Stress' in rotating discs. HELP

  • Thread starter Thread starter Vr6Fidelity
  • Start date Start date
  • Tags Tags
    Rotating Stress
AI Thread Summary
The discussion focuses on analyzing the maximum angular velocity of a 6.75" diameter solid disc made of 440c material, with specific properties such as an ultimate tensile strength of 294,426 Psi. The user aims to determine how fast the disc can rotate, estimating a maximum speed of 40K-60K RPM. They seek to quantify stress concentration due to radial holes in the disc, noting a lack of resources specifically addressing this configuration. The user initially calculated angular velocity using ultimate stress but found the results unrealistically low, prompting a switch to using Young's modulus for more reasonable outcomes. The conversation highlights the complexity of stress distribution in the disc, particularly concerning radial and tangential stress, and the need for further clarification on the effects of the holes.
Vr6Fidelity
Messages
11
Reaction score
0
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.
 
Last edited by a moderator:
Engineering news on Phys.org


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?
 


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.
 
Last edited:


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?
 
Last edited by a moderator:


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.
 


anyone?
 
Thread 'Physics of Stretch: What pressure does a band apply on a cylinder?'

Thread 'Physics of Stretch: What pressure does a band apply on a cylinder?'

Scenario 1 (figure 1) A continuous loop of elastic material is stretched around two metal bars. The top bar is attached to a load cell that reads force. The lower bar can be moved downwards to stretch the elastic material. The lower bar is moved downwards until the two bars are 1190mm apart, stretching the elastic material. The bars are 5mm thick, so the total internal loop length is 1200mm (1190mm + 5mm + 5mm). At this level of stretch, the load cell reads 45N tensile force. Key numbers...
View full post »

Thread 'Cantilever help'

I'm trying to decide what size and type of galvanized steel I need for 2 cantilever extensions. The cantilever is 5 ft. The space between the two cantilever arms is a 17 ft Gap the center 7 ft of the 17 ft Gap we'll need to Bear approximately 17,000 lb spread evenly from the front of the cantilever to the back of the cantilever over 5 ft. I will put support beams across these cantilever arms to support the load evenly
View full post »

Similar threads

Is stress a source of gravity?
6
Replies
264
Views
31K
Help with Solid Mechanics Assignment: Stress, Deflection, Beams, Macaulay's
Replies
20
Views
13K

Hot Threads

Recent Insights

Back
Top