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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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Machine Tools Laboratory
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
Machine Tools Laboratory
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
Machine Tools Laboratory
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
Machine Tools Laboratory
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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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Machine Tools LaboratoryMicromachining Cell
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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Machine Tools LaboratoryMicromachining Cell
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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Machine Tools LaboratoryMicromachining Cell
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
Machine Tools Laboratory
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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
Machine Tools Laboratory
(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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Machine Tools LaboratoryMicromachining Cell
Reverse Micro-EDM
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Arrays Fabricated via R EDM
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Arrays Fabricated via R m-EDM
Machine Tools LaboratoryMicromachining Cell
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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Machine Tools LaboratoryMicromachining Cell
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
Feed Rate & DOC = 3um
Feed Rate & DOC = 1um
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
Machine Tools Laboratory
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
Machine Tools Laboratory
Results
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Results
Machine Tools Laboratory
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
Machine Tools LaboratoryMicromachining Cell
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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Questions?