University of Southern California
Viterbi School of Engineering
Department of Aerospace and Mechanical Engineering
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AME 308 – Computer Aided-design for Aero-Mechanical Design
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HOMEWORK #9
Due week of April 7th at 2pm.
Problem 1
With the help of the “design” simulation application in NX answer the questions listed below for
the piston rod used in HW #5 (see Fig. 1).
Figure 1 – Piston Rod Dimensions
Part Requirements:
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Same as given for HW #5.
Simulation Study Requirements:
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The “Design” application should be used to perform the FEA analysis.
The analysis should be performed on the _i.prt version of the piston rod.
Two studies will need to be performed
o Static Linear Analysis (tension)
▪ Fixtures: two counterbored holes
▪ Load: Bearing load applied at interface with piston head pin in the
appropriate direction to put the piston rod in tension.
o Linear Buckling Analysis (compression)
▪ Fixtures: interface with crankshaft
▪ Load: Bearing load applied at interface with piston head pin in the
appropriate direction to put the piston rod in compression.
The material used is Aluminum 6061-T6 which has an ultimate strength of 310MPa, a yield
strength of 276MPa, a Young modulus of 68.9GPa and a Poisson ratio of 0.33.
The geometry will need to be prepared for analysis to avoid possible singularities
(defeaturing, necessary edge blends, etc.).
One will need to use the appropriate mesh density in the areas of interest. A uniform sized
mesh for the entire part is not appropriate.
Use of the convergence criteria explained during lecture to determine the appropriate
mesh size is required.
Save all necessary screenshot to support all your answers given in your report.
o Screenshot of chosen mesh distribution for each simulation.
o Screenshot of loading cases used for both simulations.
o Screenshot of the resultant displacement plot for tension analysis with an
identifier for the maximum displacement. (Hint: Use max marker option)
o Screenshot of the Von Misses stress plot for the tension analysis with an identifier
for the maximum stress value. (Hint: Use the “note” tool)
o Screenshot of for 1st failure mode for buckling analysis.
o Etc.
Hard-Copy Requirements:
In a report format answer all the questions listed below. All answers should be supported by
appropriate screenshots.
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What is the maximum load in tension the piston rod can handle without undergoing plastic
deformation?
What is the maximum load in compression the piston rod can handle without buckling?
What is your chosen mesh distribution? Explain why it was chosen (Use Max Stress vs. #
nodes plot)?
What are your chosen boundary conditions (loads and fixtures) for both simulations?
What is the maximum displacement in inches and where is it located when the piston rod
is in tension at the onset of plastic deformation?
What is the maximum stress level and where is it located when the piston rod is in tension
at the onset of plastic deformation?
What is the load required to buckle the piston rod?
Do all these quantities converge to a given value? If yes how come and if no explain why.
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Can we trust the obtained values of displacement and stress? Explain. If no what should
we do? Are all assumptions made when using a static linear analysis verified?
Knowing that the “Compression Ratio” of our engine is 22:1 will our current design of the
piston rod be able to achieve such a compression ratio without failing? If not suggest a
possible solution. (Hint: Use the piston head to determine the maximum applied
compression force on the piston rod).
Note:
Hardcopy (PDF File):
Electronic copy:
See Hardcopy requirements for problem 1.
Don’t forget to write your first name, last name and lab day on the
printout.
Save your files with the appropriate names in ONE folder (ONLY SUBMIT
THE .prt, _i.prt, .fem and .sim FILES NOT THE ADDIOTIONAL SIMULATION
FILES!). The folder name should be as follow: “last name”-HW#9.