, .
σ > 0, ; t > 0, ; a > 0, bc .
. .
Fx = σ x dy dz Fy = σ y dx dz Fa = σ a ds dz Tx = tx dx dz Ty = ty dy dz Ta = ta ds dz |
. U V, .
åU =0 Ta + Fy cos a - Tx sin a - Fx sin a - Ty cos a
Ta + cos a (Fy - Ty) sin a (Tx + Fx) (1)
åV = 0 Fa - Fx cos a+ Ty sin a - Fx cos a - Fy sin a
Fa -Fx + Tx cos a + (Ty Fy sin a) = 0 (2)
å m0 = 0
å m0 = 0 Tx dy/2 + Ty dx/2 = 0 (3)
Tx Ty dx/2 dy dz
tx dx/2 dy dz + ty dx/2 dy dz = 0
tx + ty = 0
tx = - ty (4)
- . (4) . (4) .
(1) (2) ty - t, , dx/ds = sin a, dy/ds =cos a, σ σy a.
σ a = σ x cos2a + σ y sin2a + tx sin2a (5)
ty = ((σ x σ y)/2) sin2a - tx cos2a (6)
(5) a a ¹ 90,
σ a + σ (a+90) = σ x + σ y = const. (7)
: - , max , σ min.
. .
. σmax σmin, , .
σ (5) a .
|
|
: .
tg2a0 = (8)
tg2a0 = (9)
σx σy a0 , a0 > 0.
(8) 2a0 90 90, - 45£a0 £45, , 45 .
a0 (8) (5) (6) (9).
(10)
.
.
, (6) a .
; ;
cos2a1 :
(σx - σy) + 2 tx tg2a1 = 0
tg2a1 = (11)
d a1.
(11) a1 a1+90, - . t max, tmin. tmax = - tmin. (8) (11) a1 ¹ a0+45
: 45
(6) σ = σmax; σy = σmin; tx = 0; a1 = + 45
= + (12)
(12) (10)
= + 1/2 (13)
.
.
.
:
1. d d
2. t ty
3.
4. ) d t; , .
5. d
6. ,
7.
R =
, .
, .
da ta. , . . da ta a.
5.