ansys lab1

8/12/2019 Ansys Lab1

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5003 Lab#1: Introduction to ANSYS, page 1

Engineering 5003 - Ship Structures I

Lab#1

Introduction to ANSYS Finite Element AnalysisBy C. Daley

Overview

ANSYSis a general purpose program, capable of numerical simulation of a variety of physicalproblems. The types of problems include solid mechanics, thermal, electromagnetic and fluid

dynamics. The focus in this introduction will be on solid mechanics and structural behavior. We

will be demonstrating with the release 13.0.

ANSYS has existed as a program for many years (decades). However, it has been updated

significantly over the years, and is now very much more advanced in capability. The user

interface is a modern GUI that looks similar to many CAD packages. ANSYS includes a masterprogram called Workbench, that lets the user set up a project and keep all aspects of the

simulation together and connected. From Workbench the user opens various pre- and post-

processors that allow the user to describe the problem, specify the type and aspects of the

simulation and review the results. ANSYS is like a physical laboratory, where experiments canbe constructed, tested and measured.


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ANSYS Model #1simple cantilever

Step 1: describe and sketch the problem:

In this first example we will model a simple steel cantilever, to see how the simple structure

responds to load. The problem is sketched below.

The problem description is as follows:

Geometry: 1200 x 180 x 10 mm

Load: 18000 N applied at the end of the cantilever in the string direction

Supports: the base is fixed in all degrees of freedom, all other boundaries are free.

Material: Steel, with E = 200GPa (2e11 N/m2)

Units: N, m, Pa

Step 2: estimate expected results (analytically):

The bar has the following properties:

Moment of inertia : I = 1/12 t h3 = 10 x 1803 /12 = 4.860e06 mm4

Section Modulus: Z = I/(h/2) = 54000 mm3

Base Bending Moment: M = 18000 x 1200 N-mm

Maximum stress (at base): sig = M/Z = 400 N/mm2 or MPa

Maximum deflection: d=FL3/(3 EI) = 10 mm

It is likely that the ANSYS results will be close to these, but not exactly the same. The % error

will depend on the assumptions, but differences of say +- 10% would not be unusual. ANSYSconsiders effects that are not in the analytical calculation, such as shear deformation, and

includes various numerical approximations. It is an essential part of engineering analysis and

design to cross check results and compare assumptions.


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Step 3: open ANSYS Workbench 13.0 and create a project

1) First, save the (empty) project as Cantilever1.wbpj2) The left hand window shows a set of analysis type options. Select Static Structuraland

drag the icon to the right, placing it in the Project Schematicwindow.

The Workbench user interface, with a Static Structuralanalysis set selected.

Step4: open Geometry and create the CAD model1) By Clicking Geometry in the Project window, ANSYS will open a CAD modeling

program called Design Modeler.

2) Select Millimeterlength unit for the model.3) You now see this window:


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The main window (slightly shaded and titled Graphics) is where the CAD model will be

displayed. The left side (Tree Outline on white background) lists the components in the

model (initially just 3 drawing planes and no bodies or parts). This window has another tab at

the bottom called sketching. Click it now.

4) The Sketching window lets you do 2D sketching on a selected plane:


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The sketching window lets the user create and edit a variety of 2D geometric objects. This is partof creating a sketch from which 3D objects can be made.

5)

Select the rectangle tool and sketch a rectangle, taller than wide (you mayclick the LOOK ATicon );


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6) Click the Dimensiontab (below Modify), and using the Generaldimension tool, selectthe right side of the rectangle and drag a dimension a bit to the right. Do the same for thetop. You will now see something like (a) below. In this case H5 is the width of the

rectangle and V1 is the height. Notice that the actual dimensions are shown in the Details

Viewat the lower left. You can directly type the dimensions you want and update the

height and width of the rectangle. So type in a height of 180, and a thickness of 10mm. as

in (b) below.

(a) (b)

7) To create a solid bar, hit the extrude icon


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8) Then hit Generate, and change view to isometric. You will see the solid bar in grey. Thisis all we need to do in the DesignModelerfor now. (if the extrude distance is not correct ,

you can select the Extrudecomponent in the upper left window and edit its value in the

lower left. Then hit the button.

Step4: open Model and create the Finite Element model


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1) Return to the ANSYS window, and click on the Modelfeature in the Projectwindow.

This will start the ANSYS Mechanical program, to setup the actual finite elementmodel.

2) The Mechanicalwindow looks like this;On the right is the model geometry, but 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. We can skip the Coordinate Systemsand Meshfor now. The program

will use defaults. We do have to set the loads and supports (if we would hit solve now,the program would fail and give us an error)

3) First we will set the support conditions at the base of the cantilever.


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You will need to bring the back of the bar into view. You can use these tools.

Rotate, pan, zoom smooth, zoom select and zoom all:

With the face that you want to fix in view, you need to insert a fixed support. To do this

right-click on the Static Structural component in the left hand Outlinewindow. This will

open a sub menu. Move the mouse over Insertand a 2nd

submenu opens. Select Fixed

Support(see below).

Make sure the face select option is on (in the menu bar at the top of the screen):

Point, line, face and body selector:

Now when you move the mouse over model in the main window, various faces will be

temporarily selected. Select the slender end face of the bar. The face will turn green. You

are not done yet. You need to click the Applybutton on the lower left to confirm that you

want fixity applied to the selected face.


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Now the Fixed Supportis added to the outline tree, with a check mark to indicate that all

is ok and up to date. When it is selected, the support is shown in the main window and inthe details window. It can be later deleted or edited (moved) by selecting it in the outline

tree.

4) Next we add the 18kN force to the free end of the bar. Again right click on StaticStructuralin the Outlinetree, select Insert, Force.


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Select the line that defines the top-end corner of the bar, and click Apply. Then type

18000 into the Magnitudecell (shown in yellow until given a value) in the lower left. By

default, the program picks a direction for the force and draws an arrow. You may need to

select the Click to Changebox under the Magnitudebox. Define the direction of the force

by selecting another line or face to show direction. Keep selecting until the arrow points

where you want it to. Then hit Apply.

5) There should be no question marks left in the OutlineTree, with some lightning bolts (seebelow). You can solve the model now, but first we will specify what information we want

to plot (this could also be done after solution).


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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 #1Refine the mesh.The default mesh results in only 3 bricks across the

180mm web. So the elements are about 60x60x10mm. Set the mesh size to 20mm and

compare the results. Do this by inserting a sizingcontrol in the meshpart of the project.

Deflection at end 60mm mesh 20mm mesh

deflection at end [mm]:Eqv. Stress at base [MPa]

Eqv.Stress at end [MPa]

Comment:

(how does this illustrateSt.Venants Principle ?)

Ex#1Initials of Instructor

_________


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Exercise #2Redo the analysis using plate elements.Start by returning to Design

Modeler and modifying the CAD. Create a new sketch beside the rectangle. Draw a line

180mm high and extrude it 1200mm. You will now have a plane that will be meshed as aplane, as the web of the beam. There are several things that you need to do to make this

work, but in the end you can create two beams, practically identical, but one made from

brick elements, while the other is made from plate elements, as shown below.

Deflection at end 20mm mesh brick 20mm mesh shell

deflection at end [mm]:

Eqv. Stress at base [MPa]

Eqv.Stress at end [MPa]

Comment:

Ex#2

Initials of Instructor

_________

brick

shell

ansys lab1

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