Pro-Mechanica Tutorial

MIE – 313 Design of Mechanical Components.

Spring 2000

Welcome to the world of Finite Element Analysis. This tutorial will take you

through the usage of Pro-Mechanica, one of the many softwares available for

Finite Element Analysis. During the course of this tutorial you will be analyzing 3

different kinds of models.

1. Solid model

2. Shell model

3. Axisymmetric model. [HW problem]

Further we shall concentrate only on structural analysis and avoid going into

thermal analysis.

“So fasten your seatbelts, and there is “no smoking” in here anyway.”

1. Solid model: Consider the beam shown in the above figure. It has a

varying cross section and is fixed at one end. A point load of 1000lbf is acting

at the center of the unfixed end face.

a. Now model this beam using Pro-E and save it as “SOLID- MODEL”.

b. We are now ready to run the analysis on this model.

Ø Go to the Menu Bar and under Applications click on Mechanica.

Ø You should get a screen in which will tell you the Principal Units

used for your model. Click on Continue.

Ø You will now get a menu manager as shown below. Since we are

concerned with only structural analysis click on Structure.

You will see that there are 5 subdivisions under Mec Struct. These are

the various steps to be followed in the same sequence as they appear.

a. Model: Here we set up the various constraints, loads, materials, convert it

into a shell model if necessary, etc.

Ø Applying constraints: Click on Constraints and then on Create

and then Face/Surface (because you are applying constraints on the

fixed surface).

Ø Pick the surface that is fixed and then say Done Sel. You will now

see a window as shown below.

Ø Notice that all the degrees of freedom are fixed, which means that

the face/surface is fixed in all directions.

Ø Be sure that all the buttons corresponding to ‘fixed’ are set ‘on’ and

then click on Accept.

Ø You will now get another window asking you to describe the

constraint. You could either describe it or leave it blank and say

Accept.

Ø Once this is done you should see a triangle on the surface where

the constraints have been applied.

Ø Applying loads: Click on Loads and click Create.

Ø You can create different kinds of loads as listed in the menu. But in

this problem we want a point load of 1000lbf. Hence click on Point.

Ø Under point we can either create or select. Since we do not have a

predefined point already we have to create a point. Hence click on

Create.

Ø Now say Add New and Offset Surface. Select the surface on

which the point should be placed and say Done Sel. Next, you will be

asked to select 2 surfaces to offset the point from. Select 2 surfaces

and give the dimensions such that the point is at the center as desired

and then click on Done.

Ø You will now get a window as shown below.

Ø Apply a tensile force of 1000 lb. as was required and click on

Accept.

Ø The force will be displayed as an arrow on the model. If the display

does not show a tensile force, then click on Edit and select the arrow.

Make the required changes.

Ø Applying Material Properties: Pro-mechanica has an in built

library of materials. Click on Materials and say Assign and Part. Pick

the part and say Done Sel. You will now see a window as shown below.

Select Steel and click on Accept. It will display the material properties

of steel. Click on Accept once again.

You have now set the constraints, set the loads and the material

properties. Hence you are ready to enter the second subdivision under Structure

- Analysis.

b. Analysis: Click on Analysis and you will see a window as shown.

Ø Set the analysis name to anlys1, and since we will be conducting

static analysis, set the type to Static. Under the constraint set and load

sets you will see the highlighted names. These are the sets that will be

considered during the analysis. Also set the convergence type to Single-

Pass Adaptive. This would help to converge to an approximate solution

faster and at the same time will stop the analysis if any flaws exist in the

model. (If a solution with higher accuracy is required then you can come

back later and set this Multi-Pass Adaptive and run the analysis)

Ø Click on Accept and then say Done in the new window that

appears.

c. Run: Click on Run. This will run the analysis for the applied constraints and

load sets. You will get a window as shown below. Click on Start, say Yes for

Error detection and say OK for the stress concentration warning.

Now after it has finished the analysis, click on Summary. This is the time

to pray and hope that all the good things you did in your past comes to your

rescue. If it says “RUN COMPLETED” then give your partner a high five and

shout out a loud War Cry. If not call the tutor!!!!!!

Click on Close in the summary window and then on Done in the Run window.

d. Results: Having run the analysis you should now be able to view your

results. Click on Results and a window pops up as shown below.

Ø Click on Create and name the first result window as “vonmises

stress”.

Ø Select the directory as anlys1 and click Accept. You will see a

window as shown below.

Ø Select the required fields under quantity (for this case select

Stresses and Von Mises) and click Accept. This will bring you back to

the Results window but with Vonmisesstress highlighted under both

show and edit. Now click on Show. You should be able to view the

stress distribution over the beam.

Ø Following the same procedure under Results, obtain the following:

1. Stress in the X, Y and Z direction

2. Displacement

3. Strains in the XX, YY and ZZ directions

2. Shell model: Consider a steel beam with a cross section as shown below.

It is again fixed at one end and there is a bending load of 100lb acting on the

beam at the other end. Here we consider it to be a shell model because of the

fact that the sections are very thin. Further, it takes a shorter period of time to

analyze shell models. The procedure remains the same as solid model except

for one point, which has been described later in the tutorial.

Create and save the model as “shell model”. Let the length of the beam be 10”

and also add a plate of thickness 0.25” at one end of the beam as shown below.

Now follow the same procedure as that of the Solid Model. But here once we get

into Structure>model, click on Idealizations. Now click on shells and then on

Midsurfaces and then on Create. Select a pair of parallel surfaces and click on

Done Sel. Select the next pair of parallel surfaces and click Done Sel. Do this for

all the parallel surfaces. Finally click on Done Sel again. Now to check whether

all the surfaces have been shelled, Click on

Compress>ShellsOnly>ShowCompress. Your screen should now look as

shown below. Then click on Done/Return.

Now apply the constraints on the plate (the plate has been incorporated only to

apply the constraints. It is not possible to apply constraints on the edges of the

shell model) and an edge load of 1000lbf at the other end. Apply the material

properties as steel and follow the same procedure as before. Obtain the

following results:

1. Stress – Von mises, X, Y and Z

2. Displacement

3. Strain – XX, YY and ZZ

3. Axisymmetric model: In certain cases it is easier to model only a part of

the model because of its symmetry. This can be seen in the following model.

It is a steel plate of dimension, 50”*50”*10” (l*b*h). There is a hole at the

center of the plate of radius 10”. A tensile force of 100lb is acting on either

side of the plate as shown.

In this case only 1/4th of the plate needs to be modeled because of

symmetry. Hence it is easier and faster to analyze the problem. But care should

be taken while applying the constraints.

Home Work:

Solve the above problem using Pro-Mechanica and determine the stresses

and deflections in the plate. You submission should contain the following:

1. Model.

2. Constraints applied. (explain them clearly)

3. Stress distribution.

4. Deflection.

5. Strain distribution.

6. Discussion of your results.

7. Also submit the stress and displacement fields obtained for the Solid

and Shell model obtained during the tutorial and discuss them briefly.

100 lb. 100 lb.