Assessment Procedure for Multiple Cracklike Flaws in Failure Assessment Diagram (FAD)

Assessment of multiple discrete cracklike flaws is one of the most common problems relating to pressure vessels and piping components. Under the current fitness for service (FFS) rules, such as ASME, BS, and so on, multiple cracklike flaws are usually recharacterized as an enveloping crack (defined as a single larger crack), following their assessment rules. The procedure, however, varies significantly in these FFS codes. In this paper, the interaction between nonaligned multiple unequal cracks is clarified by applying the body force method. Based on the interaction that indicates the magnification and shielding effects and the reference stress solutions, a newly developed assessment procedure for multiple discrete cracklike flaws in the failure assessment diagram is proposed.

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Assessment Procedure for Multiple Volumetric Flaws in p-M Diagram

Journal of Pressure Vessel Technology ◽

10.1115/1.3110036 ◽

2009 ◽

Vol 131 (3) ◽

Cited By ~ 3

Author(s):

Shinji Konosu

Keyword(s):

Body Force ◽

Pressure Vessels ◽

The Body ◽

Assessment Procedure ◽

Force Method ◽

Reference Stress ◽

Body Force Method ◽

Common Problems ◽

Shielding Effects

Assessment of multiple volumetric flaws is one of the most common problems relating to pressure vessels and piping components. Under the current fitness for service rules, such as ASME, BS, and so on, multiple volumetric flaws are usually recharacterized as an enveloping volumetric flaw (defined as a single larger volumetric flaw) as well as multiple cracklike flaws, following their assessment rules. However, the rules proposed in their codes will not often agree and their justification is unknown. Furthermore, they can provide unrealistic assessment in some cases. In this paper, the interaction between two differently sized nonaligned volumetric flaws such as local thin areas is clarified by applying the body force method. Unlike multiple cracklike flaws, the effect of biaxial stresses on the interaction is evident. Based on the interaction that indicates the magnification and shielding effects and reference stress solutions, a new procedure for multiple volumetric flaws is proposed for assessing the flaws in the p-M (pressure-moment) diagram, which is a simple assessment procedure for vessels with volumetric flaws.

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Assessment Procedure for Multiple Volumetric Flaws (LTAs) in p-M Diagram

Volume 6: Materials and Fabrication, Parts A and B ◽

10.1115/pvp2008-61516 ◽

2008 ◽

Author(s):

Shinji Konosu

Keyword(s):

Body Force ◽

Pressure Vessels ◽

The Body ◽

Assessment Procedure ◽

Multiple Crack ◽

Force Method ◽

Reference Stress ◽

Body Force Method ◽

Common Problems ◽

Shielding Effects

Assessment of multiple volumetric flaws (LTAs) is one of the most common problems relating to pressure vessels and piping components. Under the current Fitness for Service (FFS) rules, such as ASME, BS and so on, multiple volumetric flaws are usually recharacterized as an enveloping volumetric flaw (defined as a single larger volumetric flaw) as well as multiple crack-like flaws, following their assessment rules. However, the rules proposed in their codes will not often agree and their justification is unknown. Furthermore, they can provide unrealistic assessment in some cases. In this paper, the interaction between two different sized non-aligned volumetric flaws such as local thin areas (LTAs) is clarified by applying the body force method. Unlike multiple crack-like flaws, the effect of biaxial stresses on the interaction is evident. Based on the interaction which indicates the magnification and shielding effects and reference stress solutions, a new procedure for multiple volumetric flaws is proposed for assessing the flaws in the p-M (pressure-moment) Diagram, which is a simple assessment procedure for vessels with LTAs.

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Assessment Procedure for Multiple Crack-Like Flaws in Fracture Assessment Diagram (FAD)

Volume 6: Materials and Fabrication, Parts A and B ◽

10.1115/pvp2008-61515 ◽

2008 ◽

Author(s):

Shinji Konosu

Keyword(s):

Body Force ◽

Pressure Vessels ◽

The Body ◽

Assessment Procedure ◽

Multiple Crack ◽

Reference Stress ◽

Discrete Crack ◽

Fracture Assessment ◽

Common Problems ◽

Shielding Effects

Assessment of multiple discrete crack-like flaws is one of the most common problems relating to pressure vessels and piping components. Under the current Fitness for Service (FFS) rules, such as ASME, BS and so on, multiple crack-like flaws are usually recharacterized as an enveloping crack (defined as a single larger crack), following their assessment rules. The procedure, however, varies significantly in these FFS codes. In this paper, the interaction between non-aligned multiple unequal cracks is clarified by applying the body force method. Based on the interaction which indicates the magnification and shielding effects and the reference stress solutions, a newly developed assessment procedure for multiple discrete crack-like flaws in the Fracture Assessment Diagram (FAD) is proposed.

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A Procedure for the Assessment of the Structural Integrity of Nuclear Pressure Vessels

Journal of Pressure Vessel Technology ◽

10.1115/1.3264235 ◽

1983 ◽

Vol 105 (1) ◽

pp. 28-34 ◽

Cited By ~ 12

Author(s):

J. M. Bloom

Keyword(s):

Structural Integrity ◽

Pressure Vessels ◽

Assessment Procedure ◽

Plastic Collapse ◽

Failure Assessment Diagram ◽

Linear Elastic ◽

Failure Assessment ◽

Deformation Plasticity ◽

Margin Of Safety ◽

Two Parameters

This paper presents a simple engineering procedure that the utility industry can use to assess the integrity of typical nuclear-grade pressure vessels. The procedure recognizes both brittle fracture and plastic collapse and is based on a set of proposed failure assessment curves which make up a safety/failure plane. The plane is defined by the stress intensity factor/fracture toughness ratio as the ordinate and the applied stress/reference plastic collapse stress ratio as the abscissa. The failure assessment procedure is based in part on the British Central Electricity Generating Board’s R-6 failure assessment diagram and the deformation plasticity solutions of the General Electric Company. Two parameters, a plastic collapse parameter (Sr′) and linear elastic fracture mechanics parameter (Kr′) are calculated by the user. The point (Sr′, Kr′) is plotted on the appropriate failure assessment diagram. If the point lies inside the respective curve, the structure is safe from failure. Moreover, for a given pressure and a postulated or actual flaw size, the margin of safety of the structure can be simply determined. Consistent with Appendix A of Section XI, (Division 1) of the ASME Boiler and Pressure Vessel Code the procedure presented in this paper is limited to ferritic materials 4 in. (102 mm) and greater in thickness. Details of the derivation of the proposed set of failure assessment curves are provided along with a sample problem illustrating the use of these curves.

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Stress-Intensity Factors for an Internal Semi-Elliptical Surface Crack in Cylindrical Pressure Vessels

Journal of Pressure Vessel Technology ◽

10.1115/1.2842114 ◽

1995 ◽

Vol 117 (3) ◽

pp. 213-221 ◽

Cited By ~ 3

Author(s):

D.-H. Chen ◽

H. Nisitani ◽

K. Mori

Keyword(s):

Surface Crack ◽

Body Force ◽

Crack Problem ◽

Pressure Vessels ◽

The Body ◽

Intensity Factors ◽

Infinite Body ◽

Force Method ◽

Body Force Method ◽

Point Forces

In this paper, the surface crack problem in a cylinder subjected to internal pressure is solved. The analysis is based on the body force method, but it is different from the conventional body force method in the following point. That is, the body forces to be distributed continuously on the assumed boundaries in an infinite body are approximated by some discrete point forces acting on the outside of the assumed boundaries. By using this method combined with the resultant force boundary conditions, solutions with high accuracy are obtained.

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Some Fundamental Aspects of High Temperature Defect Assessment

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.297-300.428 ◽

2005 ◽

Vol 297-300 ◽

pp. 428-434 ◽

Cited By ~ 1

Author(s):

Shan Tung Tu ◽

Fu Zhen Xuan

Keyword(s):

High Temperature ◽

Assessment Method ◽

Damage Effect ◽

Assessment Procedure ◽

Continuum Damage ◽

Creep Failure ◽

Failure Assessment Diagram ◽

Defect Assessment ◽

Failure Assessment ◽

Dependent Failure

Current research efforts in the development of high temperature defect assessment procedure are summarized. Creep exemption criteria are proposed for the assessment of defective structures at high temperature in consideration of the effects of loadings, operating temperature and service time. Time-dependent failure assessment diagram (TDFAD) is developed that covers major failure mechanisms of defective high temperature structures. Challenges due to the welding effect are discussed. TDFAD for weldments is derived for various combinations of materials. In order to develop a unified assessment method to cope with material and loading complexity, a new failure assessment diagram based on continuum damage concept is proposed to reflect the damage effect on ductile creep failure and brittle creep fracture.

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