Stress' in rotating discs. HELP

In summary: Your equations are looking like they are using the same principle, but they are calculating the stress in different ways. Your radial stress is at a maximum in the center, while tangential stress is at a maximum on the OD. Have you looked at the graphs? I think it might help to clarify things.
  • #1
Vr6Fidelity
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Stress' in rotating discs. HELP!

I am working on an independent project where I am analyzing the maximum possible angular velocity of a solid disc of a given diameter and material.

The Diameter is 6.75"

Material is 440c
E= 29,000 Ksi
Density of .275lb/in^3
Ultimate tensile strength: 294,426 Psi (294Ksi)

How fast can this rotate?

Part2:

How do I quantify the stress concentration of RADIAL holes in this disc? I have found numerous papers on eccentric holes but not radial on the periphery. Holes are blind and tapped.

Maximum speed should be around 40K-60K RPM.

I have been using these formulas:

https://www.physicsforums.com/latex_images/14/1425557-0.png

https://www.physicsforums.com/latex_images/14/1425557-1.png

I have taken R to be zero for radial stress (the center)
and 3.375 for tangential stress.

I originally used the ultimate stress and solved for omega, but those results were 10x lower than realistic.

So i used E, and the results seem reasonable. Although I am not sure WHY I had to use E or if this was the right thing to do.

Can I get some assistance? Thanks.
 
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  • #2


You say that the holes are blind and tapped. That suggests that you plan to screw something into these holes, and if you do, that is going to load the periphery of the disk. Have you left something out of the problem statement?

You say that when you solved for omega it was "10x lower than realistic." How do you know what is realistic?
 
  • #3


Nothing screws into the holes.

The disc actually exists, so I have seen it go faster than the original numbers that resulted from using the ultimate stress.
 
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  • #4


Did a search and came up with this
http://www.utm.edu/departments/engin/lemaster/Machine%20Design/Lecture%2016.pdf

Looking through here, it looks like your using the same equations though. Why do you think your results are 10x too low? Experience? What are you defining as failure?
 
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  • #5


Ahh, thank you Minger. There is more there than I had before, a lot more.

Particularly the graphs. I had assumed radial stress to be at a maximum in the center, and tangential to me at maximum on the OD but it seems more complex than that.
 
  • #6


anyone?
 

1. What causes stress in rotating discs?

Stress in rotating discs is caused by the centrifugal force generated by the rotation, which puts pressure on the material and can lead to deformation or failure.

2. How does the speed of rotation affect stress in discs?

The faster the rotation speed, the greater the centrifugal force and therefore the higher the stress on the disc. This can lead to a shorter lifespan of the disc or even catastrophic failure.

3. What materials are most resistant to stress in rotating discs?

Materials with high strength and ductility, such as steel or titanium alloys, are more resistant to stress in rotating discs. These materials can better withstand the pressure and deformation caused by the rotation.

4. Can design changes reduce stress in rotating discs?

Yes, design changes such as increasing the thickness or diameter of the disc, or using curved rather than straight edges can help reduce stress in rotating discs. However, these changes may also affect the performance and balance of the rotating system.

5. How can stress in rotating discs be detected and monitored?

Stress in rotating discs can be detected through non-destructive testing methods such as ultrasonic or magnetic particle inspection. Regular monitoring of disc performance and visual inspections can also help identify signs of stress and potential failure.

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