Keller wrote,
>You cannot measure stress from a diffraction experiment but (try to)
>calculate it from the strain which you can measure. Please specify: is it
>macro-st.rain (=residual strain --> line shift) on polycrystalline solids or
I start to be a little bit concerned about all those people claiming and
pointing out that diffraction don't measure a residual stress but a
residual strain.
Keeping this concept a step forward than we must say also that diffraction
don't measure a residual strain at all but a d-spacing change or even more
not a d-spacing but an angular position shift (if not a TOF etc) and so on.
And also, can you really be sure that the line shift you see is a strain?
(Just to go to the extreme).
Also, this reasoning will give the conclusion that no one technique is able
to measure a stress directly; most of them measure a displacement (and
convert the displacement to a stress or load using a know stiffness, like
diffraction), some measure other physical properties (light trasmission
etc.).
So, my own idea is that people who don't know how to transform strain in
stress will measure only strain and the other are measuring stresses.
Let me stress the audience about that; may be is that I am an engineer and
not a physicist or chemist.
best regards,
Luca Lutterotti
-----------------------Luca Lutterotti----------------------------
Dipartimento di Ingegneria dei Materiali, Universita' di Trento,
via Mesiano 77, 38050 Trento, Italy
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