Design Description:

The operative component in this design is the Mechanism component. This component is not only where the material will be housed, but it will also be the mechanism that causes it to deflect.

Since the geometry of the Mechanism and Spacer components were so similar, we assumed that if we deemed via analysis that the Mechanism was successful at the upper loading limit, so too would be the Spacer.

Preliminary Analysis:

For our design, we believed we should go with a factor of safety (FOS) of 1.5, The justification for this can be seen below:

For a FOS of ~1.5, Maximum, weight should be 1500N

Average Bike: 50lb

Average Human: 180lb

Weight Sum (N) ≈ 1022N

FOS=1500/1022=1.467710372

As such, our preliminary numerical analysis was approached with that in mind. Below are photos of two simulated situations:

On the left two images, is a static loading simulation. To simulate the attachement to the bike tire, the top surface was pinned and the bottom experienced a normal force of 1500N. The bottom image is the mechanism at rest, whereas the top is the mechanism at equilibrium under the loading conditions. With the deflection maxing out at roughly half-way to the top surface of the mechanism, we found this acceptable for consistent actuation of the material.

On the right is a dynamic simulation also accounting for the shifting loading point (point of contact with the floor's surface). We found that despite there being lesser deflection under these conditions, the amount that it was experiencing was still acceptable for our purposes.

Overall, the analysis indicated that the design would perform to our needs. Ultimately, this is how we decided to begin manufacturing and testing.

Kinematic Simulations

To determine the best possible design, we conducted kinematic simulations of a simplified version of the bike charm design through SOLIDWORKS motion analysis, with the goal of finding the effect of different parameters on maximum strain and strain rate. The simulation is a mass-spring system within a rotating frame of reference, with the mechanoluminescent material simplified as a spring.

The folllowing parameters were adjusted:

Mass
Outer Ring Diameter
Mass Distance from Rotation Center
Rotations per Minute (Angular Velocity)
Spring Constant (to be modeled again)
Number of Suspending Material
Dynamic

Here are our results...

Adding more constraints like more suspending ML material causes the strain rate to reach steady state but massively reduces both strain and strain rate.

Both mass distance from rotation center and rotations per minute (angular velocity) have proportional effects on strain and strain rate

Increasing outer ring diameter allows greater mass to affect the strain and strain rate as the mass doesn't hit the walls.

Dynamic simulations show that displacement rate (and therefore strain rate as normalized by the original length) change proportional to changes in angular velocity, so increases in angular velocity lead to increases in displacement rate, and vice versa.

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