MODELLING THERMAL EFFECTS IN MACHINING BY FINITE ELEMENT

METHODS

Authors Andrea Bareggi (presenter) Andrew TorranceGarret O’Donnell

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Department of Mechanical and Manufacturing Engineering

The University of Dublin

Trinity College

Trinity College Dublin

Introduction

FE modelling for metal cutting• Stress, strain, strain rate predictions• Temperature distribution in the primary,

secondary and tertiary sub-cutting zones

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• Cutting forces, plastic deformation (shear angles and chip thickness)

• Temperature in the workpiece, chip and tool

Commercial packagesTrinity College Dublin

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ABAQUS

• Manual design of geometry, meshing and boundary condition setting

• No material library, but materials can be defined in detail

• Partial support in adaptive remeshing

• Good control of the solver

Commercial packagesTrinity College Dublin

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ADVANTEDGE

• Very efficient interface to rapidly configure a model, tool library is provided

• Extensive material library

• Uses adaptive remeshing, but controls can not be modified

• Not suitable for customising control functions

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Commercial packagesTrinity College Dublin

DEFORM 3D

• Built in “wizard” for machining

• Good material library and comprehensive material editor

• Uses adaptive remeshing, good control of meshing parameters

• The user can chose the solver and minimal control is permitted

Problem formulationTrinity College Dublin

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• Incremental Lagrangian formulation

• Implicit integration method

• Solver with sparse matrix

• Direct method

Problem formulationTrinity College Dublin

• Cutting speed: 270m/min• Feed: 0.06mm/rev• Depth of cut: 0.5mm• Effective rake angle = 0°

nose radius = 0.2mm• Cooling method: air jet• AISI 1020 steel

workpiece,1.5 mm of length, plastic

• WC insert with reduced heat capacity, rigid

workpiece

insert

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Thermal boundary conditionsTrinity College Dublin

• No cooling, natural convection, h=20 W/m²/K

• Air jet, overhead position, h=2000 W/m²/K

• Air jet, interface position, h=2000 W/m²/K

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overhead

interface

Interface nozzle dir.

Overhead nozzle dir.

ResultsTrinity College Dublin

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• Steady state condition: workpiece, interface, insert

• Temperature prediction: workpiece, chip and interface

Chip temperature(416°C)

ResultsTrinity College Dublin

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feed=0.06mm/revdepth=0.5mmspeed=270m/min

Maxworkpiecetemp. (°C)

Interface temp. (°C)

Chip temp. (°C)

CuttingForce (N)

Dry cutting 737 710 416 93Air jet cooling,

overhead721 627 389 92

Air jet cooling, interface

727 648 408 95

• Reduction of interface temperature• Best cooling in overhead position• No influence on the cutting force

ResultsTrinity College Dublin

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• Prediction of gradient temperature within the insert

• Developing of experimental techniques for investigating temperature

Temp (°C)

A=20

B=88

C=156

D=225

E=293

F=361

G=429

H=498

I=566

J=634

K=702

ConclusionTrinity College Dublin

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• Results consistency: analytical results, ADVANTEDGE simulations, preliminary temperature measurements

• Finite Elements: cost saving in experimental work, process insight in cooling and lubricating method

• 3D modelling techniques under development, in particular with cooling

Further researchTrinity College Dublin

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• Refinement of the model, estimation of the heat transfer coefficients, improved approach to jet modelling

• Simulation with different workpiece materials and cutting conditions

• Experimental validation, currently ongoing

Literature & AcknowledgementsTrinity College Dublin

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•N.A. Abukhshim, P.T. Mativenga, M.A. Sheikh, Heat generation and temperature prediction in metal cutting: A review and implications for high speed machining, International Journal of Machine Tools & Manufacture 46 (2006) 782–800•J.D. Gardner, A.Vijayaraghavan, D.A. Dornfeld, Comparative Study of Finite Element Simulation Software, eScholarship Repository, University of California, Copyright c 2005 by the authors•T. O’Donovan, Fluid flow and heat transfer of an impinging air jet, Phd. Thesis, Mechanical & Manufacturing Engineering, Trinity College Dublin, 2005•D. Umbrello, L. Filice, S. Rizzuti, F. Micari, On the evaluation of the global heat transfer coefficient in cutting, International Journal of Machine Tools & Manufacture 47 (2007) 1738–1743

Literature & AcknowledgementsTrinity College Dublin

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AcknowledgementsChristian E. Fischer, Ph.D., PE, (Scientific Forming Technologies Corporation, Columbus, Ohio, USA)

Questions?