ANSYS Workbench Analysis

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Figure 6

Figure 5

Figure 4

Figure 3

Figure 5: This shows the normal stress of the part. Our maximum stress is at the top holes in the leg because we included a load in the Z-Direction. There is also a maximum compression located at the bottom hole in the legs.

Figure 6: This screen shot represents our safety factor. The red dot in the middle begins to show up when we move the slider above 1.2.

Figure 7: This shows that the maximum deformation in the Y-direction is just under .1”.

Figure 3: This is the geometry after modeling it in ANSYS. The points in the center represent where we are going to load it.

Figure 4: Shows that we modeled the bridge not only in the Y-direction but also in the Z-direction. This can be seen in the bottom left hand corner of the screen shot.

Final Drawings

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Figure 8

Figure 8: This is our assembly drawing. It represents what the bridge should look like after its fabrication. On it you can see that we removed metal from the legs in order to adjust our figure of merit. This works because it removes weight from the object since our load is a constant and cannot be changed. Also, we specified that we would be using the aluminum alloy 6061-T651 as the material for our structure. All of our bend lines needed to be parallel to the grain in order for the bridge to be manufactured without cracking or breaking.

Figure 9: This is the part drawing for our Paper River Chasm Bridge. We specified that we wanted to break all sharp edges and corners on the part. All of our dimensions were in inch units. The part is symmetrical about two centerlines, Centerline 1 and Centerline 2. We wrote up specifications for a suggested fabrication because we knew that the folds in our bridge were going to be hard to do. These specifications were to cut an 11x12” sheet, cut out “C” sections and holes, and then fold B, A, C, then D.

Final Product

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Figure 10 Figure 11: This is a picture of Ben with our bridge. Ben loves our bridge! He’s happy with the way it was manufactured and is confident that it will support both Brady and Alissa’s weight when it undergoes the test with the loading bar apparatus.

Figure 10: This is a picture of our bridge. Here we simulated our bridge standing over a “chasm.” We did this by putting two tables together, similar to what will essentially happen when the strength of the bridge is tested. We have put a shot glass on top of it so that we could show the actual size of the bridge in comparison to something else.

en Hewson

ME Team Tipsy’s 104Q

SummaryUsing ANSYS 8.1 we came up with initial drawings for

our bridge model and tested the U-Beam section of the bridge. We then took our ANSYS 8.1 U-Beam model and modified it by adding leg supports through ANSYS Workbench.

Through Workbench, we were able to analyze how the whole system reacted under added weight. Workbench showed us the deflection of the bridge as well as stress concentrations.

To help our figure of merit value, we cut out three holes on each legs to cut down on the weight of the bridge. We then ran this new design through workbench to make sure the deflections of stress concentrations weren’t too large, which they weren’t. Finally, we calculated our figure of merit by dividing the weight the bridge supports by the weight of the bridge.

Figure 0: Using ANSYS, we were able to give our bridge dimensions and see how much the bridge would deflect or if it would break. We knew that the yielding strength of our aluminum is (37ksi). ANSYS 8.1 gave our deflection to be (70ksi) at height 1”. We were able to determine that when the load is removed from the bridge, it will permanently deform the shape of our bridge slightly (a small dent in the middle) because there is a high stress concentration where the system of chains and wooden boards hangs. We can bend the metal so that we can use two sides of the bridge to support the load. This will allow us to use a smaller height and still be able to stay under (37ksi).

Figure 1: This is a sketch of the apparatus that will be set up over the paper river. It is a “chasm” set up by two tables 8.5” apart from one another. The reason why the diagram has “H varies” for the height is because this is the sketch we used for modeling the effect the height of the beam had on deflection.

Figure 2: We calculated the stress concentration at a rivet for three different numbers of nodes. We used 31 nodes and the stress concentration was centralized around the pivot point with a maximum stress of 40.4 ksi. In our calculations, we figured that with the more nodes used, the more disbursed the stress concentration. When we tried to do the calculations with one node the program was not allowing us giving us a warning saying, “large negative pivot value (-1.669974949E-06).” Therefore we were not able to use one node in our calculations.

First Ideas/First ANSYS 8.1 Drawings

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Figure 1

Figure 0

lissa Tully

“I think our bridge is unique because of its lack of rivets in our design. I think it will withstand the test of two people standing on it”

rady White

“The shop guy said he couldn’t build it that way, so we did it anyway.”

ohn Jackson

“ME 104Q rocks!”

Restrictions We designed our bridge to fit the specifications of the

project as well as to optimize the performance of it. We did this by designing the height of the crossbar to its minimum dimension of 5/8in which supports our load of 320lbs perfectly. This means that the predicted amount of deformation in the center area of the bridge is just under 0.1in. Also, in order help maximize the figure of merit (weight supported/weight of bridge) we tried to take out excess material in areas of low stress concentrations. That is why there are 12 cutouts at each end. These cutouts reduced the weight significantly and increased out figure of merit about by about 150. One drawback to the holes however is that any sideways (z direction) load over about 60lbs pushes the limit of the yield strength to near breaking.

The bridge was designed to a safety factor closest to 1 at the weakest point. According to our ANSYS analysis, with a small sideways force and 320lb in the Y direction, the weakest point is at the center. Here the safety factor is roughly 1.2. With a larger sideways load, the risk is having the bridge collapse due to its thin legs. Here the weakest point happens to be on the inside edge of the bottom hole on each leg. At these points the safety factor is still roughly 1.15.

As you can see this bridge is designed specifically to the specs and our hope is that it will not tip sideways when loading. Excess weight was removed to raise the figure of merit and with safety factors around 1, the limits of this bridge will certainly be tested.

Objectives Our objectives were to build a bridge made of 1/16"

Aluminum alloy, either 6061-T651 or 6061-T0. However, unlike other designs, we decided to build our bridge without the use of any rivets for the reason that we did not think they were necessary and they would only make our design heavier. Because of this decision to not use rivets we were forced to design our bridge out of one piece of aluminum.

The specifications of the bridge were for it to span an 8.5 inch wide gorge and allow placement of a 1 1/16 inch diameter aluminum loading bar.  There must be 5 inches of free space between the vertical supports below the loading bar and the maximum vertical opening in the loading assembly is 8 inches to make bridge fit.  The loading jig is comprised of 5/16" threaded rods, a 5/16" eye hook, welded link chain and a 2X6 laid horizontally with plywood center support allowing a nominally stable attachment to the adjustable loading chain. 

The bridge feet must set on two 3 X 5 support areas. Each support area must be oriented with 5 inch direction parallel to the paper river with 3 inch perpendicular to the river.   The bridge must span an area large enough so that a 3X5 inch rectangle can fit under the bridge (5 inches horizontal, 3 inches vertical). The bridge must support two members of our team through the loading jig shown in class.  It must be stable against falling over.  Our design will be deemed successful if it supports the load without visible deformation or shape change.  The figure of merit will be the load (in lbs) supported divided by the weight of the bridge (in lbs).

“Our bridge is simply better than yours.”