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Abaqus Training Seminar for Machining Simulation
Mohamed Elkhateeb Date: Sept. 29. 2017
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http://engineering.purdue.edu/CLM/
Purdue University : Center for Laser-based Manufacturing
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Content
1. Machining simulation Methodology
2. Abaqus Workbench
3. 2D Machining Simulation of AISI 4140
Steel
4. 3D Machining Simulation of Ti6Al4V
Interaction
5. Conclusion
6. ALE
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1. Machining simulation Methodology
“Simulation is invaluable until it agrees with experimental results”, Prof. Yung Shin.
FEM
Geometry
2D
3D
Material
Properties
Constitutive
Type
Dynamic
Dynamic -Temp
Interaction
Property
Type
Meshing
Type
Size
Boundary Conditions
Tool
Workpiece
Running Simulation
Results
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2. Abaqus Workbench
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3. 2D Machining Simulation of AISI 4140 Steel [1] o Orthogonal Cutting of AISI 4140. o Workpiece
Material: AISI 4140 Steel Dimensions: 2mm x 0.6mm
o Cutting Tool Uncoated Tungsten Carbide Dimensions (selective): 0.2mm x 0.8mm Angles: neutral rake angle – 7o clearance angle
o Cutting Conditions Feed: 0.1mm/rev , Depth of cut (width): 2.5mm, and Cutting speed: 100m/min
Cutting direction Cutting tool
Workpiece
Feed: 0.1mm
1. Akbar F, Mativenga PT, Sheikh M. An experimental and coupled thermo-mechanical finite element study of heat partition effects in machining. The International Journal of Advanced Manufacturing Technology. 2010;46(5-8):
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3.1 Geometry Creation o Creating the geometry of the tool and workpiece through the part module. o Create each individually and then assemble them (dependent and independent assembly) in the
assembly module..
Create the part
Sketch Dimensions & Units
3D features
Partitioning
References
Sketch basic entities
Units consistency
Reference point (rigid body)
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3.2 Material
Create a material
Create a section
Assign section to partition
o Based on analysis requirements: thermal - dynamic o Cutting Tool: elastic and thermal properties o Workpiece: elastic, plastic, damage, and thermal
properties. o Partition the workpiece: damage layer (larger than
edge radius) – more stable. o The depth of cut is used as the plane stress/strain
thickness.
Workpiece
Depth of cut
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3.2 Material o Constitutive model
Used to describe the material deformation behavior. Obtained by fitting stress strain curves to certain models, e.g. Johnson cook model.
o Damage Criteria
Describe chip separation. Damage initiation: start of degradation in stiffness
Damage evolution and element deletion.
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3.3 Meshing the parts
Seed Edge
Mesh the part
Select Element type
Seed the part
Mesh region
o Area of interest; dense mesh o Other areas; coarse mesh o Mesh Sensitivity
Underfitting Overfitting Fitting Computational cost
o Element type: Coupled Temperature displacement Plain strain: homogeneous – constant
deformation in the third direction Plain stress: heterogeneous – different
Poisson’s ratio – different deformation in the third direction
o Element deletion: damage layer
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3.4 Assembly
Import parts - instances (repeatable)
Dependence on parts
Operations on parts
Partitioning (Dependent)
References
Offset overlapping parts
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3.5 Analysis Type o Dynamic – Explicit
Integrate the equations of motion through time. Using the lumped mass matrix M, the nodal accelerations easily at any given time, t, can
be calculated by:
where P is the external load vector and I is the internal load vector. Results: cutting forces, stresses, strains, displacement.
o Dynamic, Temp-Disp, explicit
where CNJ is the lumped capacitance matrix, PJ is the applied nodal source vector, and FJ is the internal flux vector.
Computationally expensive.
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3.5 Analysis Type
Analysis
Output variable
o Determine analysis type: Dynamic: no thermal analysis Dynamics
o Define simulation time o Mass scaling: simulation time
reduction o Output failure: status o Number of output intervals.
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3.5.1 Arbitrary Lagrangian-Eulerian (ALE) o ALE combines the features of pure Lagrangian analysis and
pure Eulerian analysis. Mesh motion is constrained to the material motion only where
necessary (at free boundaries) Otherwise, material motion and mesh motion are independent.
o ALE was applied only on chip area. o To apply ALE, it is required to define:
The domain Frequency No. of sweeps Smoothing parameters:
Volume Laplacian Equipotential
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3.6 Interaction
Interaction
o Define how tool is interacting with the workpiece.
o The tool is defined as rigid body: constraint - geometry and reference point.
o Define interaction properties: tangential (friction) , normal, heat generation, thermal conductance (computational cost)
o Interaction with the workpiece: surface to node area.
Property
Constraint
Rigid body constraint
Tool surface - workpiece node interaction
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3.7 Boundary conditions
o B.Cs include: fixing the bottom and left surfaces of the workpieces, applying cutting speed to the tool in the cutting direction and fixing motion in others.
o Define initial status then modify status of the tool at the step of analysis. o Define initial temperature.
Tool
Workpiece Initial Temperature
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3.8 Running simulation (Job) and results
Create a Job Submit
Single – double precision
Parallelization
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3.9 Plotting results (Cutting forces)
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3.10 Results
650 625
75 70
0
100
200
300
400
500
600
700
100m/min
Cut
ting
Forc
e (N
)
Cutting speed (m/min)
Fc Exp. Fc Sim.
Ff Exp. Ff Sim.
Von-Mises Stress Distribution
Temperature Distribution 1. Akbar F, Mativenga PT, Sheikh M. An experimental and coupled thermo-mechanical finite element study of heat partition effects in machining. The International Journal of Advanced Manufacturing Technology. 2010;46(5-8):
Simulation cutting forces compared to experimental results [1]
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4. 3D Machining Simulation of Ti6Al4V [2]
o Longitudinal Turning of Ti6Al4V. o Workpiece
Material: Ti6Al4V Dimensions: 25.4 in diameter
o Cutting Tool Uncoated Tungsten Carbide Dimensions : 0.012mm edge radius – 0.8mm nose radius Angles: 5o angle – 5o clearance angle
o Cutting Conditions Feed: 0.076mm/rev , Depth of cut (width): 0.76mm, and Cutting speed: 107m/min
2. Dandekar, C. and Shin, Y.C., “Machinability Improvement of Ti6Al4V Alloy via LAM and Hybrid Machining”, International Journal of Machine Tools and Manufacture, Volume 50, Issue 2, pp. 174-182, February 2010.
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4.1 Geometry, Materials, Meshing, and Assembly o 3D – Nose Turning
Mimics the actual machining process including the effect of nose radius.
o Johnson-cook constitutive models were used to describe the deformation and damage behaviors of Ti6Al4V [2]. o Only elastic and thermal properties were used for Tungsten carbide [2]. o 3D stress elements are used in meshing.
Workpiece Cutting Tool
A
(MPa)
B
(MPa) C n m
Melting
Temperature (oC)
Reference
Temperature (oC)
862 331 0.012 0.34 0.8 1660 20
D1 D2 D3 D4 D5
-0.09 0.25 -0.5 0.014 3.87
J-C constitutive model
J-C damage model
Mesh and Assembly
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4.2 Analysis, Interaction, and B.Cs o Dynamic, Temp-Disp, Explicit analysis was used o Property: contact, describe the behavior of interaction
Normal Tangential - friction
• Coulomb’s friction law Thermal conductance Heat Generation
o Interaction -Type General
Applies only for 3D Surface: Master Slave
Surface –surface Surface - node
o Constraint Rigid body: tool – reference point
o Tool Move only in the cutting direction with the cutting Speed
– Reference Point. Initial temperature.
o Workpiece Fully constrained surfaces (bottom and side surfaces) Initial Temperature
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4.3 Results
150
118
100
152
111
93
50 40 37
43 36 35
0
20
40
60
80
100
120
140
160
25 250 500
Cut
ting
Forc
e (N
)
Workpiece Temperature (oC)
Fc Exp. Fc Sim.
Ft Exp. Ft Sim.
Simulation cutting forces compared to experimental results [2]
2. Dandekar, C. and Shin, Y.C., “Machinability Improvement of Ti6Al4V Alloy via LAM and Hybrid Machining”, International Journal of Machine Tools and Manufacture, Volume 50, Issue 2, pp. 174-182, February 2010.
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5. Conclusion o Finite element simulation of orthogonal and
longitudinal turning was discussed. o They include: geometry creation, material definition,
meshing, assembly, selecting analysis ,methodology, defining interaction, running simulation, and visualizing results.
o Constitutive models for workpiece material are required to describe material behavior during simulation.
o Two case studies were presented and results showed agreement with experimental results.