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Simulation of chip formation during high-speed cutting Simulation of chip formation during high-speed cutting

Simulation of chip formation during high-speed cutting - PowerPoint Presentation

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Simulation of chip formation during high-speed cutting - PPT Presentation

Authors Christian Hortig and Bob Svendsen Jordan Felkner October 5 2009 Purpose Model and simulate shear banding and chip formation during highspeed cutting Carry out a systematic investigation of size and orientationbased meshdependence of the numerical solution ID: 757566

chip cutting element high cutting chip high element formation speed shear finite strain fea process simulation mesh isbn elements

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Slide1

Simulation of chip formation during high-speed cutting

Authors: Christian

Hortig

and Bob

Svendsen

Jordan

Felkner

October 5, 2009Slide2

Purpose

Model and simulate

shear banding

and

chip formation

during high-speed cutting

Carry out a systematic investigation of size- and orientation-based mesh-dependence of the numerical solution

Finite Element AnalysisSlide3

A Little Vocab

Shear Band: region where plastic shear has taken place

Adiabatic Shear Banding: shearing with no heat transfer

Mechanical dissipation dominates heat conduction

Mesh: the size and orientation of the elementSlide4

Why is this Important?

Cutting forces

Shear banding represents the main mechanism of chip formation

Results in reduced cutting forces

Tool design

Other technological aspectsSlide5

References

[1] M.

B¨aker

, J.

R¨osier

, C. Siemers, A finite element model of high speed metal cutting with adiabatic shearing,

Comput

.

Struct

. 80 (2002) 495–513.

[2] M.

B¨aker

, An investigation of the chip segmentation process using finite elements, Tech. Mech. 23 (2003) 1–9.

[3] M. Baker, Finite element simulation of high speed cutting forces, J. Mater. Process. Technol. 176 (2006) 117–126.

[4] A. Behrens, B.

Westhoff

, K.

Kalisch

, Application of the finite element method at the chip forming process under high speed cutting conditions, in:

H.K. T¨onshoff, F. Hollmann (Eds.), Hochgeschwindigkeitsspanen,Wileyvch,

2005, ISBN 3-527-31256-0, pp. 112–134.

[5] C.

Comi

, U.

Perego

, Criteria for mesh refinement in nonlocal damage finite element analyses, Eur. J. Mech. A/Solids 23 (2004) 615– 632.

[6] E. El-

Magd

, C.

Treppmann

, Mechanical

behaviour

of Materials at high strain rates, in: H. Schulz (Ed.), Scientific Fundamentals of High-Speed Cutting,

Hanser

, 2001, ISBN 3-446-21799-1, pp. 113–122.

[7] T.I. El-

Wardany

, M.A.

Elbestawi

, Effect of material models on the accuracy of

highspeed

machining simulation, in: H. Schulz (Ed.), Scientific Fundamentals of High-Speed Cutting,

Hanser

, 2001, ISBN 3-446-21799-1, pp. 77–91.

[8] D.P. Flanagan, T.

Belytschko

, A Uniform Strain Hexahedron and Quadrilateral with Orthogonal Hourglass Control, Int. J.

Numer

. Methods Eng. 17 (1981) 679–706.

[9] G.R. Johnson, W.H. Cook, A constitutive model and data for metals subjected to large strain, high strain-rates and high temperatures, in: Proceedings of the 7th International Symposium on Ballistics, The Hague, The

Netherlands, 1983. pp. 541–547.

[10] T.

Mabrouki

, J.-F.

Rigal

, A contribution to a qualitative understanding of thermo-mechanical effects during chip formation in hard turning, J. Mater. Process. Technol. 176 (2006) 214–221.

[11] M.E. Merchant, Mechanics of the metal cutting process. I. Orthogonal cutting and a type 2 chip, J. Appl. Phys. 16 (1945) 267–275.Slide6

References

[1] M.

B¨aker

, J.

R¨osier

, C. Siemers, A finite element model of high speed metal cutting with adiabatic shearing,

Comput

.

Struct

. 80 (2002) 495–513.

[2] M.

B¨aker

, An investigation of the chip segmentation process using finite elements, Tech. Mech. 23 (2003) 1–9.[3] M. Baker, Finite element simulation of high speed cutting forces, J. Mater. Process. Technol. 176 (2006) 117–126.[4] A. Behrens, B. Westhoff, K. Kalisch, Application of the finite element method at the chip forming process under high speed cutting conditions, in: H.K. T¨onshoff, F. Hollmann (Eds.), Hochgeschwindigkeitsspanen,Wileyvch, 2005, ISBN 3-527-31256-0, pp. 112–134.[5] C. Comi, U. Perego, Criteria for mesh refinement in nonlocal damage finite element analyses, Eur. J. Mech. A/Solids 23 (2004) 615– 632.[6] E. El-Magd, C. Treppmann, Mechanical behaviour of Materials at high strain rates, in: H. Schulz (Ed.), Scientific Fundamentals of High-Speed Cutting, Hanser, 2001, ISBN 3-446-21799-1, pp. 113–122.[7] T.I. El-Wardany, M.A. Elbestawi, Effect of material models on the accuracy of highspeed machining simulation, in: H. Schulz (Ed.), Scientific Fundamentals of High-Speed Cutting, Hanser, 2001, ISBN 3-446-21799-1, pp. 77–91.[8] D.P. Flanagan, T. Belytschko, A Uniform Strain Hexahedron and Quadrilateral with Orthogonal Hourglass Control, Int. J. Numer. Methods Eng. 17 (1981) 679–706.[9] G.R. Johnson, W.H. Cook, A constitutive model and data for metals subjected to large strain, high strain-rates and high temperatures, in: Proceedings of the 7th International Symposium on Ballistics, The Hague, The Netherlands, 1983. pp. 541–547.[10] T. Mabrouki, J.-F. Rigal, A contribution to a qualitative understanding of thermo-mechanical effects during chip formation in hard turning, J. Mater. Process. Technol. 176 (2006) 214–221.[11] M.E. Merchant, Mechanics of the metal cutting process. I. Orthogonal cutting and a type 2 chip, J. Appl. Phys. 16 (1945) 267–275.Slide7

References

[12] E.H. Lee, B.W. Shaffer, The theory of plasticity applied to a problem of machining, J. Appl. Phys. 18 (1951) 405–413.

[13] T. O¨

zel

, T.

Altan, Process simulation using finite element method—prediction of cutting forces, tool stresses and temperatures in high speed flat end milling, J. Mach. Tools Manuf. 40 (2000) 713–783.

[14] T. O¨

zel

, E.

Zeren

, Determination of work material flow stress and friction for FEA of machining using orthogonal cutting tests, J. Mater. Process. Technol. 153–154 (2004) 1019–1025.

[15] F.

Reusch, B. Svendsen, D. Klingbeil, Local and non local gurson based ductile damage and failure modelling at large deformation, Euro. J. Mech. A/Solid 22 (2003) 779–792.[16] P. Rosakis, A.J. Rosakis, G. Ravichandran, J. Hodowany,Athermodynamic internal variable model for the partition of plastic work into heat and stored energy in metals, J. Mech. Phys. Solids 48 (2000) 581–607.[17] R. Sievert, A.-H. Hamann, D. Noack, P. L¨owe, K.N. Singh, G. K¨unecke, R. Clos, U. Schreppel, P. Veit, E. Uhlmann, R. Zettier, Simulation of chip formation with damage during high-speed cutting, Tech. Mech. 23 (2003) 216–233 (in German).[18] R. Sievert, A.-H. Hamann, D. Noack, P. L¨owe, K.N. Singh, G. K¨unecke, Simulation of thermal softening, damage and chip segmentation in a nickel super-alloy, in: H.K. T¨onshoff, F. Hollmann

(Eds.), Hochgeschwindigkeitsspa-nen,Wiley-vch, 2005, ISBN 3-527-31256-0, pp. 446–469 (in German).[20] H.K. T¨onshoff, B. Denkena, R. Ben Amor, A. Ostendorf, J. Stein, C.

Hollmann, A. Kuhlmann, Chip formation and temperature development at high cutting speeds, in: H.K. T¨onshoff, F. Hollmann

(Eds.), Hochgeschwindigkeit-sspanen,Wiley-vch, 2005, ISBN 3-527-31256-0, pp. 1–40 (in German).[21] Q. Yang, A. Mota, M. Ortiz, A class of

variational strain-localization finite elements, Int. J. Numer. Methods in Eng. 62 (2005) 1013–1037.Slide8

References

[12] E.H. Lee, B.W. Shaffer, The theory of plasticity applied to a problem of machining, J. Appl. Phys. 18 (1951) 405–413.

[13] T. O¨

zel

, T.

Altan, Process simulation using finite element method—prediction of cutting forces, tool stresses and temperatures in high speed flat end milling, J. Mach. Tools Manuf. 40 (2000) 713–783.

[14] T. O¨

zel

, E.

Zeren

, Determination of work material flow stress and friction for FEA of machining using orthogonal cutting tests, J. Mater. Process. Technol. 153–154 (2004) 1019–1025.

[15] F.

Reusch, B. Svendsen, D. Klingbeil, Local and non local gurson based ductile damage and failure modelling at large deformation, Euro. J. Mech. A/Solid 22 (2003) 779–792.[16] P. Rosakis, A.J. Rosakis, G. Ravichandran, J. Hodowany,Athermodynamic internal variable model for the partition of plastic work into heat and stored energy in metals, J. Mech. Phys. Solids 48 (2000) 581–607.[17] R. Sievert, A.-H. Hamann, D. Noack, P. L¨owe, K.N. Singh, G. K¨unecke, R. Clos, U. Schreppel, P. Veit, E. Uhlmann, R. Zettier, Simulation of chip formation with damage during high-speed cutting, Tech. Mech. 23 (2003) 216–233 (in German).[18] R. Sievert, A.-H. Hamann, D. Noack, P. L¨owe, K.N. Singh, G. K¨unecke, Simulation of thermal softening, damage and chip segmentation in a nickel super-alloy, in: H.K. T¨onshoff, F. Hollmann

(Eds.), Hochgeschwindigkeitsspa-nen,Wiley-vch, 2005, ISBN 3-527-31256-0, pp. 446–469 (in German).[20] H.K. T¨onshoff, B. Denkena, R. Ben Amor, A. Ostendorf, J. Stein, C.

Hollmann, A. Kuhlmann, Chip formation and temperature development at high cutting speeds, in: H.K. T¨onshoff, F. Hollmann

(Eds.), Hochgeschwindigkeit-sspanen,Wiley-vch, 2005, ISBN 3-527-31256-0, pp. 1–40 (in German).[21] Q. Yang, A. Mota, M. Ortiz, A class of

variational strain-localization finite elements, Int. J. Numer. Methods in Eng. 62 (2005) 1013–1037.Slide9

Material Assumptions

Inconel

718

Alloy composed of mostly nickel and chromium

Work piece is fundamentally

thermoelastic, viscoplastic

in nature

Thermoelastic

Temperature changes induced by stress

Viscoplastic

permanent deformations under a load but continues to creep (equilibrium is impossible)

Isotropic material behaviorSlide10

Design Principle

Low cutting speeds

Low strain-rates

“Fast” heat conduction

High cutting speeds

High strain-rates

“Slow” heat conduction

Thermal softening

Shear bandingSlide11

Design Principle

Johnson-Cook and Hooke Models

Plastic deformation results in a temperature increase

Temperature increase is a function of strain (left)

Temperature increase results in softening

At points of maximal mechanical dissipation in the material, softening effects may dominate hardening (right)

Results in material instability, deformation localization and shear-band formationSlide12

Design Principle

Finite-element simulation of thermal shear-banding

Shear angle

Φ

=40°

Cutting tool angleγ=0°Plane strain

deformation

V

c

=1000 m/minSlide13

FEA: Parallel

Notch represents a geometric

inhomogenity

Idealized notched structure

discretized

with bilinear elements oriented in the predicted shear-band direction. Average element edge-length here is 0.005 mm.Slide14

FEA: Parallel

TOP

Cutting speed

vc

=10 m/min

Thermal conduction is “fast”No thermal softening

NO shear-band formation.

BOTTOM

Cutting speed

vc

=1000 m/min

Thermal conduction is “slow”

Thermal softeningShear-band formationChip formationSlide15

FEA: Rotated

Restricted to “high” cutting speed

Assume adiabatic

Idealized structure with elements oriented at 45◦ to the direction of

shearing. As before, the average element edge length here is 0.005 mmSlide16

FEA: Rotated

No shear band formation in the expected direction

Temperature distribution in the mesh from above after shearing at a rate equivalent to a cutting speed of 1000 m/minSlide17

FEA: Rotated

Why?

Constant strain elementsSlide18

FEA: Reduced Parallel

Different element edge lengths

Temperature distribution in the notched structure

discretized

parallel to the shear direction using different element edge lengths: 0.005mm (above), 0.0025mm (below).Slide19

FEA: Reduced Rotated

Different element edge lengths

Temperature distribution in the notched structure

discretized

at a 45◦ angle to the shear direction using different element edge lengths: 0.005mm (above), 0.0025mm (below).Slide20

Results of FEA Shear-band

The coarser mesh in both cases, and the rotated mesh in general, behave more stiffly, resulting in “delayed” shear-band development.Slide21

FEA: Chip Formation

δ

discretization

angle

Finite-element model for the work-piece/tool system used for the cutting

simulation. Mesh orientation relative to the cutting plane is represented here by

the angle

δ.Slide22

FEA: Chip Formation

Merchant, Lee and Schaffer Models

φ =π

/4 - 1/2

(

arctanμ − γ)φ

Shear angle

γ

 Chip angle

μ

 Coefficient of FrictionSlide23

FEA: Chip Formation

Chip formation becomes increasingly inhibited and diffuse as

δ

increases beyond

φ.

Chip formation and temperature field development for different mesh orientation angles

δ:δ=20◦ (left), δ=40◦ (middle), δ=60◦ (right).Slide24

FEA: Chip Formation

Chip formation with

γ =−5◦ and δ=30◦ for different

discretizations

. Left: 60×10 elements; middle: 150×20 elements; right: 250×30 elements. Note

the mesh-dependence of segmentation, i.e., an increase in segmentation frequency with mesh refinement.Slide25

Conclusion

Strong dependence on element size and orientation

Affects chip geometry and cutting forces

Using the mesh to fit the orientation and thickness of simulated shear bands to experimental results is somewhat questionable and in any case must be done with great care.

Better understanding of cutting forces

Better efficiency

Save moneySlide26

Questions?