Questions about 'reference stress'
Questions about 'reference stress'
(OP)
Hi all,
Couple of questions here:
I've recently started working on a project concerning limit analysis and keep coming across the term 'reference stress' (Or 'nominal stress'). Most of the literature I've gone into so far give only vague hints as to what it actually is ( stress far away from the concentration point being the recurring theme - but then how far away ?). I've been reading through Peterson's book on stress concentration factors and while it is relatively straightforward for a lot of common defects, I feel it doesn't really go into details about why the nominal stress is defined the way it is for any given problem. ( I haven't gone through it in detail so I may be mistaken about this.)
A concept that occurred to me from my read of Peterson thus far is that we could perhaps define the reference stress as the stress that would be present at the same location as the stress concentration point if the defect causing the concentration were absent ( e.g. stress at the center of a hole in a plate if the hole were absent ). Would this be a valid way to go about things ? Are there any good references that talk about this ?
So TL,DR :
1. What exactly is the physical meaning of 'reference stress' ?
2. Could the reference stress be defined as stress that would be experienced at the same location as the stress concentration point if the defect causing the concentration were absent.
Thanks in advance !
Couple of questions here:
I've recently started working on a project concerning limit analysis and keep coming across the term 'reference stress' (Or 'nominal stress'). Most of the literature I've gone into so far give only vague hints as to what it actually is ( stress far away from the concentration point being the recurring theme - but then how far away ?). I've been reading through Peterson's book on stress concentration factors and while it is relatively straightforward for a lot of common defects, I feel it doesn't really go into details about why the nominal stress is defined the way it is for any given problem. ( I haven't gone through it in detail so I may be mistaken about this.)
A concept that occurred to me from my read of Peterson thus far is that we could perhaps define the reference stress as the stress that would be present at the same location as the stress concentration point if the defect causing the concentration were absent ( e.g. stress at the center of a hole in a plate if the hole were absent ). Would this be a valid way to go about things ? Are there any good references that talk about this ?
So TL,DR :
1. What exactly is the physical meaning of 'reference stress' ?
2. Could the reference stress be defined as stress that would be experienced at the same location as the stress concentration point if the defect causing the concentration were absent.
Thanks in advance !





RE: Questions about 'reference stress'
RE: Questions about 'reference stress'
RE: Questions about 'reference stress'
2) i guess you could think of it that way, but it would be whatever stress the calc is based on. For example, some Kt are based on gross section stress (like the stress at a hole, based on Wt area) but some are based on net area (that'd be (W-D)t).
another day in paradise, or is paradise one day closer ?
RE: Questions about 'reference stress'
RE: Questions about 'reference stress'
another day in paradise, or is paradise one day closer ?
RE: Questions about 'reference stress'
Thanks for the reply rb1957. Although I'm still a bit lost since your explanation in #1 seems a bit circular - Kt is defined in terms of nominal stress and nominal stress is the stress that Kt is based on...
I wasn't aware that the term 'reference stress' wasn't used much. I suppose it's because the literature I started with for this project was from the 80s and they did refer to it as 'reference stress' at some points. Modern references seem to have shifted to 'nominal stress' now. TIL !
Also what exactly does the term 'far-field' stress mean ? Is it simply a value of stress sufficiently far away from the concentration zone ? Or is it something different ?
I'm sorry if these questions seem dumb but as many others have pointed out here - the term isn't all that well defined in literature.
RE: Questions about 'reference stress'
it is a reasonably common term in fatigue calcs (Niu uses it).
nominal stress, and far field stress, are similar terms.
At the end of this the peak stress at a stress concentration is Kt*stress. When you look at a Kt derivation it will be associated with a stress (beit reference, far field, nominal, whatever). You need to use this stress to determine the stress spectrum. Eg the Kt at a hole can be based on either gross section or net section stress.
clear as mud ?
another day in paradise, or is paradise one day closer ?
RE: Questions about 'reference stress'