Thermal Expansion of A Large Cylinder 2

[bamamack]

I am on the road and looking for some help.
What is the correct way to determine the thermal expansion (in) for the diameter of say a large diameter (120" OD x .75" thick steel cylinder? Is it based on the increase in the circumference then calculating the nominal diameter similar to rolling a plate or just use outside diameter? I understand the linear expansion formula, Delta L=alpha x L x delta T. Please explain. Thanks.

 

[imcjoek]

You will find the same dimension change applying the expansion to the diameter or the circumference since they are directly related. If you use the OD as your characteristic dimension then be sure to also apply that deltaL to that same characteristic dimension.

Using the formula you posted will be correct as long as the cylinder is not constrained in some way.

 

[bamamack]

The reason I ask is, since the diameter is hollow, there is no mass for expansion, basically no inch/degree F. The circumference would grow like a flat plate, but the Delta in circumference would add to the original circumference. The new diameter would be (Delta + Circumference)/PI. This would not be the same. Thanks

 

[dvd]

It would be the same. The Delta of stretchout for a cylinder is Pi times longer than the diametral delta. You are using the coefficient of linear expansion. This assume that all linear dimensions will expand at the same rate.