proe mechanica

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Wrench Analysis Using Pro/Mechanica

Carnegie Mellon University Department of Mechanical Engineering

Orginally developed by John Bellinger

Updated February, 2006 for Pro/E Wildfire 3.0 by David Urban

Last Updated: October, 2010 for Pro/E Wildfire 5.0 by Gary Verma and Wei Guo

Introduction

Pro/Engineer’s suite of tools includes a package called Pro/Mechanica which allows designers to

analyze structural, thermal and motion properties of parts and assemblies. Mechanica also has atoolset that can automatically optimize designs to meet certain design criteria while minimizing

cost, size or other factors. We will be using Pro/mechanica to analyze the stresses and

deformations of our wrench when it is being used to tighten a nut.

Setup

Step 1: Start ProE Wildfire from Start - All Programs - PTC - Pro/Engineer - proewildfire

Step 2: Change the working directory. Go to File - Set Working Directory, and this will bring up

a window for you to choose the directory where your wrench file has been saved. Choose

the folder where your wrench is saved, the same directory you set in the modeling part.


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Step 3: Load your wrench. Click the Open an Existing Object button and find your

wrench, then highlight it and click Open.

Step 4: Select Applications from the top menu and switch to Mechanica as shown below.

Mechanica has a set of tools used to analyze stresses, strains, and deformations. Here we will be

using it to perform a static analysis.

Step 6: This will bring up the Mechanica Model Setup screen. We will be doing a static

structural simulation, so select Structure as model type and leave the rest. Click OK.


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Defining the wrench

Before one can analyze a part with a finite element package such as Pro/mechanica, the

computer must know certain things about the model. To perform a structural simulation, the

computer must know the object's material properties and what type of analysis to perform

Step 1: To perform an analysis of the wrench, we need to tell the program what the loads on the

wrench are, what the constraints on the wrench that resist these loads are, and what material thewrench is. We also need to tell it what type of analysis to perform. We start by assigning amaterial to the wrench. Our wrench is made of 6061 aluminum, which is a general-purpose

aircraft grade aluminum. Click on the Properties in top menu bar. Then click on Materials.


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Step 2: We will now add 6061 aluminum from the library of pre-defined materials. The materialswindow will open. Select AL6061 and then press the right arrow to add that material to the

simulation.


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Step 3: We must now assign that material to your wrench. Go back to Properties on top tool bar.

Click on Material Assignments.

Step 4: This will bring up the Material Assignment toolbox. Everything should be as shown

below. Click ok and the wrench will be assigned Al6061 material.


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Adding loads and constraints

The program also must know the forces and reactions which are applied to the model. Thefollowing loads and constraints will simulate the wrench tightening a nut by someone applying

fifty pounds of force to the end opposite the jaw. The nut provides the reaction moment which

prevents the wrench from turning.

Step 1: We will now add the force applied by the person tightening the nut. We are modeling this

force as a 50 lb force downwards applied on the right wrench head. Select Insert from the top

tool bar, then Force/Moment Load.

This will bring up the Force/Moment window shown below.


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Step 2: Our problem is simple enough that it is not necessary to name our loads. However, for

problem with multiple loads it would be wise to name the load “hand force” or something

similar. Click on the top of the far wrench head. It will turn pink as shown below.


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Step 3: Type 50 into the Force… Z text box as shown below. When your window matches the

one shown below, click OK.


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Your wrench should now look like this:

Step 4: Next we must create constraints on the wrench to model the force exerted by the nut.

Click the Displacement Constraint under Insert in the top tool bar.


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This will pull up the Constraint window shown below.


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Step 5: Select the near bottom jaw of the wrench in the same way you did for the load in step 3.When properly selected, it will be pink as shown below. We want to prevent the surface from

moving, but we do not want to prevent the surface from rotating. From the Constraint window,

select the Free button for each of the three axes under Rotation.


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When your display looks like the image below, click OK in the Select window.

Your wrench should now look like:


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Step 6: Repeat constraint steps with the upper jaw. You may need to rotate your model to select

the upper jaw. To rotate the model, hold down the center mouse button while moving the mouse.When you are finished constraining the model, it will look like below. If it does not, ask a TA for

assistance. Take a screenshot of your work at this point.

.


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Running the analysis

Step 1: Next we must set up and run the analysis of the wrench. From the Analysis button on the

top tool bar, select Mechanica Analyses/Studies.

Step 2: From the Analyses and Design Studies window, select File-New Static as shown below.


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Step 3: The Static Analysis Definition window will appear. Because we only have one

constraint set and one load set, there is nothing more we need to select. Click OK.


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Step 4: We will now run the simulation. Click the Start Run (green flag).


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The program will ask if you want interactive diagnostics. Click Yes.

Step 5: Wait for the analysis to finish. Once the run completes, close the analysis and designstudies window.


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Viewing and interpreting the results

Now that the run is completed and the data saved, it's time to look at the results. pro/mechanica has a special interface from which to do this, because the same analysis includes

many different results. In our case our one analysis will yield results for stress, strain and

deformation.

Step 1: From the Analysis tab in top tool bar, select Results.

Step 2: A new window will appear. In the top toolbar select the Insert a new definition button


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Step 3: We must tell the program which results we want to see. Click the Open button on

Analysis 1.

Step 4: The first thing we want to investigate is the bending stress in the X direction. Select XX

from the list below Component as shown.


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Step 6: Next we want to tell the program how to display its results. Click the Display Options

tab. Select Continuous Tone, Deformed and Overlay Undeformed as shown below. When you

are finished click OK and Show to view the results.


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Step 7: The display now shows the deformed and undeformed shape of the wrench. The

deformed shape is greatly exaggerated because the true deformation is too small to see. We will

investigate that later. If your screen looks like below, take a screenshot of your work.


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Step 8: Next we want to determine the displacement the wrench experiences. Select Edit-Resultwindow from the top menu to change which results you want to view.


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Step 9: The Result Window Definition will reappear. Change the quantity to Displacement and

click OK and Show.

Step 10: If your result looks like the following, take a screenshot of your results.


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Step 11: Save your work to a place where you will be able to retrieve later if needed.


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Your report

Like you did in the previous tutorial, you must now save your work, upload it to your

Andrew space, and write the report. Hand in one report per team, and your report should include

the following:

1. A cover sheet that has the title "CAE Lab2 Report", group number, names of the group

members, and date of the lab.

2. Include the drawing that shows the force applied at the handle and the boundary

conditions applied at the jaw.

3. Include the shaded contour drawing that shows the contours of stress in the x-direction in

the wrench. On this graph, indicate the points of maximum stress.

4. Include the shaded contour drawing that shows the displacement of the wrench.

5. Using the equations developed in lecture and the textbook for stresses in a cantilever

beam under bending, calculate by hand the peak stress in the handle at the base where the

handle connects to the jaw. Compare these stress values to those determined through the

computer solution.

6. The wrench blanks, and the final wrench produced with the CNC machine, will be made

from 6061-T6 aluminum alloy. With a factor of safety of 2, determine (i) the maximum

force that can be applied to the handle, and (ii) the maximum torque produced by thewrench in tightening a bolt, both before yielding will occur. Draw a FBD of the wrench

when you do the calculations.

The report should be handed in at the beginning of the recitation two weeks from the lab

date.

Acknowledgment: These tutorials were developed at Carnegie Mellon University with the

support of grants from the National Science Foundation, in collaboration with Parametric

Technologies Inc.

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