Structure Analysis of 6061-T651 Aluminum Bridge

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Structure Analysis of 6061-T651 Aluminum
Bridge Team Blackboard Mechanical
Engineering University of Rochester
Material Properties
Executive Summary
ANSYS Analysis
The objective of this project was to design a
bridge and maximize its figure of merit (the
total supported load divided by the bridge
weight) such that the structure that would span
an 8 chasm and allow a 5 wide by 3 tall object
to bass below its deck. This bridge was
constructed using 6061-T651 aluminum sheet metal
and 1/8 aluminum pop rivets. Under maximum
load, the bridge should have a maximum of .1
deformation and remain suspended off the
ground. To start designing a solution to this
task, our group made preliminary sketches and
basic cardboard models to obtain a better
understanding of the load distribution and
subsequent deflections of the beams. From these
tests, we drew the conclusion that an I-beam
structure with a top sheet metal brace could
handle maximum load without the use of too much
material. A CAD of our final sketch was then
made in ANSYS Workbench and tested with an
approximate load of 500 pounds centered across
the middle of the bridge deck, where the loading
beam would rest. From the post-processing data
we found the optimum areas for rivet placement,
such that they were in the places of lowest
stress concentration as well as the stresses and
deformations involved in the loading of the
structure. Both parts and assembly drawings were
then made and submitted for machining. The final
analysis of the constructed bridge will be a load
test of the bridge suspended above the chasm with
2 group members balancing on a plank centered
about the bridge deck. A real value for figure
of merit can then be recorded and used to
determine the effectiveness of the structure.
Aluminum 6060-T651 Material Properties Aluminum 6060-T651 Material Properties
Hardness, Brinell 95
Hardness, Knoop 120
Hardness, Rockwell A 40
Hardness, Rockwell B 60
Hardness, Vickers 107
Tensile Strength, Ultimate 45000 psi
Tensile Strength, Yield 39900 psi
Elongation at Break 12 
Modulus of Elasticity 10000 ksi
Notched Tensile Strength 47000 psi
Ultimate Bearing Strength 88000 psi
Bearing Yield Strength 56000 psi
Poisson's Ratio 0.33
Fatigue Strength 13800 psi
Fracture Toughness 26.4 ksi-in½
Machinability 50 
Shear Modulus 3770 ksi
Shear Strength 29700 psi
The values for various aluminum properties are
found in the table to the right. The high
stiffness of 6061-T651 and low density .098
lb/in3 as well as high machinability made it the
perfect material choice for the task. Aluminum
pop rivets, with a 1/8 diameter, were used rated
with an ultimate tensile stress at 240 lbs. and a
breaking point stress at 400 lbs.

Equivalent Stress Plot Max stress 3.085E4 psi
Total Deformation Plot
The People
The Members of team Blackboard
Sam Selonick Kevin McNelis Chris Babcock Nick
Stadnyk
This work is supported by The University of
Rochester Mechanical Engineering Research
Department under the direction of Prof. David
Quesnel
Safety Factor Ranges from 1.0 15.0 the safety
factor is high, and bridge may have been
overbuilt in certain areas.
Plot Displaying Spot Weld Placement
We work best under pressure.
Test Setup
Design
Loading bar
I-Beam bridge
Pop Rivet
Table
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The experimental setup is depicted above. Our
bridge design was initially tested element by
element using the Equivalent Stress theory to
optimize the beam lengths. This theory was used
to make sure that the bridge did not deflect any
more than the .1 requirement.
For further Information and technical discussion,
contact
Team Blackboard Department of Mechanical
Engineering Rochester, NY 14627-0132 teamblackboar
d_at_me.rochester.edu