PSI - Issue 18

Vladimír Chmelko et al. / Procedia Structural Integrity 18 (2019) 600–607 Chmelko, V., Berta, I / Structural Integrity Procedia 00 (2019) 000 – 000

604

5

pt red ( r )   = 1 in the form

using the condition

2      −   3 2 1 r r

 −   



2    = −

3 pt

3 1 r A. r

1 ln

p A

,

(18)

1

2

( .



K +

) .

A

=

the constant A is equal

1

h

3

Using the same procedure for the Tresca criterion



= − red

1 3   ,

(19)

we get the burst pressure for full plasticization of the cross-sectional in the form

 −   

   

2

(

)

r r

2 1

1

3 1 r Aln r

p A

1

= − 

−

(20)

pt

1

2

3

4. Numerical solution of the burst pressure

Numerical solution using FEM in ANSYS served in the first phase to choose the size and shape of the pressure vessel so that the destructive pressure could be reached even in laboratory conditions. The geometry of the cylindrical vessel was chosen so that the plastic strain occurring under pressure occur only in the middle tapered (working) part outside the bottom and weld areas (Fig. 3). The finite element network was loaded with internal pressure alone and one eighth of the entire vessel model was solved using three symmetry planes.

Fig. 3 The FEM model of the experimental specimen of pressure vessel. In this model, the effects of the geometric dimensions of the experimental vessel (the length of the constriction, the ratio of the length of the coarser and thinner sections) to the result were tested. The efforts have been made to determine the impact of the toroid bottom. The effect of the weld between the bottom and the thicker part of the container was simulated by prescribing the same displacements by the nodes located in the weld area. The results showed that the influence of the weld under consideration does not have a significant effect on the deformation on the tapered part of the pressure vessel. The material tensile curve (obtained by direct measurement) recalculated for the true stress was approximated by the