PSI - Issue 68

Nedeljko Vukojević et al. / Procedia Structural Integrity 68 (2025) 379– 385 N. Vukojević et al. / Structural Integrity Procedia 00 (2025) 000–000

380

2

of various observed factors, Demeler (2024), Piepho and Edmondson (2018). Experimental design is carried out on vessel heads made by the process of incremental plastic deformation, Iseki and Kumon (1994), Trzepieciński et al. (2022). This procedure is based on the gradual plastic deformations over the entire surface of the future vessel heads. The directional action of the tool leads to different mechanical properties in the material at the local level. This phenomenon is not adequate from the aspect of safety under the influence of operating load. Different diameter and thickness of the basic sheets, as well as material grade, can cause different effects in vessel head structure, Singh et al. (2023), Xuelei and Hengan (2024), Wang et al. (2022), Vukojević et al. (2007). The goal of the experiment design presented in this paper is to obtain the interaction of individual observed factors such as: yield stress of the base material, vessel head diameter, sheet thickness and post welding heat treatment on the observed two output sizes: total impact energy and fracture toughness, Vukojević et al. (2007), Ištvanić (2022).

Nomenclature d o

outer diameter of vessel thickness of vessel

[mm] [mm]

t i

number of the test-sample (between 1 and N)

[-] [-]

N

the total number of samples

yield strength

[MPa] [MPa·m [GPa]

s YS K JIc

stress intensity factor Young's modulus of elasticity

1/2 ]

E n

Poisson coefficient total impact energy specimen thickness

[-] [J]

KV

B

[mm] [mm] [mm]

W

effective width of specimen

L

specimen length

2. Methodology The basic sheet plates are made only for the purposes of these tests. In actual production circumstances they are not made that way. Each basic sheet is made from a central circular segment and with 12 circular sections that are joined together to form a circular plate-roundel. Circular sections are made of material of the same thickness, but of different material quality. A total of 4 segmented vessel heads were made. The vessel heads are made of three different materials, in three thicknesses and three diameters, as follows: materials - P460 NL1 NT, P355 NL2, and S235 JR+N, thickness - 6 mm,10 mm, and 14 mm, and diameters - 1500 mm, 2250 mm, and 3000 mm. 2.1. Technology of samples welding The carbon equivalent for the selected samples was calculated using the Ito-Bessyo equation, Alhassan and Bashiru (2021):

! " # ' ' E $ # ) * ) + ./ M/ N/ ./ 2/ ./ M/ = + + + + + + + + B C ) )

,-

(1)

Table 1. C - equivalent

C E

C E

Sheets material and thickness

According to the certification

According to equation (1)

S235x6 mm S235x14 mm P355x10 mm P460x6 mm P460x14 mm

0,25 0,26 0,4 0,47 0,52

0,25 0,18 0,18 0,26 0,30