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 .
