- 1. IMPLEMENTING A COHESIVE ZONE INTERFACEIN A DIAMOND-COATED
TOOL FOR 2D CUTTINGSIMULATIONSFeng Qin Ninggang (George) Shen Dr.
Kevin Chou 11/15/2012The University of Alabama-Mechanical
Engineering1
2. Outline of the contents1. Introduction2. Cohesive zone
model3. Two-step FE model application4. Simulation results
analysis5. Conclusions6. Future workThe University of
Alabama-Mechanical Engineering 2 3. 1. Introduction and research
objectivesDiamond cutting tools PCD tools and CVD coated
toolsApplicable work materials High-Si Al alloys, A390 Metal matrix
composite, A359/SiC-20p Plastic matrix composite, CFRP Automotive
AerospaceThe University of Alabama-Mechanical Engineering 3 4. 1.
Introduction and research objectivesThe University of
Alabama-Mechanical Engineering 4 5. 1. Introduction and research
objectivesMethodology A two-step 2D cutting simulation Residual
deposition stress analysis (various CZM or process parameters) 2D
cutting simulation (various cutting
parameters)Objective/Significance Couple the effect of coating
deposition Investigate the effect of CZM or process parameters on
coating delamination Understand the effect of residual deposition
stresses on cutting process Demonstrate the feasibility of
evaluating coating delamination of a diamond-coated tool during
cuttingThe University of Alabama-Mechanical Engineering 5 6. 2.
Cohesive zone modelCohesive crack tip1.21 max0.8 Tn/max 0.6 0.4
0.20max 0 0.5 11.5 nforwardwakeFig. 2 The cohesive zone model for
normal tractionFig. 1 Typical traction-separation response [1]mode
described by Geubelle & Baylor [2].The University of
Alabama-Mechanical Engineering 6 7. 2. Cohesive zone model
Nomenclature:- Interface normal strengthFor n >0- Interface
tangential strength- Interface characteristic length parameter-
Critical normal and tangential separations- Non-dimensional normal,
tangential andFor n = 0total displacement The University of
Alabama-Mechanical Engineering7 8. 3. Two-step FE model
applicationCoating and substrate geometryTool material AbaqusMesh,
BCs andproperty CAE interactionsDepositionCohesive zonetemperature
Abaqus (material, elem field, BCs, interactiinput fileents,
etc.)ons and output variablesCoupled thermal-mechanicalsimulation
for deposition processWorkpiece Coupled thermal-BCsgeometry,
mechanical (speed), outpmesh, ALE simulation forut variables
andcutting processand material interactions Coupled thermal-
mechanical simulation New BC for for workpiece workpiece withdrawal
simulation(displacement load)Fig. 3 Flowchart of the simulations
with cohesive zone residual stress included in a diamond-coated
tool.The University of Alabama-Mechanical Engineering8 9. 3.
Two-step FE model applicationCoating Cohesive zone Geometry Edge
radius (re) = 50 m Coating thickness (t) = 15 m MeshSubstrate
Coating: Automatic structural meshing Substrate: Free meshing
Cohesive zone: Manual structural meshing Element Coating &
substrate: CPE4RT Cohesive zone: COH2D4 Fig. 4 Tool geometry and
configuration Analysis: Explicit coupled thermal-displacement for
both stepsThe University of Alabama-Mechanical Engineering9 10. 3.
Two-step FE model applicationTab. 1 The Cohesive Zone Parameters
for the Diamond-Coated WC Tool Fracture Deposition max maxMaterial
# E/GPa G1/GPa energy temperature/MPa /MPa(J/m2 )/C 1 55500
100000100 800 2 44400 100000 80 800 3 55500 100000100 600Tab. 2
Material Properties of the WC-Co Substrate [3,4]E (GPa) 0 (MPa)n y
(GPa) 6200.24 18036 0.2445.76 Fig. 5 Cohesive zone failure after
deposition. The University of Alabama-Mechanical Engineering 10 11.
3. Two-step FE model applicationTab. 3 Parameters & CZ
properties in 2D cutting simulationParameters ValuesEdge radius, re
(m) 50Coating thickness, (m)15ChipflowCutting speed, v
(m/sec)5Uncut chip thickness, tc (mm) 0.05, 0.45Cohesive fracture
energy (J/m2) 100InflowInterfacial tensile strength, max
(MPa)500Deposition temperature ( C) 600OutflowFig. 6 Configuration
of the 2D cutting simulation The University of Alabama-Mechanical
Engineering11 12. 4. Simulation results analysis Fracture energy
effect(a) (a)(b) (b)Fig. 7 n results of cohesive zone at different
fracture energy Fig. 8 n responses for different interface normal
strengthvalues after deposition at (interface strength 500
MPa):(fracture energy: 100 J/m2): (a) 500 MPa; (b) 400 MPa.(a)
Fracture energy 80 J/m2; (b) Fracture energy 100 J/m2. The
University of Alabama-Mechanical Engineering 12 13. 4. Simulation
results analysis Original View Zoom-in View tc = 5 mtc = 45 mThe
University of Alabama-Mechanical Engineering13 14. 4. Simulation
results analysis(a)(b)Fig. 9 Stress state of tool and workpiece at
the beginning of the simulation (a) and during the simulation
(b).The University of Alabama-Mechanical Engineering 14 15. 4.
Simulation results analysis(a) (b)Fig. 10 Initial cohesive zone
failure during the cutting: (a) Auto-Fit view; (b) Zoom-in view.The
University of Alabama-Mechanical Engineering 15 16. 4. Simulation
results analysis (a)(b)T-S curve for node 224 and 145 (c)500 (d)
224400Tn -S22 (MPa) 14530020010000 0.00020.0004 0.0006n-e22
(mm)Fig. 11 Zoomed-in view of coating delamination evolution:(a)
Initial cohesive failure after deposition; (b) Steady cohesive
failure during cutting;(c) Final cohesive failure after tool
withdrawal;(d)Traction-separation curve for nodes in an alive and
failed element, respectively.The University of Alabama-Mechanical
Engineering16 17. 5. Conclusions Interface delamination is the
major failure mode for diamond-coated tools. Due to insufficient
adhesion, and induced deposition stresses and thermo-mechanical
loads during machining A cohesive zone model is included with
deposition stresses in 2D FE simulations Different cohesive
fracture energy values and different interface normal strengths
employed in the cutting simulations Significant effect of residual
deposition stresses on cohesive zone failure The higher the stress
is, the easier to fail. Cohesive interface failure can be predicted
for diamond-coated tool with Incorporated the deposition residual
stress as the initial condition in cutting simulation Cohesive
failure is sensitive to the cutting parameter The larger the uncut
chip thickness is, the easier to fail.The University of
Alabama-Mechanical Engineering17 18. 6. Future work Deposition
temperature Tool geometry Cutting parametersThe University of
Alabama-Mechanical Engineering 18 19. AcknowledgementSponsor: NSF,
Grant #: 0728228 and 0928627 The University of Alabama-Mechanical
Engineering 19 20. Q&A Thank you for your attention! Any
Question?The University of Alabama-Mechanical Engineering 20 21.
Reference[1] Hu, J., Chou, Y. K., & Thompson, R. G. (2008).
Cohesive zone effects on coating failure evaluations of
diamond-coated tools. Surface and Coating Technology, 203,
730-735.[2] Geubelle, P. H., & Baylor, J. S. (1998).
Impact-induced delamination of composites: a 2D
simulation.Composites Part B: Engineering, 29 (5), 589-602.[3] Qin,
F. and Chou, Y. K. (2010). 2D Cutting Simulations with a
Diamond-coated Tool Including DepositionResidual Stresses,
Transactions of NAMRI/SME, Vol. 38, pp. 1-8.[4] Dias, A. M. S.,
Modenesi, P. J., & de Godoy, G. C. (2006). Computer simulation
of stress distribution duringVickers hardness of WC-6Co. Materials
Research, Vol. 9, 73-76.[5] Liu, C., Wu, B., and Zhang, J., 2010,
"Numerical Investigation of Residual Stress in Thick Titanium Alloy
PlateJoined with Electron Beam Welding," Metallurgical and
Materials Transactions B, 41(5), pp. 1129-1138.The University of
Alabama-Mechanical Engineering 21
