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

ITER G 74 MA 8 01-05-28 W0.2
( ) = é
x3
s
ù +ht
ij s
b
h
ij x3 dx3
ëê ûú ò
(2)
I - b
+ h
=
-h
t
where I ò J( x3) x3 dx
2
b
and J(x3) is defined in B 2513.
Note: The bending shape factors for this case are given in Figure IC 3211-3
3
(3) In this case, the bending components of the normal stresses can be derived by using
Eq.2 for the s11 component and Eq. 1 for the s22 component. However, the bending
components for the shear stresses s12 and s21 defined by these equations are generally
unequal.
BÊ2520 Classification of stresses obtained by elastic analysis
General classifications for stresses are given in IC 2520.
B 2521 Primary stress
The primary stress is defined as that portion of the total stress which is required to satisfy
equilibrium with the applied loading and which does not diminish after small scale permanent
deformation. Small scale permanent deformation is taken to mean deformation which results
from plastic strains that are of the same order of magnitude as the elastic strains. If the
stresses do not diminish after such small plastic strains, then it is implied that the stresses
cannot be relaxed by small deformation and can lead to plastic instability and other damage.
Within a structure, any stress field (e.g., the elastic stress field or a lower bound stress field
for limit analysis) which balances the volumetric forces and the loads applied on the surface
(mechanical loads: pressure, forces, etc.) is an upper bound to the primary stress. This
property is useful in practice because the exact value of the primary stress is not always easy
to determine. Thus, the upper bound will, more often than not, be used instead of the true
primary stress. The exact value of the primary stress may be obtained by taking the smallest
stress field which balances the forces, that is, that which leads to the lowest value of the
maximum stress intensity in the structure.
Example: For a clamped edge beam with a uniformly distributed load (w), from elastic
analysis, an upper bound to primary bending stress (Pb) corresponds to the edge bending
moment of wL 2 /12, where L is the span. However, a better (i.e., lower) upper bound to the
primary bending stress, which can be obtained from limit analysis, corresponds to a bending
moment of wL 2 /16.
Generally, mechanical stresses (B2501) produced by mechanical loads are classified as
primary.
Note: If the elastic stress analysis is conducted using a finite-element technique, the primary
membrane and bending stresses at any section have to be determined using the procedures
given in IC 2513 and IC 2514, respectively (also, see sections B 2513 and B 2514).
SDC-IC, Appendix B. Guidelines for Analysis page 6