' , ' .
' . ' (. 12.7,a) Τ , , 䳿 . 쳖 .
. 12.7. '
'
σ = F/A ≤ [σ],
F , 䳺 ,
.
' F = 2T/d,
= (ht1)l0,
l0 .
, '
σ = 2T/[dl0 (h t1)] ≤ [σ]. (1)
(1) . ϳ 䳺 . ' , . , , , . (1) ' , l0, , ' , 180 ( ).
' . , (1):
l0 ≥ 2T/[d(ht1) [σ]]. (2)
l0 l = l0 + b, .
' 䳺 . . ' '.
[σ]3Μ ' ', , .
' :
[σ]3Μ = (100...120) ( ) [σ]3Μ = (70... 80) ( );
[σ]3Μ = (160... 180) ( ) [σ]3Μ = (110...130) ( ).
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[σ]3Μ '.
' . [σ]3Μ = (20...30) .
' (. 12.7, ) , ' , ' . ' (1) . 12.7, ,
σ = 2T/[dl (h t1)] ≤ [σ]3Μ. (3)
(3) ' . , ' .