How to determine the minimum thickness of a uniform thickness rotating disk?

[Fwann15]

I’m trying to minimise the thickness of a rotating disk and I want to know what limitations there are. First it has to be a uniform thickness disk, the rotational speed, the material used and the basic geometry of the disk are known (apart from thickness). Are there any direct relationships between thickness and rotational speed/ stress? After going through nearly all research, I only found equations about the deformation, tangential and radial stress. No information on how to determine minimum thickness of a disk.

 

[Agent666]

Well, if you know the stresses via formulas you have already found they must contain a thickness parameter (stress is force/area after all)... I'll leave the rest to you to figure out, if you know the material strength put it all together....

https://engineervsheep.com

 

[jhardy1]

Does the disc have any other mechanical function (eg is it a pulley with a belt or chain?), or is just a free spinning disc like a flywheel?

Does it only run at a single speed, or does acceleration / deceleration have to be considered?

Hint:
Do the calculations for a disc with an assumed thickness of say 5 mm. Now repeat the calculations with an assumed thickness of 10 mm say. Do the stresses vary, or are they unchanged?

http://julianh72.blogspot.com

 

[Fwann15]

It is just a free-spinning disc in a Tesla Turbine, but for this problem, I can assume no net axial force acting on the disk due to pressure. No, the stresses will not vary if I only based on the equations I found. Because nearly all of the equations I found on radial and tangential stress are not a function of disk thickness (only a function of density, omega, radius and poisson ratio). The stresses did change for varying thickness on ANSYS, and so I am pretty certain there must be some relationships between thickness and the stresses of a disk.

I understand these stresses should not exceed the yield of the material, but since in the equations I used, these stresses are not a function of thickness, I can't use them to determine any limitations on the thickness of the disk. I don't know if creep will be a limiting factor as well.

 

[GregLocock]

Within the constraints you have given there is no minimum thickness, for a hand analysis. There may be some super weird buckling mode in extremis but I doubt that's in the standard flywheel equations. You ANSYS model must include other details/assumptions if it gives a different answer.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[Fwann15]

Thank you very much!