l08 Fe Modeling Cutting 1

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© WZL/Fraunhofer IPT

Finite Element Simulation of Cutting

ProcessesSimulation 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



Seite 1 © WZL/Fraunhofer IPT

Verification8

Process Modells7

FEM Software Solutions6

Simulation of serrated Chip Formation5

Chip Separation4

Boundary Conditions3

Material Models2

Introduction1

Outline




Introduction




Phases of a Finite Element Simulation

A typical finite element analysis takes place in three phasesfrom the standpoint of the user:

Data preparation with the preprocessor

– defining the geometry,

– meshing, – inputting the material data and

– defining the boundary conditions

Calculation and

Evaluation of the results with the postprocessor – potential sources of error in FE analyses include:

discretization errors from geometry interpolation whenmeshing and interpolation of the state variables,

incorrect input data (e.g. material data, process data,friction conditions),

numerical errors (e.g. in numerical integration)




Verification8

Process Modells7



Chip Separation4


Material Models2

Introduction1

Outline




Conditions in cutting operations

Forces:

100 to 104 N

Stresses:103 N/mm2

Temperature gradient:> 103 °C/mm

Temperatures:≈ 1500 °C

Strain

0,5 * 104 to 0,5 *106 1/s

0,1 to 5

Strain rate




Comparison of strain, strain rate and temperature for differentmanufacturing processes

High demands on the material model for cutting simulations

0,16 - 0,9103 - 1061 - 5Cutting

0,16 - 0,710 - 1020,1 - 0,5Sheet metal forming

0,16 - 0,710 - 1030,1 - 0,5Forging/ Rolling

0,16 - 0,710-1 - 10-22 - 5Extrusion

ThomologaStrain rate / s-1strainManufacturing process

a: T homolog = T / T melting point




Principles of metal forming: Material Laws




Conventional set-ups to determine flow stress curves

tensile test

vw

vw

l0 d

∆

d0

l

l

compression test

d0

u0 t 0

h 0

lubricant

torsion test

z

r

Mt

Mt

l

R

α γ R

adapted from: Kopp

ϕmax 0,8 to 1≈

.

ϕ 10-3

to 103

s-1

≈

ϑ 20 to 1300 °C≈

ϕmax 0,8 to 1≈

ϕ 10-3 to 102 s-1≈

.

ϑ 20 to 700 °C≈

ϕmax 5≈

ϕ 10-4 to 30 s-1≈

.

ϑ 20 to 1300 °C≈




Split-Hopkinson-Bar-Test

projectile

input bar output bar

specimen

v >> 50m/s

.ϕ to 104 s-1≈

ϑ to 1200 °C≈

tempered chamber

source: LFW, RWTH Aachen

strain gagesstriker bar




Flow stress curves

0

0

800

1400

0,5

10

5000

10000

strain

F l o w

s t r

e s s k f

1/s

N/mm2parameter:kf = f (ϕ, ϕ)ϕ, ϕ)ϕ, ϕ)ϕ, ϕ)ϑϑϑϑ = const. = RT

9SMnPb36

00

800

1600

0,5

10

5000

10000

strain ϕ

F

l o w

s t r e s s k f

1/s

N/mm2

source: LFW, RWTH Aachen

Ck45N

strain rate ϕ

strain rate ϕ




Flow stress [Mpa]

strain

Flow stress curves in DEFORM for room temperature




Flow stress [MPa]

strain

Flow stress curves in DEFORM for high temperatures (600°C)




Consitutive material laws for metal cutting

In order to reduce the number of experiments constitutvematerial laws are needed

The constitutive material law has to describe the plasticbehaviour in dependence for a wide range of strain, strainrate and temperature

For the simulation several material models have beendeveloped, which consider strain hardening, strain ratehardening and thermal softening

Most of material laws are of empircal nature

Empirical material laws describe the flow stress as afunction of strain, strain rate and temperature

σ σσ σ Flow stress = f( ε εε ε , d ε εε ε /dt, T)

Empirical material laws contain specific material

constants, which will be determined by regressionanalyses or by the least squares method) based on theexperimental measured flow stress curves




Consitutive material law by Johnson and Cook

( ) ( )( )

−

−−⋅+⋅+=

m

r m

r n

T T

T T / lnC B A 11

0ε ε ε σ &&

temperature function

plasticity viscous damping

Material constants:Reference velocity:

Room temperature:Melting temperature:

0ε &

A, B, n, C, m

T m

T r




Thermal material properties

Thermal Expansion

Defines the material's tendency to grow and shrink

with changes in temperature. Temperature dependent!

Thermal Conductivity

Conduction is the process by which heat flows from a region of higher

temperature to a region of lower temperature within a medium. The

Thermal Conductivity in this case is the ability of the material

to conduct heat within an object's boundary. Temperature dependent!




Thermal material properties

EmissivityThe emissive power (E) of a body is the total amount of radiation emitted

by a body per unit area and time. The Emissivity (e) of a body is the ratio

of E/Eblack body where Eblack body is the emissive power of a perfect black body.

Heat Capacity

The Heat Capacity for a given material is the measure of the change in

internal energy per degree of temperature change. Temperature dependent!




Verification8

Process Modells7



Chip Separation4


Material Models2

Introduction1

Outline




Simulation boundary conditions

Setting the simulation type – Lagrange (non stationary processes)

In lagrangian mode the nodes of the mesh elements are connected tothe material

– Euler (stationary processes)The Eulerian approach considers the motion of the continuum through

a fixed mesh – “Arbitrary Lagrangian Eulerian” method (ALE)

The “Arbitrary Lagrangian Eulerian” method (ALE) is becoming moreand more accepted, which is a combination of the above approachesand permits the mesh a motion independent of the material as long asthe form of the domains under consideration remains the same

Simulation mode

– Deformation

– Heat Transfer

– Coupled thermo-mechanical simulation

Time integration – Implicit

– Explicit




Boundary Conditions

Inter Object Conditions Environment Object ConditionsObject Conditions

Tool

Workpiece

2D FEM Cutting Model

Object Boundary Conditions




Boundary Conditions

Inter Object Conditions Environment Object ConditionsObject Conditions

Friction Heat Transfer

MovementTool

=

Object 1

Workpiece = Object 2






Boundary Conditions

Object Conditions


Movement

Workpiece = Object 2


FR

FN

Self Contact (Chip vs. Workpice Surface)

FR: Friction Force

FN: Normal Force

Boundary Conditions




Boundary Conditions

Object Conditions


Movement

cutting

speed vc

in

x-direction x

y

Tool is fixed in x- and y-direction!

Tool

Workpiece

Workpiece is moving in thex-direction with the prescribedvelocity vc, in the y-direction theworkpiece is fixed





Boundary Conditions

Object Conditions


Movement

Tool

Workpice

Heat Transfer





Boundary Conditions

Inter Object Conditions Environment Object Conditions


Object Conditions

Tool

Heat TransferFR

FN


FN

FN




Normal and shear stress distribution along the rake face

Normal pressure

Adapted from Usui and

Takeyama

Adapted from Zorev Adapted from Oxley and Hatton




Inter Object Conditions - Friction Models




Boundary Conditions

Inter Object Conditions Environment Object Conditions

Heat Transfer

Object Conditions

Heat Convection Heat Emissivity

Tool

Heat Radiation

Heat Convection

Heat exchange withenvironment





Verification8

Process Modells7



Chip Separation4


Material Models2

Introduction1

Outline




Chip separation

chip

X X

cutting plane d

dcr

HS,W GS,W FS,WEW DW CW BW

Tool

AS

BS

CS

DS

ES

vc

AW

ToolX X

cutting plane

HS,W GS,W FW EW DW CW BW

separationcriterion

lKR

lAS

BS

CS

DS

ESFS

vc

AW

Chip separation basedon nodal distances

Chip separation basedon a critical indicator




Cutting Plane

Cutting plane consists out of criticalelements. If one element reaches

predefined separation criterion, theelement will be deleted

Disadvantage: Volume loss of workpiece

Chip separation - Predefined critical elements




Chip separation - Without chip separation criterion by Remeshing

Old MeshElements are highly distorted

New MeshRemeshing leads to better mesh

Span Werkzeuga) b)chip tool

New Mesh




FE-Mesh

Definition of an element type Mesh density can be controlled by:

– Meshing Windows

– Weighting Factors for

Temperature

Strain Strain rate

Curvature

Criteria for calling the remeshing routine:

– Elements are critically deformed – Predefined no. of time steps

– Predefined no. of strokes

Remeshing criteria has to fulfill the following conditions:

– The critical value for the remeshing increases with the

distortion of the mesh – If a remeshing has been conducted the value of the

remeshing criteria will be reset




Definition of element type




Verification8

Process Modells7



Chip Separation4


Material Models2

Introduction1

Outline




Simulation of serrated chip formation

continuous chip formation segmented chip formation discontinuous chip formation

Ernst, 1938

Consistent strain distribution

Continuous metallographicstructure

Moderately different strainsover the chip dimensionscaused by dynamical loadsof mechanical and thermalnature

distinct segments of the chip’stop

Very different strains over thechip dimensions caused bydynamical loads ofmechanical and thermalnature

discontinuous chip segments




Simulation of serrated chip formation

simulation of serrated chip caused by deformation localisation based on modifiedmaterial characteristics

simulation of serrated chip caused by crack initiation based on breakage- andcrack hypotheses (e.g. fracture criteria)

combination of both approaches

Serrated chips can be caused by cracks and pores, adiabatic formation ofshear bands or a combination of both mechanisms.

Simulation of serrated chips can be realised by two different approaches:

Deformation localisation based on modified material




characteristics I/II

Chip formation based on manipulated flow stressdata incorporating

strain softening.

rigid-viscoplastic model

cutting edge radius: rβ = 10 µmcutting speed: vc = 25 m/min

material: TiAl6V4

E

f f e c t i v e s t r a i n

0

5

10

σ

ε

0σ

undamaged

damaged

A

B

C

E

deformation

s t r e s s

Deformation localisation based on modified material




characteristics I/II

material:

AlSI 1045

cutting speed:vc = 1000 m/min

feed:

f = 0.1 mm

7,65 7,75 7,85 7,95 8,050

50

100

150

200

feed forceexperiment

7,65 7,75 7,85 7,95 8,05

time / ms

0

50

100

150

200

f o r c e / N

feed forcesimulation

cutting forceexperiment

cutting force

simulation

dφ /dt

6•105 s-1

2•

105

s-1

i ii iii

i: shear initiation

ii: sliding

iii: new segmentation




Crack initiation based on breakage and crack hypotheses

Phase 2.2: Crack Initiation

The accelerated sliding is initialised by acrack on the workpiece material surface

The crack region is characterised by uniaxialprincipal tensile stresses

Cracks can be simulated by failure criteriaconsidering the deformation history applyinga following law

Phase 2.1: Shearing Initiation

The Material Law does not fulfil theconditions in front of the cutting edge

Strain rate hardening (damping) in extremeconditions distorts the calculated results

0 1 2 3 40

1000

2000

3000

5000

Real Plastic Strain

f l o w

S t r e s s a t 1 0 0 ° C

/ ( N / m m ² )

4000 0,001

10000

50000

100000

strain rate / s-1

( )∫ε

=k

0

1,0)max(σC F




First Contact Start of Shearing Crack Initiation Gliding

End of Gliding New Segmentation

M a t e r i a l S p e e d / m / m

i n

0

12,5

25

37,5

50

62,5

75

90

Segmented Chip Simulation reveals periodic sticking zone

Start of Shearing Crack initiation

strain rate




Verification of Segmented Chip Simulation

Theory ofvan Luttervelt & Pekelharing

FEM-Simulation

secondary shear zone(sticking zone)

tertiary shear zone

primary shear zone

cutting time tc / ms cutting time tc / ms

SimulationMeasurement

0,0 0,4 0,8 1,2

r e l a t i v e c u t t i n g f o r c e F c /

b [ N / m m ]

0

100

200

300

400

500

600

700

800

0,0 0,4 0,8 1,2




Verification8

Process Modells7



Chip Separation4


Material Models2

Introduction1

Outline

FEM S f S l i f FEM Si l i f h C i P




FEM Software Solution for FEM-Simulation of the Cutting Process

MSC.Marc

O tli




Verification8

Process Modells7



Chip Separation4


Material Models2

Introduction1

Outline

O th l tti (2D FE d l)




Orthogonal cutting process (2D FE-model)

workpiece

tool

chip

chvr

cvr

If depth of cut ap >> uncut chip thickness h

State of plane strain condition is reached

Simulation of the High Speed Cutting Process




Cutting speed vc = 3000 m/minFeed f = 0.25 mm

vc







Comparison of of different thermal properties of the tools




Orthogonal truning 2D (vc = 300 m/min, f = 0,1 mm, ck45)

Ceramic-InsertThermal conductivity λ = 35 W/mK

WC-InsertThermal conductivity λ = 105 W/mK

Tmax = 650°C Tmax = 550°C

Comparison of of different thermal properties of the tools

Temperature distribution in dependency of the coating andits thickness




533

3 µm 6 µm

TiN Al2O3

TiN

6 µm0

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)

HW: HW-K10/20

TiN3 µm

TiN6 µm

HW TiN6 µm

Al2O3

6 µmcoatingthickness

Tsp

2D FE-model for tool wear simulation




V e r s c h l e i ß V B [ m m ]

Schnittzeit, t [min]

V e r s c h l e i ß m a r k e n b r e i t e ,

V B [ m m ]

tK

VBK

tK+1

∆∆∆∆t = tK+1 - tK

VBK+1

AB



V B [ m m ]

tK

VBK

tK+1

∆∆∆∆t = tK+1 - tK

VBK+1

AB



V B [ m m ]

tK

VBK

tK+1

∆∆∆∆t = tK+1 - tK

VBK+1

AB

Phase 1:

Thermo-mechanicalFE-simulation of the cuttingprocess till steady statesolution is obtained.

Phase 2:

Call of the User subroutineto calculate tool wearwear rate dW/dt x time t

= wear

Phase 3:

Tool geometry updating independence of wear

Wear

VB>VBtool life

Abort

V B < V B t o o l l i f e

Temperatur

)T

C exp(C V dt / W

S n2

1 −⋅⋅⋅=∂ σ

Usui‘s tool wear model:

Weargrowth

(a)

Weargrowth

(a)

Tool wearincrease

VBStandzeitTool life

Phase 4: Methodology for moving the nodes at the rake face




gy g

workpiece vc

tool

vc

Werkzeug

chip

tool

ϕA

B

X

5 µm5 µm

nX

A

B

ABϕ‘

∆W

∆W cos ϕ‘

∆W sin ϕ‘ϕ ϕ‘

X

A

B

ABϕ‘

∆W∆W

∆W cos ϕ‘∆W cos ϕ‘

∆W sin ϕ‘∆W sin ϕ‘ϕ ϕ‘

X

node square element

rake

Phase 4: Methodology for moving the nodes at the flank face




Workpiecevc

Tool

nDnA

nB nC

A B C D

nDnA nB nC= = =workpiece

flank

node square element

Tool5 µm

Results of the tool wear simulation




γ γγ γ eff = -26°

αααα0 = 7°Time:5 min

Tool

Time:

15 min

Time:25 min

Time:35 min

93 µm

Process: Part Turning

Work material: 16MnCr5 (case hardened)

Cutting Speed: vc = 150 m/min

Feed: f = 0,06 mmDepth of cut: ap = 1 mm

Cooling: dry

Verification of the tool wear simulation for the flank wearvc = 150 m/min, f = 0.06 mm, ap = 1 mm, dry




p

0

0,02

0,040,06

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]

γ γγ γ eff = -26°

αααα0 = 7°Time:

5 min

Tool

Time:

15 min

Time:

25 min

Time:

35 min

93 µm

Longitudinal Turning, 3D FE-Model




orthogonal cut

f

vc

major cutting edge

3D turning process

workpiece

ap

f

k

n

vc

major cutting edge

minor cutting edge

created surface

3D simulation needed for the consideration of the workpiece surface

Why 3D modelling?

Cutting process simulation




Turning Drilling Milling

Calculation of the thermo-mechanical tool-load-collectivefor an ideal dimensioning of the tools‘

micro- and macrogeometry

Input and output parameters of a FEA-based cutting model




Workpiece / Tool

geometriesmaterial data

contact conditionsboundary conditionscutting conditions

Input and output parameters of the cutting simulation




Tool

strainstressestemperatures

process forceswear

Chip Formationtemperaturesstressesdeformationsstrain rate

kind of chipchip flowchip breakage

Workpiece / Tool

geometriesmaterial data

contact conditionsboundary conditionscutting conditions

Workpiecestraintemperatures

deformation

burr formationdistortionprospective:residual stresses,

surface qualities,like: roughness,dimensional- and formdeviation

Setup of a 3D FE-Model




15°

7,5°

15°

Setup of a 3D FE-Model - specification of the tool holder




Z

YX

RotZ=6°

Rotx=-6°

Tool holder:

Kennametal ID: PCLNL252M12 F4 NG27

Rake angle γ γγ γ 0 = -6°

Relief angle α αα α 0 = 6°

Tool inclination angle λ λλ λ s = -6°

Tool cutting edge angle κ κκ κ r = 95°

Setup of a 3D FE-Model - tool position




f

ap

rworkpiece

r tool

r tool =r workpiece

Setup of a 3D FE-Model - Mesh of the workpiece




3D Simulation




vc = 300 m/minf = 0,1 mmworkpiece: AISI 1045tool: K10

3D FE-Model - Post Processing




Temperature (°C)

For better visualization

the tool is hidden





Temperature (°C)


the tool is hidden





Strain distribution


the tool is cut





Strain Ratedistribution


the tool is cut

Models of Cutting Inserts




Roughing geometry

CNMG120408RN

Finishing geometry

CNMG120408FN

Simulation of the chip flow

Chip breaker FNChip breaker RN




Material: C45E+N

Cutting material:

HC P25

Insert:

CNMG120408

Insert geometry:

Cutting velocity.:

vc = 300 m/min

Feed:

f = 0,1 mm

Depth of cut:

ap = 1 mmDry cutting

Chip breaker FN Chip breaker RN

α0 γ 0 λS κ r6° -6 ° 95°-6°

ε

90°

α0 γ 0 λS κ r6° -6 ° 95°-6°

ε

90°

Simulation of the chip flow

Chip breaker FNChip breaker RN




α0 γ 0 λS κ r6° -6 ° 95°-6°

ε

90°

α0 γ 0 λS κ r6° -6 ° 95°-6°

ε

90°

Chip breaker FN Chip breaker RN

Material: C45E+N

Cutting material:

HC P25

Insert:

CNMG120408

Insert geometry:

Cutting velocity.:

vc = 300 m/min

Feed:

f = 0,1 mm

Depth of cut:

ap = 1 mmDry cutting

Comparison of simulation and real chip flow




CNMG120408Chip breaker NF

HC-P15

κ r = 95°

γ n = -6°

λs = -6°

C45E+N

ap = 1,9 mm

f = 0,25 mm

vc = 200 m/min

dry

vc

vf

Drilling: Modelling of size effects

Task:




Task:

Development of a consistent 3D-calculation-model based on the FE-method

for scaling the boring process in consideration of size effects

Reibung

Werkstück

Bohrwerkzeug

PlastischeVerformung

Stofftrennung

Reibung

f

n

drill

frictionfriction

work piece

separation of materialplasticdeformation

Previous results: 3D FE calculation model for d = 1 – 10 mm

Material modeling Measuring the drill geometry FE boundary conditions




g g g y y

Tool FEM-Model)T,,( εεσ=σ &

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

Elementsize

Number of elements

Remeshing strategy

Degree of freedom

FE-Simulation of the drilling process with d = 1 mm (DEFORM3D)

Machining conditions




Tool:rigidnumber of elements: 90 000

Workpiece:visco-plastic (LFW-material law),temperatur fixed at boundary nodesnumber of elements: 100 000

Contact:coulomb friction (µ =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




workpiece material: C45E+N

cutting tool material: HW K20

cutting speed:

feed:

vc = 35 m/min

f = 0.012 mm

Model evaluation: scale efect of the chisel edge length

66




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

32

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:rn = 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 major cutting edge (center)




Cutting speed: vc = 35 m/min Workpiece: C45E+NFeed: f = 0,012 * d Cutting tool material:HW-K20Coolant: none Verrundung: rn = 4 µm

d = 3 mm

0

100

200

300

400

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:




Work material: Quenched and tempered AISI 1045 (normalized)

Tool material: coated WC

Cutting parameters:

tool:

no. of teeth: Z = 4

diameter: D = 32 mm

process:

Engagment angle: φA – φE = 180°

feed f = 0.5 mm

feed per tooth: fZ = 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

κ

pa

z

Work piece

tool

r

n

f

f v





Axial and radial rake angle:

• axial rake angle γaxial = 9°

• radial rake angle γradial = 5°

γ axial

Depth of cut ap





f

ap

rWork piece

r tool

r tool = rWork piece

View

Feed f

Work piece geometry

Finding the best work piece geometry




1 2

1. Simplifiedwork piecegeometry

2. Simplified work

piece geometry

3. Simplified workpiece geometry

Simulation results for the 1. simplified work piece model

rough elements within the

k i




back

work piece

simulation of chip formationnot accurate enough

Final work piece geometry

l f i h

Simulation results for the 3. simplified work piece model




left right

Post Processing for the face milling operation




Chip formation for the left

side of the work piece:

Results for the face milling operation




side of the work piece:

at the beginning very thinchips are produced

chip curling starts for higher

undeformed chip thickness

ExperimentSimulation

Results for the face milling operation




.

Full agreement

ExperimentSimulation

Introduction1

Outline




Verification8

Process Modells7



Chip Separation4


Material Models2

simulation experiment

Verification of the FE-model




comparison

simulation experiment

m a x . p r i n c i p l e s t r e s s

toolchip

workpiece

primaryshear zone

0.05 mm

cutting temperaturescutting forces

chip geometry

cutting temperaturescutting forces

chip geometry

Temperature measurment




technical specifications

temperature range: app. 250 -1200 °C

maximum time resolution: 2 ms

measured temperature independent of surface emissivity

workpiecechipfiber

Temperature measurement by a two-color pyrometer




technical specifications

temperature range: app. 250 -1200 °C

maximum time resolution: 2 ms

measured temperature independent of surface emissivity

insert

chip

measuring spot

quartz fiber(∅∅∅∅ 0.26 mm)

0.5 mm

fiber

major

cuttingedge

aluminium steel / titaniumfeed 0 25 mm 0 1 mm u r e

Combination of temperature and force measurement




a u u stee / t ta ufeed 0,25 mm 0,1 mmdepth of cut 2 mm 1 mm

0

100

200

300

N

500

C u

t t i n g f o r c e F c

C h

i p t e m p e r a t

Cutting speed

Alternative measurement position - workpiece surface




°C

200

300

400

500

600

700

0 20 40 60 80 100

T e m p e r a t u r e

Cutting speedm/s

distance to cutting edge 1 mm

4.5 mm

measuring point

quartz fibre

Positioning of the measurement spot




Alternative measurement position - top of the chip




cementedcarbide tip

quartz fibre

measuring point

cutting insert

1000

Alternative measurement position - top of the chip

quartz fibre




°C

400

600

800

1000

0 1000 2000 3000 4000 5000 6000

T e m p e r a t u r

Schnittgeschwindigkeitm/min

HartmetallspitzeOptik

cementedcarbide tip

quartz fibre

measuring point

cutting insertcutting speed

t e m p e r a t u r

e

opticcemented carbide tip

600 r a t u

r eSimulation Experiment

Force Measurement




400

[N]

200

100

500

0

Cutting force Fc

Experimentvc = 3000 m/min

Simulationvc = 3000 m/min

Cutting force Fc

0

200

400

0 2000 4000 6000

Cutting speed vc [m/min]

C h i p t e m p e

[ ° C ]

AA7075f = 0,25 mmap = 2 mm

Verification of the simulated chip formation by in-situ photography




microscope

workpiece

light barrier

tool tool

workpiece (etched)

vc

• in-situ photography of the orthogonal cutting process, suitable for all materials

• cutting speed up to vc = 2000 m/min realized

• double exposure -> two images in a defined time range down to 4 mikroseconds-> to analyse the chip flow, chip breakage and chip velocitiy vch

Discontinuous cut Continuous cut

vc,max = 5000 m/minf free

In-situ photography of chip formation - realised setups




s

e t u p 2

r o t . w o r k p i e c e

+ etched workpiece+ force and temperature

measurement

+ etched workpiece+ measurement of forces

- no temperaturemeasurement

s e t u p 1

r o

t . t o o l

+ force and temperaturemeasurement

+ real world process- no etched workpiece

s e

t u p 3

r o t . w

o r k p i e c e

f = freeap = free

workpiece = freetool = free

workpiece: AISI1045

Results of in-situ photography - chip geometry, first image




feed: f = 0,1 mm

depth of cut: ap = 1 mm


magnification: 100

shear angle Φ = 28°

lenth of contact zone: 0.2064 mm

thickness of chip root: 0.1013 mm

maximal thickness of chip : 0.123 mm

minimal thickness of chip : 0.056 mm

depth of chip root: 0.041 mm

workpiece: AISI1045

Results of in-situ photography - chip geometry, second image




feed: f = 0,1 mm



magnification: 100


lenth of contact zone: 0.358 mm

thickness of chip root: 0.155 mm

minimal thickness of chip : 0.061 mm

maximal thickness of chip : 0.112 mm

depth of chip root: 0.073 mm

0,5 mmworkpiece: AISI1045

feed: f = 0,1 mm

Results of in-situ photography - chip geometry (Dt = 40 µs)




vc = 460 m/min

vc = 515,5 m/min

vc = 522,1 m/min

,



magnification: 100


change in shear angle∆F = 18%

change of the contactlength ∆lk = 40%

workpiece: AISI1045

Results of in-situ photography - compression of the segment




feed: f = 0,1 mm



magnification: 200

workpiece: AISI1045

Results of in-situ photography - shearing of the segment




shearing

feed: f = 0,1 mm



magnification: 200

time difference:∆t = 20 µs

Cutting

simulation

Fixed input

parametermaterial parameter,fi i ffi i

Benchmark-Analysis

cutting parameter 1

i

Outlook:Benchmark-Analysis to choose the best tool geometry




#

determination of thethermomechanical

loadspectrum, chipflow, chip form

Q,

T,Fi,

firction coefficients

+

temp wear stress chipflow

tool A + - ++ -

tool B - -- o +

tool C ++ ++ + +

A B C

tool

F l a n k w e a r V B

cutting parameter 2

optimisedtool-and

tool carrier-geometry

tool+

A B C

cutting parameter

vc1, ap1, f1

1vc2, ap1, f1

2

coating+

TiN TiAlN AlO2

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-

Questions




Test?

Name two friction models. What are the advantages and the disadvantgeas of

this models?How is the strain rate effecting the flow stress curve of a material?

What are the demands on a temperature measurement setup which allows theevaluation of simulation results?

Explain the difference between the orthogonal cutting process and thelongitudinal cutting process

Explain the difference between a plastic and an elastic-plastic flow stress curve!

Determination of flow stress

• depth of cut, ap

• cutting speed, vc• rake angle, g

• conv. flow stress curves, kf

• assumptions of friction conditions, µ• cutting conditions




orthogonal cutting tests

• cutting forces (Fc, Fp)

• chip thickness (hch)

• contact length (lk)

measurement

simulation, e.g. FEM

• forces and stresses• temperature• strain

• strain rate

calculation

comparisson

evaluation of the real flow stress curve

kf = f(strain, strain rate, temperature)

Chip separation criteria and breakage criteria




elastic tool

FE-Mesh




vcf

elastic tool

ideal-plastic

workpiece (AISI 1045)

0.5 mm

x

y

488 °C

Comparison of simulated and measured results




assumption of material properties is suitable

good agreement of simulated and measured temperatures

l08 Fe Modeling Cutting 1

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