Surface roughness (µmRa)

urface roughness analysis 1.6 1.2 0.8 0.4 0 Room temperature

60

90

Work temperature (°C)

Al/SiC/30p/220

120

0.8

Cutting speed 40 m/min

0.7

Cutting speed 120 m/min

Cutting speed 80 m/min

0.6 0.5 0.4 0.3 0.2 0.1 0 Room temperature

60 90 Work temperature (°C)

120

Al/SiC/30p/600

Coarser reinforcement - improvement in roughness at 60 to 90°C temperature (at 40 and 80 cutting speed) Finer reinforcement - smaller improvement in roughness at 60°C temperature (at 40 & 80 cutting speed). Further increase in temperature deteriorates the surface quality. 59

Major Research Contributions



A comprehensive analysis of chip formation was realized from this study, which gives the effect of volume, size of reinforcement and processing parameters on the machining of chip formation in Al/SiCp composites.



Analytical model incorporating the specific nature of tool–chip friction in the 3-D or oblique machining of composites has been formulated.



Correlation between the machining force components, surface roughness, micro-hardness, residual stresses, and the processing parameters as well as composition of composite materials has been arrived at. These correlations help choose suitable processing conditions and composition of composites to improve machined surface quality and integrity.

60

Major Research Contributions



The best optimized combination of machining conditions to enhance the surface quality/integrity on machined surfaces of Al/SiCp composite is use of 0.8 mm tool nose radius, W2 type insert geometry, 0.05 mm rev-1 feed rate, 40 m min-1 cutting speed and 0.2 mm depth of cut. (In case of Al/SiC/20p/600 composites instead of W2 use of W1 type insert geometry is beneficial).



Based on the hot machining experiments, it is observed that moderate heating (in the range of 60 to 90ºC) of Al/SiCp composite material prior to machining reduces cutting forces and surface roughness. Thus, hot machining could be a suitable alternative for machining of Al/SiCp composites.

61

Conclusions Chip Formation Mechanism 



At lower feed, depth of cut and cutting speed favorable type chips such as thin flakes, needle type and segmented chips are observed. In finish turning, the coarser particles acts as a chip breaker and improve the surface roughness.

Mechanics of Machining  



Cutting forces are more sensitive to size than volume fraction. Change in size of reinforcement causes a significant change (40–50 %) in radial forces and lower change (10–15 %) in cutting and feed forces. Radial forces are higher with coarser reinforcement due to the debonding, fracturing and pulling-out of coarser particles at tool-work interfaces.

62

Conclusions Surface Roughness  Surface roughness is more sensitive to size than volume fraction .  Wiper insert improves surface roughness due to additional pressure applied by extended cutting edge and wiping away the loosely adhering particles on surfaces.  Cavities formed may also get filled by Al-matrix due to wiping action of wiper inserts.  Lowest (~ 0.13 µmRa) and highest (~ 2.47 µmRa) surface roughness is observed on Al/SiC/30p/600 and Al/SiC/20p/220 respectively. Micro-hardness Variation and Surface Residual Stresses  AMZ (~ 120–210 µm) & (~ 90–150 μm) coarser and finer reinforcement respectively  DWH is higher (~ 60 %) for finer than coarser reinforcement composites (~ 45 %).  Correlation between residual stress and micro-hardness exists. Micro-hardness increases with compressive stress and reduces with tensile stresses.  At increased feed rate, cutting speed and depth of cut thermal stresses are predominant and introduce tensile stresses on machined surfaces. 63

Conclusions Analytical Modeling of Machining Force Components  Reinforcement particles change frictional behavior at chip-tool & work-tool interfaces.  For coarser reinforcement COF is (0.326) and for finer reinforcement it is (0.314).  Assumption of 40 % particles contributing to the abrasion yields results comparable well with experimental results for finer reinforcement. However, for coarser reinforcement it is about 60%. Multiple-Objective Optimization  Optimized machining conditions: r2-I2-f1-V1-d1 (0.8 mm TNR, W2 type insert geometry, 0.05 mm/rev feed rate, 40 m/min cutting speed and 0.2 mm DOC) Hot Machining Experiments  Moderate heating (60 to 90°C) of work material prior to machining reduces the phenomena of pull-out and fracture of reinforcement (especially in coarser reinforcement composites) and improves the surface roughness  The influence of heating on the metallurgical and mechanical characteristics of work surfaces needs to be investigated further. 64

Future Scope 

On the machined surfaces, the reinforcement particles in the composites act as sites for the crack initiation and deteriorate the fatigue strength of product. Hence, the study on fatigue resistance can be valuable for improving the product life.



Further investigations by considering variety of particle size and volume fraction of reinforcement in composites.



Detailed investigations on prior heating of composite materials using concentrated heating with laser heat source and its effect on metallurgical and mechanical characteristics of work surfaces is necessary.



Machinability and surface characteristics of these materials by non-conventional processes such as ultrasonic machining (USM) and laser beam machining (LBM) needs to be investigated.

65

List of publications International journals 1.

2.

3.

4.

Uday A. Dabade, Suhas S. Joshi, R. Balasubramaniam and V.V. Bhanuprasad, “Surface Finish and Integrity of Machined Surfaces on Al/SiCp Composites”, JMPT , Vol. 192-193, 1st October 2007, pp 166-174. Uday A. Dabade, Abeesh C. Basheer, Suhas S. Joshi, V.V. Bhanuprasad and V. M. Gadre, “Analysis and Modeling of Surface Roughness in Machining of Metal Matrix Composites using ANN”, JMPT, Vol. 197, Issues 1-3, 1 February 2008, pp 439-444. Uday A. Dabade and Suhas S. Joshi, “Analysis of Chip Formation Mechanism in Machining of Al/SiCp Composites”, JMPT , Available online. Uday A. Dabade and Suhas S. Joshi, “Modeling of Chip-tool Interface Friction to Predict Cutting Forces in Machining of Al/SiCp Composites” Accepted for publication in International Journal of Machine Tools and Manufacturer.

International conferences 5.

6.

7.

Uday A. Dabade, Suhas S. Joshi, R. Balasubramaniam and V.V. Bhanuprasad, “Surface Finish and Integrity of Machined Surfaces on Al/SiCp Composites”, Proceedings of The Seventh Asia Pacific Conference on Materials Processing, 7th APCMP, 2006, organised by National University of Singapore (NUS) and Navyang Technological University, Singapore. Uday A. Dabade, Suhas S. Joshi and V.V. Bhanuprasad, “Some Aspects of Improving Integrity of Machined Surfaces on Al/SiCp Composites”, Proceedings of the Second International Conference on Recent Advances in Composite Materials, ICRACM 2007, Organised by Banaras Hindu University, Varanasi, during 20-23rd February 2007 at New Delhi, India. Uday A. Dabade and Suhas S. Joshi, “Characteristics of Machined Surfaces of Al/SiCp Metal Matrix Composites”, Paper accepted for presentation and publication in an International Conference on Future Trends in Composite Materials and Processing (INCCOM-6), at IIT Kanpur, India, during 12-66 14th December 2007.

List of publications International conferences 8.

9.

10.

Uday A. Dabade and Suhas S. Joshi, “Effect of Size of Reinforcement on Machined Surface Roughness of Al/SiCp Metal Matrix Composites”, Proceedings of International Conference on Precision engineering (COPEN 2007), at Trivandrum, India, during 13-14th December 2007. Uday A. Dabade and Suhas S. Joshi, “Analysis of Chip Formation Mechanism in Machining of Al/SiCp Composites”, Proceedings of Eight Asia-Pacific Conference on Materials Processing, 8th APCMP, 2008, Organised by National University of Singapore (NUS), Navyang Technological University (NTU), Singapore and Guangdong University of Technology, China, during 15–20th June 2008. Uday A. Dabade and Suhas S. Joshi, “Effect of Abrasive Reinforcement on Work Hardening during Machining of Metal Matrix Composites”, Proceedings of Eight Asia-Pacific Conference on Materials Processing, 8th APCMP, 2008, Organised by National University of Singapore (NUS), Navyang Technological University (NTU), Singapore and Guangdong University of Technology, China, during 15–20th June 2008.

National conferences 11.

12.

Uday A. Dabade and Suhas S. Joshi, “Surface Integrity and Surface Finish of Machined Surface of Al/SiCp Composites”, ‘Precision Engineering’ (COPEN 2005) held at Jadavpur University, Kolkata, INDIA on 19-20th December 2005. Uday A. Dabade and Suhas S. Joshi, “Machining of Al/SiCp Metal Matrix Composites: A Review”, Proceedings of National Seminar on Advances in Product Development (APD 2006)” held at MNNIT Allahabad,17-18th February 2006. 67

68