Failure of component of D2 and 62-65 Rc

[dharhay]

We have had a failure of a component of D2 hardened to 62 to 65 Rc. The part flew into four pieces, fortuneately no one was hurt.

The ID of the part was under a stress of 10000 psi. Holes are very close and as a stress riser contributed to the catastrophic failure.

Some specifics:the thickness is 60mm, OD is 792mm, ID is 415mm, the holes are 22mm dia, the thin ligament is 11.5mm.

I would not have selected D2 to take the tensile load of the pressure on the ID to hold it to a roll shaft.

However, not rushing into any conclusions. Could the D2 be used in this application with simple changes?

I attach a photo of the failed component.

Dave Harhay
Bronx Int'l.

 

[Metalguy]

How was the 10ksi calculated--shrink fit? Can you change the location of the small holes--the stress raisers? Any other loads? Why a tool steel?

"You see, wire telegraph is like a very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? Radio operates the same way: You send signals here, they receive them there. The only difference is there is no cat." A. Einstein

 

[TVP]

D2 is optimally hardened in the range of 58-62 HRC. It has quite poor fracture toughness when hardened any higher.

 

[EdStainless]

Are you sure that there was no bending or flexing? I suspect that is what happened.

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Plymouth Tube

 

[metengr]

I would question the location of the holes as being one of the cause of the failure. They are way too close to the bore.

 

[desertfox]

Hi

Looks like the holes being to close to the edge of the component as caused this failure due to creating a stress raiser.
A rough rule of thumb "holes should be 1.5 * hole dia away from an edge"
Are the holes for bolts?

desertfox

 

[dharhay]

Thanks for your questions.
I am not sure why D2 was selected, this was done at another division.

I did an FEA on the part with theoretical critical pressure on the ID and that pressure creates the 10000psi on the ID that was mentioned. Holes show a stress near 30000psi.

The hardness was to be in the range of 58-62 per drawing, but actual values were higher in many parts of the disk. The disk did not have any bending, it was pure radial force of an hydraulicly expanding hub.

Yes, the holes are for studs that hold 5 disks together.

My suggestion is to make the discs from 4140 and induction harden the OD which is a surface that product rides over. The ID will be more ductile to withstand the pressure of the hydraulic hubs. Of course move the holes further away from the center.

Thanks again for your opinions.

Dave Harhay
Bronx Int'l.