×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Pressure rating of thick cylinder

Pressure rating of thick cylinder

Pressure rating of thick cylinder

(OP)
Hi,

I have been trying to figure out the pressure rating of a thick cylinder under pressure and ran into a few problems,

1) I have come across different criterias for distinction between thick and thin cylinders (i.e. Thin cylinder if D/t>10 or if t<r/10 or if r>5*t). So I went with the one that occured in most books including Roark's handbook which is t<r/10.

2) I calculated the Von Mises stress using Lame's equations (attached file). But the Von Mises using these equations does not match with the FEA simulated results with a difference of 11% (attached file showing boundary conditions).

So, the question is am I using the right approach (i.e. correct formulaes) and why do you think my analytical Von Mises stress value is so far from the FEA Von Mises stress value?

RE: Pressure rating of thick cylinder

vtmike;
If you have access to ASME B&PV Code books, I would review Section VIII, Div 1 for thickness formulas. Despite this being structural with pressure, the same concept and formulas would apply for internal or external pressurized cylindrical components (pressure vessels).
 

RE: Pressure rating of thick cylinder

That's a CAD picture, what does the mesh look like and what elements did you use?

gwolf

RE: Pressure rating of thick cylinder

Reference check review example on the PRESSURE DESIGN DRIECTORY EU design code. ANSYS SOFTWARE.

RE: Pressure rating of thick cylinder

It's difficult to say without looking at the FEA results, but your formula for Von Mises is only applicable at the inner radius. You really need to look at the mean (membrane) stress, say at the mid-thickness. At the external radius the principal stress, sig 3 = Po (the pressure) and hence the von mises stress will be larger than the value you calculated. At the mid-thickness the radial stress is some value not equal to zero, and hence the von mises stress will be larger also. For external pressure you should also look at buckling of course.  

corus

RE: Pressure rating of thick cylinder

Incidentally, there's not much need for an FEA model in this case, but if anything you should have used a 2D axisymmetric model.

corus

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources