Press fit and welded members

[Ippy00]

I am researching the effects of adding a shrink fit up onto a hollow shaft. The project entails that the previous design consisted of a hub welded onto a 4" steel shaft from 2 sides. As the welds could not withstand the load, the new design was switched to a shrink fit hub with a weld on the back.

My question is, how can I calculate safety factors though a press fit and a weld?

I understand the formulas to calculate the stress on a weld and the radial/tangential stresses on the press fit, but how do I go about combining the two to find the maximum load the two can withstand?

 

[EdDanzer]

Depending on the wall thickness there maybe now gain from the press fit. Your problem is a good candidate for FEA to see what caused the failure. If the original loads show the design is ok then the application as different loads than assumed.

Ed Danzer

http://www.danzcoinc.com

http://www.dehyds.com

 

[desertfox]

Hi lppy

Well what sort of weld do you have is it a fillet? if so the fillet weld normally fails under shear, you don't say what the type of load is on your device, buts lets say its a torsional force, so you can calculate the force to cause failure of the weld or the allowable force on the weld under torsion, secondly you can calculate the torsional force that will cause your hub to spin on the shaft, which will depend on the friction coefficient you use.
Having calculated the two torsional forces you can add them together and compare them against the actual load the device see's in service and the ratio of these forces will give you the safety factor.

http://www.roymech.co.uk/Useful_Tables/Mechanics/Cylinders.html#Interference

http://www.roymech.co.uk/Useful_Tables/Form/Weld_strength.html#Weld_Examples

desertfox