Crack Tip Opening Angle as a Fracture Resistance Parameter to Describe Ductile Crack Extension and Arrest in Steel Pipes under Service Pressure

Amara, M. Ben; Pluvinage, G.; Capelle, J.; Azari, Z.

doi:10.1134/s1029959915040086

Cited by 15 publications

(3 citation statements)

References 20 publications

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“…Sometimes, to avoid the effects of the zigzag pattern on actual crack surfaces in tests or mesh size of FE models, it is better to calculate CTOA of several different complementary positions on the upper and lower crack surfaces, ψ i , and to average over these values by Equation 3 (Figure 5B). The key nodes used to determine the values of ψ i should be in the range of 0.5–1.5 mm behind the crack tip 26 . After a series of trial calculations, it is found that under the current meshing strategy, the results of the above two methods are consistent.…”

Section: Numerical Results and Discussionmentioning

confidence: 96%

A novel unified characterization parameter of in‐plane and out‐of‐plane constraints based on critical CTOA

Zhen

Chang

Cao

et al. 2021

Fatigue Fract Eng Mat Struct

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There is much controversy in using laboratory specimens to predict the fracture behavior of large industrial constructions because of their different constraints. Although several parameters have been proposed to characterize the constraint effect, there are still some limitations. To address this issue, a novel unified characterization parameter of constraint based on the critical crack tip opening angle (CTOAC) is defined. Firstly, the calibrated finite element technologies for simulation of static and dynamic crack are used to determine the equivalent plastic strain (εp) distribution around the crack tip and the evolution history of CTOA for specimens with different in‐plane and out‐of‐plane constraints, respectively. Secondly, the feasibility of the equivalent plastic strain at the crack tip when CTOA reaches its critical value to unified measure both in‐plane and out‐of‐plane constraints is investigated. The results indicate that the area APEEQ surrounded by the isoline of equivalent plastic strain εp can describe both in‐plane and out‐of‐plane constraints and the interaction between them. Finally, a novel constraint characterization parameter η is defined. It is found that there is a linear relationship, which depends only on the material and regardless of the selection of the εp isoline, between the normalized fracture toughness CTOAC/CTOAref and η1/2. The work in this paper is expected to realize the matching of constraints between different laboratory specimens or industrial constructions.

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Section: Numerical Results and Discussionmentioning

confidence: 96%

A novel unified characterization parameter of in‐plane and out‐of‐plane constraints based on critical CTOA

Zhen

Chang

Cao

et al. 2021

Fatigue Fract Eng Mat Struct

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“…A challenging task in this respect is to extend the service life of pipe steel structures by improving their mechanical properties [2]. Specifically, the fracture toughness, the major characteristic of crack resistance, has to be increased [3,4]. Procedures and equipment for fracture toughness testing are well standardized, ensuring good reproducibility of results [5].…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, analysis of the literature data [4][5][6][7][8] shows that modern low-carbon steel structures produced by thermomechanical processing of the initial sheet have different sensitivity to the concentrator shape and temperature/force loading parameters. It is therefore important to understand 2 Advances in Materials Science and Engineering the fracture mechanisms operating at different stress stiffness values.…”

Section: Introductionmentioning

confidence: 99%

Effect of Temperature-Force Factors and Concentrator Shape on Impact Fracture Mechanisms of 17Mn1Si Steel

Panin

Maruschak

Власов

et al. 2017

Advances in Materials Science and Engineering

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The influence of the notch shape on the impact fracture of 17Mn1Si steel is investigated at different temperatures with the focus placed on the low-temperature behavior. An approach towards fracture characterization has been suggested based on the description of elastic-plastic deformation of impact loaded specimens on the stage of crack initiation and growth at ambient and lower temperatures. The analysis of the impact loading diagrams and fracture energy values for the pipe steel 17Mn1Si revealed the fracture mechanisms depending on the notch shape. It was found that the testing temperature reduction played a decisive role in plastic strain localization followed by dynamic fracture of the specimens with differently shaped notches. A classification of fracture macro- and microscopic mechanisms for differently notched specimens tested at different temperatures was proposed which enabled a self-consistent interpretation of impact test results.

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The CTOA as a Parameter of Resistance to Crack Extension in Pipes Under Internal Pressure

Amara

Pluvinage²,

Capelle

et al. 2016

Fracture at All Scales

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Different methods of CTOA measurements are described: Optical microscopy coupled with digital image correlation, analytical analysis of experimental load-displacement curves or simulation by Finite Element method. Using a Modified Compact Tension (MCT) specimen at room temperature, tests are performed to measure the value of the CTOA of API 5L X65 pipe steel. The influence of thickness on CTOA has been studied and explained through a "triaxial stress constraint". Crack extension is modelled by the finite element method using the CTOA criterion coupled with the node release technique. Crack velocity, arrest pressure and crack extension at arrest have been determined. Values of the CTOA are not intrinsic to materials. Like other measures of fracture toughness, it is sensitive to geometry and loading mode. This sensitivity can be described by a constraint parameter. For the thickness effect, the constraint parameter T z is very appropriate.

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Crack Tip Opening Angle as a Fracture Resistance Parameter to Describe Ductile Crack Extension and Arrest in Steel Pipes under Service Pressure

Cited by 15 publications

References 20 publications

A novel unified characterization parameter of in‐plane and out‐of‐plane constraints based on critical CTOA

A novel unified characterization parameter of in‐plane and out‐of‐plane constraints based on critical CTOA

Effect of Temperature-Force Factors and Concentrator Shape on Impact Fracture Mechanisms of 17Mn1Si Steel

The CTOA as a Parameter of Resistance to Crack Extension in Pipes Under Internal Pressure

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