Spring 2007, METBD350 - FEA Applications I

Prof. Dave Johnson, dhj1@psu.edu

Penn State - Erie, The Behrend College

Homework Assignment 3A

Concepts:

ANSYS

ANSYS Workbench

Bottom-Up Modeling (KP -> Lines -> Areas) 2D Axisymmetric Element Types ANSYS Parameters and APDL Boolean Options (KEEP ?) Features for load application Density Material Property Units Inertia/Body Loads Solution: Multiple Load Steps Multiple SOLVES RESTARTS Load Step Files Postprocessing: Multiple Load Steps

[Optional] Model section in CAD as thin 3D, export as Parasolid (or IGES), import to DesignModeler, "THIN" or "Midsurface" and keep the face ON the XY plane to make a 2D model Features for load application 2D Axisymmetric Element Types Rotational velocity (inertia) load Solution: Multiple Load Steps Multiple Environments One Environment w/Multiple Steps ? Postprocessing: Multiple Solutions and report organization



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A tractor trailer sized brake drum is shown (with a 90 degree sector cutaway) in the figure above. The dimensions are given in the cross- section figure below. This drum is made of a ductile cast iron with an elastic modulus of 24.0e6 psi, Poisson's ratio of 0.3, and a density given as 0.246 lbm/cu. in.  To permit axisymmetric modeling, the circle of 12 discrete 3/4" diameter bolt holes is treated as a continuous feature about the "revolved" geometry.  Decide on an appropriate constraint and document your assumption for this boundary condition.

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Several loads are to be considered, individually:

• Inside pressure over a 5" wide band (simulating the brake pad contact) of 1000 psi.
• The drum spins about its axis at 120 rad/sec which corresponds to a truck speed of nearly 80 mph.
• Combined loading of both the pad pressure and the angular rotation.

  Turn in:

• A plot showing the mesh - document all element types and their purpose
• A plot showing constraints and ALL loading - include a  statement defining the bolt circle modeling and constraint.
• A hand calculation of the weight of this part compared to the ANSYS solution output of the total mass of your model.  (During solution, ANSYS writes the total mass in the Output Window).
• A plot showing the equivalent stress for each of the load cases.
• Evaluate the mesh error of all three load steps.
• Compare the drum FEA hoop stress to a simple hand calculation based on strength of materials, pressure vessel formula.  (Plot the model hoop stress, SZ, from the first load step to make this comparison).  Include your reference for the pressure vessel formula.
• ANSYS:  The modeling session log file (with comments added).