Rotating bend failure?

First cracks formed around the shaft indicating the stress was seen as the shaft rotated. This would indicate the stress was directional possible cause by bending or misalignment.
When the shaft broke metal lifting is seen across the surface indicated by blue arrows.
Lifting is slightly directional and has ridges that propagate back to one generate point which is probably where the break final break started.
I would like a second opinion.

Quick Drawing

Neat: do you know Boney?

Did you do that all by your self - the break, I mean! You'd think it'd take a member of management to screw it up that bad. Wait a minute, I am a member of management.

Between two pillow block brgs. Not enough shaft, too much rotor, poor alignment - all three.

These shaft failure posts are always interesting.

The photo shows a flange... I assume that is rigid? Sprockets I'm not familiar with... rigid or flexible (in accomodating misalignment).

Is there a shoulder or key or other stress rise in the area of the break?

Any historical vib records or alignment records that might be relevant?

What type of bearing?

Do you know the shaft material? What is the black outer discolored layer? What is the black everywhere else? On first glance it looks as if there has been a crack for awhile and this environmental black contaminant has settled into the crack for a long time.

The outer areas of the failure seem to resemble photo's or torsional failure or cracks initiating on the surface. If I ignore those, the rest looks like a textbook fatigue failure pattern with beach marks starting on the right and the final failure cresent shaped area on the left. But if you have a metalurgist on site, my recommendation is to involve him early. I know that ours comes up with things that no-one else ever sees.

Sam Boney who? I'm related to a Boney.

Pete,

Not sure about the bearing yet. I'll know more monday. The flange is rigid. This shaft is attached to a rock crusher roll. The sprocket drives a top roll.

Waylon,

Bony-Maroney-get it?

Danny

Hey Waylon, good to see you here. Hope everything is going good for you.

One Question, looks like the break was near the flange, how was the flange attached to the shaft?

Mike

Interesting to see more failures being posted here. Maybe we should make a separate thread or forum dedicated for Root Cause Analysis or Failure Analysis? This should be under the Improving Reliability. What do you think, Terry?

Kind of looks like bearing to bearing misalignment. Does the flange have a pilot to allow zero-zero misalignment?