и ф = ( « ф)т (4 .3 8 )
M u s ta h k a m lik sharti
»Ф ф , / , ]
(4-39)
S hakl o ‘ z g a rish i p o te n sia l e n e rg iy a s in i u m u m iy h o i uchun (4 .2 4 ) ga
b in o a n q u yid a g ic h a yo zish m u m k in :
1 + '“ - [ o f +
ct \ + cr
I - (cr,cr2 + cr2cr3 + cr.cr,) ] .
(4 .4 0 )
иФ=- 3E
O d d iy c h o ‘ zilis h d a o q u v c h a n lik chegarasi uchun (c r, = с гж ; <т,
= = 0 )
q u y id a g i ifodaga ega boM am iz;
1
+ M 2
( " * L “
3E
(1 4 ) va (1 5 ) n i (1 2 ) ga q o ‘ ysak,
y o k i
yla ] + 0 2 +
<*l - (0-,0-2 + CT2CT3 + (7.С7,) = CT„;
( f f,
-CJ2f + (ст, -
СГ.
) 2 + (-
cr, ) 2
(4.41)
(4 .4 2 )
(4 .4 3 )
k e lib c h iq a d i.
B u la rn i e ’ tib o rg a olsak, m u s ta h k a m lik sh a rtin i
f a -
° г ) 2 + f a 2
~ ) 2 + f a ; “ ^ Л
- ~
= И
n (4 .4 4 )
k o ‘ rin is h d a , to ‘ rtin c h i nazariya b o ‘ y ic h a e k v iv a le n t k u c h la n is h n i esa
cr.., (cr, - c r , ) 2 + (o \, - cr. ) 2 + (ex. - cr, ) 2
(4 .4 5 )
ko ‘ rin is h d a ifodalasa boMadi.
T a jrib a la r to ‘ rtin c h i nazariya c h o ‘ z ilis h va s iq ilis h g a b ir x il ish la yd ig a n
p la s tik m a te ria lla r uchun t o ‘ g 'r i va aniq n a tija la r b e ris h in i k o ‘ rsatadi.
S hunday q ilib , b iz m u s ta h k a m lik n in g t o ‘ rtta asosiy va k la s s ik n a za riya
la ri b ila n qisqacha ta n ish ib c h iq d ik . A m m o m u s ta h k a m lik n a za riya la ri shu-
с т т
/J~7\ ’ ip
n in g o ‘ zi b ila n tu g a m a y d i. B u m asala b o ‘ y ic h a M o r, Y u .l. Y a g n , G.S. P isa
renko, A .A . Lebedev, Y a .B . F rid m a n k a b i ta n iq li o lim la r b a ra k a li qalam
tebratganlar.
