Plastic collapse stresses based on flaw combination rules for pipes containing two circumferential similar flaws

Hasegawa, Kunio; Li, Y.; Kim, Y.-J.*; Lacroix, V.*; Strnadel, B.*

Journal of Pressure Vessel Technology, 141(3), p.031201_1 - 031201_5, 2019/06

https://doi.org/10.1115/1.4042991

When discrete multiple flaws are in the same plane, and they are close to each other, it can be determined whether they are combined or standalone in accordance with combination rules provided by Fitness-For-Service (FFS) codes. However, specific criteria of the rules are different amongst these FFS codes. On the other hand, plastic collapse bending stresses for stainless steel pipes with two circumferential similar flaws were obtained by experiments and the prediction procedure for collapse stresses for pipes with two similar flaws were developed analytically. Using the experimental data and the analytical procedure, plastic collapse stresses for pipes with two similar flaws are compared with the stresses in compliance with the flaw combination criteria. It is shown that the calculated plastic collapse stresses based on the flaw combination criteria are significantly different from the experimental and analytical stresses.

Fatigue crack growth calculations for two adjacent surface cracks using combination rules in fitness-for-service codes

Lu, K.; Li, Y.

AIMS Materials Science, 4(2), p.439 - 451, 2017/03

https://doi.org/10.3934/matersci.2017.2.439

Fatigue crack growth behaviour for adjacent two surface flaws in accordance with combination rules

Lu, K.; Li, Y.; Hasegawa, Kunio*; Lacroix, V.*

no journal, , 

When multiple flaws are found in a structural components, fitness-for-service (FFS) codes such as ASME Code Section XI, BS 7910 and FKM Guideline provide flaw combination rules. However, the specific criteria are different among FFS codes. In this paper, fatigue flaw growth for adjacent surface flaws in a pipe subjected to cyclic tensile stress were obtained by numerical calculations using different combination rules. In addition, fatigue lives taking into account interaction effect between the two flaws were conducted by extended finite element method (X-FEM). As the calculation results, it is found that the fatigue lives calculated by the X-FEM are close to those by the ASME Code. Finally, it is worth noticing that the combination rule provided by the ASME Code is appropriate for fatigue flaw growth calculations.