2_2D_Thread

2011 ANSYS, Inc. July 12, 2013 1

2D axisymmetric threaded connection

2011 ANSYS, Inc. July 12, 2013 2

Any 3D Model which has a symmetrical behavior around an axis can be modeled by 2D Axisymmetric

Axisymmetric Conditions:

Axisymmetric Geometry (e.g. Cylinders)

Axisymmetric Loading Condition (e.g. Uniform pressure inside pipe)

Axisymmetric Boundary condition(BC) (e.g. Uniform displacement support on cross section)

Benefit:

Significant Reduction of Modeling time

Significant Reduction of Computational time

Improvement of accuracy and convergence

Axisymmetric Modeling

2011 ANSYS, Inc. July 12, 2013 3

Objective: Convert a 3D to a 2D axisymmetric threaded connection model and

analyze stresses under the influence of internal pressure and tensile force

Contact with initial interference

Roller support

1000 psi pressure

10000 lb tensile force

Problem Statement

Note: All Three Axisymmetric Conditions are valid in this model - Cylindrical symmetry because of cylindrical shape - Axisymmetric loads: uniform internal pressure - Axisymmetric BC: Roller Support on one side of cylinder

3D Model 2D Model

Note: The tensile force and uniform internal pressure values are equal to the ones applied to the full 3D model

2011 ANSYS, Inc. July 12, 2013 4

3D versus 2D comparison

Axisymmetric model provided

Fewer number of elements fewer number of degrees of freedom (DOF)

Higher quality of elements More accurate solution

Less time for meshing

Less time for solution

# of Elements=761,028 # of Elements=1,287,316 # of DOF=3,861,948

# of Elements=3,721 # of Elements=11,851 # of DOFs=23,702

2011 ANSYS, Inc. July 12, 2013 5

Steps

Extract the planar geometry from 3D model

Create 2D model in positive quadrant (Positive X and Positive Y)

Properly Reorient model to make Y axis as symmetric axis

Change geometry setup from 3D to 2D

2D meshing and including local controls to account for possible threaded connections

Apply load and boundary condition

Solve

Post Process

2012 ANSYS, Inc. July 12, 2013 6 Release 14.5

Project Schematic 1. From the Toolbox insert a Static

Structural system into the Project Schematic.

2. From the Geometry cell, RMB and Import Geometry > Browse. Import the file connector_full.x_t provided with this PPT

3. Double click the Geometry cell to start DesignModeler.

1.

2.

3.

Note: RMB= Right Mouse Button


Unit Selection DM starts with a prompt to select desired length unit. Select Inch and click OK.

Click the Generate button on the toolbar. The 3D model will appear in the graphics window. Note: By default, DM imports the geometry in the XYPlane


Slicing Select Create>Slice. Click on the XYPlane in the Tree View, then click

Apply in the Details View. Click Generate in the Toolbar.

Note: The cross-section of the model to be used for 2D has to lie on the global positive XY plane. If not the case, you need to reorient it to the correct plane either by: Importing the geometry on a different base

plane than the default XYPlane. Select Import geometry, RMB/Edit Selections, select ZX or YX Plane

Rotate the geometry. Create/BodyOp1, choose Type to be Rotate and choose the appropriate Axis and Angle.


Extract cross section

Select the first two Solids in the Tree while holding the Ctrl key. Right Click, and choose Suppress Body.

Click Thin/Surface on the Toolbar. In the Details View, set the Selection Type to Faces to Keep. Select the two cut faces of the two parts on the right-hand side. Apply. Set Thickness to 0. Generate.


Set Analysis Type to 2D

At the Workbench project level, select Geometry then go to View/Properties

Select 2D for Analysis Type.

Double click the Model cell to start the Mechanical application.

Note: Make sure that Analysis Type is set to 2D before opening your model in ANSYS Mechanical. You can not switch from 3D to 2D after you open in Mechanical


Settings in ANSYS Mechanical

Click on Geometry on the Outline Tree. In the Details, set the 2D Behavior to Axisymmetric

Select the Surface Bodies to assign appropriate material model

Insert the Contact Tool to generate Initial Contact information (Select Connections. RMB/Insert Contact Tool). Notice Interference between threads

Under Connections, select Contact Region, in the Details View, set:

Contact Type to Frictional

Friction Coefficient: 0.1

Interface Treatment: Add Offset, Ramped Effects

Update Stiffness: Each Iteration, Aggressive


Mesh settings

Select Mesh, RMB, Insert Sizing. Choose selection filter to Edge Select and select mode to Box Select. Box select the contact area as shown, click Apply in Details View. Choose Type to Number of Divisions, set the number to 10 and Behavior to Hard. Generate Mesh


Visualize and Verify the Axisymmetric Model

To check and verify the axisymmetric shape, the 3D representation of model can be visualized as the following:

1- in workbench:

go to main menu tools options

Select Appearance from tree and check the "Beta Options"

2- In Mechanical,

Right click on your Model Tree and insert Symmetry condition

In the detail Menu select 2D AxiSymmetric as the TYPE

With number of repeat and angle difference, you can control the number of division and the amount of expansion

((Num Repeat-1)*Delta_Teta = total expansion angle) e.g. (37-1)*10 = 360 so Num Repeat=37 and Delta_Teta=10

3- Click on Mesh in the tree to see the 3D view.


Analysis Settings 1 In the Details of Analysis Settings, set Number of Steps

to 2 and Large Deflection On.

Note: No load is being applied in the first load step to allow the solver to overcome the interference between the threads

Select Static Structural, RMB, Insert Frictionless Support, select the bottom edge of the model, click Apply


Analysis Settings 2

Select Static Structural, RMB, Insert Pressure, select the inner edges (left hand side) of the model, click Apply. In the Tabular Data, enter 1000 psi for Step 2

Select Static Structural, RMB, Insert Force, select the top of the model, click Apply. In the Details View, change Define By to Components. In the Tabular Data, enter 10000 lbf for Step 2 in Y direction


Solve & Post Processing Select Solution, RMB, insert Total Deformation, Equivalent Stress and Stress Tool Solve & Post Process

Equivalent Stresses Safety Factor

2_2D_Thread

Documents

Transcript of 2_2D_Thread