Forming strain head formed from pipe

[ElCidCampeador]

Hi, I'm trying to find out the forming strain according to equations of table UG-79-1, ASME VIII div.1 Ed.'15.
Case: hemispherical head formed from pipe (A 333 Gr.6).
What are Rf and R0? I mean, Rf=R final sphere, but R0? At the beginning I have a pipe, not a plate, so it's not equal to infinite, isn't it? Thank you

 

[Don56]

If one assumes you are going to cut part of the pipe away and form the hemisphere by pushing a transverse section of pipe through a die or spinning it on a mandrel, Ro is infinity for the longitudinal axis of the blank and Ro is the center line radius of the original pipe if it is a hot formed pipe. Ro changes between the two constantly.

 

[ElCidCampeador]

What should I choose in order to calculate the forming strain? I need to know it in order to determine if heat treatment is necessary or not.

 

[SnTMan]

ElCidCampeador, choose the one that gives the highest forming strain, and post form heat treat (or not) accordingly.

I admit I cannot understand how you plan to fabricate a head from pipe, let alone why.

Regards,

Mike



The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[ElCidCampeador]

This head has a big opening in the middle and for me it's cheaper to take a pipe and form it at the end. Moreover, I could use the left part of the pipe as shell of the vessel. The problem is that the head is emisperical so...what is the highest forming strain? If I take Ro=0, the equation of table UG-79-1 becomes nonsense; if I take Ro=Rpipe, the strain becomes 0, because Rf=Ro=1 (the inside radius of the head is equal to the starting radius of pipe, because it's emispherical); and finally, if I take Ro=infinite I would have a finite value, but this is the case of the head made from plate (which is not this one).

 

[Don56]

I reeally can't see what you are trying to do or how. How about a sketch?

 

[LittleInch]

Do you mean this?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[ElCidCampeador]

The problem is not HOW. My supplier will form a head from a pipe (but I don't know exactly how) so that at one end the pipe will have the shape of a hemispherical head with a big hole in the middle (This hole it's the starting hole inside the pipe which is reduced by the effect of the forming). But this is not the problem.
My problem is: what is the forming strain of the final head? I need to know it in order to decide if doing a post forming heat treatment or not, according to what ASME requires.

 

[SnTMan]

In the longitudinal direction, R0 = infinity. The term Rf/R0 goes to zero. Post form heat treat (or not) per UCS-79.

Regards,

Mike



The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[LittleInch]

But is it a head with a hole in it or a reducer he's making?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.