Modeling and CMOD Mapping of Surface-Cracked Wide Plates

2008 ◽  
Author(s):  
Da-Ming Duan ◽  
Yong-Yi Wang ◽  
Yaoshan Chen ◽  
Joe Zhou
Keyword(s):  
Test Data ◽  
Driving Force ◽  
Mouth Opening ◽  
Quality Data ◽  
Crack Mouth Opening Displacement ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Crack Driving Force ◽  
Strain Capacity ◽  
Test Conditions

Curved wide plate (CWP) tests are frequently used to measure the tensile stress and strain capacity of pipeline girth welds. The parameters affecting the CWP measurement include specimen geometry and cooling setups. High-quality data is obtained when valid test conditions are confirmed. Crack mouth opening displacement (CMOD) is often measured in CWP tests. CMOD is a direct indicator of the amount of deformation at the cracked plane. It is an indirect indicator of the crack driving force (CDF) imparted on the crack. For a given test geometry and material, certain relationships can be derived between the measured CMOD and the more conventional representation of crack driving force, such as CTOD (crack tip opening displacement) and J-integral. Such relationships are a key element in fracture toughness testing standards. This kind of relationship is also particularly useful in strain-based design where CWP specimens are used for strain capacity and flaw growth prediction. In this paper finite element (FE) analysis is first used in modeling CWP testing conditions for X100 specimens with girth weld flaws to validate the test conditions. A novel approach called CMOD mapping is then developed to characterize the flaw behavior which, by making a direct use of CMOD test data from the CWP tests, is used to estimate the crack growth in the CWP. Finally analysis of strain limits using crack driving force (CDF) for the CWP specimens is also given by comparing experimental test data and FE estimation.

Test for Crack Opening Displacement of Steel Fiber Reinforced Concrete under Three-Point Bending

2010 ◽  
Vol 36 ◽  
pp. 157-161 ◽  
Author(s):  
Tin Gyi Zhang ◽  
Yuan Bao Leng ◽  
Dan Ying Gao
Keyword(s):  
Crack Opening Displacement ◽  
Crack Opening ◽  
Mouth Opening ◽  
Crack Tip ◽  
Crack Mouth Opening Displacement ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Critical Crack ◽  
Critical Crack Opening ◽  
Crack Tip Opening

Based on the principle of electrical measurement method, the clip gauge was made to measure the crack opening displacement (COD).Through the three-point bending test on the specimens of steel fiber reinforced high strength concrete (SFHSC), the effect of the fiber volume fraction (ρf) upon the critical crack opening displacement (the critical crack tip opening displacement and the critical crack mouth opening displacement) was studied. The result shows that the effect of ρf on mouth-tip ratio (the ratio of critical crack mouth opening displacement to critical crack tip opening displacement) can reflect its effect upon the critical crack opening displacement. According to the geometrical relationship between the initial crack length and the critical crack opening displacement，calculation method for the initial crack length was proposed. Based on the test result, the formula was established for calculating the critical crack tip opening displacement.

Effect of Material Properties on the Plastic Straining Capacity of Defective Welds

2005 ◽  
Vol 475-479 ◽  
pp. 2659-2662 ◽  
Author(s):  
Wim De Waele
Keyword(s):  
Weld Metal ◽  
Test Data ◽  
Material Properties ◽  
Mouth Opening ◽  
Crack Mouth Opening Displacement ◽  
Crack Mouth ◽  
Opening Displacement

This paper describes the effect of the interrelation between the base and weld metal postyield characteristics on the CMOD (Crack Mouth Opening Displacement) and the straining capacity of a defective weld. The effect is discussed and illustrated by means of test data obtained from standard CTOD and tension loaded wide plate tests.

Evaluation of J/CTOD for Clamped SE(T) Specimens With Welds

2011 ◽  
Author(s):  
Guowu Shen ◽  
William R. Tyson ◽  
James A. Gianetto ◽  
Dong-Yeob Park
Keyword(s):  
Yield Strength ◽  
Mouth Opening ◽  
Crack Mouth Opening Displacement ◽  
Homogeneous Material ◽  
J Integral ◽  
Center Line ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Element Analysis ◽  
Integral Evaluation

In BS 7448, Part 2, the stress intensity factor, J-integral and crack tip opening displacement (CTOD) equations developed for evaluation of fracture toughness of a homogeneous material using experimentally measured quantities, such as load-load line displacement, are applied to SE(B) specimens with yield-strength-mismatched welds. The accuracy of this procedure was studied by Gordon and Wang using finite element analysis (FEA). Recently, the so-called “η factor” method for J-integral evaluation of SE(T) specimens with weld-center-line-cracked and yield-strength-mismatched welds was studied by Ruggieri using detailed FEA calculations and the load separation method proposed by Paris et al. For application to strain-based design of pipelines, CANMET has developed equations to evaluate J-integral and CTOD resistance curves for clamped SE(T) specimens of homogeneous materials using experimentally measured load and crack-mouth-opening displacement (CMOD) in a single-specimen procedure similar to that in ASTM E1820. In the present study, the accuracy of using these equations for J-integral evaluation of clamped SE(T) specimens with weld-center-line-cracked and strength-mismatched welds was studied. It was found that the errors in J and CTOD using the equations developed for SE(T) specimens of homogenous materials for these strength-mismatched welds are similar to those for SE(B) specimens with the same weld geometry and mismatch level as reported by Gordon and Wang. It was also found that using the higher of the strength of base and weld metals σY (= (σYS+σTS)/2), (i.e. (σY)w for overmatching and (σY)B for undermatching) in converting J to CTOD gives reasonable and conservative CTOD evaluations for specimens with weld-center-line-cracked and yield-strength-mismatched welds.

scholarly journals An Investigation of Softening Laws and Fracture Toughness of Slag-Based Geopolymer Concrete and Mortar

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5200
Author(s):  
Yao Ding ◽  
Yu-Lei Bai ◽  
Jian-Guo Dai ◽  
Cai-Jun Shi
Keyword(s):  
Fracture Toughness ◽  
Inverse Analysis ◽  
Mouth Opening ◽  
Crack Mouth Opening Displacement ◽  
Unstable Fracture ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Tension Softening ◽  
Initial Fracture ◽  
Crack Tip Opening

This paper aimed to determine the softening laws and fracture toughness of slag-based geopolymer (SG) concrete and mortar (SGC and SGM) as compared to those of Portland cement (PC) concrete and mortar (PCC and PCM). Using three-point bending (TPB) tests, the load vs. mid-span displacement, crack mouth opening displacement, and crack tip opening displacement curves (P-d, P-CMOD, and P-CTOD curves) were all recorded. Bilinear softening laws of the PC and SG series were determined by inverse analysis. Furthermore, the cohesive toughness was predicted using an analytical fracture model. The cohesive toughness obtained by experimental study was consistent with that predicted by analytical method, proving the correctness of the tension softening law obtained from inverse analysis. In addition, both initial and unstable fracture toughness values of SG mortar were lower than those of PC mortar given the same compressive strength. Moreover, the initial fracture toughness of SG concrete was generally lower than that of PC concrete, whereas the unstable fracture toughness exhibited an opposite trend.

Critical Crack Tip Opening Displacement for X70 and X80 Steels - A Parametric Study

2017 ◽  
Vol 898 ◽  
pp. 719-724 ◽  
Author(s):  
Xiao Ben Liu ◽  
Qing Quan Duan ◽  
Bao Dong Wang ◽  
Hong Zhang
Keyword(s):  
Mouth Opening ◽  
High Strength ◽  
Crack Mouth Opening Displacement ◽  
Specimen Thickness ◽  
Pipe Steels ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Critical Crack ◽  
Line Pipe ◽  
Crack Tip Opening

High strength line-pipe steels are widely used in long distance gas pipelines. Fracture toughness is one major parameter in the performance evaluation of these line-pipe steels. For high strength line-pipe steels, critical crack tip opening displacement (CTOD) is one typical quantity for fracture toughness. In this paper, a series of experimental studies were conducted to investigate the influences of steel property and specimen thickness on critical CTOD by three points bending tests for X70 and X80 line-pipe steel. Results showed that the critical CTOD is mainly depended on the plastic crack mouth opening displacement of the specimen. For the same size specimens, the critical CTOD of X80 steel was much less than X70 steel. The specimen thickness had a significant influence on the plastic crack mouth opening displacement. With the decrease of the specimen thickness, the critical CTOD increased.

Significance of Biaxial Stress on the Strain Concentration and Crack Driving Force in Pipeline Girth Welds With Softened HAZ

2007 ◽  
Author(s):  
Ming Liu ◽  
Yong-Yi Wang
Keyword(s):  
Driving Force ◽  
Hoop Stress ◽  
Surface Strain ◽  
Biaxial Stress ◽  
Material Anisotropy ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Crack Driving Force ◽  
Loading Sequence ◽  
Longitudinal Strains

The effect of the biaxial stress and HAZ softening on the crack driving force of girth weld defects was investigated using finite element analyses (FEA). The defects were of elliptic shape and located on the inner surface of the pipe. The crack driving force is represented by the crack tip opening displacement (CTOD) normal to the cracked plane (Mode I). The effect of hoop stress on a homogeneous pipe was revisited at first. It was found that the application of hoop stress tends to increase the crack driving force. However, in the practical range of longitudinal strains (≤4.0%), the effects of hoop stress is not monotonic. For example, at a constant longitudinal strain, as the pre-existing hoop stress increases, the driving force may firstly increase then decrease. The combined effect of HAZ softening and biaxial stress was then studied. With the application of hoop stress, the increase of the crack drive force due to HAZ softening was amplified. It was found that the crack driving force can be closely correlated with the surface strain measured over a structurally significant scale right above the defect. In addition, the effects of loading sequence and material anisotropy on the crack driving force were also briefly examined. The increase of the crack driving force from the hoop stress is more pronounced when it is applied prior to the application of longitudinal strains than the reverse loading sequence. The material anisotropy was found to further increase the crack driving force and therefore representative material models are necessary to analyze the anisotropy effects.

Numerical Analysis of the Crack Driving Force of Mismatched Girth Welded Pipes Subject to Large Plastic Deformations

2021 ◽  
Author(s):  
Kai Wu ◽  
Hong Zhang ◽  
Yue Yang ◽  
Xiaoben Liu
Keyword(s):  
Crack Length ◽  
Driving Force ◽  
Crack Depth ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Plastic Deformations ◽  
Crack Driving Force ◽  
Ground Deformations ◽  
Global Strain ◽  
Large Plastic Deformations

Abstract Strength mismatched pipes with part-through cracks can suffer large plastic deformation from permanent ground deformations caused by geohazards. Thus, the crack driving force involved in engineering critical assessments plays an important role in guaranteeing pipeline integrity when pipes are subjected to complex loads induced by a hostile environment. In this paper, Python scripts are developed to generate up to 200 finite element models of strength mismatched pipes with various crack sizes under large plastic deformations based on the commercial software ABAQUS. The effects of crack length, crack depth, and strength mismatch factors on the evolution of crack tip opening displacement (CTOD) and global strain were investigated. An approximately linear relationship was observed in all cases tested with global strain values varying from 0.5% to 3%. Meanwhile, the value of the CTOD increased with the increase of crack length and crack depth, and decreased with increasing mismatch factor from the undermatch to the overmatch conditions. The effect of the crack depth on the CTOD is comparatively larger than the crack length, which presented an obvious change of the CTOD for deep cracks coupled with undermatched conditions. Overmatched welding only affected the value of CTOD slightly, while a drastic increase of CTOD value was observed for the undermatched welding conditions, especially for deep and long cracks.

Fracture Behaviour of Thin Sheet Stainless Steel

2012 ◽  
Vol 525-526 ◽  
pp. 549-552
Author(s):  
Nenad Gubeljak ◽  
Darko Jagarinec ◽  
Jožef Predan ◽  
John Landes
Keyword(s):  
Fracture Toughness ◽  
Stainless Steel ◽  
Crack Initiation ◽  
Driving Force ◽  
Crack Tip ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Crack Driving Force ◽  
Integrity Assessment ◽  
Crack Tip Opening

The differences in fracture behavior between the compact tension C(T) and the middle tensile M(T) specimens make structure integrity assessment uncertain. Two different types of specimens C(T) and M(T) specimens made from stainless steel have been used for fracture toughness testing at the room temperature by the principles of the ASTM 1820-05 standard procedure. Stable crack initiation and crack propagation occurred for the C(T) specimens at lower values of crack driving force than for the M(T) specimens. Crack tip opening displacement-CTOD has been directly measured on the surface of specimens by using a stereo-optical grading method. The critical crack tip opening displacement at crack initiation CTODi has been measured as a plastic Stretch Zone Width (SZW) during a post test fractographic inspection. Comparison between the CTOD-R curves of both types of specimens shows some difference between the C(T) and the M(T) specimens, but a more significant difference appeared in the crack driving force, as consequence of different constraint (triaxiality) of the C(T) versus the M(T) specimens. Therefore, the result obtained by test on laboratory C(T) specimens cannot be directly used as fracture toughness material properties in a structure integrity assessment, except as a conservative lower bound estimate.

scholarly journals Experimental Study on the Fracture Parameters of Concrete

2020 ◽  
Author(s):  
Zhanqiao Wang ◽  
Jin Gou ◽  
Danying Gao
Keyword(s):  
Steel Fiber ◽  
Volume Fraction ◽  
Mouth Opening ◽  
Critical Stress Intensity Factor ◽  
Crack Mouth Opening Displacement ◽  
Crack Tip Opening Displacement ◽  
Fiber Volume ◽  
Opening Displacement ◽  
Critical Crack ◽  
Fracture Parameters

Abstract: This study was aimed to determine the influence of the volume fraction of steel fibers and on fracture parameters of concrete. Fifty notched steel fiber reinforced concrete (SFRC) beams and ordinary concrete beams with dimensions of 100mm×100mm×515mm were cast and tested via three-point bending test. Among them, the type of steel fiber is milling type (MF), and the volume fraction of steel fiber added is 0%, 0.5%, 0.5%, 1.5%, 1.5%, 2%, respectively. The effects of the steel fiber volume fraction (VF) on the critical stress intensity factor (KIC), fracture energy (GF), the deflection at failure(δ0), the critical crack mouth opening displacement (CMODC) and the critical crack tip opening displacement (CTODC)were studied. Through the analysis of test phenomena and test data such as load-deflection (P-δ) curve, load-crack mouth opening displacement (P-CMOD) curve and load-crack tip opening displacement (P-CTOD) curve following conclusions are drawn: With the increase of steel fiber volume fraction, some fracture parameters increase gradually and maintain a certain linear growth. The gain ratio of fracture parameters increases significantly, and the gain effect is obvious. Through this law of growth, the experimental statistical formulas of fracture energy and critical stress intensity factor are summarized.

scholarly journals Experimental Study on the Fracture Parameters of Concrete

Materials ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 129
Author(s):  
Zhanqiao Wang ◽  
Jin Gou ◽  
Danying Gao
Keyword(s):  
Steel Fiber ◽  
Volume Fraction ◽  
Mouth Opening ◽  
Critical Stress Intensity Factor ◽  
Crack Mouth Opening Displacement ◽  
Crack Tip Opening Displacement ◽  
Fiber Volume ◽  
Opening Displacement ◽  
Critical Crack ◽  
Fracture Parameters

This study aimed to determine the influence of the volume fraction of steel fibers on the fracture parameters of concrete. Fifty notched steel-fiber-reinforced concrete (SFRC) beams and ordinary concrete beams with 100 mm × 100 mm × 515 mm were cast and tested via a three-point bending test. Among them, the type of steel fiber was the milling type (MF), and the volume fraction of steel fiber added was 0%, 0.5%, 1%, 1.5% and 2%, respectively. The effects of the steel fiber volume fraction (VF) on the critical stress intensity factor (KIC), fracture energy (GF), the deflection at failure(δ0), the critical crack mouth opening displacement (CMODC) and the critical crack tip opening displacement (CTODC) were studied. Through the analysis of test phenomena and test data such as the load-deflection (P-δ) curve, load-crack mouth opening displacement (P-CMOD) curve and load-crack tip opening displacement (P-CTOD) curve, the following conclusions are drawn: with the increase of the steel fiber volume fraction, some fracture parameters increase gradually and maintain a certain linear growth. The gain ratio of the fracture parameters increases significantly, and the gain effect is obvious. Through this law of growth, the experimental statistical formulas of fracture energy and the critical stress intensity factor are summarized.

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