211 / 352
207
Maximal equivalent stress in the zone of gap, calculated by FEM for the claw without
reinforcement is
e1
= 13.3 kN/cm
2
, so applied stress concentration factor is
k
=
e1
/
2
= 13.3/3.74 = 3.56.
Normal stress
Shear stress
Membrane stress
Bending stress
Stress [kN/cm
2
]
Deformation energy [kNcm]
Equivalent stress
Deformation energy
Figure 3.2: Behaviour of the claw 90
o
without reinforcement
Claw 45º
Nominal stress in section remote from gap, at the pressure 0.25 bar, is for:
o
Pipe
317x14.2 -
1
=
pR
1
/t
1
= 0.25
15.85/1.42 = 2.79 kN/cm
2
.
o
Pipe
267x12.5 -
2
=
pR
2
/t
2
= 0.25
13.35/1.25 = 2.67 kN/cm
2
.
Distribution of stress components and deformation energy is presented for claw 45
o
without reinforcement in Fig. 3.3, and with reinforcement in Fig. 3.4.
Maximal equivalent stress in the zone of gap in FEM calculation for the claw without
reinforcement is
e1
= 20.4 kN/cm
2
, for the claw with reinforcement
e2
= 10.6 kN/cm
2
.
Applied stress concentration factor in the first case (without reinforcement) is
k
=
e1
/
2
= 20.4/2.67 = 7.64
and in the second case (with reinforcement) is
k
=
e2
/
2
= 10.6/2.67 = 3.93.