(, , )
.
, x Cy .
x
dA dy, dA=b*dy. dA , .. y h/2 +h/2,
y:
x y .
2. :
Jx1=Jx + a2;
Jy1=Jy + b2;
, , . Jy1x1=Jyx + abF; ("a" "b" ).
Jx1=Jxcos2a + Jysin2a Jxysin2a; Jy1=Jycos2a + Jxsin2a + Jxysin2a;
Jx1y1= (Jx Jy)sin2a + Jxycos2a;
a>0, .. Jy1 + Jx1= Jy + Jx
( ) . , , . . = 0, .. , = 0. , . , : ,
a0>0 Þ .. , . , , . :
Jmax + Jmin= Jx + Jy. 0. , :
Jx1=Jmaxcos2a + Jminsin2a; Jy1=Jmaxcos2a + Jminsin2a; Jx1y1= (Jmax Jmin)sin2a;
. .
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