ma kuchlanish nol boMadi:
cr - cr
va
t
=
0
.
а
шах
a
Demak, maksimal normal kuchlanish sterjenning ko‘ndalang kesimida
vujudga kelar ekan.
Eng katta urinma kuchlanish esa sterjen o‘qi bilan 45° burchak tashkil
etgan kesimda hosil boMadi, chunki a = 45° boMganda sin2or = l boMadi.
1
Tmax —
2
0
’
Shu kesimda normal kuchlanishlar urinma kuchlanishlarga teng boMadi:
2
a = 90° boMganda, ya’ni sterjen o‘qiga parallel boMgan kesimlarda ikka
la kuchlanish ham nolga teng boMadi: cr9o„ = 0 ; ^ = 0 .
4.1-misol. 4.3‘-rasm, a, b, d, - da tasvirlangan elementlaming qiya ke-
simlarida hosil bo ‘ladigan normal va urinma kuchlanishlar aniqlansin.
n„
cr
„ =
— a
=
t
a=45
max
a)
b)
d)
4.3'-rasm, a da tasvirlangan element uchun о ,- ст2- 0; ст3= -50 MPa;
a = 30°; u holda:
o a = —50cos2 30° = -3 7 ,5 M P a ;
та = - y s in ( - 6 0 ° ) = -21,7 MPa
4.3‘-rasm,
b
da tasvirlangan element uchun
ct
,=
50
MPa;
g 2=ct3=0.
a= 30°; u holda:
cr, = -50cos2(-30°) = - 3 1,5 MPa
Ta = y ( s in - 6 0 ° ) = -21,7 MPa
4.3'-rasm, d da tasvirlangan element uchun ст,=
ct
,= 0;
ct
3= -50MPa;
a= -30°; u holda:
о a = -50cos2 (-30°) = -37,5 MPa
та = у sin- (60°) = -21, IM P a .
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