Comparison between Fracture Behaviour of Pipe-Line Ring Specimens and Standard Specimens

2013 ◽  
Vol 577-578 ◽  
pp. 637-640 ◽  
Author(s):  
Nenad Gubeljak ◽  
Andrej Likeb ◽  
Jožef Predan ◽  
Yu. G. Matvienko
Keyword(s):  
Fracture Behaviour ◽  
Strain Relaxation ◽  
Crack Tip ◽  
Fatigue Loading ◽  
Single Edge ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Single Edge Notch ◽  
Pipe Line ◽  
Edge Notch

Thethin walled structures as pipe-line are often unsuitable for standard testingof fracture toughness. One possibility is applying non-standard modifiedspecimens with simple testing procedure, but measured fracture behaviour isconsequence of loading conditions and geometry of specimen. In this paper thedifferences in fracture behaviour of single edge notch bending (SENB) and ringpipe-line bended specimens are discussed. Especially uneven fatigue crack frontas consequence of complex fatigue loading caused different fracture behaviour,than standard single edge notch bending (SENB) specimens. The stress-strainconditions at the crack tip are analysed by finite element modelling. Thecritical crack tip opening displacement has been determined as a crack tipsurface strain-relaxation by using stereo-optical grading method. Comparisonbetween CTOD-R curves of both types of specimens shows difference in crackdriving force.

scholarly journals RESPONSE AND DAMAGE EVOLUTION OF SINGLE EDGE NOTCHED TIMBER BEAMS UNDER THREE-POINT BENDING

2020 ◽  
Vol 26 ◽  
pp. 94-99
Author(s):  
Eliška Šmídová ◽  
Petr Kabele ◽  
Michal Šejnoha
Keyword(s):  
Damage Evolution ◽  
Image Correlation ◽  
Single Edge ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Three Point Bending ◽  
Single Edge Notch ◽  
Failure Patterns ◽  
Edge Notch ◽  
Timber Beams

Two groups of small-size single edge notched beams (SENB) made of European spruce (Picea abies) were tested in three-point bending (3PB) until failure under displacement control. The first group comprised of eight solid and two glued laminated (GL) timber beams manufactured with (a) the single edge notch at the bottom of the mid-span and (b) the reduced ligament depth. The second group consisted of four GL timber beams with the single edge notch only. We employed digital image correlation (DIC) to quantify strains and displacements, capture the damage evolution, and track the sequence of failure patterns. In this work, we present response of the beams in terms of load vs. crosshead displacement of the moving crosshead and load vs. crack tip opening displacement (CTOD).

Wide Range Compliance Solutions for Various Fracture Test Specimens Using Crack Mouth Opening Displacement

2017 ◽  
Author(s):  
Claudio Ruggieri ◽  
Rodolfo F. de Souza
Keyword(s):  
Mouth Opening ◽  
Crack Mouth Opening Displacement ◽  
Width Ratio ◽  
Fracture Test ◽  
Single Edge ◽  
Opening Displacement ◽  
Element Analysis ◽  
Single Edge Notch ◽  
Wide Range ◽  
Edge Notch

This work addresses the development of wide range compliance solutions for tensile-loaded and bend specimens based on CMOD. The study covers selected standard and non-standard fracture test specimens, including the compact tension C(T) configuration, the single edge notch tension SE(T) specimen with fixed-grip loading (clamped ends) and the single edge notch bend SE(B) geometry with varying specimen spam over width ratio and loaded under 3-point and 4-point flexural configuration. Very detailed elastic finite element analysis in 2-D setting are conducted on fracture models with varying crack sizes to generate the evolution of load with displacement for those configurations from which the dependence of specimen compliance on crack length, specimen geometry and loading mode is determined. The extensive numerical analyses conducted here provide a larger set of solutions upon which more accurate experimental evaluations of crack size changes in fracture toughness and fatigue crack growth testing can be made.

Integrity of Longitudinal Welds in Pipelines: Bridging Scales

2018 ◽  
Author(s):  
Marion Erdelen-Peppler ◽  
Christoph Kalwa ◽  
Jens Schröder
Keyword(s):  
Circumferential Stress ◽  
Ring Expansion ◽  
Structural Behavior ◽  
Single Edge ◽  
Crack Tip Opening Displacement ◽  
Single Edge Notch ◽  
Wide Range ◽  
Edge Notch ◽  
Longitudinal Welds ◽  
The Impact

Toughness testing of the heat affected zone (HAZ) of longitudinal welds is increasingly often required in pipeline standards and specifications. This includes simple tests such as the Charpy impact test that was designed to serve as quality test as well as enhanced methods including crack tip opening displacement (CTOD) tests that are necessary to conduct an engineering critical assessment (ECA). If occasional low toughness values are observed, the question turns towards assessing the impact of such numbers and how representative they are of the behavior of a pipe in service. The significance of low toughness values measured in laboratory testing can be judged on basis of ring expansion and hydraulic burst tests. The current study summarises an extensive test series to quantify the toughness of submerged arc welds (SAW) obtained by different test methods. The tested pipes cover a wide range of material including medium strength X70 up to high strength X100. Their welds are characterized in terms of fracture toughness properties with single edge notch tension (SENT) and single edge notch bending (SENB) tests. Different constraint levels are obtained within each series by introducing notches of standard depth as well as shallow notches. Structural behavior is characterized with burst tests as well as ring expansion tests containing notches in the longitudinal weld. The experimental results are assessed within dedicated finite element studies. The assessment is conducted for pipes serving as pressure containment, thus having circumferential stress resulting from internal pressure. Based on the results achieved the conclusion can be drawn that the standard route including high constraint CTOD leads to overly conservative results concerning the integrity of longitudinal welds. A better representation of structural behavior is observed in ring expansion tests.

Plastic Rotational Factor Calculation for Shallow-Notched SE(B) Specimens

2014 ◽  
Vol 783-786 ◽  
pp. 2322-2326 ◽  
Author(s):  
Yoichi Kayamori ◽  
Takehiro Inoue ◽  
Yukito Hagihara
Keyword(s):  
Plastic Hinge ◽  
Single Edge ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Edge Notch ◽  
New Equation ◽  
Hinge Model ◽  
Testing Standards ◽  
Crack Tip Opening ◽  
Rotational Factor

The plastic part of crack tip opening displacement (CTOD) is derived from the plastic hinge model for deep-notched single edge-notch bend (SE(B)) specimens in BS, WES and ISO CTOD testing standards, and a typical plastic rotational factor is given by a constant value of 0.4. This value is appropriate for deep-notched SE(B) specimens, but is not suitable for shallow-notched SE(B) specimens. In this study, a new equation of calculating the plastic rotational factor was obtained by using the Electric Power Research Institute (EPRI) scheme. The equation shows the effect of crack length and strain hardening on the plastic rotational factor, and is useful for evaluating CTOD in shallow-notched SE(B) specimens.

Transformation of BS7448-CTOD to ASTM E1290-CTOD

2008 ◽  
Author(s):  
Yoichi Kayamori ◽  
Takehiro Inoue ◽  
Tetsuya Tagawa
Keyword(s):  
Strain Hardening ◽  
Strain Hardening Exponent ◽  
Test Results ◽  
Single Edge ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Edge Notch ◽  
Crack Tip Opening ◽  
The Relationship ◽  
Single Edge Notch Bend

Experimental and analytical investigations into Crack Tip Opening Displacement, CTOD, were conducted to demonstrate the relationship between BS7448-CTOD and ASTM E1290-CTOD. CTOD test results showed that ASTM-CTOD was occasionally much lower than BS-CTOD both in single edge notch bend specimens and in CT specimens for low-strength structural steels, and this tends to be more remarkable in CT specimens. In addition, the analytical results of simplified elastic-plastic facture parameter calculation using the Electric Power Research Institute scheme demonstrated that the ratio of ASTM-CTOD to BS-CTOD was not constant but varied according to CTOD changes. Material factors such as the yield stress, the strain hardening exponent, specimen size and configurations influenced the CTOD ratio, and low strain hardening exponent in the Ramberg-Osgood relation and CT specimen configuration significantly decreased the CTOD ratio. An equation that transforms BS-CTOD into ASTM-CTOD is proposed in this study. This equation gives a good estimate of ASTM-CTOD from BS-CTOD.

scholarly journals Numerical Analysis of the Influence of In-Plane Constraints on the Crack Tip Opening Displacement for SEN(B) Specimens Under Predominantly Plane Strain Conditions

2016 ◽  
Vol 21 (4) ◽  
pp. 849-866 ◽  
Author(s):  
M. Graba
Keyword(s):  
Numerical Analysis ◽  
Plane Strain ◽  
Crack Tip ◽  
Strain Hardening Exponent ◽  
Single Edge ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
New Formula ◽  
Crack Tip Opening ◽  
The Relationship

Abstract This paper presents a numerical analysis of the relationship between in-plane constraints and the crack tip opening displacement (CTOD) for single-edge notched bend (SEN(B)) specimens under predominantly plane strain conditions. It provides details of the numerical model and discusses the influence of external load and in-plane constraints on the CTOD. The work also reviews methods for determining the CTOD. The new formula proposed in this paper can be used to estimate the value of the coefficient dn as a function of the relative crack length, the strain hardening exponent and the yield strength - dn(n, σ0/E, a/W), with these parameters affecting the level of in-plane constraints. Some of the numerical results were approximated using simple mathematical formulae.

Effect of Residual Stresses on Ductile Crack Growth in Pipeline Steel

2016 ◽  
Vol 850 ◽  
pp. 403-408
Author(s):  
Xiao Min Zhuo ◽  
Jie Xu ◽  
Peng Peng Li ◽  
Yu Fan ◽  
Zhi Sun
Keyword(s):  
Residual Stresses ◽  
Crack Growth ◽  
Pipeline Steel ◽  
Crack Tip ◽  
Crack Growth Resistance ◽  
Ductile Crack ◽  
Single Edge ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Ductile Crack Growth

In this study, the effects of residual stresses on the ductile crack growth resistance was investigated using single-edge-notched bending (SENB) and single-edge-notched tension (SENT) specimens as well as axisymmetric model. Weld residual stresses were introduced by the so-called eigenstrain method. The crack tip opening displacement (CTOD) and constraint parameter R were calculated for different specimens and residual stresses. Results show that the residual stresses slightly reduced the ductile crack growth resistance. However, crack tip constraint R elevated with the increase of residual stress.

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