1 ansys model of a cylindrical fused silica fibre steven zech embry-riddle aeronautical university...
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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.