Strictly-speaking, Nominal means "name". For example, many structural steels are given a grade based on their tensile properties. ASTM A709 has a Grade 36 and a Grade 50, which have a mininum yeild strength of 36 KSI and 50 KSI, respectively. You could say that Grade 36 has a nominal yield strength of 36 KSI. In this case, the name is based on the minimum allowable yeild stress.
While I cannot think of an example off the top of my head, there could well be instances where the "nominal" value is different than the minimum value.
The best illustrative example of the term "nominal" is in pipe sizes. A piece of "6-inch pipe" might have an OD of 6.625 and a wall of 0.280 so, while neither the OD or ID will measure 6.000 inches, it will carry a nominal size of "6-inch".
Come now -- was that really appropo? As you well know, 2 x 4 was the original rough cut dimension. I have actually measured some in a previous life. That quote is like saying, "my Frigidaire is really a Coldspot." In my case, it actually is a Frigidaire and OK it is also a coldspot but not in name only functionally.
One definition of Nominal is; in name but not necessarily in fact. As used here, I would take it to mean approximately but not to disagree with redpicker's def.
What I meant is not important enough to explain. It was intended in a manner of jesting and explaining a joke usually is not very funny. I suppose the joke is on me.
Maybe I made up the coldspot but my feeble memory told me there was a refrigerator with brand name of coldspot.
Engineering Language/Grammar Skills is a forum here on eng-tips where I get and give some chuckles (laughs) and levity seems to be tolerated there to a large degree but these eng-tips forums are intended for serious discussions so I should be more careful about chiming in inappropriately and thereby creating confusion.
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Hopefully my serious comment made some sense i.e.: One definition of Nominal is; in name but not necessarily in fact. As used here (nominal yield stress), I would take it to mean approximately or average yield stress.
For example; if a linear dimension is given as 5" + - .010", one might say, "the nominal dimension is 5".
No worries. If I had a nickel for every time I had to explain a joke, trust me, I'd have a lot of nickels. FYI, please no NOT limit your jokes/levity to just 1 forum, I am certain most of us welcome it.
I too have used your interpretation of the word "nominal".
One definition of Nominal is; in name but not necessarily in fact. As used here (nominal yield stress), I would take it to mean approximately or average yield stress.
I have to disagree. With respect to yield stress, I have found the "nominal" value to nearly always refer to the minimum yield stress than an approxiamte or average value. I agree, that in many other contexts, "nominal" can be described as "approximate" or "average" (as in, "the column was under a nominal compressive load of 800 Lbs"), but with respect to yield stress, nominal refers to, more often than not, the minimum specified yield stress.
I suspect this is the point of the original post. Obviously, the OP was wanting to understand what is meant by Nominal Yield Stress. Like I said, in my experience, the term nearly always refers to the minimum yield stress. This is because nominal means "in name", many materials are characterized (and named) based on their minimum yield strength. It would be incorrect (and dangerous), however, to use a value reported as the "Nominal Yield Stress" for the minimum yield stress in a calculation because if you are going to use a value to base strength calculations on, you had better be sure it represents the specified minimum yield strength (SMYS), and it's not just a "name".
As Red says, in strength the nominal strength is also the grad identification, which is the minimum strength.
In those same specifications though we take the nominal composition to be the middle of the specified range.
Nominal is a soft enough term that it needs to be used as little as possible. There is no exact meaning.
I have to agree since it is two against one. Actually all seriousness aside, hee hee, I agree with you 100%. I usually go to metals Handbook or another reliable source like MIL specs , Machinery's Handbook, metal suppliers data, etc to obtain stress values for any calcs.
I assumed that ASTM A36 was a coincidence that the spec name was the minimum yield stress and just thought it was kind of nice to help my memory. Another example is USS EXTen 50 which is min 50ksi yield stress. I don't recall seeing a designation as Nominal yield stress applied to either one of these rather only minimum yield stress but maybe I just overlooked the Nominal reference.
Of course the criteria of "temperature" is not mentioned above. The minimum yield stress at a higher temperature will be lower than the "nominal yield stress".
