For me, yield stress (either 0.2% proof stress or upper yield stress depending on whether or not there is a yield point) is a special point in the stress-strain curve measured using a tensile standardized sample of the material in question. Therefore, it should be a stress instead of a strength. The same should be applicable to the ultimate tensile stress. It is also a special point in the stress-strain curve, namely the stress at maximum load.
However, my colleagues do not stop speaking of strength. From my point of view, the notion of strength is more related to components. Of course, I see the simiarity, which is especially obvious if we consider a tensile sample as a kind of simple component.
By the way, the pronouncation of stress is much easier for native german speaker than the pronouncation of strength ;-)
Hi Frank,
please see the attachment. Those author(s) define the yield strength.
But in the same sentence they say that from its nature the yield strength is a 'stress'.
From my understanding it should be named as yield stress, becauce it is a stress value.
But it may be that in the stress-strain community the yield strength is the more common expression for that point of the stress-strain curves due to the fact that it is a special characteristic point having a special value (strength).
But also in the second link the yield point is named the yield strength.
However same authors also use the term yield stress (please see the last section of the chapter on 'Ductile' materials).
Congratulations Frank, you have pick up a very curious issue.
So let's wait for some more comments.
https://en.wikipedia.org/wiki/Yield_(engineering)
https://en.wikipedia.org/wiki/Stress%E2%80%93strain_curve
Strength that still maintains after a sample is failed is yield strength and the resulting curve after failure follows a straight/linear path and the stress that is posed by this strength is yield stress--------------?
Thus Ijaz
the stress at the 'yield point' should be named 'yield strength' as the colleagues of Frank do?
Hi Gerhard,
thank you for the links. Indeed, the English Wikipedia site is considered a kind of reference. Yield strength is mainly used there. Another criterion might be based on the instances found in a google search: "Yield strength" produces 491.000 results, "yield stress" produces 531.000 results, not really a significant difference. But perhaps we will still see more technical arguments.
Frank
Hi
Semantic issue, thjs.
In my view, strength is an engineering term, so as to mark the stress where a construction element will start to change its shape. (and UTS is where it will fail. btw that is an engineering- not a true stress )
Metal physicists speak of yield stress. That denotes the onset of irreversible (plastic) deformation,
Hi Frank, concept of stress was introduced in the field of solid mechanics to describe internal mechanical state of deformed body under mech load. Concept of strength is fundamental in estimating the result of solid reaction on mech loading. In such approach, maximal acting stress (or equivalent stress in the case of non uniaxial stress state) should be compared with allowable stress of the body material. Such stress is determined by dividing the ultimate stress of the material by factor of safety. In this case, yield stress(point) of ductile material test diagram or ultimate stress(point) of brittle material are considered in terms of strength characteristics and are often used as yeild strength or ultimate strength.
Dear colleagues, I support the opinion that term "yield stress" is a much more preferable than "yield strength". Really, in common case the beginning of plastic flow is far from failure moment (or strength loss). We have similar situations in some fields, when traditions in terminology plays bad service...
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