If multiple discrete flaws are detected that are in close proximity to one another, alignment rules are used to determine whether the flaws should be treated as nonaligned or as coplanar. Alignment rules are defined in many fitness-for-service codes and standards in the world. However, the criteria of the alignment rules are different in these codes and standards. This paper introduces the current alignment rules and, in addition, interaction of stress intensity factors for nonaligned through-wall flaws was calculated by finite element analysis. Also, brittle fracture experiments were performed on carbon steel plates with two nonaligned flaws. From these calculations and experiments, authors studied the effect of stress intensity factor interaction on fracture behavior and proposed a new alignment rule for linear elastic fracture mechanics evaluation.

1.
ASME
, 2007, B&PV Code Section XI.
2.
American Petroleum Institute
, 2007, “
Fitness-for-Service
,” API 579-1/ASME FFS-1.
3.
British Standards
, 2005, BS 7910.
4.
FKM
, 2004, “
Fracture Mechanics Proof of Strength for Engineering Components
.”
5.
Commissariat a L’Energie Atomique
, 2002, “
Guide for Defect Assessment and Leak Before Break Analysis
,” A16.
6.
AFCEN
, 2005, “
Inservice Inspection Rules for the Mechanical Components of PWR Nuclear Islands
,” RSE-M.
7.
JSME
, 2004, “
Rules on Fitness-for-Service for Nuclear Power Plants
,” S NA1-2004, in Japanese.
8.
The Japan Welding Engineering Society
, 1997, WES 2805, in Japanese.
9.
Hasegawa
,
K.
,
Miyazaki
,
K.
, and
Kanno
,
S.
, 2001, “
Interaction Criteria for Multiple Flaws on the Basis of Stress Intensity Factors
,” ASME PVP 2001, Atlanta, GA, Vol.
422
, pp.
23
29
.
10.
Kamaya
,
M.
, 2003, “
Study on Fracture Mechanics Related to Multiple Micro-Structural SCC
,” Ph.D. thesis, Kyoto University, Kyoto, Japan.
11.
Yokobori
,
T.
,
Uosumi
,
M.
, and
Ichikawa
,
M.
, 1971, “
Interaction Between Overlapping Parallel Elastic Cracks
,”
J. of the Japanese Society for Strength and Fracture for Materials
,
6
(
2
), pp.
39
50
.
12.
FRANC2D V2.7, two-dimensional fracture analysis code, developed by the Cornell Fracture Group, Cornell University, Ithaca, NY, http://www.cfg.cornell.eduhttp://www.cfg.cornell.edu.
13.
Tada
,
H.
,
Paris
,
P. C.
, and
Irwin
,
G. R.
, 2000,
The Stress Analysis of Cracks Handbook
,
3rd ed.
,
ASME
,
New York
.
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