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6002 Lab#2: more ANSYS, page 1
Engineering 6002 - Ship Structures I
Lab#2
Single Frame analysis By C. Daley
Overview
In this lab we will model a single tee-section frame. Once
again, we will use SpaceClaim to create the geometry model
of the problem, and then use ANSYS to model the structural
behavior. We will explore some more features of both
SpaceClaim and ANSYS.
The lab will focus on;
- Build skills in SpaceClaim
ANSYS Model #2 – Single tee frame model
Step 1: describe and sketch the problem:
The aim is to model a beam that represents a single tee frame in a ship. The whole section looks
like an unsymmetrical I beam as shown below. To compare with beam results we will analyze
the case of a cantilever beam, with a load 0.2MN on the first half of the beam.
6002 Lab#2: more ANSYS, page 2
Step 2: estimate expected results (analytically):
The first step is to determine the moment of inertia of the beam, and then the value of EI.
The response that we might expect is;
Step 3: open ANSYS Workbench 19.0
1) First, save the (empty) project as Beam1.wbpj 2) The left-hand window shows a set of analysis type options. Select Static Structural and
drag the icon to the right, placing it in the Project Schematic window.
6002 Lab#2: more ANSYS, page 3
Step4: open Geometry and create the CAD model
1) By Clicking Geometry in the Project window, ANSYS will open a CAD modeling
program called SpaceClaim. You will see a window like this;
2)
3) If you want to change options or units, you can go to the file tab and select SpaceClaim
Options. This will let you change Units (mm are default) and many other options.
6002 Lab#2: more ANSYS, page 4
You now see the main window where the CAD model will be displayed, just as in Lab#1.
4) In the Design tab there are many drawing and editing tools. Let’s start by changing the
sketch plane to a vertical plane, so we can draw cross sections of our beam in a vertical
plane and then extrude them (pull them) to make a horizontal beam. To do this select the
sketch plane icon at the bottom of the screen.
Then move the mouse above the existing sketch plane and click.
NOTE: anytime you wish you can hit Undo to erase mistakes and re-do your steps.
5) Draw the component rectangles.
We need to draw the cross section of the beam. There are many ways to do this,
depending on the user’s knowledge of various commands and features. Here we will use
a way that will work with a few simple steps, and without much chance of error. We will
draw half the beam and mirror it to produce the whole x-section.
Start by selecting Plan View . Now zoom in so you see the origin. Now
select the rectangle creation tool in the Sketch area of the Design tab. By default
snapping to the grid (and many other features) is on. As you move the mouse over the
grid you will see a + snapping to the grid. Move the mouse so the + is at the origin
6002 Lab#2: more ANSYS, page 5
and left-click-hold-drag the mouse. As you drag you will see something like the
following;
Both rectangle dimensions are shown. If you start typing (while dragging or after) the
dimension will become what you type. By hitting Tab you can change to the other
dimension. So while you are dragging (or after) type 150 for the horizontal dimension
and 15 for the vertical dimension. You should see;
Now create a second rectangle, starting at the upper left corner of the first rectangle, of
dimensions 4 and 160. You should see;
Now create a third rectangle, starting at the upper left corner of the second rectangle, of
dimensions 37.5 and 20. You should see;
6002 Lab#2: more ANSYS, page 6
6) Mirroring
Now click on Mirror in the Create part of the menu. You will see
in the upper left of the main window. Click on the left side of one
of the rectangles;
6002 Lab#2: more ANSYS, page 7
You will now see at the upper left.
To select everything. Move the mouse above and to the left of the sketch and click-hold-
drag to select everything. As soon as you release, everything will be mirrored.
7) Trimming
Now we need to remove all interior lines so we only have the profile. There is a
command called Trim-Away . Select it and zoom into the sketch near the top. As
you move the mouse over a line, it will highlight the line. If you click, the line (line
6002 Lab#2: more ANSYS, page 8
portion) will be deleted. The interior lines are actually duplicates (bounding two
rectangles), so you will have to click twice to remove them. Remove all interior lines and
you will see;
8) Filleting
Now we need to add the 5mm fillets to the underside of the flange. We will use the pull
tool and do all four fillets at once. Click on the Pull tool . The mode will change
to 3D , the cursor will change and the sketch will fill in;
You need to select four points at the lower edge of the upper flange. Hold the Ctrl key
down and select just the four points. After you select the first you will see;
Then after selecting all four you will see;
6002 Lab#2: more ANSYS, page 9
With all 4 points selected, click and drag. You will see something like;
with the corners all being filleted. If you tap the space bar, you will be able to edit the
fillet radius. Type 5. When complete you will see;
9) Check Dimensions
You can check your final cross section by using the dimension tool to all
various dimensions. The tool is under the Detail tab. Everything should be as expected.
6002 Lab#2: more ANSYS, page 10
10) Extrude the X-Section
The next step is to extrude the section to create a beam 1000 mm long. Use the center
mouse button to rotate the section a bit (so it not a perfect plan view);
Now select the pull tool. Click in the cross section and start dragging to create a solid
beam. You will see the pull length highlighted in blue (177.93 below) . You can just type
1000 and the beam will snap to its full length.
6002 Lab#2: more ANSYS, page 11
11) Create patches for loads
The last thing to do is to draw a line splitting the bottom of the plate into two parts, so
that we will later be able to apply a load on half the beam. While we are at it we may as
well split the flange face as well. To do this we need to create a sketch plane on the plate
face. In 3D view, rotate the model, so you can see the bottom. Then select sketch mode
and select the bottom face. A grid will form, aligned to the bottom face. Selecting plan
view will make drawing easier. Select the line toll and draw a line across the exact middle
of the plate. As you hover the mouse over the edge of the plate, you will see a small icon
indicating the middle of the edge of the plate. Draw a line splitting the plate. Hit Esc to
stop the drawing.
Repeat these steps for the top flange;
This completes all work in SpaceClaim.
6002 Lab#2: more ANSYS, page 12
Step5: open Model and create the Finite Element model
1) Return to the ANSYS window, and click on the Model feature in the Project window.
This will start the ANSYS ‘Mechanical’ program, to setup the actual finite element
model.
2) The Mechanical window shows the 1 part.
At first the model is shown with no mesh or loads yet. On the left is a list of the model
features that have to be set. By default, the material to be used will be structural steel.
Note:
A green checkmark means that everything is OK
A yellow lightning bolt means that something hasn’t been done, but its ready to be
done.
A question mark means that there is something missing, or not yet set. ANSYS can’t
solve the model if there are any question marks.
Select the Mesh icon in the Project and right-click Generate Mesh.
The mesh on the body is ;
6002 Lab#2: more ANSYS, page 13
3) Now we will set the applied load and support condition on the beam.
First we fix the near end of the beam. Right-click on static structural, select Insert
and select Fixed Support;
Now click on the end face of the beam (ensure that faces are selected )
Now click Apply in the panel on the left that lists Details of Fixed Support.
You should see the face highlighted in purple and a green check by fixed support
under Outline.
6002 Lab#2: more ANSYS, page 14
Right-click on static structural, select Insert
and select Force;
Now select the top face of the flange (the ½ near the fixed support)
Now click Apply in the panel on the left that lists Details of Force.
Edit the magnitude to be 200,000N and have its direction as down.
Now you can the system/
4) To specify output, right click on Solution in the tree, and select Insert, then Stress, then
Equivalent Stress. Do the same to select Total Deformation.
6002 Lab#2: more ANSYS, page 15
5) When you select the Equivalent Stress under Solution in the tree, the von-Mises
equivalent stresses will be plotted on the deformed shape. The max stress is 3.3188e8,
which is in Pa. This is 332 MPa, and is not close to our simple estimate of 172Pa. If you
click on Total Deformation, it shows a max value of .0013682, or 1.37 mm, compared
with our estimate of 0.825 mm. These values are not close to our simple analytical
estimates. What has gone wrong?
Note that the deformation pattern doesn’t even have a shape as expected. This pattern is
indicative of shear.
So I calculated what the shear deformation would be and added it to the bending. The
new estimate (from Desmos) is 1.34 mm, which is much closer to the ANSYS result.
Note also that the shape of deflection in Desmos is similar to ANSYS. See
https://www.desmos.com/calculator/07813vczty
6002 Lab#2: more ANSYS, page 16
Self Study Exercises: Student:________________________
For each of these exercises, modify the model that you have developed above to explore
the model behavior and answer the questions given. Show the instructor your results and
make sure that it is recorded that you have completed the exercises.
Exercise #1 – Add a cutout (draw on surface and pull through) to the beam and
determine the effects.
How much has the max stress changed?
Exercise #2 – Redo the analysis by extending the free end by 2m (to 3m), and load
the free end only with 20000N down. What situation does the new analysis represent?