Proposed Updates to the Buried-to-Surface Flaw Recharacterization Rules in Annex E of BS 7910

2019 ◽  
Author(s):  
Bostjan Bezensek ◽  
Yuri Tkach ◽  
John Sharples ◽  
Harry Coules
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Subcritical Crack Growth ◽  
Surface Flaw ◽  
Ductile Material ◽  
Material Behaviour ◽  
Metallic Structures ◽  
Section 8 ◽  
Fatigue And Fracture

Abstract BS 7910 “Guide to Methods for Assessing the Acceptability of Flaws in Metallic Structures” [1] is undergoing revision for the next edition. Updates are proposed for the Annex E flaw recharacterization guidance. The changes aim to make Annex E more applicable to real structures and to improve the synergy between the subcritical crack growth such as by fatigue and fracture of an embedded flaw. Several studies were done by WEE/37 fracture panel focusing on brittle and ductile material behaviour to support the proposed changes. These studies are summarised in the paper. The main modifications in the proposed updated Ann ex E are in: • Removal of use of Annex E for brittle fracture. • Updated guidance on recharacterized surface flaw length for ductile fracture. • Optional guidance on use of geometry-based criterion for embedded flaw break-through under ductile conditions. • Alignment of fatigue crack growth in Section 8 with the flaw break-through in Annex E.

Reeled CRA Clad/Lined Pipeline Installation: Seastate Optimisation From Fatigue and Fracture Perspective

2018 ◽  
Author(s):  
Daowu Zhou ◽  
T. Sriskandarajah ◽  
Heidi Bowlby ◽  
Ove Skorpen
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Low Cycle Fatigue ◽  
Superposition Method ◽  
Cycle Fatigue ◽  
Limit States ◽  
Simplified Approach ◽  
Fatigue And Fracture ◽  
Girth Welds

The deformation mechanism in reel-lay of corrosive resistance alloy (CRA) clad/lined pipes can facilitate defect tearing and low cycle fatigue crack growth in the girth welds. Pipe-lay after straightening will subject the CRA welds to high cycle fatigue. The permissible seastate for installation will be governed by failure limit states such as local collapse, wrinkling of the liner, fatigue and fracture. By means of a recently completed offshore project in North Sea, this paper discusses seastate optimisation when installing pipelines with CRA girth welds, from a fatigue and fracture perspective. The additional limiting requirement in CRA welds to maintain CRA liner integrity can lead to significant assessment work since all critical welds shall be examined. AUT scanned defect data were utilised to maximise permissible seastates based on fatigue allowance from a fatigue crack growth calculation. An alternative simplified approach to derive the crack growth based on a superposition method is studied. It enables a straightforward real-time prediction of crack growth and has the potential to be used during the offshore campaign to improve the installation flexibility. Post-installation fracture assessment under more critical seastates is examined for CRA partial over-matching welds. A comparison of CDF between conventional ECA procedure and 3D FE is provided.

Recharacterization of Subsurface Flaw to Surface Flaw Based on Equivalent Fatigue Crack Growth Rate

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
Valery Lacroix ◽  
Yinsheng Li ◽  
Bohumir Strnadel ◽  
Kunio Hasegawa
Keyword(s):  
Growth Rate ◽  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Point Of View ◽  
Surface Flaw ◽  
Aspect Ratios ◽  
Crack Growth Rates ◽  
Factor Interaction

A subsurface flaw located near a component surface is transformed to a surface flaw in accordance with a flaw-to-surface proximity rule. The recharacterization process from subsurface to surface flaw is adopted in all fitness-for-service (FFS) codes. However, the criteria of the recharacterizations are different among the FFS codes. In addition, the proximity factors in the rules are generally defined by constant values, irrespective of flaw aspect ratios. This paper describes the stress intensity factor interaction between the subsurface flaw and component free surface and proposes a proximity factor from the point of view of fatigue crack growth rates.

Remaining Lives of Fatigue Crack Growths for Pipes With Subsurface Flaws and Subsurface-to-Surface Flaw Proximity Rules

2016 ◽  
Vol 138 (5) ◽  
Author(s):  
Genshichiro Katsumata ◽  
Yinsheng Li ◽  
Kunio Hasegawa ◽  
Valery Lacroix
Keyword(s):  
Experimental Data ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Surface Flaw ◽  
Japan Society ◽  
Rule Based ◽  
Aspect Ratios ◽  
Inner Surface ◽  
American Society

If a subsurface flaw is located near a component surface, the subsurface flaw is transformed into a surface flaw in accordance with a subsurface-to-surface flaw proximity rule. The recharacterization process from subsurface to surface flaw is adopted in all fitness-for-service (FFS) codes. However, the specific criteria of the recharacterizations are different among the FFS codes. Recently, the authors have proposed a new subsurface-to-surface flaw proximity rule based on experimental data and equivalent fatigue crack growth rate calculations. In this study, fatigue crack growth calculations were carried out for pipes with subsurface flaws, using the proximity rule provided in the current ASME (American Society of Mechanical Engineers) Section XI and JSME (The Japan Society of Mechanical Engineers) codes and the proposed subsurface-to-surface flaw proximity rule. Different pipe sizes, flaw aspect ratios, and ligament distances from subsurface flaws to inner surface of pipes were taken into account. The results indicate the current proximity rule gives less conservative fatigue lives, when the aspect ratios of the subsurface flaws are small.

Fatigue Crack Growth for Subsurface Flaws Near Component Surface and Proximity Rules

2013 ◽  
Author(s):  
Kunio Hasegawa ◽  
Yinsheng Li ◽  
Katsumasa Miyazaki ◽  
Koichi Saito
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Behavior ◽  
Surface Flaw ◽  
Crack Growth Behavior ◽  
Fatigue Crack Growth Behavior ◽  
Asme Code ◽  
Tensile Experiment ◽  
Surface Proximity

If a subsurface flaw is located near a component surface, the subsurface flaw is transformed to a surface flaw in accordance with a flaw-to-surface proximity rule. The re-characterization process from subsurface to surface flaw is adopted in all fitness-for-service (FFS) codes. However, the criteria of the re-characterizations are different among the FFS codes. Cyclic tensile experiment was conducted on a carbon steel flat plate with a subsurface flaw at ambient temperature. The objective of this paper is to compare the experiment and calculation of fatigue crack growth behavior for a subsurface flaw and the transformed surface flaw, and to describe the validity of the flaw-to-surface proximity rule defined by ASME Code Section XI, JSME S NA1 Code and other codes.

European Fitness-for-Service Network (FITNET): Fatigue Module Development

2005 ◽  
Author(s):  
Jean-Jacques Janosch ◽  
Michel Huther ◽  
Nigel Taylor ◽  
Steve Maddox ◽  
Mustafa Kocak
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Critical Issue ◽  
Service Network ◽  
Metallic Structures ◽  
Ship Structure ◽  
Load Carrying ◽  
Module Development

FITNET is a four-year European thematic network with the objective of developing and extending the use of fitness-for-service (FFS) procedures for welded and non-welded metallic structures throughout Europe. It is partly funded by the European Commission within the fifth framework program and it was launched in February 2002. The network currently consists of about 50 organisations from 17 European countries and supported by institutions from USA, Japan and Korea. Further information can be found in the FITNET TN website: http://www.eurofitnet.org. The FITNET FFS Procedure is built up in four major analysis modules namely fracture, fatigue, creep and corrosion. The first official draft is available in early 2006 in the form of an official CEN document. Industrial components are as a rule exposed to fluctuating loads and hence consideration of fatigue damages accumulation or of fatigue crack growth is a critical issue. The aim of this paper is to present the features and the main analysis routes of the FITNET FFE Fatigue Module of the FITNET FFS Procedure to assess the fatigue life of the load carrying metallic components manufactured with and without welds. The paper includes an industrial case from ship structure for the application of two fatigue assessment routes.

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