Page Comparison

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Changes to ribs:
1. Fillets on the spar corners → Adding a fillet in the ribs is ideal for force distribution but we also need to think about how the spar would fit into the new shape/lock in place
2. An idea I had would be to make a 3d print that fits onto the spar and then slides into the rib? not sure if this makes sense but in my head it seems like the spar needs to a rectangular cutout to slot into for good fit
Future sims:
1. Run the sim again with the same parameters to see changes
2. Simulate maximum AOA/lift scenario?
  1. This is to see what the limits of our design would be
  2. Will need to determine the lift force and angle it correctly so more work

I will try to run the sim (in ANSYS) with the updated rib with the following new conditions found
Sohee Yoonto try in SW
Ran a some calculations using fixed wing calculator to determine lift forces instead of following the study:
- Hope this gets more realistic/related numbers for our use
- Takeoff Lift Force 159.8447 N
  Cruising Lift Force 173.5784 N
  Max Lift Force 200.3639 N
- Takeoff lift < cruising lift because of velocities chosen
- Max lift force is assuming max CL at cruise speed
  - ie. cruising and attempting max climb rate
For a “worst” case scenario, will use max lift force of 200 N
The forces acting on each rib was calculated:
- 200 N (over two wings) → 200 N / 2 = 100 N (over one wing) → 100 N / 8 (ribs) = 12.5 N per rib

Solidworks Analysis #2 with New Sim Conditions:

Before the simulation:

Previously, when I ran the simulation I did not set the von Mises stress scale but this time I set the Max to be the yield strength of balsa wood provided by Solidworks material property (2e+7 Pa). Hence, anything red means that the balsa wood will fracture.
- I verified the value was accurate since wood doesn’t really have a defined yield strength and this source (https://www.matweb.com/search/datasheet_print.aspx?matguid=81c269f50f424573a4f9978cfcb41bc8) states that the Modulus of Rupture is 2.16e+7 Pa (which is quite close to the value Solidworks provided)
The setup of the analysis is basically the same as before, note that the shape of the ribs have been adjusted slightly.

Three Situations were simulated based off of Nathaniel’s calculations above:

* All situations have the force placed at the Top (a) or Bottom (b) face of the ribs

Takeoff Lift Force

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Conclusion from this study:

Takeoff, Cruising, and Max lift forces pass the simulation as none of them resulted in red spots!
- Why is this different from the last time we simulated on Solidworks? This is because I manually set the max value on the von Mises stress scale to relate to the Balsa wood property. Before, it was automatically set by Solidworks to around ~5.5e+5 (less than 2e+7), therefore it was inconclusive whether the red parts meant the ribs would fracture.
When the force is placed on the bottom, it results in slightly more stress than when placing the force on the top of the ribs (this was concluded by comparing the Max stress points). But because of how small the difference is we can assume they’re (force on top and bottom) identical.
Since the Max lift force passed the simulation, I tried running a few tests with greater forces (200 N and 300 N) to see where the greatest amount of stress appear
- Based on the simulation, it looked like the middle cutout experienced the most amount of stress, specifically near its corners. This is unlike our previous simulation, where there was a dense amount of stress on the spar cutouts.
  - Possible reason: The bottom half of the new rib shape is closer to the chord line, hence there isn’t a lot of support/material on the bottom which might be causing more stress towards the middle of the cutouts
  - Possible reason: The way the LE and TE supports are assembled might be supporting the front and back of the ribs more than before