abaqus training seminar for machining simulation training.pdf · purdue university : center for...

Purdue University : Center for Laser-based Manufacturing

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Abaqus Training Seminar for Machining Simulation

Mohamed Elkhateeb Date: Sept. 29. 2017


http://engineering.purdue.edu/CLM/



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



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



2. Abaqus Workbench



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):



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)



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



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.



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



3.4 Assembly

Import parts - instances (repeatable)

Dependence on parts

Operations on parts

Partitioning (Dependent)

References

Offset overlapping parts



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.



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.



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



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



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



3.8 Running simulation (Job) and results

Create a Job Submit

Single – double precision

Parallelization



3.9 Plotting results (Cutting forces)



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]



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.



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



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



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.



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.

abaqus training seminar for machining simulation training.pdf · purdue university : center for...

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