multiple stress concentration factors 1

[LeeEccles]

If I have a stepped shaft, that is, a shaft that changes from one diameter to a smaller diameter along its length; subject to an axial load and torsional load, how do I address the problem of stress concentrations at the step?

Having calculated the nominal direct and shear stress values at the step, I've applied stress concentration factors to each of these stresses independantly ( values from Peterson's ). I've then determined the equivalent von Mises stress at a point taking into account both the increased direct and shear stresses.

Is this the correct procedure or is there data for combined stress situations that may be less severe than the case I've considered?

 

[joekm]

Not knowing how the loads are combining, then I'd say this is probably how I would approach it.

Regarding the stress concentration, a semi-circular groove located either in the face of the step or in the larger shaft portion near the transition can be used to reduce the stress concentration at the step change. Furthermore, if you truly have a step-change in diameter, then any eccentriciy in the shaft alignment will eventually cause cracking at that point. In practice, it's difficult to eliminate such eccentricities. Therefore, I would highly recommend doing something to reduce the severity of that transition.

...this, of course, assumes I've correctly visualized what you are saying