Gouge Assessment for Pipes and Associated Transferability Problem

2009 ◽  
Vol 294 ◽  
pp. 15-25 ◽  
Author(s):  
Mohammed Hadj Meliani ◽  
G. Pluvinage ◽  
J. Capelle
Keyword(s):  
Fracture Toughness ◽  
Aspect Ratio ◽  
Internal Pressure ◽  
High Aspect Ratio ◽  
Fracture Resistance ◽  
Pipe Steel ◽  
Failure Assessment Diagram ◽  
Failure Assessment ◽  
Resistance Criterion ◽  
Two Parameter

The purpose of this work is to assess a gouge defect in a pipe submitted to internal pressure. To do that a method is used which is based upon a failure assessment diagram and, more precisely, upon a Modified Notch Failure Assessment Diagram (NMFAD) which has been proposed as a mesofracture approach. The safety factor has been determined under conservative conditions; i.e for a X52 pipe steel having a relatively low fracture toughness and a severe gouge defect with high aspect ratio and high constraint. In addition, a mesofracture approach to the fracture toughness transferability problem has been proposed. The crack (K-T) methodology has been modifed to create the ( –Teff) two-parameter fracture resistance criterion.

Revision of ISO 27306 for CTOD Toughness Correction for Constraint Loss

2016 ◽  
Vol 879 ◽  
pp. 54-59
Author(s):  
Fumiyoshi Minami ◽  
Mitsuru Ohata ◽  
Yasuhito Takashima
Keyword(s):  
Fracture Toughness ◽  
Fracture Mechanics ◽  
Stress Criterion ◽  
Failure Assessment Diagram ◽  
Failure Assessment ◽  
Fracture Assessment ◽  
International Standardization ◽  
Diagram Approach ◽  
Weibull Stress

As the result of the international standardization work in Japanese IST project, ISO 27306 were published in 2009 for correction of CTOD fracture toughness for constraint loss in steel components. ISO 27306 employs an equivalent CTOD ratio based on the Weibull stress criterion, which leads to more accurate fracture assessment than the conventional fracture mechanics assessment. On the occasion of the 1st periodical review, the revision of ISO 27306 has been proposed from Japan. This paper describes the key contents of the new ISO 27306. A case study is included on the fracture assessment of a wide plate component according to FAD (failure assessment diagram) approach specified in BS 7910:2013.

Multiscale toughness amplification in natural composites

2012 ◽  
Vol 1420 ◽  
Author(s):  
Francois Barthelat ◽  
Reza Rabiei ◽  
Ahmad Khayer Dastjerdi
Keyword(s):  
Fracture Toughness ◽  
Aspect Ratio ◽  
High Aspect Ratio ◽  
High Performance ◽  
Mechanical Performance ◽  
Process Zone ◽  
Organic Matrix ◽  
Natural Composites ◽  
Fracture Tests ◽  
High Concentrations

ABSTRACTHard biological materials such as bone and nacre exhibit remarkable mechanical performance, particularly in terms of fracture toughness, despite the weakness of their constituents. Mechanical performance of nacre and bone can largely be explained through their staggered microstructure where stiff inclusions of high aspect ratio are embedded in a softer matrix. The mineral inclusions provide hardness and stiffness while the organic matrix introduces ductility. The high performance of these natural structures is unmatched by any synthetic ceramic, which therefore makes them a substantial source of inspiration for development of new artificial materials. While the modulus and strength of these structures are well understood, fracture toughness remains unclear and controversial. In this work, chevron double cantilever beam fracture tests show that the interfaces in nacre have a low toughness, comparable to that of the tablets (in J terms). This highlights the important role of structural design on fracture toughness. At the next step, a fracture model is presented to explain the toughness amplification observed in natural staggered structures based on two essential extrinsic toughening mechanisms: crack bridging and process zone. The modeling results show that toughness can be further amplified by incorporating high concentrations of small inclusions with high aspect ratio. This conclusion is applicable to construction and optimization of natural and biomimetic composites.

Critical Crack Sizes of Pressure Vessels Based on Failure Assessment Diagram Under Design Requirements

2019 ◽  
Author(s):  
Yuebing Li ◽  
Weiya Jin ◽  
Mingjue Zhou ◽  
Zengliang Gao
Keyword(s):  
Fracture Toughness ◽  
Pressure Vessels ◽  
Design Standards ◽  
Critical Crack ◽  
Failure Assessment Diagram ◽  
Failure Assessment ◽  
Section Viii ◽  
Design Requirements ◽  
Assessment Standards ◽  
Material Fracture

Abstract Standards or codes for defects assessment usually accompany their own design standards, such as, ASME BPVC section VIII and API 579-1/ASME FFS-1, GB 150 and GB/T 19624. The development of defects assessment standards should be adapted to the design requirements of pressure vessels. The consistency between fitness-for-service (FFS) procedures and design requirements of pressure vessels is discussed in this work. As a key link between FFS procedures and design standards, the required material fracture toughness not only depends on the methods of FFS procedures such as failure assessment diagram, but also on the design requirements. A procedure based on failure assessment diagram under design requirements is proposed to calculate critical crack sizes. The result can give some meaningful suggestions for the development of standards or codes.

scholarly journals Toughening effect of mullite whisker within low-density ceramic proppants

2019 ◽  
Vol 28 ◽  
pp. 2633366X1989062 ◽  
Author(s):  
Jianying Hao ◽  
Baolin Mu ◽  
Yunfeng Gao ◽  
Pinbo Bai ◽  
Yuming Tian ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Low Density ◽  
Toughening Mechanism ◽  
Mullite Whiskers ◽  
Crystal Phases ◽  
Crack Bifurcation

Main crystal phases of low-density ceramic proppants prepared by bauxite and feldspar are granular corundum and whisker-shaped mullite. Mullite whiskers are interlocked with one another and piled up inside the pores. High aspect ratio of mullite whiskers inside the pores can greatly enhance the fracture toughness. The dominant toughening mechanism for the proppants is attributed to crack bifurcation and deflection and pulling out and bridging effect of mullite whiskers.

A Comparison of Notch Failure Assessment Diagram Methods for Assessing the Fracture Resistance of Structures Containing Non-Sharp Defects

2014 ◽  
Author(s):  
Anthony J. Horn ◽  
Peter J. Budden
Keyword(s):  
Failure Mechanism ◽  
Fracture Resistance ◽  
Failure Criteria ◽  
Test Results ◽  
Failure Assessment Diagram ◽  
Failure Assessment ◽  
Different Types ◽  
Definition Of ◽  
Made In

This paper analyses and compares a range of Notch Failure Assessment Diagram (NFAD) methods for assessing the fracture resistance of structures and components that contain defects with non-sharp tips. As micromechanistic failure criteria for predicting fracture from notch tips have developed, several forms of NFADs have been proposed over the last 20 years with notable developments having been made in the last 10 years. This paper quantifies the differences between four different types of NFAD approach and uses test results from test specimens containing notches of varying acuities to evaluate each approach. The results highlight significant differences in fracture predictions between the different NFAD approaches due to differences in the definition of the NFAD axes, the failure loci, the assumed failure mechanism and the corresponding micromechanistic failure criteria employed by each method.

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