ramesh sing_iit bombay

8/3/2019 Ramesh Sing_IIT Bombay

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Hybrid and Reconfigurable

Micromanufacturing Processes

Ramesh Singh

Machine Tools Laboratory

Department of Mechanical Engineering

Indian Institute of Technology Bombay


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Outline Overview of Machine Tools Lab

Reconfigurable laser manufacturing processesat micro/meso scales

Laser-assisted mechanical micromachining

Laser surface hardening

Laser cladding Laser brazing

Laser texturing

Reverse EDM

Creating nanofinished cavities in single crystal

sapphire

Manufacturing process simulation


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Research Interests


Micromachining

Characterization& modeling steels

/layered pyrolyticcarbon

Burr formation

High speedmicromillingmchinedevelopment

Reconfigurablefiber laser

manufacturing

Laser-assisted

micromachiningLaser hardening

Laser cladding

Laser brazing ofceramics andmetals

Laser surface

texturing

EngineeredSurfaces

FunctionalResponse

hydrophobicity/hydrophilicity

Tribologicalresponse

Finite ElementSimulations

Electromagneticforming

Ring rollingFlow forming

Compositedamage


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Machine Tools Lab FacilitiesCapital Equipment and instrumentation

Mikrotools CNC Multi-purpose Micromachining Center

EMCO Precision CNC Lathe Hardinge Vertical Machining Center

100 W Single Mode Fiber Laser

Excimer Laser Micromachining Facility

Wyko NT 9100 White Light Interferometer

Zeiss 3D Coordinate Measuring Machine

Kistler Mini and large size force Dynamometers Acoustic Emission Sensing System

Nikon Tool Makers Microscope

Micro-hardness Testing Machine

Image Analyzers

National Instruments Data Acquisition System/High speed

DigitizerComputational Facilities

Deform 3D and 2D with Machining simulation modules

ANSYS and ABAQUS

Pro-Engineer

MATLAB and Simulink

COMSOL Digimat


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Characterization Tools and Equipments


Measuring

microscope

White light interferometer Coordinate measuring

machine

Stereo and metallurgical microscopeFiber laser


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Issues in Tool-based

Micromanufacturing

Processing difficult-to-machine steels, superalloys andceramics

Hard facing and repair techniques at micro/meso scales

Slow process requires innovative solutions to increase

productivity Surface finishing is extremely challenging; traditional rigid

tool based grinding processes may be difficult

Stiffness issues in the micro-machine tool

Precise servo control for positional accuracy


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Improvements in Micromanufacturing

Hybridization of mechanical micromachining

Laser-assisted mechanical micromachining

Reconfigurable laser manufacturing

Fabrication of arrayed microstructures to

improve productivity Reverse micro-EDM

Development of soft tool nanopolishing

methods Hydrodynamic nanopolishing



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Laser Assisted Mechanical

Micromachining (LAMM)

Limitations of mechanical micromachining Range of materials

Tool flexural strength/machine-tool system stiffness

Slow process

Hybrid laser assisted mechanical micromachining(LAMM) Integrates thermal softening with mechanical micro-cutting

Thermal softening of workpiece results in low cutting forces

Overcomes limitations of machine-tool system stiffness,

flexural strength and low MRR


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Machine Tools LaboratoryMicromachining Cell

LAMM Setup

Laser Characteristics:

Yb fiber laser

2-35 W

l = 1060 nm (invisible)

Spot size = 70/110 mm

Tool Post

Dynamometer

Tool

Laser Collimator

Lens

X-Y Stage

Workpiece

Y-Z Stage

XY

Tool Post

Tool

Focused Laser BeamX-Y Precision Stages

Cutting Direction(Y-axis)

Workpiece Feed (X-axis)

Dynamometer

Singh et al., 2007


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Laser Assisted Machining

Laser

C ollimator

Assembly

C utting Tool

and

Workpiece

Laser

C ollimator

Assembly

C utting Tool

and

Workpiece

m-Milling Turning


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Laser-Assisted Micromilling

Surface roughness

0

0.1

0.2

0.3

0.4

0.5

0.6

0.70.8

0.9

2.5 12.5 22.5 27.5 37.5 47.5 52.5 62.5 72.5 77.5 87.5 97.5 103 113 123 128 138 148

Distance of cut (mm)

Surfaceroughness(micr

Surface Roughness Without Laser

Surface Roughness With Laser

Comparison of surface roughnesswith and without laser in laser

assisted on A2 tool steel (62 HRc)

Without laser

With laser


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Forces in LAMM

0

5

10

15

20

25

30

Cutting Force Thrust Force

Force

(N)

0 W

10 W35 W

56%

Drop

46%

Drop

Effect of laser power on forces. Cutting conditions: 300 mm tool width,

10 mm/min cuting speed and 25 mm nominal depth of cut


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Experimental Setup

CAD drawing of LAMM-based

orthogonal cutting setupSnap of the LAMM setup


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Total

RS

The stresses which exist in a body after removal of all external forces. RS one of the most imp. parameter in controlling the functional

performance

The origins induced by non-uniform plastic deformation

RS due toMechanical

loading

RS due toThermal

loading

RS due to PhaseTransformation

Generation of RS in machining:

Elastic-plastic deformation

Elasticity recovery

After relaxation, plastic strain results in

compressive RS

Residual Stresses in LAMM


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Surface Residual Stresses

-350

-300

-250

-200

-150

-100

-50

0

30 mm/min 60 mm/min

Conventional

LAMM

15 m Uncut Chip Thickness

0

50

100

150

200

250

30 mm/min 60 mm/min

Conventional

LAMM

25m Uncut Chip Thickness

The residual stress in thrust direction becomes more

compressive (~ 34%) in LAMM

A significant reduction in tensile residual stress (50%-60%) can

be obtained with laser assistance cutting direction.

The laser heating and the mechanical load, the surface layer

expansion exceeds the thermal expansion of the substrate

surface.

This differential expansion between the surface and the

substrate induces more compressive residual stresses in LAMMcompared to conventional cutting

Thrust Direction Cutting Direction

cutting

Thrust

34 %

14 %

47 %

73 %


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Johnson-Cook model

It defines the flow stress as a function of strain, strainrate, and temperature during machining

Friction model:

](x)/Kexp[1/ chipNm chips Km 006.0 chipKm,with

qN Nmax c(x) [1-(x/L ) ]

Finite Element Modeling of LAMM

m

roomm

roomn

TT

TTCBA 1ln1)(

0


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.

pp

T T T T T k k k Q C c V

x x y y z z t x

Laser beam is modeled as moving heat source

Cylindrical window whose diameter is equal to that of laserbeam

The heat in this heat exchange process is Q

)T-hA(T wpwd PQ

Therefore, total heat in machining is given by

Heat due to plastic work + Heat due to friction + Laser heat

The governing heat conduction equation:

Modeling of Laser Moving Heat Source:

Finite Element Modeling of LAMM


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Cutting conditions and results:

Heat window and boundary

conditions:

Test No. Depth of

cut (mm)

Cutting Conditions Measured Simulated

Cutting

speed

(m/min)

Feed rate

(mm/rev)

Cutting force

(N)

Cutting

force (N)

%

Error

2 (LAM) 0.25 100 0.125 130 121.38 6.6

3 (LAM) 0.25 200 0.125 95 103.54 8.9

4 (LAM) 0.25 200 0.25 185 200.5 8.1

All six degrees of freedom ( ux, uy, uz, fx, fy,fz 0)are constrained for the workpiece

Tool is constrained in X and Y-direction and

velocity is imparted along Z-axis.


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Simulation video

Simulations and results:

Results

177.28 N

121.38 N103.54 N

200.53 N

1

Cutting force variation

Test 1 (Conv) Test 2 (LAM)

Test 3 (LAM) Test 4 (LAM)

Reduction in

Fc =

32%
http://../DERORM_2D/July/Shi_Reports/Test_2_LAM/Test_2.wmvhttp://../DERORM_2D/July/Shi_Reports/Test_2_LAM/Test_2.wmvhttp://3d_lam_test_2.wmv/http://../DERORM_2D/July/Shi_Reports/Test_2_LAM/Test_2.wmvhttp://3d_lam_test_2.wmv/http://../DERORM_2D/July/Shi_Reports/Test_2_LAM/Test_2.wmv


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Prediction of residual stresses in DEFORM

The material model must be an elastic-plastic.

The simulation has to be executed for a total time step long enough to reach the steady-state

condition

After several time steps, the tool has to be released from the machined surface (unloading

phase)and the workpiece is allowed to cool to an atmospheric temperature

Unloading phase simulation may be done either by keeping the same step time as used during

cutting or by keeping one second step time for less number of steps.

The numerical in depth residual stress profiles have to be gathered on machined surface using

State Variable option in DEFORM 3D.


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Reconfigurable fiber lasermanufacturing



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Fiber Lasers

Maintenance free

High wall plug efficiency

Excellent beam quality (M2

< 1.1)

Available in single mode &

multimode

Available with high power

up-to 50 KW Compact in size & portable

Properties Fiber

Laser

Nd:YAG CO2 Disc

Wall Plug

Efficiency

30% ~ 5% ~10% 15%

Output Powers to 50kW to 6kW to 20Kw to 4kWBPP (4/5 kW) < 2.5 25 6 8

Life 100,000 10,000 N.A. 10,000

Cooling Air/water Water water water

Floor Space (4/5

kW)

< 1 sq. m 6 sq. m 3 sq. m 4 sq. m

Operating Cost/

hr

$21.31 $38.33 $24.27 $35.43

Maintenance Not

Required

Often Required Often

CO2 and Nd:YAG lasers have been used in materials processing

but fiber lasers have following advantages:


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Laser Optics Setup

Indian Patent Application No

442/MUM/2011 Filed on 17February 2011

Method and device for

generating laser beam of

variable intensity distribution

and variable spot size

T t l t & i h


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(a) (b)Micrographs at P = 100 W and scan rate =

600 mm/min (a) beam diameter = 400

mm; (b) beam diameter = 200 mm

Temperature plot

(a)d= 400,(b)d= 200;

(Power=100W, scan rate 600

mm/min)

2 2

0 2 2

0

2 2 2 2

2 ' (( ') ')exp[ ] exp[ ] '

8 ( ') 4 ( ') 4 ( ')

' '[ ( ) ( )]

2 ( ') 2 ( ')

tP dt z x vt x

T T dxK t t a t t a t t

y x y xerf erf

a t t a t t

Temperature plot & micrographs

in laser hardening

Temperature distribution for uniform moving heat source

(a) (b)

H d C l l ti & H d


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Hardness distribution plot (P=100W,

beam diameter 200mm, scan

rate800mm/min)

Hardness Calculation & Hardness

Plot

[24]

Microstructure of LSH specimen. (A- martensite

needles, B-transition zone, C-un-transformed

zone) (P=100W, beam diameter- 400mm, scanrate 400mm/min)(500X)

C i f G i d


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Comparison of Gaussian and

Uniform Intensity Beam

Contour plots for Gaussian & Uniform intensity beam (P=100W, Beam diameter: 400mm, Scan rate: 600mm/min)

Schematic showing Gaussian &

Uniform intensity beam beam

hardened geometries


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Overlap Study

27

Hardness Vs % overlap

(P= 70W, Scan rate 600 mm/min, beam diameter:300mm)

0

100

200

300

400

500

600

700800

10% Overlap 20% Overlap 30% Overlap

Hardness(Hv)

First pass Overlap Second pass

ObjectiveTo find the effect of overlap on

hardness and to find optimum overlap

0

10

20

3040

50

60

70

80

90

%numberoffinegrains(below

1.2m)

57%39%

38%

First pass

Overlap

Second pass


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28

Increase in martensite and finer grain formation in second

pass

(A) (B)

Inverse Pole Figure (IPF) showing martensite in(A)specimen without overlap (B) Specimen with 20%

overlap

(A) (B)

Phase map showing martensite in(A) specimen

without overlap (B) Specimen with 20% overlap

EBSD Results in First & Second Pass


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Wear Test

29

Different types of hardened patterns

Objectives: To find effect of micro-scale hardened patterns on wear

resistance

To compare wear of different hardened geometries & to find

out optimum hardened geometry

Specimen size of diameter 10 mm and beam with size of 300 m


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Pin on disk set-up

Pin on Disk Setup


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PREPLACED LASER CLADDING


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PREPLACED LASER CLADDING

PHASE DIAGRAM

Material Selection

Substrate: IS 2062 Clad: Ti-Co mixture (85 wt.% Co)

Ti-Co phase diagram (Massalaki et al., 1990)


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PROCESS

El t l A l i


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Elemental Analysis

34

010

20

30

40

50

60

70

80

90

0 0.2 0.4 0.6 0.8

Percentage of Cobalt

Percentage of Cobalt

Distance f rom centre of clad

Ph A l i


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Phase Analysis

35

M d R


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Measured Responses

Clad

Geometry

Hardness

Residual

Stresses

Nikon Measuring

Microscope

Microhardness Tester (

Shimadzu-HMV)

X-Ray Diffraction Tests


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37

EFFECTOFPARAMETERSON HARDNESS

0

50

100

150

200

250

B I C

60 mm/min

180 mm/minHardnes

s(HV)

Location

More

Dilution

0

50

100

150

200

250

B I C

100W

60WHardnes

s(HV)

Location

83%

increase

0

50

100

150

200

250

B I C

28 m

7 mHardnes

s(HV)

Location

D?

Default

Parameters:P= 100 W;

v= 100 mm/min;

d= 28 microns


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38

Higher presence ofintermetallic compound athigher temperatures

Gradual change due to

higher dilution (Fe- bcc)

Investigating thistechnology for getting adesired value of hardness

help create bettersolutions aimed atimproving wearresistance.

EFFECTOFPARAMETERSON HARDNESS

(fcc)

(ordered

fcc)


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Initially-

Compressive residual stresses in the normal

Tensile residual stresses in the shear direction

After Cladding

Increase in value of compressive stresses in normal direction

Compressive stresses in the shear direction.39

EFFECTOFPARAMETERSON RESIDUAL STRESSES

-700

-600

-500

-400

-300

-200

-100

0

10060 mm/min 180 mm/min

Normal Stress

Shear Stress

-500

-450

-400

-350

-300

-250

-200

-150

-100

-50

060 W 100 W

Normal Stress

Shear Stress

Shear stress goes

down by 50% as

laser power

reduced by 40%

-700

-600

-500

-400

-300

-200

-100

07 microns 28 microns

Normal Stress

Shear Stress

ResidualStresses

(Mpa)

Difference in the coefficients of thermal expansion of the substrate and clad material leads to

generation of compressive stresses.

As the laser beam moves forward, the molten metal consolidates with the resolidified metal

which has been left behind.

Solidification begins at bottom, hence bonding internally in normal direction

Use for Repair

75% decrease inbeam diameter

increases shear

stress by 53%

Default

Parameters:

P= 100 W;

v= 100 mm/min;

d= 28 microns

FEM in Abaq s


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FEM in Abaqus

40

Laser Brazing with Active Cusil


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Power (W) BeamDiameter/Crater

diameter (m)

Feed rate(mm/min)

Results/Remarks

50 30/300 7 Week joint/Failure

60 30/300 7 success

70 30/300 7 Success

80 30/300 7 Success/Alarm

Table. Gaussian beam parametric study

Substrates: Alumina and SS 316, ABA: Cusil foil

Dia.30 m

Alumina

SS 316

Butt

joint

Laser Brazing with Active Cusil

Alloy

Laser Texturing


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Laser Texturing


(a) (b) (c)

7.2m

-21.1m -20.6m

2.7m

40

50

60

70

80

90

100

1 2 3Contactangle(degree)

Reference

Surface

Laser

Textured

Surface

Results of sessile drop test


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Reverse Micro-EDM


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Arrays Fabricated via R EDM


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Arrays Fabricated via R m-EDM


6x6 array 4x4 array

Reverse EDM of Ti6Al4V for Textured


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Measured

Contact

angle on

Reverse

Micro EDM

pattern is to

around 1120

Reverse EDM of Ti6Al4V for Textured

Surfaces


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Hydrodynamic Nanopolishing


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Applications of Nanopolished Surfaces

Optics (High power laser)

Military fields (Heat seeking missiles)

Electronics (Silicon wafers)

Industrial (Precision tools)

Nanopolishing Methods

Diamond Turning

Precision Grinding

Thermo-chemical Polishing

Laser-Beam Polishing

Ion Beam Polishing

Nanopolsihing


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Hydrodynamic Polishing

Process

HDP Characteristics Minute volume removing process

Insensitive to vibrations

Machining rate: Capability of a particle

Number of particles

Quasi-deterministic

Profiled surface machiningcapability

HDP Polishing Setup


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Experimental Setup

P R


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Factors

Load (N) Abrasive

size (m)

Spindle

speed (rpm)

Stiffness

(shore A)

Roughness (m) Remarks

7.5 1 2400 90 0.0035 Optimum

7.5 0.05 3600 90 0.0193 Worst

Process Response

Conformal HDP of Single Crystal


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Machining using CNC turning machine

Spherical cavity on single crystal sapphire

Feed Rate and Depth of Cut while machining as low as 1m/rev

Conformal HDP of Single Crystal

Sapphire Cavity

52

Machined Sample Drawing:

M hi i d C f l HDP f


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Initial experiments indicate with reducing tool insert radius the surface

roughness reduces

Surface Roughness reduced by reducing the feed rate and doc

Machining and Conformal HDP of

Single Crystal Sapphire

53

Surface Roughness Data( 0.05mm tool & 1m FR & DOC )

Region Sa (nm)

center 508.72

near center 566.099

near extrimity 412.2278947

extremity 446.1415

Average Sa 476.431

0

500

1000

1500

2000

center near center near

extremity

extremity

AverageSurfac

eRoughness,Sa(nm)

Feed Rate & DOC = 5um



O i i i f


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Optimization of

Machining Process

54

Sa = 1040nm Sa = 265nm

Visibly low-crack surface


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Conformal Hydrodynamic

Polishing Mechanism

55

Designed at Machine Tools Lab, IIT Bombay


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Video

56


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Surface Roughness reduction by upto 75%

Minimum Surface Roughness reached = 209 nanometers

Polishing Results

57200

350

500

650

center near center near extrimity extremity

AverageSurfac

eRoughness,

Sa(nm

) Pre-machined

Polishing by 0.06m


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Micro-Crack free Surface

58

Cracks

CracksCracks

Best Pre-machined Surface After Polishing


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PROCESS SIMULATION


Fully Coupled Electromagneto Thermo


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Fully Coupled Electromagneto-Thermo-

Mechanical Model for E.M. Forming in

COMSOL

Slide 5


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Deformation profileRadial Lorentz body

force

Slide 15

Model prediction error for the maximum deformation at tube center

- using coil C1 is less than 4% and

- using coil C2 is less than 12%

Shorter coil produces more peak deformation at the centre.


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Preliminary simulation of in-line backward

flow forming process in Deform 3D

Physical Description of FE model

3D rigid-plastic FE model


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Material flow

Longitudinal cross section ofthe spun tube showed build up

and craters

Distribution of displacements in

axial direction

Negative displacement of

material under the rollers

Positive displacement of material

at the end of tube


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Stress Distribution 64

Radial stress Circumferential stress

Axial stress

Radial Ring Rolling Simulation in


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g g

Deform 3D


Results


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Results


Various Damage Mechanisms in


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Various Damage Mechanisms in

composite materials

18-Nov-11 67

Various mechanisms of damage in composite

laminates by [Talreja et al. (2006)]

Representative Volume Element


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Representative Volume Element

RVE)

18-Nov-11 68

1.Representative volume element is used to

predict various properties of the bulkmaterial

2.RVE is also used to predict initiation and

propagation of various damage mechanisms.

3.A micromechanics based software Digimatis used for generation of RVE with periodic

boundary conditions.

4.ABAQUS is used to perform simulations.

Summary


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Summary

Hybridization of existing tool-based

micromachining methods

Reconfigurable laser manufacturing

Arrayed microstructures for enhanced

productivity Novel super-finishing method

Process simulation


Acknowledgements


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Acknowledgements

Prof. Suhas Joshi, Prof. K. Narasimhan, Prof.

Shreyes Melkote

Students

Sachin Mastud

Vijay Doiphode Mahesh Teli

Prashant Kumar

Ishank

Yogesh Wagh

Vivek Varkal

Harshita

PushkarMachine Tools LaboratoryMicromachining Cell


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