Drinking Straw
MSC.Patran 2005 r2
MSC.Marc 2005 r2
Estimated Time for Completion: ~45min
Experience Level: Lower
Topics Covered
• Topics covered in Modeling
• Importing Geometry file with FEA data.
• Neutral format (.out)
• Creating controlling node and MPC
• Multi-point Constraint element are created to connect the controlling
node and the structure.
• Creating Elastic-perfectly plastic material.
• The material non-linearity is approximated by a constant.
• Topic covered in Analysis
• Applying Large Displacement/Small Strains Analysis.
• Topics covered in Review
• Creating XY plots and animations.
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Problem Description
• In this example, a bendable straw is fully stretched
by applying displacement conditions at both ends.
Plastic deformation occurs during the increments.
Fmax=?
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Problem Description
• In this example problem, we apply Symmetric boundary conditions at the
center of the pipe to reduce the number of elements and the analysis
time. The following condition is applied at the boundary
• uy=θx= θz=0 on the symmetric boundary.
• The geometry and the Boundary conditions are axisymmetric. However
there can be unsymmetric results due to the unstability. Instead fully
axisymmetric conditions, only symmetric boundary conditions are
applied to the half of the geometry.
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Summary of Model
• Straw
• Dimensions:
• Diameter=0.016m,
• Total Length=0.083m,
• Thickness=0.0001m
• Material properties: Polystyrene
• Young’s Modulus =1.0x108 Pa,
• Poisson’s ratio=0.3,
• Yield strength= 1.0x106 Pa
0.023m
t=0.0001m
0.016m
0.083m
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Goal
• We will determine the maximum stress in the structure.
• We will determine the minimum load to extend the drinking
straw.
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Expected Results
• Deformed Shape
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Create Database and Import a Geometry File
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Click File menu / Select New
In File Name enter bendablestraw.db
Click OK
Select Analysis Code to be MSC. Marc
Click OK
Click File menu / Select Import
Select Object to be Model
Select Source to be Neutral
Select the model file, straw_geom.out
Click Apply.
Click Yes
Click Yes
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You will see elements and nodes in
the current viewport.
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Create a Node
Create a node to control the upper rigid surface
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Click Element icon
Select Action to be Create
Select Object to be Node
Select Method to be Edit
In Node ID List, enter 15000
Uncheck Auto Execute
In Node Location List, enter
[0,0,0]
Click Apply
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This is the node created.
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You can visualize nodes by toggling
this icon.
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Create a MPC
Create Multi-Point Constraints on the left end of the model.
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Select Action to be Create
Select Object to be MPC
Select Method to be
Rigid(Fixed)
Click Define Terms
Select Create Dependent
Uncheck Auto Execute
In Node List, enter Node
2048:2978:31, or select all
nodes on x=0 plane except
Node 15000.
Click Apply
Select Create Independent
In Node List, enter Node
15000, or select the node
made in the previous slide.
Click Apply
Click Apply
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Make sure that you do not select the
centered node in the Dependent Terms
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Create Boundary Conditions
Create the Boundary Conditions for the fixed end.
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Click Loads/BCs icon
Select Action to be Create
Select Object to be Displacement
Select Type to be Nodal
In New Set Name, enter fixed
Click Input Data
In Translations, enter <0,0,0>
In Rotations, enter <0,0,0>
Click OK
Click Select Application Region
Select Geometry Filter to be FEM
In Select Nodes, enter Node
11502:12432:31 or select the nodes
on the right end of the model
Click Add
Click OK
Click Apply
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Create Boundary Conditions
Create the Boundary Conditions for the moving end.
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Click Loads/BCs icon
Select Action to be Create
Select Object to be Displacement
Select Type to be Nodal
In New Set Name, enter disp_x
Click Input Data
In Translations, enter <-0.03,0,0>
In Rotations, enter <0,0,0>
Click OK
Click Select Application Region
Select Geometry Filter to be FEM
In Select Nodes, enter Node 15000
or select the centered node on the
left end of the model
Click Add
Click OK
Click Apply
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Create Boundary Conditions
Create the Boundary Conditions for the symmetric boundary.
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Click Loads/BCs icon
Select Action to be Create
Select Object to be Displacement
Select Type to be Nodal
In New Set Name, enter sym
Click Input Data
In Translations, enter < , ,0>
In Rotations, enter <0,0, >
Click OK
Click Select Application Region
Select Geometry Filter to be FEM
In Select Nodes, select the node on
the symmetric boundary of the
model
Click Add
Click OK
Click Apply
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Create the Material Properties
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Click Materials icon
Select Action to be Create
Select Object to be Isotropic
Select Method to be Manual
Input
In Material Name, enter
polystyrene
Click Input Properties
Select Constitutive Model to be
Elastic
In Elastic Modulus, enter 1e8
In Possion Ratio, enter 0.3
Click OK
Click Apply
Click Input Properties again
Select Constitutive Model to be
Plastic
Select Type to be Perfectly
Plastic
In Yield Stress, enter 1e6
Click OK
Click Apply
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Create the Element Properties
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Click Properties icon
Select Action to be Create
Select Object to be 2D
Select Type to be Thin Shell
In Property Set Name, enter prop1
Select Options to be
Homogeneous
Click Input Properties
Click Mat Prop Name icon
Select polystyrene
In [Thickness], enter 1e-4
Click OK
In Application Region, enter Elm
1:10650 or select all elements
Click Add
Click Apply
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Run Analysis
Analysis Options for the first load step
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Click Analysis icon
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Select Action to be Analyze
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Select Object to be Entire Model
Select Method to be Full Run
In Job Name, enter straw_ext
Click Load Step Creation
Click Solution Parameters
Select Linearity to be NonLinear
Select Nonlinear Geometry
Effects to be Large
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Displacement(Updated
Lagr.)/Small Strains
Click Load Increment Parameters
Select Increment Type to be
Adaptive
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In [Trial Time Step Size:], enter
0.01
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Click OK
Click Iteration Parameters
In Max # of Iterations per
Increment, enter 100
Click OK
Because of the structural unstability of
Click OK
the example, the results and the analysis
Click Apply
time are dependent on the analysis
Click Cancel
options.
Click Apply
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Read Results
Read Results File
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In the Marc Job Monitoring window, if
the Exit Number is 3004, the problem
has been solved successfully.
Click Cancel
Select Action to be Read Results
Select Object to be Result Entities
Select Method to be Attach
Click Select Results File
Select straw_ext.t16
Click OK
Click Apply
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Review and Display Results
Plot the Displacement Result
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Click Results icon
Select Action to be Create
Select Object to be Quick Plot
In Select Results Cases, select the
last result (Time=1.00000)
Click Fringe Attributes icon
Click Spectrum, and select the one
you want.
Select Style to be Continuous
Select Shading to be Shaded
Click Deform Attributes icon
Uncheck Show Undeformed
Click Select Results icon
In Select Fringe Result, select
Displacement, Translation
In Select Deformation Result,
select Displacement, Translation
Click Apply
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Review and Display Results
Plot the Nodal Reaction Force at the Controlling Node (Load vs. Displacement Curve)
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Select Action to be Create
Select Object to be Graph
Select Method to be Y vs X
In Select Result Case(s), select all
cases
Click Target Entity icon
In Select Nodes, enter Node 1 or
select the controlling node in the
viewprot
Click Select Results icon
Click Display Attributes icon
In XY Window Name, enter 5 or title
number you want
Click Select Results icon
Select Y to be Result
In Select Y Result, select Force,
Nodal Reaction
Select Quantity to be X Component
Select X to be Result
Click Select X Result
In Select X Result, click
Displacement, Translation
Select Quantity to be X Component
Click OK
Click Apply
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Review and Display Results
Plot the Elastic Strain Energy
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Select Action to be Create
Select Object to be Graph
Select Method to be Y vs X
In Select Result Case(s), select all
cases
Click Display Attributes icon
In XY Window Name, enter 3 or title
number you want
Click Select Results icon
Select Y to be Global Variable
In Variable, select Elastic Strain
Energy
Select X to be Global Variable
Select Variable to be Time
Click Apply
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Results
• Displacement Results
At time=0.0
At time=0.2
At time=0.4
At time=0.6
At time=0.8
At time=1.0
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Results
• von-Mises at time=0.15
Max=1.62E6 MPa
• von-Mises at time=0.38
Max=1.87E6 MPa
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Results
• Load vs. Displacement
Max=0.46N
• Strain Energy vs. Displacement
(time=displacement factor)
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Animation
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Further Analysis (Optional)
• Problem modification
• Bending Straw: Rotate the one end of the straw 90°. Is the MPC still
applicable?
• Modeling
• Modify the geometry to have axisymmetric conditions. Solve it and
find the difference from the current results.
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