iter structural design criteria for in-vessel components (sdc-ic)

ITER G 74 MA 8 01-05-28 W0.2
p
Plastic strain eij is calculated incrementally by using the flow rule given in ICÊ3024.2.3. In
the case of a material which can strain harden, the plastic strain modifies the yield criterion.
This modification is determined by means of the hardening rule given in ICÊ3024.2.4.
BÊ3024.2.3 Flow rule
p
The flow rule provides the incremental plastic strain de ij for a given incremental stress dsij.
The incremental plastic strain at any point can be obtained by using the following steps.
1) At the start of a step, the current stress, strain, and plastic strain at a given point
is known. By definition, the current stress is on the current yield surface which
is known:
2
3
* * 2
f( s©, ij s ) s© ij s© ij s
where
= - ( ) =
s'ij is the deviatoric stress.
SDC-IC, Appendix B. Guidelines for Analysis page 32
0,
2) For a given stress increment dsij , the deviatoric stress increment ds'ij can be
calculated. The point under consideration will undergo further plastic
deformation if s'ij ds'ij > 0. The stress increment will cause an elastic strain
increment only if s'ij ds'ij £ 0.
3) If further plastic deformation occurs, the plastic strain increment is determined
by the normality rule (Reuss equations)
de
p
ij
f
= dl = s© ij dl
s©
ij
.
Defining an equivalent plastic strain increment by
p
de =
p p
deijdeij 2
,
3
which can be written in an expanded form as
( ) + ( - ) + ( - )
2
de =
ì
2
2
í de11 - de22 de22 de33 de de
3 î
12
p p p
+
æ 2 2 2
( de ) + ( de ) + ( de
ö ü
6
è 12 23 31)
ø ý
þ
p p p p p p p 2
33 11
dl can be solved as
dl
d p
3 e
= *
2 s ,
and the incremental plastic strain components are then given by :
,