Metal Thermal Expansion Question (CTE mismatch)

[metalman8357]

Hi guys,

I have a quick question about the thermal expansion and CTE mismatch of metals. Basically I have a bronze bearing riding over a shaft and inside a journal. The bronze bearing is press fit into the steel journal (ID of journal = 1.124", OD of Bronze bearing = 1.125")and the steel male drive shaft rides inside this assemble. The steel male drive shaft has an OD of 1.000", and the bronze bearing has an ID of 1.003". This gives 0.003" clearance. Our operating temperature is 500 degrees F. At this temperature, is it possibly for this whole assembly to lock up?? I know bronze wants to expand more than the steel, but I'm not sure how this behaves when it is being constrained on all sides by the steel journal. Any input would be greatly appreciated.

Thanks,
M

 

[Compositepro]

Yours is not an unusual application. I believe that the main way to avoid problems here is to keep the bronze thickness low. The steel outside the journal may also need to be heated, or at least insulated from the rest of the structure to allow it to heat and expand. In some cases the bushing can be cut into three segments or shoes with one being spring-loaded.