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ANSYS Model of a Cylindrical Fused Silica Fibre

Steven ZechEmbry-Riddle Aeronautical University

Dr. David Crooks and Dr. Calum TorrieUniversity of Glasgow

29 June 2006

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OverviewNOTE: This Tutorial was designed for a person with some general

Knowledge of ANSYS.

Model a Cylindrical Fused Silica Fibre using Beam elements.

Extract the energy in the tapered region and compare to overall energy.

Material Properties: EX = 7.2E10 PRXY = 0.17 Density = 2202

Boundary Conditions: Constrained at one end.

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Designing the Fibre

• Enter ANSYS • Create 4 Keypoints [at the points: (0,0); (0,0.375); (0,0.38); (0,0.39)]

• Main Menu > Preprocessor > Model > Create > Keypoints> On Working Plane (This is used to create 3 lines)

• Create 3 Lines• Main Menu > Preprocessor > Model > Create > Lines > Straight Lines

(pick Keypoint 1 and then keypoint 2 to create the first line, repeat for 2,3 and 3,4). The 3 Lines will be used to Create designated regions which will define a base, tapered neck and the fibre.

• Define Material Properties & Element Type• Main Menu > Preprocessor > Material Props > Material Models >

Structural• > Linear > Elastic > Isotropic [enter EX: 7.2e10; PRXY: 0.17]

• > Nonlinear> Density [Density: 2202] • Main Menu > Preprocessor > Element Type > Add/Edit/Delete > Add >

BEAM 189 (Beam > 3 node 189) > OK > Close

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Designing the Fibre

• Defining the 3 “BEAM” Sections• Main Menu > Preprocessor > Sections >Beam >

Common Sections• For ID 1 [Name: Top, Sub-Type: Circle, R: 1.5e-3, N:

100] > Apply• For ID 2 [ID: 2, Name: Bottom, Sub-Type: Circle, R:

470e-6, N: 100] > OK• Main Menu > Preprocessor > Sections > Taper

Sections > by XYZ Location (see Create Taper Section box below)

• Taper section ID 3 [Name: Taper, Beg. Sec. ID: 1 Top, XYZ Loc. Beg. Sect: 0, 0.38; End Sec. ID: 2 Bottom; XYZ Loc. End Sect: 0, 0.375

• > OK

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Designing the Fibre (Meshing)

• Meshing (creating the BEAM Elements)• Main Menu > Preprocessor > Meshing >

MeshTool (see image to the Right)

• Element Attributes > Lines > Set• Pick Line 1 > Apply [SECT: 2 Bottom] > Apply• Pick Line 2 (may need to zoom in) > Apply [SECT: 3 Taper] >

Apply• Pick Line 3 > Apply [SECT: 1 Top] > OK

• Size Controls > Global > Set (see image below)

• [NDIV No. of element Divisions: 10] – this sets the number of Divisions per segment. The Beam is divided into 3 line segments so 30 elements will be produced. > OK

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Designing the Fibre (Meshing)

• MeshTool > Mesh > Pick All

- NOTE: If the structure does not show the next command is needed

• In the ANSYS Command Prompt Type: /ESHAPE, 1 [enter] EPLOT [enter] – zoom in to see structure of elements if desired.

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Applying a Load & Solving

• Applying the Load• Main Menu > Preprocessor > Loads > Define Loads > Apply >

Structural > Displacement > On Keypoints – click fit view

• Pick the top keypoint (keypoint 4) > Apply > All DOF > OK

• Solution• Main Menu > Solution > Analysis

Type • > New Analysis > Modal > OK• > Analysis Options [No. of

Modes to extract: 6; NMODE: 6; Calc. Elem Results: Check Yes] > OK > OK

• SAVE (Utility Menu > File > Save OR type SAVE in the ANSYS Command Prompt.)

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Solving. . .

• Main Menu > Solution > Solve > Current LS – Begin Solution of Current Load Step > OK

• When the solution is done click [Close] and proceed to Post-Processing

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Post-Processing

• Finding the Energy• Main Menu > General PostProc > Read Results > by Pick

This will show the 6 solutions (or modes) and the frequency at which the mode exists.• Pick Set 1 > Read > Close

• Main Menu > General PostProc > Element Table > Define Table > Add [Item: Energy > SENE] > OK > Close

• For a list of each element and its energy at the picked frequency:• Main Menu > General PostProc > Element Table > List Elem Table

• For the total energy at the picked frequency: • Main Menu > General PostProc > Element Table > Sum of Each Item >

OK• To get an Energy of a Different Frequency or Mode:

• Main Menu > General PostProc > Read Results > by Pick• Pick Frequency > Read > Close

• Main Menu > General PostProc > Element Table > Define Table > Update

• Main Menu > General PostProc > Element Table > Sum of Each Item > OK

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Energy in the Tapered Neck

• Selecting the Elements in the Neck• Utility Menu > Select > Entities > Lines > By Num/Pick

• Select line 2 > OK (Raise Hidden)• > Elements > Attached to > Lines > Apply > Plot

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Energy in the Tapered Neck

• Finding the Energy• Repeat the process from finding the total energy only

Results will be for selected region only. • Selecting Everything

• Utility Menu > Select > Everything• Utility Menu > Plot > Elements (or type EPLOT in the ANSYS

Command Prompt

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Applying gravity and Using Stress Stiffening Effects

Steven ZechEmbry-Riddle Aeronautical University

3 August 2006

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Setting up an example model

• Create a Pendulum using the methods from “ANSYS Model of a Cylindrical Fused Silica Fibre” by the same Author

• Choose an element that has stress stiffening effects (i.e. BEAM189) and add material properties

• Create keypoints, lines and Beam sections.• Apply mesh and all Displacement criteria in the

pre-processor (Prep7)

This was made with the Information from Wilde FEA Ltd. and the ANSYS Product Help

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Adding Gravity to the ANSYS Model

• Applying Gravity• Main Menu > Solution (can also be applied in Preprocessor) >

Define Loads > Apply > Structural > Inertial > Gravity > Global.• To apply gravity (or to “Simulate Gravity”), An acceleration must be

applied in the opposite direction of gravity. Example: if gravity is in the negative y-direction (i.e. -9.81 m/s2) then apply an ACEL Y of +9.81. (See figure)

• Solving using a Static Solution (Including Stress Stiffening)• A Static solution must be ran before the Modal solution to calculate

the Eigen values and eigenvectors to properly model Stress stiffening as a result of gravity.

• Main Menu > Solution > Analysis Type > New Analysis > Static > OK

• Solve

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Adding Gravity cont. . .• Modal Solution

• Main Menu > General PostProc (to avoid error messages)

• Main Menu > Solution > Analysis Type • > New Analysis > Modal

> OK• > Analysis Options [No.

of Modes to extract: 24; NMODE: 24; Calc. Elem Results: Check Yes; PSTRES: Check Yes] > OK > OK

• SOLVE• Review the Results

The PSTRES command uses the Eigen values and Eigenvectors calculated in the Static

solution to add stress stiffening, which is needed to simulate gravity in the model.