Drinking Straw

Estimated Time for Completion: ~45minExperience Level: Lower

MSC.Patran 2005 r2MSC.Marc 2005 r2

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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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• In this example, a bendable straw is fully stretched by applying displacement conditions at both ends. Plastic deformation occurs during the increments.

Problem Description

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

0.083m

0.016m

0.023mt=0.0001m

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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

a. Click File menu / Select Newb. In File Name enter bendablestraw.dbc. Click OKd. Select Analysis Code to be MSC. Marce. Click OKf. Click File menu / Select Importg. Select Object to be Modelh. Select Source to be Neutrali. Select the model file, straw_geom.outj. Click Apply.k. Click Yesl. Click Yes

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You will see elements and nodes in the current viewport.

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Create a NodeCreate a node to control the upper rigid surface

a. Click Element iconb. Select Action to be Createc. Select Object to be Noded. Select Method to be Edite. In Node ID List, enter 15000f. Uncheck Auto Executeg. In Node Location List, enter [0,0,0]h. Click Apply

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You can visualize nodes by toggling this icon.

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This is the node created.

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Create a MPCCreate Multi-Point Constraints on the left end of the model.

a. Select Action to be Createb. Select Object to be MPCc. Select Method to be Rigid(Fixed)d. Click Define Termse. Select Create Dependentf. Uncheck Auto Executeg. In Node List, enter Node

2048:2978:31, or select all nodes on x=0 plane except Node 15000.

h. Click Applyi. Select Create Independentj. In Node List, enter Node 15000,

or select the node made in the previous slide.

k. Click Applyl. 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

a. Click Loads/BCs iconb. Select Action to be Createc. Select Object to be Displacementd. Select Type to be Nodale. In New Set Name, enter fixedf. Click Input Datag. In Translations, enter <0,0,0>h. In Rotations, enter <0,0,0>i. Click OKj. Click Select Application Regionk. Select Geometry Filter to be FEMl. In Select Nodes, enter Node

11502:12432:31 or select the nodes on the right end of the model

m. Click Addn. Click OKo. Click Apply

Create the Boundary Conditions for the fixed end.a b

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Create Boundary Conditions

a. Click Loads/BCs icon b. Select Action to be Createc. Select Object to be Displacementd. Select Type to be Nodale. In New Set Name, enter disp_xf. Click Input Datag. In Translations, enter <-0.03,0,0>h. In Rotations, enter <0,0,0>i. Click OKj. Click Select Application Regionk. Select Geometry Filter to be FEMl. In Select Nodes, enter Node 15000

or select the centered node on the left end of the model

m. Click Addn. Click OKo. Click Apply

Create the Boundary Conditions for the moving end.b

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Create Boundary Conditions

a. Click Loads/BCs icon b. Select Action to be Createc. Select Object to be Displacementd. Select Type to be Nodale. In New Set Name, enter symf. Click Input Datag. In Translations, enter < , ,0>h. In Rotations, enter <0,0, >i. Click OKj. Click Select Application Regionk. Select Geometry Filter to be FEMl. In Select Nodes, select the node

on the symmetric boundary of the model

m. Click Addn. Click OKo. Click Apply

Create the Boundary Conditions for the symmetric boundary.b

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Create the Material Properties

a. Click Materials iconb. Select Action to be Createc. Select Object to be Isotropicd. Select Method to be Manual

Inpute. In Material Name, enter

polystyrenef. Click Input Propertiesg. Select Constitutive Model to be

Elastich. In Elastic Modulus, enter 1e8i. In Possion Ratio, enter 0.3j. Click OKk. Click Applyl. Click Input Properties againm. Select Constitutive Model to be

Plasticn. Select Type to be Perfectly

Plastico. In Yield Stress, enter 1e6p. Click OKq. Click Apply

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Create the Element Properties

a. Click Properties iconb. Select Action to be Createc. Select Object to be 2Dd. Select Type to be Thin Shelle. In Property Set Name, enter prop1f. Select Options to be

Homogeneous g. Click Input Propertiesh. Click Mat Prop Name iconi. Select polystyrenej. In [Thickness], enter 1e-4k. Click OKl. In Application Region, enter Elm

1:10650 or select all elementsm. Click Addn. Click Apply

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Run Analysis

a. Click Analysis iconb. Select Action to be Analyzec. Select Object to be Entire Modeld. Select Method to be Full Rune. In Job Name, enter straw_extf. Click Load Step Creationg. Click Solution Parametersh. Select Linearity to be NonLineari. Select Nonlinear Geometry Effects

to be Large Displacement(Updated Lagr.)/Small Strains

j. Click Load Increment Parametersk. Select Increment Type to be

Adaptivel. In [Trial Time Step Size:], enter

0.01m. Click OKn. Click Iteration Parameterso. In Max # of Iterations per

Increment, enter 100p. Click OKq. Click OKr. Click Applys. Click Cancelt. Click Apply

Analysis Options for the first load stepa

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Because of the structural unstability of the example, the results and the analysis time are dependent on the analysis options.

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Read ResultsRead Results File

a. In the Marc Job Monitoring window, if the Exit Number is 3004, the problem has been solved successfully.

b. Click Cancelc. Select Action to be Read Resultsd. Select Object to be Result Entitiese. Select Method to be Attachf. Click Select Results Fileg. Select straw_ext.t16h. Click OKi. Click Apply

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Review and Display ResultsPlot the Displacement Result

a. Click Results iconb. Select Action to be Createc. Select Object to be Quick Plotd. In Select Results Cases, select the

last result (Time=1.00000)e. Click Fringe Attributes iconf. Click Spectrum, and select the one

you want.g. Select Style to be Continuoush. Select Shading to be Shadedi. Click Deform Attributes iconj. Uncheck Show Undeformedk. Click Select Results iconl. In Select Fringe Result, select

Displacement, Translationm. In Select Deformation Result,

select Displacement, Translationn. Click Apply

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Review and Display ResultsPlot the Nodal Reaction Force at the Controlling Node (Load vs. Displacement Curve)

a. Select Action to be Createb. Select Object to be Graphc. Select Method to be Y vs Xd. In Select Result Case(s), select all casese. Click Target Entity iconf. In Select Nodes, enter Node 1 or select the controlling node in the viewprotg. Click Select Results iconh. Click Display Attributes iconi. In XY Window Name, enter 5 or title number you wantj. Click Select Results iconk. Select Y to be Resultl. In Select Y Result, select Force, Nodal Reactionm. Select Quantity to be X Componentn. Select X to be Resulto. Click Select X Resultp. In Select X Result, click Displacement, Translationq. Select Quantity to be X Component r. Click OKs. Click Apply

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Review and Display ResultsPlot the Elastic Strain Energy

a. Select Action to be Createb. Select Object to be Graphc. Select Method to be Y vs Xd. In Select Result Case(s), select all

casese. Click Display Attributes iconf. In XY Window Name, enter 3 or title

number you wantg. Click Select Results iconh. Select Y to be Global Variablei. In Variable, select Elastic Strain

Energyj. Select X to be Global Variablek. Select Variable to be Timel. Click Apply

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• Displacement Results

Results

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At time=0.0

At time=1.0

At time=0.2

At time=0.4

At time=0.6

At time=0.8

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Results

• von-Mises at time=0.38

• von-Mises at time=0.15

Max=1.87E6 MPa

Max=1.62E6 MPa

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Results• Load vs. Displacement

• Strain Energy vs. Displacement (time=displacement factor)

Max=0.46N

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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.