interference fits mar 120 - interference fits. ws 13 - 2 mar 120 - interference fits model...

INTERFERENCE FITS

MAR 120 - Interference Fits

WS 13 - 2MAR 120 - Interference Fits

Model Description:Two types of interference fit modeling are demonstrated in this workshop. Interference fits can be modeled geometrically or by specifying an Interference Closure amount in the MSC.Marc Contact Table and using congruent geometry. This workshop will show that the same results are achieved for both methods.


Objectives: Investigate contact cable parameters. Contact analysis using deformable-deformable contact

Required: A file named interference_fit.igs in your working directory.


Exercise Overview:

• Import the geometry.

• Mesh the deformable bodies.

• Define the deformable contact bodies.

• Define the materials and properties.

• Modify the contact parameters and the contact table.

• Submit the job to analysis.

• Evaluate the results.


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Create a new database. Name it Interference_Fit.db.

a. Select File / New.b. Enter Interference_Fit as the

file name.c. Click OK.d. Select MSC.Marc as the

Analysis Code. e. Click OK.

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Step 1. Create a New Database


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Import the required geometry.

a. Select File / Import.

b. Switch the Source to IGES.

c. Select interference_fit.igs as the File name.

d. Click Apply.

Step 2. Import the Geometry


Step 2. Import the Geometry (Cont.)

e. Click OK on the Import Summary Page.

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The ‘Import Summary’ Page shows what types of entities were imported into the MSC.Patran

database. After clicking OK, the geometry should look like the image to the left.

The geometry that was imported should consist of 3 surfaces. One large Lug with 2 Pins. The Lower Pin has the interference of 0.01 inches built into the geometry.

The Upper Pin geometry is congruent with the Lug geometry. The interference fit in this case will be created by the Interference Closure Contact Parameter which will

force a gap between the two bodies.


Step 3. Create the Elements

Create the finite element mesh.

a. Elements:Create / Mesh / Surface.

b. Select the Paver Mesher.

c. Verify that Quad8 elements are selected. Quad8 elements are higher-order elements with mid-side nodes.

d. Select all three Surfaces in the view port.

e. Unselect the Automatic Calculation.

f. Enter 0.1 for the Global Element Length value.

g. Click Apply.

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After meshing, the viewport should look like the image above.

When using Plane Strain, Plane Stress, and Axisymmetric Elements, the Element Normal Direction must point in the +Z

Direction. These elements are oriented properly.

To check the Element Normal Direction, choose the Verify/Element/Normal option and turn on the option to draw

the vectors.


Step 4. Fix the Left Edge of the Lug

Create the Boundary Condition fixing the left edge of the Lug.

a. Loads/BCs: Create / Displacement / Nodal.

b. Enter Fixed as the New Set Name.

c. Click on Input Data.

d. Enter <0,0, > for the Translation.

e. Click OK.

f. Click the Select Application Region Button.

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g. Confirm the Geometry Filter is set to Geometry.

h. Select the Curve of Edge option in the Select Menu.

i. Select the left edge of the Lug.

j. Click Add.

k. Click OK.

l. Click –Apply-.

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Step 4. Fix the Left Edge of the Lug (Cont.)

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Step 5. Define the Deformable Contact Body for the Lug

Create the deformable contact body for the Lug.

a. Loads/BCs: Create / Contact / Element Uniform.

b. Confirm Deformable Body as the Option.

c. Enter Lug as the New Set Name.(要選 discrete的選項 )

d. Select 2D as the Target Element Type.

e. Click on Select Application Region form.

f. Confirm that the Geometry option is selected for the Geometry Filter.

g. Select the Lug Surface.

h. Click Add.

i. Click OK.

j. Click Apply.

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After you click Apply, you will see the contact markers

(pink circles) in the viewport.


Step 6. Define the Deformable Contact Body for the Upper Pin

Create the deformable contact body for the Upper Pin.


b. Confirm Deformable Body as the Option.

c. Enter Upper-Pin as the New Set Name.(要選 analytic的選項 )




g. Select the Upper Pin Surface.

h. Click Add.

i. Click OK.

j. Click Apply.

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Step 7. Define the Deformable Contact Body for the Lower Pin

Create the deformable contact body for the Lower Pin.


b. Confirm Deformation Body as the Option.

c. Enter Lower-Pin as the New Set Name. (要選 analytic的選項，原因可參考 course note 8-13頁 )




g. Select the Lower Pin Surface.

h. Click Add.

i. Click OK.

j. Click Apply.

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Step 8. Define the Steel Material Properties

Define the Steel material.

a. Materials: Create / Isotropic / Manual Input.

b. Enter Steel as the Material Name.

c. Click on Input Properties.

d. Confirm Elastic as the Constitutive Model.

e. Enter 30e6 as the Elastic Modulus.

f. Enter 0.3 as the Poisson Ratio.

g. Click OK.

h. Click Apply.

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Step 9. Define the Element Properties

Define the Element Properties.

a. Properties: Create / 2D / 2D Solid.

b. Enter Steel as the Property Set Name.

c. Confirm Plane Strain as the Option.

d. Confirm Standard Formulation.

e. Click on Input Properties.

f. Click on Mat Prop Name icon.

g. Choose Steel from the Existing Material list.

h. Click OK.

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i. Click in Select Members panel.

j. Select all three Surfaces.

k. Click Add.

l. Click Apply.

Step 9. Define the Element Properties (Cont.)

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The Non-Positive Definite option is needed in this

problem due to the existence of rigid body modes. The

rigid body modes are due to the fact that there are no

constraints on the pins in the model except for the contact

with the lug. Without this option, the analysis would end in a 2004 Exit Number.

Step 10. Analyze the Model

Setup and launch the Analysis.

a. Analysis: Analyze / Entire Model / Full Run.

b. Enter Interference_Fit as the Job Name.

c. Click on Job Parameters.

d. Click on Solver Options.

e. Check the Non-Positive Definite option.

f. Click OK.

g. Click on the Contact Parameters option.


Step 10. Analyze the Model (Cont.)

h. Click on the Contact Detection button.

i. Check the Activate Quadratic Contact(此選項打開之後計算結果似乎會有差異？ )，先不要選 Option.

j. Click OK.

k. Click OK.

l. Check the Assumed Strain Option.

m. Click OK.

n. Click on the Load Step Creation button.

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When running models with Higher-Order Elements, such as Quad8 elements, turning on the Quadratic Contact option will allow the contact algorithm to include the mid-side nodes in the contact detection. The analysis will have more accurate contact regions and smoother stress contours. Without this option, the

mid-side nodes on the external surface (3D) or edges (2D) will be ignored and the elements will be assumed to be linear elements.

We are turning on the Assumed Strain option because we are using Standard Formulation Plain Strain elements and the Assumed Strain option will provide more accurate results. It is recommended to use the Assumed Strain option for Standard

Plain Strain, Plane Stress, and Hex Elements.



o. Click on Solution Parameters.

p. Click on Load Increment Params.

q. Enter 1.0 for the [Trial Time Step Size ].

r. Click OK.

s. Click on Contact Table.

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Most interference fit problems can be solved over one increment. More may be required if

there is material plasticity included in the model. To tell MSC.Marc to solve the job in one

increment, we can set the Trial Time Step Size parameter to 1.0, which is the same as the

default Total Time for the Increment.

The default setting for the Trial Time Step Size parameter is 0.01 (or 1% of load).



t. Click on the [T] boxes on the diagonal until they are blank [ ]. This will turn off the self-contact checking.

u. Turn off contact between the Upper Pin and Lower Pin. Since these two bodies will never be touching, we can turn off the contact checking.

v. Select the Lug and Lower-Pin in the Body Pairs Section.

w. Enter 0.015 for the Distance Tolerance and press the Enter key.

x. Select the Lug and Upper-Pin in the Body Pairs Secton.

y. Enter .01 for the Interference Closure and press the Enter key.

z. Click OK.

By setting a Distance Tolerance larger than the geometric interference between the Lug and Lower Pin, the contact algorithm will be able to recognize the penetration and resolve the contact. If we left the default setting of 0., the calculated Distance Tolerance may not be large enough to recognize the interference.(因為一開始就穿剌進去，如此marc沒辦法辨視初始穿剌，預設值為 element

smallest edge 之 1/20for shell，所以本題此值為 0.005，而一開始穿剌之值為 0.01大於此值，故需將此值設大於 0.01如此才能辦視穿

剌，而將穿剌之元素捉回表面 )

By setting the Interference Closure between the Lug and the Upper Pin to 0.01, we are telling the MSC.Marc contact algorithm

to add a gap of that value between the two bodies.

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aa. Click OK.

ab. Click Apply. (Click yes to Overwrite the Job Step.)

ac. Click Cancel.

ad. Click Apply.

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Step 11. Monitor the Job

Monitor the job.a. Analysis: Monitor / Job.b. Select Interference_Fit as the Job Name.c. Click Apply.d. Click Cancel when the job is complete.e. Click on View Status File.f. Close the Status File Window.

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Notice that the job was completed in 1 increment and took 4 cycles to converge.

For jobs with an interference fit combined with external loading, set the first load case to resolve the interference fit and add additional load cases for the external loads. The external load cases should use the standard load

incrementation settings.


Step 12. Attach the Results

Read (Attach) results.

a. Analysis: Read Results / Result Entities / Attach.

b. Click on Select Results File form.

c. Select file Interference_Fit.t16.

d. Click OK.

e. Click Apply.

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Notice that the stress results from the two interference fits are nearly identical.

We can make the plot cleaner by unposting the geometry from the viewport and modifying some of the Fringe and Deformation settings. The following steps

will show these settings.

Step 13. Plot the Stress

Post-process results.

a. Results: Create / Quick Plot.

b. Select the last result case.

c. Select Stress, Global System as the Fringe Result.

d. Select Displacement, Translation as the Deformation Result.

e. Click Apply.

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Step 14. Modify the Fringe and Deformation Attributes

Post-process results.

a. Click the Plot/Erase ToolBar icon.

b. Click Erase under the Geometry Heading.

c. Click OK.

d. Click the Fringe Attributes icon.

e. Change the Fringe Edge color to Black.

f. Change the Display to Element Edges.

g. Turn off the Max/Min Labels.

h. Click on the Deformation Attributes icon.

i. Turn off the Show Undeformed option.

j. Click Apply.

The resulting plot is shown on the next page.

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Step 14. Modify the Fringe and Deformation Attributes (Cont.)

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We now have just the deformed mesh in the viewport and the element edges are shown in black. Feel free to try out different settings for the Fringe and Deformed plots.


Step 15. Quit MSC.Patran

interference fits mar 120 - interference fits. ws 13 - 2 mar 120 - interference fits model...

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