Effects of Rotation on Strain in a Disk

[sid_galt]

If a hollow disk of say radius R is heated which causes it to expand a bit and a solid disk of radius slightly greater than R is fixed inside it after which both cool down, the solid disk will be in compression and the hollow disk in tension right?

Now if this disk is rotated at a some speed v, what will happen? Will the the compression and tension balance each other out or will the disk get even more strained?

 

[FredGarvin]

You've just described the standard press fit for a lot of rotating components like bearing inner races, labby seals, turbine and compressor discs, etc...

When you heat up the outer member and insert the inner, the result will be the inner member in compression and the outer in tension. When the assembly rotates, the result will be that the outer member will grow at a higher rate than the inner. At some point the speed will be enough to overcome the press fit and the two members will have no press fit any longer (and the assembly will come apart unless further restraint is provided, like a nut).

 

[sid_galt]

Thank you.

What branch of engineering do such systems come under?

 

[FredGarvin]

That is design methodology combined with mechanics of materials. Most designers will use fit tables or the like, they or others have developed for such applications. Stress analysts will some times have to look at the stresses induced to verify that the levels are appropriate for the environment and use.

In my company, we have devoted individuals that are responsible for things such as clamp groups and stress analysis of particular components. We work together quite often to make sure we don't miss anything when designs are being worked up.