Unloading after Plastic Deformation
Unloading after Plastic Deformation
(OP)
When a structure (say, a cylindrical tensile test coupon, for simplicity) is loaded beyond Fty, but not broken, and then unloaded, what does the unloading curve really look like? It's drawn often enough in the textbooks: they always show a straight line back down with slope E to the x-axis, and then mention that the strain at this point is the permanent deformation of the structure. Assuming that the material in question has a well defined elastic zone, and the peak stress is in the plastic range, why is the unloading line straight? Can the moving dislocations and grain boundaries in the material (when it is being stressed plastically) go a little bit back to their initial state when relieved?
| _________Ftu
| __----/
| _/ /
| Fty_/ /
| / / <--- Is the unloading line really straight?
| / /
| / /
|/ /
--------------------------
0 epermanent
(Hope the drawing works out
)
I expect the answer is no, but I'm trying to make sense of some test data...
| _________Ftu
| __----/
| _/ /
| Fty_/ /
| / / <--- Is the unloading line really straight?
| / /
| / /
|/ /
--------------------------
0 epermanent
(Hope the drawing works out
)I expect the answer is no, but I'm trying to make sense of some test data...
STF





RE: Unloading after Plastic Deformation
RE: Unloading after Plastic Deformation
Regards,
Cory
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