PSI - Issue 20

Nikolay A. Makhutov et al. / Procedia Structural Integrity 20 (2019) 9–16 Nikolay A. Makhutov et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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also for national security in Russia and other oil/gas producing and transporting countries; Makhutov (2002), Makhutov and Permyakov (2005), Makhutov (2017). High internal pressure combined with external loading and aggressive environment, along with the potential presence of local damages make assessment of strength and integrity of long-distance pipelines a formidable challenge. Significant number of accidents at LDP is caused either by violation of technology of pipeline construction and operation or by unauthorized branch cutting-in that are associated with large plastic deformations and substantial changes of the pipeline geometry.

Nomenclature D 0

inner diameter of the pipe

reduction of ultimate plasticity due to multiaxiality of the stress state

D en

elasticity modulus normalized strain

E

/ y e e e

normalized nominal strain in the smooth part of the pipeline

n e

{ e 1 , e 2 , e 3 } principle strains e c

true strain at fracture in the neck region

intensity of true strains

e i

maximum local strain in crimp zone

e max

maximal normalized secondary elasto-plastic strain in the crimp maximal local elasto-plastic strain in the crimp zone

max cr e e max cr

strain at ultimate strength

e u e y F F 0 K t K σ K e m n y n u S c h

the yield strain

cross sectional area of a pipeline

cross sectional area of a smooth standard specimen

eccentricity

theoretical stress concentration factor

stress concentration factor strain concentration factor strain hardening exponent safety factor against yielding

ultimate safety factor

stress at fracture in the neck region

current and the critical value of the pipeline pressure

p, p c

is the thickness of the pipe

δ μ

Poisson's ratio {σ 1 , σ 2 , σ 3 } principle stresses / y normalized stress σ i

intensity of true stresses intensity of engineering stresses

σ i 0 σ m

membrane stress

maximum local stress in crimp zone nominal fracturing stress in the crimp zone

σ max σ n cr

ultimate strength the yield stress

σ u σ y σ θ ψ c €

,

relative principle stresses

/

1, 2, 3

j

1

j

j

circumferential stress

relative narrowing in the specimen neck at fracture (reduction of area)