PSI - Issue 81

Olha Zvirko et al. / Procedia Structural Integrity 81 (2026) 41–46

44

= 1 + 1.464 ( ) 1.65 .

(5) Here p is internal pressure; F is a net section axial force; is inner radius of a pipe, 598 mm; is outer radius of a pipe, 610mm; is parametric angle, 2 =0 corresponds to a point on the surface, 2 =1 is the deepest point of the crack. The values of the coefficients ( , , , ) were used according to API 579-1 / ASME FFS-1 (2016).

a

b

Fig. 2. Schemes of a cylinder with internal semi-elliptical cracks in longitudinal (a) and circumferential (b) directions (API 579-1/ASME FFS-1 (2016)).

Distributions of SIF along the crack front in a pipe, depending on crack orientation and a/c ratio, are presented in Fig. 3.

a

b

c

d

Fig. 3. Distribution of SIF along the crack front: a – longitudinal direction, a/c = 1/3; b – circumferential direction, a/c = 2/3; c – longitudinal direction, a/c = 1/3; d – circumferential direction, a/c = 2/3.