Analysis of Stresses in a Long Cylindrical Pressure Vessel
Prepared by Prof. Charlton S. Inao
Answer Key to Exam ansysFrom Srinivas,Sambana,Datti
Problem• A long cylindrical pressure vessel of inside
diameter 10 cm and outside diameter 20 cm is
subjected to an internal pressure P= 10,000 N/cm2
.2D Structural solid element PLANE 82 is used to
perform the analysis. Poisson Ratio =0.3 and the
Young Modulus of elasticity is 2.1 e7 N/cm2. Axis
symmetric option is selected for element behavior.
One material model is defined. Solid modeling
approach is employed and geometric entity model.
The maximum deflection, tangential and radial
stresses induced in the pressure vessel are
determined if stress is taken 10 cm arbitrarily along
the y axis.
Inside diameteer =10 cmOutside diamter=20 cmPressure =10 Kn/cm2
Material element Solid Structural Plane 82(Quad 8 Node 82) Poissons Ratio= 0.3Youngs modulus=2.1e 7 N /cm2
Element Behavior =Axissymmetric
Stress shall be taken 10 cm arbitrarily along y axis
Utility Menu>Change Jobname> type ‘Pressure Vessel’
Utility Menu> File > Change title
Main Menu> preprocessor>>Element Type>Add/Edit/Delete>Add>Structural
Solid>Quad 8 Node 82>Ok
In the Element Type> click Options>element behavior K3, >Axis Symmetric>Ok
Main menu>Preprocessor> Material props> Material Models>Define material Model Behavior>Structural> Linear>Elastic>Isotropic> EX=2.1 E7;>PRXY>0.3> Ok
Preprocessor> Modeling>Create>Keypoints>In Active CS
Keypoint No. X Y Z
1 10 0
2 20 0
3 20 10
4 20 10
Modeling
Utility or Pulldown Menu>List >Keypoints> Coordinates Only (To see the list or tabulation of
keypoints)
Main Menu>Preprocessor> Modeling>Create>Areas>Arbitrary>Through KPs>Pick
keypoints 1,2,3,4 and click OK
MainMenu> Processor> Meshing> Size Controls>Manual Size>Global >Size> Global element sizes> enter 20 for No . Of
Element Divisions>Ok
•
Sizing of elements
Main menu> pre processor>meshing>Mesh> Areas>Free> Pick All
Meshing
Utility Menu> Select EntitiesSelect
1. Nodes from entity Type drop down Box
2. By Location from the Selection Criteria
3. Y coordinates from Location Setting
4. 0 for Min, Max5. From Full for Selection
Function Setting6. Apply followed by
Plot7. Close the Select
Entities by OK
Main menu>Preprocessor> Loads>Define Loads>Apply>Structural>Displacements>On
Nodes>Pick All
Apply Constraints/displacement =0
Apply U,ROT on Nodes dialog box, select Uy for DOF to be constrained and click Ok
After constraints are applied on Y direction for all the nodes, the screen should look like this
In the utility menus> Select>Entities
• Select nodes (Entity Type)
• By Location(Selection Criteria)
• Y coordinates (Location Settings)
• 10 ( for Min , Max)
• From Full(Selection function Setting)
• Apply
• Plot
• Ok
Main Menu>Preprocessor>Coupling/Ceqn>Couple DOFs> Pick All.. Enter 1 for Set Reference Number, Select Uy for Degrees of
Freedom Label and click OK
Utility Menu>Select>EverythingUtility Menu>Plot>Replot
Utility Menu>Select Entities
Nodes (Entity Type)
By location (Selection Criteria)
X Coordinates (Location settings)
10 (Min,Max)
From Full (Selection Function Setting)
Apply
Plot
OK (close the Select Entities Dialog Box)
Main Menu>Preprocessor>loads>Define Loads>Apply> Structural> Pressure> On Nodes>Pick
All
Apply Pressure On Nodes
Apply PRES on Elements dialog box> enter 10000 for Load PRES Value> Click OK
When the pressure of 10000 N/cm2 is applied to all the nodes , the screen should appear like this
Utility Menu>Select>EverythingUtility menu>Plot>Elements>
Save DB in the Ansys Toolbarmain Menu >Finish
SOLUTION PHASE
Main Menu>Solution>Solve>Current LS
Click OK>Solve Current Load Step dialog box
Click Close on the Note quoting Solution is Done
Close the /Status Command Window..
Main Menu>Finish
Utility Menu>Plot Cntrls>Style>Symmetry Expansion>2D Axis Symmetric
On the 2D Axis Symmetric Expansion dialog box>select ¾ Expansion for Selection Expansion Amount ,Ok
Utility Menu> Plot> Replot
Main Menu>General Postproc>Plot Results>Contour Plot>Nodal X Component of Stress>Ok
On the Contour Nodal Solution Data dialog box, select Nodal Solution>Stress>Z –Component of Stress>Click OK
to view the Hoop Stress
In the main menu, select General Postproc>ListResults>Nodal Solution
On the List Nodal solution Data dialog box, select Nodal Solution>Stress>X-Component of Stress>OK
Review and close the PRNSOL Command window.
Utility Menu> File> Exit.Exit from Ansys>Save Everything >OK
Minimum Hoop Stress 16.66 N/mm2 at inner radiusMaximum Radial Stress 9.985 N/mm2 at inner radius
The End
Thank You