A Critical View on the Significance of HAZ Toughness Testing

2004 ◽  
Author(s):  
Andreas Liessem ◽  
Marion Erdelen-Peppler
Keyword(s):  
Structural Reliability ◽  
Weld Seam ◽  
Test Procedure ◽  
Small Scale ◽  
Final Conclusion ◽  
Test Procedures ◽  
Current Test ◽  
Good Shape ◽  
Toughness Testing ◽  
Haz Toughness

Within the heat affected zone (HAZ) along the weld seam of LSAW linepipes discrete microstructural regions of reduced toughness can not be avoided and are commonly designated with the term Local Brittle Zones. The nature of these LBZ has been intensively investigated and the gathered knowledge is exploited in today’s steel technology, plate processing and pipe manufacturing. The HAZ toughness has been improved in general by reducing MA constituents and by austenite grain refinement. Nevertheless local areas of low toughness within the CGHAZ can not be avoided completely. They are statistically distributed in every pipe. Furthermore it seems to be widely accepted that the structural reliability of LSAW linepipe produced and inspected with state-of-the-art technology is not influenced as these areas of low toughness have a limited size and distribution. This has been demonstrated by numerous investigations including small scale (CVN, CTOD), wide plate and burst tests. The essence of these investigations is that the failure behaviour of linepipe containing part wall defects in the HAZ is toughness independent. So far researcher’s world is clear and in good shape. Nevertheless many linepipe specifications tend to stipulate stringent test requirements with regard to acceptance criteria for the HAZ. In the occurrences of test failures a re-test procedure for test lot acceptance is carried out. As a matter of fact the LBZ are present along the weld seam over limited areas in each pipe. Therefore such a re-test procedure is regarded to be inappropriate in terms of quality inspection as it randomly sorts out pipes just by the statistical chance. With regard to HAZ toughness the pipes failed by this test do not differ from those pipes accepted and released for dispatch. As a final conclusion it can be stated that the existing test procedures for the HAZ toughness testing of the main standards and specifications do not reflect the current developments with regard to improved HAZ toughness achieved by the development of optimised steel composition and with regard to the enhanced defect detection probability along with modern NDT inspection methods. An amendment of the current test procedures in this direction is proposed. Therefore proposals are made as start for a common discussion.

HAZ Toughness: Realistic Testing for Pipeline Integrity

2011 ◽  
Author(s):  
Alexander U. Amadioha ◽  
Adam C. Bannister ◽  
Simon Slater ◽  
Martin Connelly
Keyword(s):  
Fracture Toughness ◽  
Large Scale ◽  
Crack Depth ◽  
Small Scale ◽  
Specific Test ◽  
Fracture Toughness Testing ◽  
Seam Weld ◽  
Wide Range ◽  
Toughness Testing ◽  
Haz Toughness

Fracture toughness testing of the heat-affected zone (HAZ) of linepipe seam welds is a requirement for most pipeline projects. Occasionally, low individual values can be measured in the HAZ and these have been attributed to, among other factors, the statistical nature of the HAZ and the associated probability of encountering local brittle zones. The structural significance of these outliers has remained a subject of debate between linepipe users and manufacturers [1], especially as their low significance can be demonstrated via large-scale structurally-representative tests [2–3]. To circumvent the higher cost of such large-scale testing, constraint-corrected fracture toughness testing can be used such that the conditions in the small-scale test more closely reflect those in service. However, there is little consistency between the many test and application codes in terms of how such tests should be carried out, and what steps are required to demonstrate that the measured toughness is structurally representative. Furthermore, the level of benefit to be obtained cannot be easily predicted. In the current study, a range of fracture mechanics tests was conducted on the HAZ of the longitudinal seam weld of a grade X65 U-O-E SAW pipe. Varying degrees of constraint, scale and loading mode were evaluated to establish the characteristic toughness of the HAZ in a statistical manner, with over fifty specimens tested in total. The specimens tested included notched bend (SENB) and tension (SENT) designs as well as surface notched tension (SNT), all with varying crack depth. The range of specimen and loading types, when compared with the requirements of the various relevant standards, highlighted the contradictory nature of current standards. The toughness established for each set of specific test conditions was used in a theoretical Engineering Critical Assessment (ECA) assuming various levels of applied stress, residual stress and flaw size inputs. The wide range of conclusions that would have been reached based on the small-scale toughness tests carried out under varying levels of constraint was easily demonstrated via the ECA. The conflicting requirements of several testing and application standards for longitudinal welds should be addressed, and their consistency with current approaches for girth welds improved. The study also shows that a single-parameter fracture criterion is an insufficient indicator of real HAZ toughness and constraint (metallurgical and geometrical) level must also be considered. The use of standard deeply-notched CTOD specimens, representing high constraint, gives a highly pessimistic view of seam weld integrity, especially when subsequently combined with an ECA.

Toughness Evaluation on Seam Weld HAZ of High Strength UOE Linepipe

2006 ◽  
Author(s):  
Nobuyuki Ishikawa ◽  
Toyohisa Shinmiya ◽  
Satoshi Igi ◽  
Joe Kondo
Keyword(s):  
Fracture Behavior ◽  
Structural Reliability ◽  
Base Material ◽  
High Strength ◽  
Small Scale ◽  
Seam Welding ◽  
Toughness Evaluation ◽  
Surface Notch ◽  
The Relationship ◽  
Haz Toughness

Heat affected zone (HAZ) along with the weld seam of LSAW has discrete microstructure and usually shows lower toughness than base material. Grain coarsening and formation of M-A constituents governs the HAZ toughness, and a lot of efforts have been made to improve HAZ toughness. However, it is impossible to completely reduce the effect of microstructural change by seam welding. Especially, higher strength or heavy wall linepipes which have richer chemistry tend to have lower HAZ toughness. Therefore, it is important to understand the relationship between microstructural characteristics and toughness of HAZ and fracture behavior of HAZ region in order to ensure the structural reliability of seam welded region. In this paper, fracture behavior of X70 grade heavy wall UOE linepipe was investigated. Wide plate tensile test was conducted with the surface notch introduced on to the coarse grain HAZ, as well as the small scale testing such as Charpy and CTOD test. Fracture mechanics analysis was also carried out to understand the critical condition for brittle fracture of HAZ, and compared with the experimental results.

Reliability of Laboratory Tests for the Control of Oral Anticoagulation

1974 ◽  
Vol 32 (02/03) ◽  
pp. 483-491
Author(s):  
E. A Loeliger ◽  
M. J Boekhout-Mussert ◽  
L. P van Halem-Visser ◽  
J. D. E Habbema ◽  
H de Jonge
Keyword(s):  
Human Brain ◽  
Laboratory Tests ◽  
Test Procedure ◽  
Rabbit Brain ◽  
Normal Range ◽  
Test Procedures ◽  
Discrimination Power ◽  
Power Of The Test ◽  
Assay Procedure ◽  
Low Sensitivity

SummaryThe present study concerned the reproducibility of the so-called prothrombin time as assessed with a series of more commonly used modifications of the Quick’s onestage assay procedure, i.e. the British comparative reagent, homemade human brain thromboplastin, Simplastin, Simplastin A, and Thrombotest. All five procedures were tested manually on pooled lyophilized normal and patients’ plasmas. In addition, Simplastin A and Thrombotest were investigated semiautomatically on individual freshly prepared patients’ plasmas. From the results obtained, the following conclusions may be drawn :The reproducibility of results obtained with manual reading on lyophilized plasmas is satisfactory for all five test procedures. For Simplastin, the reproducibility of values in the range of insufficient anticoagulation is relatively low due to the low discrimination power of the test procedure in the near-normal range (so-called low sensitivity of rabbit brain thromboplastins). The reproducibility of Thrombotest excels as a consequence of its particularly easily discerned coagulation endpoint.The reproducibility of Thrombotest, when tested on freshly prepared plasmas using Schnitger’s semiautomatic coagulometer (a fibrinometer-liJce apparatus), is no longer superior to that of Simplastin A.The constant of proportionality between the coagulation times formed with Simplastin A and Thrombotest was estimated at 0.64.Reconstituted Thrombotest is stable for 24 hours when stored at 4° C, whereas reconstituted Simplastin A is not.The Simplastin A method and Thrombotest seem to be equally sensitive to “activation” of blood coagulation upon storage.

scholarly journals Non-inferiority test for a continuous variable with a flexible margin in an active controlled trial : An application to the "Stratall ANRS 12110 / ESTHER" trial

2020 ◽  
Author(s):  
Arsene Sandie ◽  
Nicholas Molinari ◽  
Anthony Wanjoya ◽  
Charles Kouanfack ◽  
Christian Laurent ◽  
...  
Keyword(s):  
Confidence Interval ◽  
Active Control ◽  
Error Rate ◽  
Type I Error ◽  
Clinical Monitoring ◽  
Small Scale ◽  
Type I ◽  
Test Procedures ◽  
Power Estimate ◽  
Control Intervention

Abstract Background: The non-inferiority trials are becoming increasingly popular in public health and clinical research. The choice of the non-inferiority margin is the cornerstone of the non-inferiority trial. When the effect of active control intervention is unknown, it can be interesting to choose the non-inferiority margin as a function of the active control intervention effect. In this case, the uncertainty surrounding the non-inferiority margin should be accounted for in statistical tests. In this work, we explored how to perform the non-inferiority test with a flexible margin for continuous endpoint.Methods: It was proposed in this study two procedures for the non-inferiority test with a flexible margin for the continuous endpoint. The proposed test procedures are based on test statistic and confidence interval approach. Simulations have been used to assess the performances and properties of the proposed test procedures. An application was done on clinical real data, which the purpose was to assess the efficacy of clinical monitoring alone versus laboratory and clinical monitoring in HIV-infected adult patients.Results: Basically, the two proposed test procedures have good properties. In the test based on a statistic, the actual type 1 error rate estimate is approximatively equal to the nominal value. It has been found that the confidence interval level determines approximately the level of significance. The 80%, 90%, and 95%one-sided confidence interval levels led approximately to a type I error of 10%, 5% and 2.5% respectively. The power estimate was almost 100% for two proposed tests, except for the small scale values of the reference treatment where the power was relatively low when the sample sizes were small.Conclusions: Based on type I error rate and power estimates, the proposed non-inferiority hypothesis test procedures have good performance and are applicable in practice.Trial registration: The trial data used in this study was from the ”Stratall ANRS 12110 / ESTHER”, registered with ClinicalTrials.gov, number NCT00301561. Date : March 13, 2006, url : https://clinicaltrials.gov/ct2/show/NCT00301561.

scholarly journals Experimental Testing of a Size-Exclusion Chromatography Method Used for Evaluation of Molecular Parameters of Equine Anti-Ebola Immunoglobulin

2019 ◽  
Vol 19 (4) ◽  
pp. 261-267
Author(s):  
Е. Yu. Mishalova ◽  
E. V. Gordeev ◽  
V. N. Lebedev ◽  
S. A. Melnikov ◽  
S. A. Nimirskaya ◽  
...  
Keyword(s):  
Specific Activity ◽  
Experimental Testing ◽  
Horse Serum ◽  
Test Procedure ◽  
Size Exclusion ◽  
Array Detector ◽  
Test Procedures ◽  
Molecular Parameters ◽  
Hplc System

Haemorrhagic fever caused by the Ebola virus is a highly hazardous infectious disease with a mortality rate of 50– 90 %. Heterologous immunoglobulins with a high virus-neutralizing titer are an important element of the WHO-endorsed set of measures for emergency prevention and treatment of the disease. Specific activity of these products is largely determined by their fractional composition, and, in particular, by molecular mass distribution (MMD). The size-exclusion-high-performance liquid chromatography (SEC-HPLC) has traditionally been used for determination of the MMD of the target protein in human immunoglobulin-based products. The use of this method for evaluation of molecular parameters of heterologous immunoglobulin requires confirmation of its specificity, accuracy and precision, and establishment of the chromatographic system suitability criteria in the context of a new test object.The aim of the study was to test the applicability of the SEC-HPLC method to the assessment of molecular parameters of anti-Ebola immunoglobulin derived from horse serum.Materials and methods: three batches of purified equine anti-Ebola immunoglobulin were used in the study. Normal equine and human immunoglobulins of the IgG isotype were used as reference standards. The HPLC test procedures described in the European Pharmacopoeia 9.6 and State Pharmacopoeia of the Russian Federation, 14th ed., were used for determination of monomers and other immunoglobulin fractions. An Agilent 1260 Infinity (Agilent, USA) HPLC system with a diode array detector and an Agilent Bio SEC-3 HPLC column were used for quality evaluation of the tested products.Results: the resolution factor between IgG monomer and dimer peaks (1.69 and 2.10), and the chromatographic column efficiency (>2000) make it possible to use the SEC-HPLC system for evaluation of molecular parameters of heterologous immunoglobulin. The study demonstrated reproducibility of the test procedure.Conclusions: the study confirmed the applicability of the SEC-HPLC procedure for evaluation of molecular parameters of anti-Ebola immunoglobulin derived from horse serum. It demonstrated the compliance of the purified immunoglobulin to the national and international quality requirements in terms of «Molecular parameters».

Test procedure and sample size determination for a proportion study using a double-sampling scheme with two fallible classifiers

2017 ◽  
Vol 28 (4) ◽  
pp. 1019-1043 ◽  
Author(s):  
Shi-Fang Qiu ◽  
Xiao-Song Zeng ◽  
Man-Lai Tang ◽  
Wai-Yin Poon
Keyword(s):  
Sample Size ◽  
Null Hypothesis ◽  
Test Procedure ◽  
Sample Size Determination ◽  
Double Sampling ◽  
Score Statistic ◽  
Wald Statistic ◽  
Test Procedures ◽  
Practical Applications ◽  
Logit Transformation

Double sampling is usually applied to collect necessary information for situations in which an infallible classifier is available for validating a subset of the sample that has already been classified by a fallible classifier. Inference procedures have previously been developed based on the partially validated data obtained by the double-sampling process. However, it could happen in practice that such infallible classifier or gold standard does not exist. In this article, we consider the case in which both classifiers are fallible and propose asymptotic and approximate unconditional test procedures based on six test statistics for a population proportion and five approximate sample size formulas based on the recommended test procedures under two models. Our results suggest that both asymptotic and approximate unconditional procedures based on the score statistic perform satisfactorily for small to large sample sizes and are highly recommended. When sample size is moderate or large, asymptotic procedures based on the Wald statistic with the variance being estimated under the null hypothesis, likelihood rate statistic, log- and logit-transformation statistics based on both models generally perform well and are hence recommended. The approximate unconditional procedures based on the log-transformation statistic under Model I, Wald statistic with the variance being estimated under the null hypothesis, log- and logit-transformation statistics under Model II are recommended when sample size is small. In general, sample size formulae based on the Wald statistic with the variance being estimated under the null hypothesis, likelihood rate statistic and score statistic are recommended in practical applications. The applicability of the proposed methods is illustrated by a real-data example.

Standardization of SENT (or SE(T)) Fracture Toughness Measurement: Results of a Round Robin on a Draft Test Procedure

2016 ◽  
Author(s):  
Sanjay Tiku ◽  
Nick Pussegoda ◽  
Morvarid Ghovanlou ◽  
W. R. Tyson ◽  
Aaron Dinovitzer
Keyword(s):  
Fracture Toughness ◽  
Test Procedure ◽  
Potential Drop ◽  
Round Robin ◽  
Single Specimen ◽  
Test Program ◽  
Round Robin Test ◽  
Fracture Toughness Testing ◽  
Growth Measurement ◽  
Toughness Testing

Fracture toughness of steels is conventionally measured using bend specimens and provides a conservative estimate of toughness when the actual loading is in tension. There has been widespread interest in characterizing the toughness that occurs with reduced constraint to better reflect constraint conditions typical of a relatively shallow girth weld flaw. There is currently a standardized approach to measure fracture toughness in tension loaded specimens, however, it requires testing of multiple specimens to generate a resistance curve. Recent developments in fracture toughness testing and analysis of tension loaded specimens have led to publications by CANMET and Exxon Mobil Upstream Research Company toward development of a single-specimen procedure. As part of an initiative to enhance the state of the art in strain based design and assessment methods, with the intent of providing support for the standardization of appropriate weld testing methods, BMT under a Pipeline research Council International (PRCI) project has combined the two single-specimen approaches and developed a recommended practice for fracture toughness testing using single-edge-notched tension SENT (or SE(T)) samples with fixed grip loading. The procedure has been assessed by means of a round robin test program involving laboratories from around the world. Girth welds were fabricated and base metal, heat affected zone and weld center line specimens were prepared and sent to round robin participants. For the round robin program all the participants used a double clip gauge arrangement for direct CTOD measurement and electric potential drop measurement or unloading compliance method for crack growth measurement. In this paper, the results of the round robin test program including comparison of J and CTOD resistance curves will be presented and discussed.

Burn Chamber Test of Ex Situ Thermal Impulse Sensors

2020 ◽  
Vol 74 (5) ◽  
pp. 515-524
Author(s):  
Benjamin R. Anderson ◽  
Natalie Gese ◽  
Ray Gunawidjaja ◽  
Hergen Eilers
Keyword(s):  
Research Laboratory ◽  
Large Scale ◽  
Current Method ◽  
Ex Situ ◽  
Small Scale ◽  
Average Temperature ◽  
Current Test ◽  
Oxide Precursor ◽  
The Us ◽  
Lab Test

Recently, we reported on a novel ex situ thermal impulse sensing technique (based on lanthanide-doped oxide precursor nanoparticles) for use in structural fire forensics and demonstrated its functionality in small-scale lab-based tests. As a next step we have now performed a large-scale lab test at the US Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF) Fire Research Laboratory using a burn chamber with three sand burners. In this test we demonstrate our technique’s ability to determine the average temperature experienced by surfaces during the fire. While we successfully demonstrate our techniques accuracy, we also discover several previously unknown vulnerabilities. Namely, we find that: (1) our current method of embedding sensors in paint results in our sensor particles being difficult to recover (due to a large quantity of debris), (2) the current test panels have poor survivability, (3) debris from the fire tests interferes with excitation of dopant Dy ions (limiting our sensors’ functionality), and (4) dispersal in paint results in suppression of the (metastable)tetragonal-to-monoclinic phase transition of ZrO2. To overcome these vulnerabilities we are evaluating new panel materials, paints, and lanthanide-dopants.

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