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8/19/2019 Fe Simulation of Cutting Processes
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© WZL/Fraunhofer IPT
Finite element simulation of cutting
processes
Simulation Techniques in Manufacturing Technology
Lecture 8
Laboratory for Machine Tools and Production Engineering
Chair of Manufacturing Technology
Prof. Dr.-Ing. Dr.-Ing. E.h. Dr. h.c. Dr. h.c. F. Klocke
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Summary and Outlook9
Applications of the FE cutting simulation at the WZL 8
Criteria for the evaluation of FE software 7
Friction and wear models for the FE cutting simulation6
Damage models for the FE cutting simulation and multiphase simulation 5
Constitutive material laws for the FE cutting simulation4
CAD modelling for the FE cutting simulation3
Requirements of the FE cutting simulation 2
Introduction 1
Outline
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Influencing factors on the cutting process
Workpiece material
structure
texture
mechanicalproperties
hardness
residual stresses
Cutting zone
chip forming
mechanisms
cooling lubricant
cutting parameters
contactconditions
e.g.: friction, wearheat transfer
Tool
cutting material
coating
geometry
tool holder
Machine
machine design
drive system
clamping device
Bildeines
Prozesses
M
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Cutting process in comparison to other processes
Source: Jaspers
Process Strain Strain rate / s-1 Thomolog
Extrusion 2 – 5 10-1 – 10-2 0.16 – 0.7
Forging /
Rolling0.1 – 0.5 10 – 10+3 0.16 – 0.7
Sheet metalforming
0.1 – 0.5 10 – 10+2 0.16 – 0.7
Cutting 1 – 5 10+3 – 10+6 0.16 – 0.9
Cutting process
Extreme conditions in the cutting process
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Seite 5 © WZL/Fraunhofer IPT
Outline
Summary and Outlook9
Applications of the FE cutting simulation at the WZL 8
Criteria for the evaluation of FE software 7
Friction and wear models for the FE cutting simulation6
Damage models for the FE cutting simulation and multiphase simulation 5
Constitutive material laws for the FE cutting simulation4
CAD modelling for the FE cutting simulation3
Requirements of the FE cutting simulation2
Introduction 1
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Requirements to the FE cutting simulation
Reproduction of the macro/ micro geometry of the tools and kinematic of the cuttingprocess
Modelling of the thermo mechanical material behavior for the entire temperature andstrain rate range
Implementation of damage approaches, texture microstructure and phase transformation
Simulation of chip form (remeshing routine, material separation, etc.)
Consideration of friction, wear and coating
Modelling of heat generation and transfer (conduction, convection, radiation)
Consideration of the influence of cooling lubricant
Utilization of the Lagrangian solving method (instationary cutting processes)
Generation of a finely structured FE mesh and adaptive remeshing (very high element
deformation because of higher gradients of deformation, temperature and tension) Appropriate computation time (explicit time integration, parallelization, etc.)
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Cutting simulation: Input- und output parameters
Tool
StrainTension
Temperature
Cutting forcesWear
Chip formation
TemperatureTension
DeformationRate of deformation
Chip typeChip flowChip crack Component
Strain
TemperaturesDeformation
Burr formationDistortionFuture: Residual stresses
Surface quality, e.g.: roughnesschanges in shape,Measurement and position
Component / tool
GeometryMaterial dataContact conditionsBoundary conditionsCutting conditions
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Outline
Summary and Outlook9
Applications of the FE cutting simulation at the WZL 8
Criteria for the evaluation of FE software 7
Friction and wear models for the FE cutting simulation6
Damage models for the FE cutting simulation and multiphase simulation 5
Constitutive material laws for the FE cutting simulation4
CAD modelling for the FE cutting simulation3
Requirements of the FE cutting simulation2
Introduction 1
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Macro- und micro tool geometry
Major clearance angle: a = 10°Twist angle: d = 35°
Cutting material: HW-K20Grain size: DK = 0.5 – 0.7 µm
Construction dimensions DIN 6539Type: N
Diameter: d = 1 mmDrill-point angle: s = 118°
Querschneide
Freifläche
Hauptschneide a
d
chisel edge
flank face
major cutting edge a
d
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Definition of element type
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Creation of tool models close to reality
Macrogeometry
4 mm
Drilling tool FEM-modelDetermination of the tool geometry
Microgeometry
6 µm6 µm
Real tool CAD-model
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Zusammenfassung und Ausblick 9
Outline
Zusammenfassung und Ausblick Zusammenfassung und Ausblick Zusammenfassung und Ausblick Summary and Outlook9
Applications of the FE cutting simulation at the WZL 8
Criteria for the evaluation of FE software 7
Friction and wear models for the FE cutting simulation6
Damage models for the FE cutting simulation and multiphase simulation 5
Constitutive material laws for the FE cutting simulation4
CAD modelling for the FE cutting simulation3
Requirements of the FE cutting simulation2
Introduction 1
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Thermo-mechanical behavior of material
i iB u
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Thermo-mechanical behavior of material
Quelle: Diss-Abouridoaune
( , , )T s s
200
250
300
350
400
450
0 0.1 0.2 0.3 0.4
AA6063-T6
d
/dt=10-3
s-1
& T=20°C
, -
, M P a
300
350
400
450
10-3
10-1
101
103
AA6063-T6
=0.1 & T=20°C
d
/dt , s-1
0
150
300
450
0 100 200 300 400 500
AA6063-T6
=0.1 & d
/dt=1s-1
T , °C
StrainRateHardening StrainHardening Thermal Softening
Source: Diss- Abouridouane
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Empirical models: e.g. Johnson-Cook-Modell
Micro mechanical models: e.g. enhanced Macherauch-Vöhringer-Kocks-model
Semi-empirical models: e.g. Zerilli-Armstrong-model for bcc-materials
Constitutive material modelling for the FE cutting simulation
Source: Diss-Abouridouane
n -1/2G 1 2 3 4 5σ = Δσ +C exp -C T +C Tln( ) +C +C L
Initial densityof dislocations Dislocation jam
Influence of temperatureand strain rate
Influence of grain size
m
n r 0
m r
T T(A B ) (1 Cln( / )) (1 )
T T
s
Strain hardening Strain rate sensitivity Thermal softening
1/ p1/ q
* 0a 0
0
kT1 ·ln
G
s s s Athermal processes Damping processThermal activated processes
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Determination of High speed flow curves
Source: LFW
Split-Hopkinson-Pressure-Bar
AusgangsstabEingangsstab
Lager
Lager
Joch Projektil
Rohr
Zugprobe
Deckel mit
Luftanschluss
Pressluftbehälter mitSchnellöffnungsventil
AusgangsstabEingangsstab
Lager
Lager
Joch Projektil
Rohr
Zugprobe
Deckel mit
Luftanschluss
Pressluftbehälter mitSchnellöffnungsventil
Split-Hopkinson-Tension-Bar
Strain rate: 500 s-1 – 10000 s-1
Temperature range: 93 K – 1273 K
Projectile speed: 2,5 m/s – 50 m/s
Projectile mass: m = 3,15 kg
GewedaProf. El-Magd
Joke Projectile Input rodTensile specimen
Output rod
Tube Cover with airconnection
Air cylinder withquick release valve
Lager Lager Probe
Temperier-
kammer AusgangsstabEingangsstab
Rohr
Preßluftbehälter
Projektil
Auffangbehälter Collection bagSample
Input rod Output rod
Tube
Projectile
Air cylinder
Temperaturechamber
Bearing
BearingBearing
Bearing
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Material law for high strain rate deformation
Source: Diss-Brodmann
dt B K a B K
k n
n
ad f
)(1
400
500
600
700
800
0 0.2 0.4 0.6 0.8
d / dt =5010 s
-1
4889 s-1
4350 s-1
4294 s
-1
3450 s-1
3439 s-1
2558 s-1
2529 s-1
0.001 s-1
o : r
K = 960 MPaB = 0.031n = 0.182 / K = 6.25·10
-6s
A A7075 T7351Druckversuche
w a
h r e
S p a n n u n g ,
M P
a
True plastic strain, -
Lines: CalculationSymbols: experiments
Pressure tests
T r u e S
t r e s s ,
M P A
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Outline
Summary and Outlook9
Applications of the FE cutting simulation at the WZL 8
Criteria for the evaluation of FE software 7
Friction and wear models for the FE cutting simulation6
Damage models for the FE cutting simulation and multiphase simulation 5
Constitutive material laws for the FE cutting simulation4
CAD modelling for the FE cutting simulation3
Requirements of the FE cutting simulation2
Introduction 1
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Failure mechanisms
Source: Diss-Abouridouane
Loading type
Shear stress Tensile stress
TiAl6V4
20 µm 20 µm
Shear lokalisation model
(Imperfections theory)
Pore growth model
(Hancock-Mackenzie)
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Damage modelling for the FE cutting simulation (ductile fracture)
Macro mechanical failure models
– Equivalent stress/ strain model: Dσ = σv,f / Dε = εv,f
– Gosh-Model: DGosh
= (1+σ2
/σ1
) σ1
2
– Ayada-Model: dD = (σm/σv) dεv
Micro mechanical failure models (Pore growth models)
– Hancock-Mackenzie-Modell
– Gurson-Tveergard-Needleman-Model
– Johnson-Cook-Model
Source: Diss-Abouridouane
mf 1 2 3 4 5
v 0 m
σ ε Tε = D + D exp -D 1+ D ln 1+ Dσ ε T
mf n
v
σ3ε = ε + α exp -
2 σ
2
2V m1 1
V,M V,M
σ 3σ0 = + 2fq cosh - 1+ q f
σ 2σ
s
0s
E
εf
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Failure limit at tensile stress (r: Notch radius)
Source: Diss-Abouridouane
0
0.5
1.0
1.5
0 0.5 1.0 1.5 2.0 2.5
glattr = 1.2 mmr = 0.8 mmr = 0.4 mmr = 0.02 mm
TiAl6V4, = 200°Cdynamisch
f
= 0.09+3.54*exp(-2.61*sm
/sv
)
0
0.5
1.0
1.5
0 0.5 1.0 1.5 2.0 2.5
glattr = 1.2 mmr = 0.8 mm
r = 0.4 mmr = 0.02 mm
TiAl6V4, = 200°Cquasistatisch
f = 0.09+5.2*exp(-2.35*s
m/s
v)
Mehrachsigkeit sm
/sv
l o k a l e p l a s t i s c h e B r u c h - V e r g l e i c h s d e h n
u n g f
0
0.2
0.4
0.6
0.8
1.0
0 0.5 1.0 1.5 2.0 2.5
glattr = 1.2 mmr = 0.8 mmr = 0.4 mmr = 0.02 mm
TiAl6V4, = 20°Cquasistatisch
f = 0.05+2.89*exp(-2.35*s
m/s
v)
0
0.2
0.4
0.6
0.8
1.0
0 0.5 1.0 1.5 2.0 2.5
glattr = 1.2 mmr = 0.8 mmr = 0.4 mmr = 0.02 mm
TiAl6V4, = 20°Cdynamisch
f = 0.05+2.33*exp(-2.49*s
m/s
v)
L o c a
l p
l a s
t i c
f a i l u
r e - e q u
i v a
l e n
t s t r e
s s ε
f
Multiaxiality
dynamic
dynamicquasi-static
quasi-static
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Criteria for chip formation
Geometrical separationcriterion
Separation whenthe cutting edge falls below acritical distance dcr to thenext workpiece node
Without a specificseparation criterion
Separation throughcontinuous remeshing forductile material behavior
Physical separation criterion
Separation while exceedingan defined, maximumequivalent stress or atpredefined maximumtensions
Werkzeug
vc
As
Bs
Cs
DsEs
Hs,w Gs,w Fw Ew Dw Cw Bw
X X
Schnittebene
Fs
I
IKR
Trenn-kriterium
Werkzeug
vc
As
Bs
Cs
DsEs
Hs,w Gs,w Fw Ew Dw Cw Bw
X X
Schnittebene
Fs
I
IKR
Trenn-kriterium
Werkzeug
As
Bs
Cs
Ds
Es
Hs,w Gs,w Fs,w Ew Dw Cw Bw
X X
dcr
dSchnittebene
vc
Span
Werkzeug
As
Bs
Cs
Ds
Es
Hs,w Gs,w Fs,w Ew Dw Cw Bw
X X
dcr
dSchnittebene
vc
Span
Distorted gridtopology
New networkedgrid topology
Tool Tool
Tool
Separationcriterion
Tool
Chip
Sectional plane
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Chip separation - without chip separation criterion by remeshing
Old Mesh
Elements are highly distorted
New Mesh
Remeshing leads to better mesh
Span Werkzeug a) b)Chip Tool
New Mesh
Microstructure-based 3D modeling for micro cutting AISI 1045
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0
300
600
900
1200
0 0.5 1.0 1.5 2
True plastic strain , , -
T r u
e s t r e s s
M P a
CompressionTension
Ø 0.1x0.1 mm
Shear
0.1x0.1x0.1 mmQuasi-static
FE model
Experiment
Tension stress
Compression stress
Shear stress
Concept of the Representative Volume Element (RVE)
Macrostructure
Microstructure
RVE
Representativeness check of the RVE Capture of all significant microstructuralinhomogeneities
Pearlite
Cross section Longitudinal section
Two-phase 3D FE model(0.1 x 0.1 x 0.1 mm)
Ferrite
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Microstructure-based 3D FE model: Validation
50
40
30
20
10
N22%
3% 19%7%
M i x t u r e m o
d e l
d = 1 mm, vc = 35 m/min, f = 12 µm
Test
Nmm
I s o
t r o p
i c m o
d e l
I s o
t r o p
i c m o
d e l
M i x t u r e m o
d e
l
Test
00
4
8
12
16
20Feed force
TorqueChip
Drill
Workpiece
Microstructure
Chip form
Holes
Workpiece
Drill
FerritePearlite
Two-phase FE model formicro drilling in
ferritic-pearlitic carbon steel C45N
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Influence on the formation of residual stresses
The complete coupling of the various parameters influencing the formation of residualstresses has not been done
Source: Preckel
Metallurgical
state
Thermal
state
MechanicalState
Thermally-induced phasetransformation
Heat gain
Residual stresses
Input parameters for thermo-mechanical-metallurgic simulation
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(residual stresses)
Microstructure, initial state of texture
Time dependent thermo-mechanical state of stress
Mathematical approach for the diffusion controlled transformation kinetics: Advanced Johnson-Mehl-Avrami-Kolmogrow-model, 1940
Mathematical approach for the phase transformation without diffusionKoistenen-Marburger-relation, 1959
TTT/TTA-diagram for not isotherm conditions (high strain rate)
Thermal material properties, depending on temperature (cp, l r …)
Mechanical material properties, depending on temperature (E, u a ...)
Elasto-viscoplastic material law
Consideration of grain orientation, texture, micro damages, inclusions, etc.
Description of the damage behavior on high strain rates Tool wear model
O
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Outline
Summary and Outlook9
Applications of the FE-cutting-simulation at the WZL 8
Criteria for the evaluation of FE software 7
Friction and wear models for the FE cutting simulation6
Damage models for the FE cutting simulation and multiphase simulation 5
Constitutive material laws for the FE cutting simulation4
CAD modelling for the FE cutting simulation3
Requirements of the FE cutting simulation2
Introduction 1
Friction model for FE cutting simulation
Th l l d t th k i d t l t t
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Thermal load at the workpiece and tool contact zone
1 Primary shear zone2 Secondary shear zone at rake face
3 Jam and separation zone4 Secondary shear zone at flank face5 Run-up deformation zone
Structure in the workpiece
Cutting edge
Tool
Tool flankCutting surface
Shear edge
Structure in the chip
2
vc
1
5
3
4
600
700
650
600
400450500
300 310
380 ºC13080
50030
Workpiece
chip
tool
Material: steelElastic limit: kf = 850 N/mm
2 Cutting material: HW-P20Cutting velocity: v
c
= 60 m/minChip thickness: h = 0,32 mmRake angle: o = 10º
Distribution of temperature in the contact
zone(according to Kronenberg
Friction model for FE cutting simulationD f ti t th k i d t l t t
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Deformation at the workpiece and tool contact zone
Turning tool
Shear zone
0,1 mm
Material: C53E
Cutting material: HW-P30Cutting velocity.: vc = 100 m/minChip section: ap x f = 2 x 0,315 mm
2
Cutting edge1 Primary shear zone2 Secondary shear zone at rake face
3 Jam and separation zone4 Secondary shear zone at flank face5 Run-up deformation zone
Structure in the workpiece
Cutting edge
Tool
Tool flankCutting surface
Shear edge
Structure inthe chip
2
vc
1
5
3
4
Friction model for FE cutting simulationM h i l t t th k i d t l t t
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Mechanical stress at the workpiece and tool contact zone
,
Normal stress:
Shear stress:
Tool
According to Oxley and Hatton
Contact zone
1 Primary shear zone2 Secondary shear zone at rake face
3 Jam and separation zone4 Secondary shear zone at the flank face5 Run-up deformation zone
Structure in the workpiece
Cutting edge
Tool
Tool flankCutting surface
Shear edge
Structurein the chip
2
vc
1
5
3
4
Friction model for FE cutting simulation
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k m R
N R s
Friction model for FE cutting simulation
Coulomb friction model :
Shear friction model:
with
Continuous passover from dynamic friction(Coulomb) to static friction (shear):
Z.B.: Usui-model
τR – shear stress from friction
s N – normal stress
k – yield stress in shear according to Mises
k f – yield stress according to Misesµ, m – friction coefficients
Coulomb friction
Shear friction
reality
Orowan / Özel
UsiuShaw /Wanheim and Bay
reality
N s
N s
R
R
3
f k k
= 1 − exp(−
)
Static frictionDynamic friction
Wear model for FE cutting simulationDifferent types of wear at the cutting blade and wear mechanisms
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Different types of wear at the cutting blade and wear mechanisms
Sliding mechanisms Not-gliding mechanisms
Abrasion Adhesion Delamination Diffusion electrochemical Oxidation
Cutting
edge
Edge chippage
Crater wear
Flank abrasion
Oxidation notch
Flank wear
Crater wear
Built-up edge
Tool
Flank
Cutting-surface
Workpiece
Chip
Wear model for FE cutting simulation
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Wear model for FE cutting simulation
Tool life acc. to Taylor: Tool life acc. to Hasting:
B
AT
v
k
c C v T
T = tool lifeu = temperature
k, A, B = constantCv = T für vc = 1 m/min
Empirical tool wearmodels
Physical tool wearmodels
Tool wear modelling
Differentialwear modelsTool life equations
Model acc. to Usui: Model acc. to Takeyama:Model acc. to Archard:
H
S F K
dt
dV
3
)T
C(
1chn
2
eCvσdt
dV R
E
eDv Gdt
dV c
dV/dt: wear-volume-rate
H: hardnessF: mechanical loadS: cutting length
K, C1, C2, G, D: constant
sn: normal stressVch: chip sliding speedu: temperature
Abrasion + Diffusion Adhesion
Adhesion / Abrasion
Object boundary conditions
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Boundary Conditions
Inter Object Conditions Environment Object ConditionsObject Conditions
Tool
Workpiece
2D FEM Cutting Model
Object boundary conditions
Object boundary conditions
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Boundary Conditions
Inter Object Conditions Environment Object ConditionsObject Conditions
Friction Heat Transfer
MovementTool
=
Object 1
Workpiece = Object 2
2D FEM Cutting Model
Object boundary conditions
Boundary conditions
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Boundary Conditions
Object Conditions
Friction Heat Transfer
Movement
Workpiece = Object 2
2D FEM Cutting Model
FR
FN
Self Contact (Chip vs. Workpiece Surface)
FR: Friction Force
FN: Normal Force
Boundary conditions
Object boundary conditions
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Boundary Conditions
Object Conditions
Friction Heat Transfer
Movement
Cutting
speed vc in
x-direction
x
y
Tool is fixed in x- and y-direction!
Tool
Workpiece
The workpiece is moving in
x-direction with the prescribed
velocity vc. It is fixed in y-direction
Object boundary conditions
Object boundary conditions
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Boundary Conditions
Object Conditions
Friction Heat Transfer
Movement
Tool
Workpiece
Heat Transfer
Object boundary conditions
Object boundary conditions
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Boundary Conditions
Inter Object Conditions Environment Object Conditions
Friction Heat Transfer
Object Conditions
Tool
Heat TransferFR
FN
j y
FN
FN
Object boundary conditions
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Boundary Conditions
Inter Object Conditions Environment Object Conditions
Heat Transfer
Object Conditions
Heat Convection Heat Emissivity
Tool
Heat Radiation
Heat Convection
Heat exchange withenvironment
j y
Outline
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Seite 42 © WZL/Fraunhofer IPT
Summary and Outlook9
Applications of the FE-cutting-simulation at the WZL 8
Criteria for the evaluation of FE software 7
Friction and wear models for the FE cutting simulation6
Damage models for the FE cutting simulation and multiphase simulation 5
Constitutive material laws for the FE cutting simulation4
CAD modelling for the FE cutting simulation3
Requirements of the FE cutting simulation2
Introduction 1
FEM software solution for FEM simulation of the cutting process
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g
MSC.Marc
Criteria for the evaluation of FE software
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Source: SIMULIA, ANSYS, LSTC, TWS, SFTC, COMSOL
Criteria
Programm ABAQUS ANSYS/ LS-DYNA AdvantEdge DEFORM COMSOL
Creation of geometries Creation of geometriesand import of CAD data Import of CAD data Creation of simplegeometries andimport of CAD data
Creation of simplegeometries andimport of CAD data
Creation of simplegeometries and importof CAD data
Material catalogue No, has to be defined Yes, expandable Yes, wide Yes, new catalogueimportable
yes
Element type Every type Every type tetrahedron,rectangle
tetrahedron, rectangle Every type
Time integration Implicit / Explicit Implicit / Explicit Explicit Implicit Implicit
Remeshing routine none none yes yes yes
use general general cuttingprocess Deforming process general
Influence on simulation
computation
High, by Python Possible, by Fortran no High, by Fortran High, by Matlab
parallelisation possible possible possible possible possible
Usage at the WZL Eigenfrequency analysis,elast. Tool behavior,elasto-plastic componentbehavior
no no Cutting simulation Thermo-elasticdeformation
Outline
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Summary and Outlook9
Applications of the FE cutting simulation at the WZL 8
Criteria for the evaluation of FE software 7
Friction and wear models for the FE cutting simulation6
Damage models for the FE cutting simulation and multiphase simulation 5
Constitutive material laws for the FE cutting simulation4
CAD modelling for the FE cutting simulation3
Requirements of the FE cutting simulation2
Introduction 1
Applications of the FE cutting simulation at WZL
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Research focus at the WZL:
Process optimization
Material modelling
Drilling Milling
2D, e.g. Planing
Turning
Simulation of the high speed cutting process
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Cutting speed: vc = 3000 m/min
Feed: f = 0.25 mm
vc
Simulation of the high speed cutting process
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Simulation of the high speed cutting process
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Simulation of the high speed cutting process
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Simulation of the high speed cutting process
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Simulation of the high speed cutting process
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Simulation of the high speed cutting process
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Comparison of different thermal properties of the tools
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Orthogonal turning 2D (vc = 300 m/min, f = 0,1 mm, C45E)
Ceramic-InsertThermal conductivity l = 35 W/mK
WC-InsertThermal conductivity l = 105 W/mK
Tmax = 650°C Tmax = 550°C
3 6TiN 570
Temperature distribution in dependency of the coating andits thickness
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533
3 µm 6 µm
TiN Al2O3
TiN
6 µm 0
510
520
530
540
550
560
570
C a
l c u
l a t e d t e m p e r a
t u
r e a
t t h e
c h i p b o
t t o m
s i d e
T S p
/ ° C
Heat conductivity:HW: 100 W/(mK)TiN: 26,7 W/(mK)
Al2O3: 7,5 W/(mK)
Material: C45E+NTensile strength: Rm = 610 N/mm²
557
539
509
539
Heat capacity:HW: 3,5 J/(cm³K)TiN: 3,2 J/(cm³K)
Al2O3: 3,5 J/(cm³K)
Cutting Material: HW-K10/20
TiN3 µm
TiN6 µm
HW TiN6 µm
Al2O36 µm
CoatingThickness
Tsp
FE-Based calibration process for tool wear model
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. - - -
vc = 250 m/min vc = 200 m/min vc = 150 m/min
Cutting time t
T o o
l - w e a r
V B
Wear curve
C2
lg C1
1/T
l g { w / (
n V S
) }
l g { w / (
n V S
) }
Regression analysis FE-analysis
Temperature
Normal-
tension
Sliding speed
dW/dt
Machining experiments
Determination of thespecific materialparameters C1 and C2
)T
C(
1chn
2
eCvσdt
dW
t = 1 mint = 4 min
t = 6 mint = 10 min
Modeling
2D FE model for tool wear simulation
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V
e r s c h l e i ß V B [ m m ]
Tool life
Phase 3: Methodology for moving the nodes at the rake face
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node square element
Rake
Tool
Tool
Workpiece vc
Chipvc
Phase 3: Methodology for moving the nodes at the flank face
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nDn A nB nC
A B C D
nDn A nB nC= = =Workpiece
Flank
node square element
Tool5 µm
Verification of the tool wear simulation for the flank wearvc = 150 m/min, f = 0.06 mm, ap = 1 mm, dry
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0
0,02
0,04
0,06
0,08
0,1
0 5 10 15 20 25 30 35
Experiment
Simulation
F
l a n k w e a r w i d t h
V B [ m m ]
Cutting time t [min]
eff = -26°
0 = 7°Time:
5 min
Tool
Time:
15 min
Time:
25 min
Time:
35 min
93 µm
Setup of a 3D FE model
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15°
7,5°
15°
Setup of a 3D FE model - specification of the tool holder
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Z
YX
RotZ=6°
Rotx=-6°
Tool ho lder:
Kennametal
ID: PCLNL252M12 F4 NG27
Rake ang le 0 = -6°
Relief ang le 0 = 6°
Tool in cl inat ion ang le ls = -6°
Tool c utt ing edge angler = 95°
Setup of a 3D FE model - Tool position
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f
a p
r workpiece
r tool
r tool = r workpiece
Setup of a 3D FE model - Mesh of the workpiece
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3D simulation
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Workpiece: AISI 1045
Tool: K10
vc = 300 m/minf = 0,1 mm
Cutting Force Fc
Temperature
3D FE model - Post processing
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Temperature (°C)
For better visualization
the tool is hidden
3D FE model - Post processing
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Temperature (°C)
For better visualization
the tool is hidden
3D FE model - Post processing
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Strain distribution
For better visualization
the tool is cut
Strain
3D FE model - Post processing
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Strain Ratedistribution
For better visualizationthe tool is cut
Strain Rate
Models of cutting inserts
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Roughing geometry
CNMG120408RN
Finishing geometry
CNMG120408FN
Simulation of the chip flow
Material:Chip breaker FNChip b reaker RN
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Material:
C45E+N
Cutting material:
HC P25Insert:
CNMG120408
Insert geometry:
Cutting velocity.:vc = 300 m/min
Feed:
f = 0,1 mm
Depth of cut:
ap = 1 mm
Dry cutting
a0 0 lS r 6° -6 ° 95°-6°
90°
a0 0 lS r 6° -6 ° 95°-6°
90°
Simulation of the chip flow
Chip breaker FNChip b reaker RNMaterial:
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a0 0 lS r 6° -6 ° 95°-6°
90°
a0 0 lS r 6° -6 ° 95°-6°
90°
Material:
C45E+N
Cutting material:
HC P25Insert:
CNMG120408
Insert geometry:
Cutting velocity.:vc = 300 m/min
Feed:
f = 0,1 mm
Depth of cut:
ap = 1 mm
Dry cutting
Comparison of simulation and real chip flow
CNMG120408
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Chip breaker NF
HC-P15
r = 95°
n = -6°
ls = -6°
C45E+N
ap = 1,9 mm
f = 0,25 mm
vc = 200 m/min
dry
vc
vf
Drilling: Modelling of size effects
Task:
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Development of a consistent 3D computation model based on the FE method
for scaling the drilling process in consideration of size effects
Reibung
Werkstück
Bohrwerkzeug
PlastischeVerformung
Stofftrennung
Reibung
f
n
drill
FrictionFriction
Workpiece
Separation of materialPlasticdeformation
Previous results: 3D FE computation model for d = 1 – 10 mm
Material modeling Measuring the drill geometry FE boundary conditions
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Tool FEM-Model)T,,( ss
Strain hardening
Plasticity
Damping mechanism
Relaxation
Dynamic strain ageing
Temperature influence
Loss of cohesion
Failure mechanism
Cutting parameters
Tool: rigid / elastic
Friction law
Heat transfer
Element size
Number of elements
Remeshing strategy
Degree of freedom
FE-Simulation of the drilling process with d = 1 mm (DEFORM 3D)
Machining conditions
Workpiece material: C45E+N
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Tool:rigidnumber of elements: 90 000
Workpiece:visco-plastic (LFW-material law),temperatur fixed at boundary nodesnumber of elements: 100 000
Contact:
coulomb friction ( =0,2)heat transfer (conduction & convection)
Computing time and drilling depth:2000 h; 0.18 mm (70% of the major cutting edge)
Boundary Conditions
Workpiece material: C45E+NTool material: HW-K20Cutting speed: 35 m/minFeed: 0.012 mm/UFeed velocity: 133 mm/minCooling lubricant: none
Verification of the chip formation
Experimental chip formation Chip formation in the simulation
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Workpiece material: C45E+N
Cutting tool material: HW K20
Cutting speed:
Feed:
vc = 35 m/min
f = 0.012 mm
Model validation: Scaling effect of the chisel edge length
6
6
32 Workpiece:
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0
1
2
3
4
5
1 2 3 4 5 6 7 8 9 10
kf,max
= 2 * Fz,max
/ (d * f )
Bohrerdurchmesser d [mm]
s p e z i f i s c h e V o r s c h u b k r a f t k f , m a x
[ k
N / m m
2 ]
0
1
2
3
4
5
1 2 3 4 5 6 7 8 9 10
kf,max
= 2 * Fz,max
/ (d * f )
Bohrerdurchmesser d [mm]
s p e z i f i s c h e V o r s c h u b k r a f t k f , m a x
[ k
N / m m
2 ]
Experiment
20
22
24
26
28
30
1 2 3 4 5 6 7 8 9 10
Durchmesser d [mm]
V e r h ä l t n i s
( d Q
/ d ) [ % ]
Feed:f = 0,012 * d
Cutting speed:vc = 35 m/min
Corner radius:r n = 4 µm
Cutting tool material:
HW-K20
Workpiece:C45E+N
Cooling:None
Simulation
Diameter d [mm]
S p e c
i f i c f e e d
f o r c e
k f , m a x
[ k N / m m
2 ]
Drill diameter d [mm]
Model validation: Temperature at the main cutting edge (center)
400
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Cutting speed: vc = 35 m/min Workpiece: C45E+N
Feed: f = 0,012 * d Cutting tool material:HW-K20Coolant: None Rounding: r n = 4 µm
d = 3 mm
0
100
200
300
1 3 8 10
Diameter d [mm]
T e m p e r a
t u r e a
t t h
e
m a
j o r c u
t t i n g e
d g e T
[ ° C ]
Experiment
Simulation
Modelling of the face milling process
Materials and cutting parameters:
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Work material: Quenched and tempered AISI 1045 (normalized)
Tool material: Coated WC
Cutting parameters:
– No. of teeth: z = 4
– Diameter: D = 32 mm
– Engagement angle: φ A – φE = 180°
– Feed: f = 0.5 mm
– Feed per tooth: f Z = 0.125 mm
– Depth of cut: ap = 0.8 mm
– Tool leading angle: κr = 90°
– Tool inclination angle: λ = -5°
– No. of rev.: n = 2250 min-1
p a
z
Workpiece
Tool
r
n
f
f v
Modelling of the face milling process
A i l d di l k l
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Axial and radial rake angle:
Axial rake angle γaxial = 9°
Radial rake angle γradial = 5°
γaxial
r tool = r Workpiece
Depth of cut ap
Feed f
Modelling of the face milling process
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f
a p
r Workpiece
r Tool
tool Workpiece
View
Feed f
Workpiece geometry
1. Simplified
Finding the best workpiece geometry
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1 2
p
workpiece
geometry
2. Simplified work-
piece geometry
3. Simplified work-
piece geometry
Simulation results for the 1. simplified workpiece model
Rough elements within thework piece
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back
Simulation of chip formationnot accurate enough
Final workpiece geometry
Left Right
Simulation results for the 3. simplified workpiece model
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Left Right
Chip formation for the left
side of the work piece:
Results for the face milling operation
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p
at the beginning very thin
chips are produced chip curling starts for higher
undeformed chip thickness
ExperimentSimulation
Verification of the FE model
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.
Full agreement
FE based sensitivity analysis
Heat capacityVaried inputparameters:
Goal outputparameters:
Cutting force Fc
P i f F
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Thermalconductivity
Heatcapacity
Flowstress
Cutting force
Feed force
Passive force
Temperature
FrictionToolmicro-geometry
Thermal conductivity
Flow stress
Friction coefficient
Tool micro-geometry
pa a ete s pa a ete s Passive force Fp
Feed force Ff
Temperature T
Influence
low
medium
high
Legend
Outline
Introduction 1
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Summary and Outlook 9
Applications of the FE cutting simulation at the WZL 8
Criteria for the evaluation of FE software 7
Friction and wear models for the FE cutting simulation6
Damage models for the FE cutting simulation and multiphase simulation 5
Constitutive material laws for the FE cutting simulation4
CAD modelling for the FE cutting simulation3
Requirements of the FE cutting simulation2
Cutting
simulation
Fixed input
parametert i l t
Benchmark-Analysis
Cutting parameter 1
Outlook:
Benchmark-Analysis to choose the best tool geometry
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#
Determination of thethermomechanical
loadspectrum, chipflow, chip form
Q,
T,Fi,
material parameter,friction coefficients
+
Temp Wear Stress Chipflow
Tool A + - ++ -
Tool B - -- o +
Tool C ++ ++ + +
A B CTool
F l a n
k w e a r
V B
Cutting parameter 1
Cutting parameter 2
Optimised
tool-
and
tool carrier-
geometry
Tool+
A B C
Cutting parameter
vc1, ap1, f 1
1vc2, ap1, f 1
2
Coating+
TiN TiAlN AlO2
Summary
Machining process: System of complex physically coherent operations
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A holistic and comprehensive simulation of the machining has not been achieved with
conventional empirical or analytical approaches
FEM is a promising method for the holistic simulation of machining – High flexibility
– Implementation of various models that describe the aspects of machining
– Complete reproduction of the machining process
The FE cutting Simulation gives good results under the following boundary conditions: – Realistic reproduction of the tools macro/ micro geometry
– Adequate modeling of the thermo mechanical material behavior
– Exact capturing of the boundary conditions (friction, heat transfer, wear , cooling lubricant, damage,micro structure, etc.)
Questions
What are the ranges of temperature, strain and strain rate in cutting operations?
What is the range of strain rate that can be realized by the Split Hopkinson Bar Test?
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What is the range of strain rate, that can be realized by the Split-Hopkinson-Bar-Test?
Name two friction models. What are the advantages and the disadvantgeas of thesemodels?
How is the strain rate effecting the flow stress curve of a material?
What are the demands on a temperature measurement setup which allows the evaluation
of simulation results?
Explain the difference between the orthogonal cutting process and the longitudinal cuttingprocess!
Explain the difference between a plastic and an elastic-plastic flow stress curve!