stress decay distance for seal groove

[DowneastTech]

I have a thick wall, steel shell (cylinder) with two internal seal grooves. These grooves are stress risers. Now the literature specifies a stress decay distance of k x square root of (R x t) for various types of discontinuities. The value of k used varies from Pi/2 to Pi/4 to 1.0 to 0.5 and sometimes 1.1. How does one select the appropriate value for k ? I presume that it depends on the type of stress, but so far, I haven't been able to see a pattern. Can anyone help with this?

Best regards,
Downeast Tech

DowneastTech
Mechanical Engineer
Magnus R & D, Cypress, TX

 

[MintJulep]

The problem with the literature is that it never has exactly your case.

If you need to know, you gotta test it.

 

[GregLocock]

or model it.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[MintJulep]

...or model it. Except that I wouldn't trust an unverified model, so you've got to test anyway.

 

[arto]

p.s. if you have 2 O-ring grooves, be sure to vent in between so you don't get a "pressure trap" from thermal expansion etc.

 

[GregLocock]

Oddly, I would, in this case since I see no practical way of correlating in detail, other than to compare the k from the book with the k from the model.

I'm assuming this is a fatigue problem, not statics.



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[diamondjim]

Who are you using for a reference?
Peterson?