PSI - Issue 2_A

Nedeljko Vukojević et al. / Procedia Structural Integrity 2 (2016) 2982 – 2988 Author name / Structural Integrity Procedia 00 (2016) 000–000

2983

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structural parts or parts that will lead to the destruction of the subject matter. If it is already possible to take samples then the question is where to take, and whether the results of the tests on these samples relevant to the assessment of complete pressure vessels.

Nomenclature d o

outer diameter of vessel, d i inner diameter of vessel,

[mm] [mm] [mm]

t i

thickness of vessel,

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

N

the total number of samples

[-]

 YS yield strength, K Ic stress intensity factor

[MPa] [MPa·m

1/2 ]

a c E J Ic

critical crack length

[mm] [GPa]

Young's modulus of elasticity

critical J-integral Poisson coefficient specimen volume

[N/mm]

[-]



V [mm 3 ] K u min. value of stress intensity factor where the probability of fracture zero 1/2 ] K o normalizing factor that satisfies the probability of the existence of P s =0,3679; (ln·ln(1/0,3679)=0) m Weibull module [-] B specimen thickness [mm] W effective width of specimen [mm] L specimen length [mm] Tested pressure vessel were produced by plastic deformation of a single piece of the steel quality 40Mn6. The vessels are large dimensions: diameter d o =998/d i =800 mm, wall thickness t = 99 mm, and a length 4000 mm. Considering the dimensions and the production technology there are certain discrepancies dimensions, but that does not affect their functionality. Tested specimens series have been taken out from the central part of the vessel (M samples), in the area of the bottom vessel head (samples B) and the top vessel head (samples T). Figure 1 presents the location of the taken specimens for testing fracture toughness. Different sizes of three point bend (SEB) specimens are used for testing, specimens data and the test results are presented in Table 1. [MPa·m

Table 1. Samples data and results SENB specimens location and dimensions, WxBxL (mm)

No.

Yield strength  YS (MPa)

Stress intensity factor, K Ic ( MPa√m )

Critical crack lenght, a c (mm)

1 2 3 4 5 6 7 8 9

T T T B B B B B

15x30x160 15x30x160 15x30x160 12x25x125 12x25x125 12x25x125 12x25x125 12x25x125 12x25x125 25x25x125 25x25x125 25x25x125

328,7 328,7 328,7 319,5 319,5 319,5 319,5 319,5 319,5 331,5 331,5

129,2

53,6 28,5 21,2 63,1 61,1 66,0 58,1 64,4 58,3 58,4 58,4

94,3 81,3

142,2 139,9 145,4 136,5 143,7 136,7 158,9 158,9

M M M M

10 11 12

331,5

143,5

47,6