Chemistry Reference
In-Depth Information
function t(
x
) can be presented as follows:
p
6
x
,
(4.4)
t
(
x
)
=
k
sin
b
that is fully corresponds to Frenkel conclusion, except for arbitrarily cho-
sen numerical coefficient in brackets (6 instead of 2).
FIGURE 4.2
Schematic picture of shear deformation and corresponding stress - strain (t
- g
sh
) function [25].
Further calculation of t
o
by method, described in Ref. [3], and its com-
parison with the experimental values t
x
indicated their close correspondence
the possibility of realization of the above-offered yielding mechanism at the
segmental level [18].
Inconsistency of t
oY
and t
Y
values for metals results to a search for anoth-
er mechanism of yielding realization. At present, it is commonly accepted
that this mechanism is the motion of dislocations by sliding planes of the
crystal [3]. This implies that interatomic interaction forces, directed trans-
versely to the crystal sliding plane, can be overcome in case of the pres-
ence of local displacements number, determined by stresses periodic field in
the lattice. This is strictly different from macroscopic shear process, during
which all bonds are broken simultaneously (the Frenkel model). It seems
obvious that with the help of dislocations total shear strain will be realized at the
