O-Ring Estimated Time for Completion: 30 minutes Experience Level: Lower MSC.Marc 2005r2 MSC.Patran...
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Transcript of O-Ring Estimated Time for Completion: 30 minutes Experience Level: Lower MSC.Marc 2005r2 MSC.Patran...
O-Ring
Estimated Time for Completion: 30 minutesExperience Level: Lower
MSC.Marc 2005r2MSC.Patran 2005r2
2
Topics Covered
• Creating rigid and deformable contact boundary conditions
• Using axisymmetric elements
• Using Ogden material model
• Transforming geometries
• Associating finite elements to geometries
• Modifying analysis output requests
• Plotting and graphing the results
3
Problem Description
• In many applications, a contact between two parts are very critical. For example, the contact pressure between an O-ring and a hatch for a submarine need to be sufficiently large to prevent leakage. The groove and the O-ring need to be designed to provide the specified contact pressure. The ring also needs to survive the maximum loading condition.
O-ring
Hatch
Submarine’s entrance
Contact pressure must be sufficiently large to prevent leakage.
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• In this example problem, the analysis of a 3D model of O-ring is simplified using a 2D model. The ring is compressed by the hatch into the groove. An Ogden rubber model is used to model the ring. The hatch and the groove are assumed rigid.
• We will use Patran to complete the problem description from a given 2D meshed model and analyze it by using Marc.
Problem Description
Section A-A
A
A
Hatch
O-ring
Groove
Ring radius, R = 10”Cross section radius, r = 0.25”
R
r
5
Summary of Model
Term Modulus (psi) Exponent1 9.12 1.32 0.17 5.03 -0.14 -2.0
HatchRigid contactWith specified motion<-0.12,0,0>
O-ringDeformable contact
Ogden material model with 3 termsBulk Modulus is 1.45E9 psi.
10”
0.25”
GrooveRigid contact
[0,0,0]x
y
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Goal
• We will determine the contact pressure between an O-ring and a hatch at the closed position.
• Minimum principal (maximum compressive) stresses will also be investigated to provide information about the survival of the ring.
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Create Database
a. Click File menu / Select New
b. In File Name enter oring.db
c. Click OK
d. Select Analysis Code to be MSC. Marc
e. Click OK
a
bc
d
e
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Import Model
A given model
x
y
[0,0,0]
a. Click File menu / Select Import
b. Select Source to be MSC. Patran DB
c. Locate and select file oring_model.db
d. Click Apply
Notes: The coordinate of a given model is not correct for axisymmetric analysis. The model needs to be transformed.
x
y
z
Working plane to be used with axisymmetric analysis
a
b
c
d
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Transform Model
Transform geometries to the correct coordinate for axisymmetric analysis
Notes: When transforming geometries, the checkbox for Delete Original Entities should be checked. Otherwise, the entities will be duplicated. The numbering of the new entities will be different from the original ones.
a
a. Click Geometry icon
b. Select Action to be Transform
c. Select Object to be Curve
d. Select Method to be Rotate
e. In Rotation Angle, enter -90
f. Check Delete Original Curves
g. In Curve List, enter Curve 1 2 (or select Groove and Hatch)
h. Click Apply (Click Yes when asked to delete the original curves)
i. Select Method to be Translate
j. In Direction Vector, enter <0 10 0>
k. Check Delete Original Curves
l. In Curve List, enter Curve 3 4 (or selected Groove and Hatch)
m. Click Apply (Click Yes when asked to delete the original curves)
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m
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Transform Model
Transform elements to the correct coordinate for axisymmetric analysis
a. Click Elements icon
b. Select Action to be Transform
c. Select Object to be Element
d. Select Method to be Translate
e. In Numbering Option, Starting ID(s), enter 1
f. In Direction Vector, enter <0 10 0>
g. Check Delete Original Elements
h. In Element List, enter Elm 1:667 (or select all elements)
i. Click Apply
a
b
c
d
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f
g
h
i
This will keep the ELEMENT numbers of the transformed elements to start from 1. The NODE numbers of the transformed nodes, however, start after the last node number of the original node set.
Transforming elements automatically transform nodes attached to the elements being transformed.
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Create Deformable Contact
a. Click Loads/BCs icon
b. Select Action to be Create
c. Select Object to be Contact
d. Select Type to be Element Uniform
e. Select Option to be Deformable Body
f. In New Set Name, enter oring_contact
g. Select Target Element Type to be 2D
h. Click Select Application Region
i. Select Geometry Filter to be FEM
j. Select all elements on screen or enter Elm 1:667
k. Click Add
l. Click OK
m. Click Apply
a
b
c
d
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g
h
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k
l
Select all elements on screen by drawing a rectangle to include all elements of the ring
m
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Create Rigid Contacts
a
b
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h
i
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k l
a. Select Option to be Rigid Body
b. In New Set Name, enter groove_contact
c. Select Target Element Type to be 1D
d. Click Input Data
e. Check Flip Contact Side
f. Click OK
g. Select Application Region
h. Select Geometry Filter to be Geometry
i. Select Groove on screen or enter Curve 6
j. Click Add
k. Click OK
l. Click Apply
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Create Rigid Contacts
a. In New Set Name, enter hatch_contact
b. Click Input Data
c. In Velocity, enter <-0.12,0,0>
d. Click OK
e. Select Application Region
f. Select Hatch on screen or enter Curve 5
g. Click Add
h. Click OK
i. Click Apply
Notes: Make sure the contact sides are correct as shown in Summary of Model.
a
b
c
d
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f
g
h i
16
Define Material
a. Click Materials icon
b. In Material Name, enter rubber
c. Click Input Properties
d. Select Constitutive Model to be Hyperelastic
e. Select Model to be Ogden
f. Select Number of Terms to be 3
g. Enter values in Property Name as shown
h. Click OK
i. Click Apply
a
b
c
d
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hi
17
Define Element Properties
Quad Elementselection tool
a
a. Click Properties icon
b. Select Type to be 2D Solid
c. In Property Set Name, enter oring_prop
d. Select Options to be Axisymmetric
e. Click Input Properties
f. Click Material icon and select rubber
g. Click OK
h. Click Select Members textbox so that Selection Tool appears
i. Click Quad Element icon
j. In Select Members select all elements on screen or enter Elm 1:667
k. Click Add
l. Click Apply
b
c
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Create Load Step
This is to make sure that the Hatch is moved to the specified position since the contact motion was specified by velocity.
a
a. Click Analysis icon
b. Click Load Step Creation
c. In Load Step Name, enter close_gap
d. Click Solution Parameters
e. Click Load Increment Params
f. In Total Time, enter 1.0
g. Click OK
h. Click OK
i. Click Output Requests
j. Click Select Nodal Results
k. Click Contact Normal Stress, Contact Normal Force, and Contact Status
l. Click OK
m. Click OK
n. Click Apply
o. Click Cancel
b
c
d
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f
gh
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lmn
o
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Select load step
a. Click Load Step Selection
b. In Step Select, select close_gap and unselect Default Static Step
c. Click OK
d. Click Apply
** Wait until analysis is completed **
Read results file
e. Select Action to be Read Results
f. Click Select Results File
g. Locate file oring.t16
h. Click OK
i. Click Apply
Run Analysis and Read Results
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a. Click Results icon
b. In Select Result Cases, select the last increment
c. In Select Fringe Result, select Stress, Contact Normal
d. Select Quantity to be X Component
e. In Select Deformation Result, select Displacement, Translation
f. Click Apply
Plot Contact Stresses
Max contact stress (pressure) is 6.95 psi.
a
b
c
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f
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Graph Contact Stresses Along the Surface of the Ring
Create a curve to represent a surface of the ring
This curve will be used for the purpose of plotting
Use “Ctrl” button to select nodes on the ring’s surface.
a
a. Click Geometry icon
b. Select Action to be Create
c. Select Object to be Curve
d. Select Method to be 2DArcAngles
e. In Radius, enter 0.25
f. In Start Angle, enter -90
g. In End Angle, enter 270
h. In Center Point List, enter [0,10,0]
i. Click Apply
b
c
d
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i
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Graph Contact Stresses Along the Surface of the Ring
a
Associate nodes to the curve
a. Click Elements icon
b. Select Action to be Associate
c. Select Object to be Node
d. Select Method to be Curve
e. In Select Nodes, select all nodes along the boundary of the ring
f. In Select a Curve, select the curve on the ring surface or enter Curve 7
g. Click Apply
Notes:
Hold “Ctrl” button once and click on screen to activate the use of polygon selection tool. Double click to finalize the selection.
Use View Corners zoom to zoom in for easier selection.
b
c
d
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g
Select nodes on screen
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a. Click Results icon
b. Select Object to be Graph
c. In Select Result Case, select last increment
d. In Select Y Result, select Stress, Contact Normal
e. Select Quantity to be X Component
f. Select X to be Path Length
g. Click Target Entities icon
h. Select Target Entity to be Path
i. Select Addtl. Display Control to be Curves
j. In Select Path Curves, select curve on the ring from screen or enter Curve 7
k. In Point Per Segment, enter 100
l. Click Apply
Graph Contact Stresses Along the Surface of the Ring
a
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Plot Minimum Principal Stresses
Max compressive stress is 6.98 psi.
a. Select Object to be Quick Plot
b. In Select Result Case, select last increment
c. In Select Fringe Result, select Stress, Global
d. Select Quantity to be Min Principal
e. In Select Deformation Result, select Displacement Translation
f. Click Apply
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b
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d
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f