Instructions MAE 323 Lab Instructions 1
Problem Definition Determine how different element types perform for modeling a cylindrical pressure vessel over a wide range of r/t ratios, and how the hoop stress (σ θ ) in the cylindrical section compares to theoretical equations for thin and thick cylinders under internal pressure, p. Learning Objectives To gain familiarity with element types Learn to validate FE models and qualify FEA results MAE 323 Lab Instructions 2
In Lab 7, the entire FEA process is completed, with the focus being on element type comparison (meshing) and post-processing FEA Process Geometry Lab 7 focus Meshing Loads and Boundary Conditions Solving Lab 7 focus Post-processing MAE 323 Lab Instructions 3
Analysis Description The analysis will be performed using 4 different element types and 4 different r/t ratios based on the base configuration given in figure below. The model dimensions should be parameterized in such a way that the thickness can be changed without re-creating the geometry. Maintain a constant element size of.2 in and use triangle/tetrahedral elements for all models. MAE 323 Lab Instructions 4
Geometry Description The pressure vessel possesses the following characteristics for all models: Inner radius (r0)=3.5, p=1500 psi. Four different values of thickness should be investigated: t=.25,.5, 1,1.5. MAE 323 Lab Instructions 5
Shell Elements Model Setup: Geometry Creation In DM, based on the image in Slide 3, create geometry using a (quarter-circle) arc with R = 3.5 inches and an extrude of Depth = 10 inches You should have a surface body when you are finished MAE 323 Lab Instructions 6
Shell Element Model Setup: Mechanical Setup Transfer your geometry to a Static Structural Analysis System. Your Analysis Type under Geometry Properties should be 3D Open Mechanical Expand your Geometry in your Model tree, click on the Surface Body Change your thickness to 0.25 inches Make your Offset Type: Middle (Membrane) MAE 323 Lab Instructions 7
Shell Element Model Setup: Mechanical Setup Properly constrain your model so that all degrees of freedom (DOFs) are supported so that your model will not experience rigid body motion Consider symmetric conditions Ask the question, how many DOFs do the elements that comprise this model have? Apply a pressure normal to the face of your model with magnitude 1500 psi. The pressure direction should be towards the outside of your model MAE 323 Lab Instructions 8
Shell Element Model Setup: Mechanical Setup Now that you model is setup, choose the parameters that you want to track so that you can get the hoop stress results for the varying model thicknesses Refer to the Lab 7 Template for the r/t ratios that you should be analyzing to populate Table 1 in the Template Record the hoop stress values Also be sure to record the Total Number of DOFs in your model to populate Table 2 in the Template. MAE 323 Lab Instructions 9
Solid Elements Model Setup: Geometry Creation In DM, using the image on Slide 3 and the dimensions on Slide 4, create the model below You should have a Solid body when you are finished MAE 323 Lab Instructions 10
Solid Elements Model Setup: Mechanical Setup Drag a Static Structural Analysis to share your geometry Your Analysis Type should be 3D Properly constrain your model by Determining the DOFs that need to be supported Considering symmetry Apply a pressure of 1500 psi normal to your model MAE 323 Lab Instructions 11
Solid Elements Model Setup: Mechanical Setup Parameterize the thickness, stress, and number of nodes in your model Using the results from your analysis, populate Tables 1 and 2 in the Lab 7 Template MAE 323 Lab Instructions 12
Plane Strain Model: Geometry Creation In DM, using the image on Slide 3 and the dimensions on Slide 4, create the geometry below using a combination of Extrudes and Thin Surfaces Make sure you have a Surface Body when you are finished MAE 323 Lab Instructions 13
Plane Strain Model: Mechanical Setup Back on your Project Page Click on the geometry Component for your Plane Strain model and under the Properties change your Analysis Type from 3D to 2D Then drag a Static Structural Analysis to share your geometry Open Mechanical In Mechanical, make your 2D behavior Plane Strain Constrain your model Consider symmetry Ask what DOFs need to be support Apply a pressure of 1500 psi on the appropriate geometry Track your hoop stress and total number of DOFs based on your changing r/t ratio Populate Tables 1 and 2 in the Template MAE 323 Lab Instructions 14
Axisymmetric Model: Geometry Creation In DM, using the image on Slide 3 and the dimensions on Slide 4, create the geometry shown below Make sure you have a Surface Body when you are finished MAE 323 Lab Instructions 15
Axisymmetric Model: Mechanical Analysis Setup On your Project Page Make sure your Analysis Type is 2D for your Axisymmetric model Drag a Static Structural Analysis to share your Geometry In Mechanical Change your 2D behavior to Axisymmetric Properly support your model Consider symmetry And DOFs Analysis Track your hoop stress and total number of DOFs based on your changing r/t ratio Populate Tables 1 and 2 in the Template MAE 323 Lab Instructions 16