Proposal of New Code Case for Alternative UT Flaw Evaluation and Acceptance Criteria of Subsurface Flaw Near Component Surface in Section VIII Division 2 and Division 3

2019 ◽  
Author(s):  
Susumu Terada
Keyword(s):  
Stress Intensity ◽  
Stress Intensity Factors ◽  
Research Work ◽  
Intensity Factors ◽  
Acceptance Criteria ◽  
Safety Level ◽  
Surface Flaws ◽  
Section Viii ◽  
Division 2 ◽  
Current Code

Abstract The current proximity rules for subsurface flaws near the surfaces of component in Section VIII Division 2 and Division 3 are different from those of Section XI. The current acceptance criteria of Sec. XI were revised in 2008 in order to eliminate the discontinuity of acceptable and unacceptable flaws based on the research work by Dr. K. Hasegawa and Dr. K. Miyazaki el. The fracture mechanics evaluation for the current and proposed alternative acceptance criteria for subsurface flaws near a component’s surfaces based on Section XI have been performed. The stress intensity factors for transformed surface flaws of the current acceptance criteria for subsurface flaws near component’s surfaces are much larger and too conservative compared with the overall acceptance criteria. It is confirmed herein that the proposed alternative converting rules have enough fracture margin. Therefore, the safety level of this proposal is almost the same as that of the current code. The proposed alternative acceptance criteria may avoid unnecessary weld repairs, and eliminate the discontinuity of acceptable and unacceptable flaws in the area near the component’s surface.

Experimental Determination of Side Boundary Effects on Stress Intensity Factors in Surface Flaws

1975 ◽  
Vol 97 (1) ◽  
pp. 45-51 ◽  
Author(s):  
M. Jolles ◽  
J. J. McGowan ◽  
C. W. Smith
Keyword(s):  
Stress Intensity ◽  
Crack Length ◽  
Taylor Series ◽  
Stress Intensity Factors ◽  
Taylor Series Expansion ◽  
Correction Method ◽  
Intensity Factors ◽  
Surface Flaws ◽  
Plate Width

A technique consisting of stress-freezing photoelasticity coupled with a Taylor Series Expansion of the maximum local in-plane shearing stress known as the Taylor Series Correction Method (TSCM) is applied to the determination of stress intensity factors (SIF’s) in flat bottomed surface flaws of flaw depth/length ratios of approximately 0.033. Flaw depth/thickness ratios of approximately 0.20 and 0.40 were studied as were plate width/crack length ratios of approximately 2.33 and 1.25, the former of which corresponded to a nearly infinite width. Agreement to well within 10 percent was found with the Rice-Levy and Newman theories using a depth-modified secant correction and equivalent flaw depth/length ratios. The Shah-Kobayashi Theory, when compared on the same basis, was lower than the experimental results. Using a modified net section stress correction suggested by Shah, agreement with the Shah-Kobayashi Theory was greatly improved but agreement with the other theories was poorer. On the basis of the experiments alone, it was found that the SIF was intensified by about 10 percent by decreasing the plate width/crack length from 2.33 to 1.25.

Finite Element Analysis of Stress Intensity Factors in the Cracking of Brittle Materials under Biaxial Loading

2016 ◽  
Vol 834 ◽  
pp. 67-72
Author(s):  
H. Ayas ◽  
Hamid Hamli Benzahar ◽  
Mohamed Chabaat
Keyword(s):  
Finite Element ◽  
Stress Intensity ◽  
Stress Intensity Factors ◽  
Biaxial Loading ◽  
Research Work ◽  
Von Mises Stress ◽  
Intensity Factors ◽  
Element Analysis ◽  
Proposed Model ◽  
Von Mises

The present study evaluates the von Mises stress distribution around the crack tip and stress Intensity Factor (SIF) under biaxial mixed modes during the propagation of a crack interacting with two nearby circular inclusions. The finite element method is used for determination of stress intensity factors by ABAQUS software. The stress field and the SIF are determined for different crack’s length .A brittle material such as a glass having an equivalent elasticity modulus and a Poisson rain this research work. Besides, the proposed model is a rectangular specimen with an edge crack subjected to tensile stresses according to the modes (I & II) of rupture .Obtained results are compared and agreed with those determined by other researchers.

Stress Intensity Factors and Weight Functions for Longitudinal Semi-Elliptical Surface Cracks Inside Thick-Walled Cylinders Using Highly-Refined Finite-Element Models

2010 ◽  
Author(s):  
Adam R. Hinkle ◽  
James E. Holliday ◽  
David P. Jones
Keyword(s):  
Finite Element ◽  
Stress Intensity ◽  
Crack Growth ◽  
Stress Intensity Factors ◽  
Weight Functions ◽  
Finite Element Models ◽  
Surface Cracks ◽  
Intensity Factors ◽  
Surface Flaws ◽  
Field Singularity

Fracture mechanics and fatigue crack-growth analysis rely heavily upon accurate values of stress intensity factors. They provide a convenient, single-parameter description to characterize the amplitude of the stress-field singularity at the crack tip, and are used to correlate brittle fracture and crack growth in pressure vessel and piping applications. Mode-I stress intensity factors that have been obtained for longitudinal semi-elliptical surface flaws on the inside of thick-walled cylinders using highly-refined finite element models are investigated. Using these results, weight function solutions are constructed and selected geometries are validated.

Introduction of Subsurface Proximity Criteria in the World and Stress Intensity Factors for Transformed Surface Flaws

2017 ◽  
Author(s):  
Kunio Hasegawa ◽  
Yinsheng Li ◽  
Genshichiro Katsumata ◽  
Pierre Dulieu ◽  
Valéry Lacroix
Keyword(s):  
Stress Intensity Factor ◽  
Free Surface ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Stress Intensity Factors ◽  
Intensity Factors ◽  
Surface Flaws ◽  
The World ◽  
Before And After ◽  
American Society

Net-section stress at the ligament between component free surface and subsurface flaw increases when the ligament distance is short. It can be easily expected that stress intensity factors increase when the subsurface flaw locates near the free surface. To avoid catastrophic failures caused by ligament failure, fitness-for-service (FFS) codes provide flaw-to-surface proximity rules. The proximity rules are used to determine whether the flaws should be treated as subsurface flaws as-is, or transformed to surface flaws. The stress intensity factor for the transformed surface flaw increases furthermore. The increment of the stress intensity factor before and after transformation depends on the location of the subsurface flaw. Although the concept of the proximity rules are the same, the specific criteria for the rules on transforming subsurface flaws to surface flaws differ amongst FFS codes. Particularly, the criteria are different amongst the same organizations of ASME (American Society of Mechanical Engineers). The proximity criteria of the FFS codes in the world were introduced in this paper. In addition, the stress intensity factors based on the different criteria used in the ASME Codes are compared.

Comparison of Stress Intensity Factors of Two Flaws and a Combined Flaw Due to Combination Rules

2002 ◽  
Author(s):  
Kunio Hasegawa ◽  
Masaki Shiratori ◽  
Toshiro Miyoshi ◽  
Nagatoshi Seki
Keyword(s):  
Stress Intensity ◽  
Stress Intensity Factors ◽  
Intensity Factors ◽  
Combination Rules ◽  
Influence Function Method ◽  
Surface Flaws ◽  
Close Proximity ◽  
Asme Code ◽  
Calculation Results ◽  
Service Inspection

If the flaws detected during in-service inspection are multiple discrete flaws that are in close proximity to one another, the flaws are evaluated as to whether they are combined or not, in accordance with combination rules in the ASME Code. The combination rules require that multiple flaws shall be treated as a single combined flaw if the distance between the adjacent flaws is equal to or less than the dimension of the flaw depth. After the coalescence of the multiple flaws, the flaw length becomes larger and then the stress intensity factor of the combined flaw would be expected to be significantly larger. Stress intensity factors for two surface flaws and a combined flaw under membrane stress and bending stress were analyzed using influence function method. From the calculation results of the stress intensity factors for two flaws and the combined flaw, it is shown that less conservative combination rules are appropriate, as compared to the existing combination rules in the ASME Code.

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