Recent Progress in Development of Ductile Fracture Arrest Methodology Based on CTOA: Test Standard, Transferability and Methodology

2020 ◽  
Author(s):  
S. Xu ◽  
C. Bassindale ◽  
J. Xue ◽  
B. W. Williams ◽  
X. Wang
Keyword(s):  
Crack Velocity ◽  
Damage Mechanics ◽  
Loading Rate ◽  
Test Procedure ◽  
Full Scale ◽  
Correction Factors ◽  
Type Specimens ◽  
Model Calculations ◽  
Resistance Curves ◽  
Fracture Arrest

Abstract Significant progress has been made in development of a new fracture arrest methodology based on a toughness parameter designed to characterize propagation — the crack-tip opening angle (CTOA). A CTOA test procedure using lab-scale DWTT-type specimens has been standardized by ASTM, and recently published experimental work has demonstrated transferability of CTOA from DWTT to full-scale pipe. This paper will present the basic methodology for determination of CTOA using DWTT-type specimens (i.e., ASTM E3039) and other specimens such as modified double-cantilever-beam (MDCB). Recent numerical studies using cohesive zone models (CZM) and others based on damage mechanics will be discussed, including models of full-scale pipe fracture. The effects on CTOA of loading rate, specimen flattening and constraint (bending vs. tension) will be reviewed. The effect on CTOA of loading rate between quasi-static and impact (covering five orders of magnitude) is small or negligible, being within experimental scatter. Observed differences between surface and mid-thickness CTOA values will be discussed. Models of DWTT specimens using damage mechanics have shown that the CTOA for tensile loading is the same at the surface and mid-thickness and equal to the mid-thickness value for bend loading, but that the surface CTOA is significantly larger than the mid-thickness CTOA in bending. Model calculations have revealed the dependence of crack velocity on stress for a given CTOA, enabling construction of fracture resistance curves (pressure required to propagate fracture as a function of crack velocity). These first-principles curves based on CTOA can then be used in the Battelle two-curve model (BTCM) to replace empirical resistance curves based on Charpy absorbed energy (Cv). It has been known for some time that Cv over-represents the propagation resistance for high-strength high-toughness steels, requiring empirical “correction factors” to Cv in the BTCM. Experiments have shown that there is a non-linear correlation between Cv and CTOA, explaining the need for correction factors to Cv and supporting the use of CTOA as a more appropriate propagation toughness.

Analysis of Data From a Full-Scale Burst Test on 1219 mm OD Grade 550 Pipe: Implications for the Prediction of Fracture Velocity

2016 ◽  
Author(s):  
Brian Rothwell ◽  
Cindy Guan ◽  
Satoshi Igi
Keyword(s):  
Traditional Approach ◽  
Large Diameter ◽  
Crack Tip ◽  
Management Program ◽  
Full Scale ◽  
Correction Factors ◽  
Long Distance ◽  
Line Pipe ◽  
Fracture Arrest ◽  
Fracture Velocity

In recent years, considerable doubt has arisen over the prediction of the level of toughness required to arrest a propagating fracture in higher-strength line pipe. It has been clear for many years that the most widely used traditional approach, the Two-Curve Method (TCM) developed at Battelle in the early 1970s, could not be applied directly when the required toughness, expressed as full-size Charpy energy, exceeded about 80–90 J. Initially, this issue was addressed by the adoption of empirical correction factors, but more recently, there have been indications that this approach is no longer effective for modern, high-strength materials. Additional information, which in general can only be derived from well-characterized burst tests, is essential to furthering understanding of the fracture arrest problem under conditions that are typical of modern, long-distance, large-diameter pipeline design. In the context of the Coastal GasLink (CGL) project, TransCanada has carried out a program of full-scale burst testing at the Spadeadam test site of DNV GL. The tests were supported by LNG Canada and the TransCanada Technology Management Program. These tests are described in another paper at this conference [1]. Though most of the testing was directed towards the assessment of different crack arrestor designs, one half of one test contained a run of four pipes of progressively increasing Charpy energy, up to a very high level (over 450 J). The fracture was observed to run through all four pipes, before being arrested by a crack arrestor fitted to a fifth pipe having lower toughness. Nearly all approaches to determining requirements for fracture arrest depend, directly or indirectly, on relationships between fracture velocity (for given levels of fracture resistance) and the driving force, generally considered to be directly related to the pressure in the plane of the crack tip. By comparing measured fracture velocity with the crack tip pressure determined either directly at pressure transducer locations or by comparison with propagation velocities within the expansion wave, conclusions can be drawn regarding the accuracy of existing relationships. Most previous work regarding correction factors has been based simply on discrepancies between predicted and observed propagation and arrest behaviour. Direct comparisons of observed and predicted fracture speed potentially provide much more data and focus more clearly on where model deficiencies may lie. The current analysis focuses on comparisons with the predictions of the traditional TCM and those of a transient model developed by JFE. While data from the present work are clearly limited, this approach appears to present a way of recalibrating fracture velocity formulations that may extend the range over which traditional, Charpy-based approaches can be applied. For the future, the incorporation of additional results from other recent, well-characterized burst tests would be extremely valuable in this respect.

Experiment of Polyester Wastewater Treatment by Aerobic Membrane Bioreactor and an Engineering Application

2012 ◽  
Vol 518-523 ◽  
pp. 2130-2137
Author(s):  
Si Hao Lv ◽  
Hui Chang ◽  
Zhi Hui Liang ◽  
Yan Yan Zeng ◽  
Hong Bo Fan
Keyword(s):  
Water Quality ◽  
Pilot Study ◽  
Membrane Bioreactor ◽  
Suspended Solids ◽  
Loading Rate ◽  
Engineering Application ◽  
Full Scale ◽  
Effluent Water ◽  
Small Influence ◽  
Volumetric Loading

A pilot study was carried out to evaluate the application of aerobic submerged MBR in treating polyester wastewater and a full scale system in which MBR was adopted as the key aspect was put forward to treat the polyester wastewater of Zhuhai Yuhua Polyester co., Ltd., China. The pilot study revealed that HRT could be affected by the influent COD, and a HRT larger than 36h was proposed for treating polyester wastewater by MBR. Volumetric loading rate and sludge loading rate ranged in 0.7-2.0 kgCOD/m3•d and 0.09~0.24 kgCOD/ kgMLSS•d respectively were of small influence on the COD removal. DO in the range of 2.5-4.0 mg/L seemed to be optimal for avoiding limitations due to oxygen concentration and creating an effective turbulence. The modified full scale system which includes anaerobic digesting tank and MBR followed by a stabilization pond was verified to be effective to treat the polyester wastewater in the latest two years. The results illustrated that the effluent water quality could meet the discharge limits of water pollutants (DB 44/26-2001) which was established in Guangdong, China. Observed sludge yield of the system fluctuated between 0.10-0.18 gMLSS/gCOD and averaged at 0.137 gMLSS/gCOD. The membrane permeate at around 10 L/m2h, TMP of less than 0.7bar, and total mixed liquor suspended solids (MLSS) between 6-7g/L were suitable to operate the MBR.

The Full-Scale Pacs Archive

1996 ◽  
Vol 37 (3P2) ◽  
pp. 838-846 ◽  
Author(s):  
S. A. Nissen-Meyer ◽  
U. Fink ◽  
M. Pleier ◽  
C. Becker
Keyword(s):  
Digital Image ◽  
Conventional Radiography ◽  
Full Scale ◽  
Model Calculations ◽  
Analog To Digital ◽  
Alternative Technologies ◽  
Transition Strategy ◽  
Hospital Operations ◽  
Picture Archiving And Communication ◽  
Image Archives

Purpose: Increasing percentages of digital modalities in radiology, in particular of digital image acquisition in conventional radiography, call for digital reporting, communication, and archiving techniques. These techniques are prerequisites for the “filmless” hospital. The first 2 have been covered extensively in the literature and by vendors. However, as regards online digital image archives there are still no satisfactory concepts available in the medical field. The present paper puts forward some suggestions as to how this situation could be improved. Material and Methods: Analyses of radiology operations consider the prevailing PACS (picture archiving and communication system) archive concepts that use optical discs to be too small, too slow and too cumbersome to manage and therefore unable to function as comprehensive image archives for filmless hospitals. We suggest borrowing and adapting the well tested archive technologies from space research and the oil and broadcasting industries which have much higher capacities and speeds and better software interfacing possibilities. With such technologies the needs of filmless hospital operations can be met. Results: A feasible concept for a transition strategy from conventional analog to digital archives is presented. Model calculations of the necessary investments and potential savings, including generous placement of viewing stations in the entire hospital, indicate amortization periods of 3.8–4.8 years. Conclusion: Alternative technologies for digital image archives already today make full-scale PACS for filmless hospitals technologically and conceptually feasible and financially mandatory.

scholarly journals A comparison of friction modifier performance using two laboratory test scales

2018 ◽  
Vol 233 (2) ◽  
pp. 201-210 ◽  
Author(s):  
L Buckley-Johnstone ◽  
M Harmon ◽  
R Lewis ◽  
C Hardwick ◽  
R Stock
Keyword(s):  
Test Procedure ◽  
Full Scale ◽  
Data Sets ◽  
Test Machine ◽  
Performance Study ◽  
Friction Modifier ◽  
Additional Information ◽  
Large Spread ◽  
Dry Contact ◽  
The University

This paper describes two methods, carried out at two different test scales, for assessing the friction modifier performance. Study A used the wear data from a full-scale rig test at the voestalpine Schienen GmbH and compared it with the wear data from twin disc tests using the SUROS test machine at the University of Sheffield. Study B compared the ‘retentivity’ data, from a full-scale rig at the University of Sheffield, with the data from the SUROS tests. Study A concluded that a good correlation existed between the two scales although assumptions made in the full-scale contact calculation introduce a large spread into the results. There was a greater correlation between the two data sets at more severe contact conditions. Study B showed a different baseline coefficient of traction between the two scales and that a longer test length is required to fully evaluate the ‘retention’ of the friction modifier on the full-scale rig. The paper expands on a previous conference presentation on the same subject. Additional information on the test procedure and test rigs is included here. Surface and subsurface analyses of the SUROS test samples have also been added. The analyses have shown that applying the friction modifier leads to a similar wear mechanism as for the dry contact, but the wear is less severe and there is less subsurface deformation. A discussion describing the differences in test scales and comparing lab tests to field operation is also included.

Further Extension of the Unloading Compliance Method to Measure J-R Curves Based on CMOD Data

2008 ◽  
Author(s):  
Sebastian Cravero ◽  
Claudio Ruggieri
Keyword(s):  
Fracture Toughness ◽  
Crack Growth ◽  
Test Procedure ◽  
Crack Mouth Opening Displacement ◽  
Evaluation Procedure ◽  
Test Technique ◽  
Resistance Curves ◽  
Unloading Compliance ◽  
Resistance Data ◽  
Unloading Compliance Method

Laboratory testing of fracture specimens to measure resistance curves (J-Δa) have focused primarily on the unloading compliance method using a single specimen. Current estimation procedures (which form the basis of ASTM 1820 standard) employ load line displacement (LLD) records to measure fracture toughness resistance data incorporating a crack growth correction for J. An alternative method which potentially simplifies the test procedure involves the use of crack mouth opening displacement (CMOD) to determine both crack growth and J. This study provides further developments of the evaluation procedure for J in cracked bodies that experience ductile crack growth based upon the eta-method and CMOD data. The methodology broadens the applicability of current standards adopting the unloading compliance technique in laboratory measurements of fracture toughness resistance data (J resistance curves). The developed J evaluation formulation for growing cracks based on CMOD data provides a viable and yet simpler test technique to measure crack growth resistance data for ductile materials.

The Assessment of Residual Stress Effects on Ductile Tearing Using Continuum Damage Mechanics

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Andrew H. Sherry ◽  
Mark A. Wilkes ◽  
John K. Sharples ◽  
Peter J. Budden
Keyword(s):  
Residual Stress ◽  
Crack Growth ◽  
Damage Mechanics ◽  
Numerical Study ◽  
Growth Behavior ◽  
Full Scale ◽  
Crack Growth Behavior ◽  
Specimen Thickness ◽  
Good Prediction ◽  
Ductile Tearing

This paper presents the results of a numerical study undertaken to assess the influence of residual stresses on the ductile tearing behavior of a high strength low toughness aluminum alloy. The Gurson–Tvergaard model was calibrated against conventional fracture toughness data using parameters relating to void nucleation, growth, and coalescence. The calibrated model was used to predict the load versus ductile tearing behavior of a series of full-scale and quarter-scale wide-plate tests. These center-cracked tension tests included specimens that contained a self-balancing residual stress field that was tensile in the region of the through-wall crack. Analyses of the full-scale wide-plate tests indicated that the model provides a good prediction of the load versus the ductile tearing behavior up to approximately 3mm of stable tearing. The influence of residual stress on the load versus the crack growth behavior was accurately simulated. Predictions of the load versus the crack growth behavior of full-scale wide-plate tests for crack extensions greater than 3mm and of the quarter-scale tests were low in terms of predicted load at a given amount of tearing. This was considered to result from (i) the “valid” calibration range in terms of specimen thickness and crack extension, (ii) the development of shear lips, and (iii) the differences in the micromechanism of ductile void formation under plane strain and under plane stress conditions.

Dynamic Fracture of Concrete–3D Numerical Study of Compact Tension Specimen

2011 ◽  
Vol 82 ◽  
pp. 39-44 ◽  
Author(s):  
Joško Ožbolt ◽  
Akanshu Sharma ◽  
Hans Wolf Reinhardt
Keyword(s):  
Finite Element ◽  
Strain Rate ◽  
Crack Velocity ◽  
Loading Rate ◽  
Compact Tension ◽  
Compact Tension Specimen ◽  
Crack Branching ◽  
Tension Specimen ◽  
Loading Rates ◽  
Inertia Forces

The behavior of concrete structures is strongly influenced by the loading rate. Compared to quasi-static loading concrete loaded by impact loading acts in a different way. First, there is a strain-rate influence on strength, stiffness, and ductility, and, second, there are inertia forces activated. Both influences are clearly demonstrated in experiments. For concrete structures, which exhibit damage and fracture phenomena, the failure mode and cracking pattern depend on loading rate. Moreover, theoretical and experimental investigations indicate that after the crack reaches critical speed of propagation there is crack branching. The present paper focuses on 3D finite-element study of the crack propagation of the concrete compact tension specimen. The rate sensitive microplane model is used as a constitutive law for concrete. The strain-rate influence is captured by the activation energy theory. Inertia forces are implicitly accounted for through dynamic finite element analysis. The results of the study show that the fracture of the specimen strongly depends on the loading rate. For relatively low loading rates there is a single crack due to the mode-I fracture. However, with the increase of loading rate crack branching is observed. Up to certain threshold (critical) loading rate the maximal crack velocity increases with increase of loading rate, however, for higher loading rates maximal velocity of the crack propagation becomes independent of the loading rate. The critical crack velocity at the onset of crack branching is found to be approximately 500 to 600 m/s.

A Study of Shear Crack Propagation in Gas-Pressurized Pipelines

1982 ◽  
Vol 104 (4) ◽  
pp. 338-343 ◽  
Author(s):  
E. Sugie ◽  
M. Matsuoka ◽  
T. Akiyama ◽  
H. Mimura ◽  
Y. Kawaguchi
Keyword(s):  
Crack Propagation ◽  
Crack Velocity ◽  
Shear Crack ◽  
Controlled Rolling ◽  
Full Scale ◽  
Pipe Length ◽  
On Line ◽  
Pressurized Pipelines ◽  
Quenching And Tempering ◽  
Crack Propagation And Arrest

Full-scale burst tests were carried out five times on line pipes of 48 in. o.d. × 0.720 in. w.t., Grad. X-70 manufactured by the controlled rolling and the quenching and tempering processes. It was found that the critical notch ductility for arresting a shear crack depends on the pipe length within which the crack is to be arrested. This result is well explained by solving the equation which governs change of crack velocity. The behavior of shear crack propagation and arrest can be well analyzed regardless of the existence or nonexistence of separation by Charpy energy.

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