Development of Test on Sent Specimens to Study Geometry Effects

2012 ◽  
Author(s):  
Patrick Le Delliou ◽  
Joumana El-Gharib
Keyword(s):  
Structural Integrity ◽  
Test Procedure ◽  
Crack Size ◽  
Test Procedures ◽  
Engineering Structures ◽  
Loading Mode ◽  
Piping Systems ◽  
Carbon Manganese Steels ◽  
Geometry Effects ◽  
Low Constraint

The accurate prediction of ductile fracture behaviour plays an important role in structural integrity assessments of critical engineering structures under fully plastic regime, including nuclear reactors and piping systems. Many structural steels and aluminium alloys generally exhibit significant increases in fracture toughness, characterized by the J-integral, over the first few mm of stable crack extension (Δa), often accompanied by large increases in background plastic deformation. Conventional testing programs to measure crack growth resistance (J-Δa) curves employ three-point bend, SEN(B), or compact, CT. However, laboratory testing of fracture specimens to measure resistance curves (J-Δa) consistently reveals a marked effect of absolute specimen size, geometry, relative crack size (a/W ratio) and loading mode (tension vs. bending) on R-curves. These effects observed in R-curves have enormous practical implications in defect assessments and repair decisions of in-service structures under low constraint conditions. Structural components falling into this category include pressurized piping systems with surface flaws that form during fabrication or during in-service operation. This paper presents the on-going work to develop specimens and test procedures to study geometry effects (e.g., triaxiality effects) in the brittle to ductile transition of carbon-manganese steels, the basic idea being to compare the results obtained on these specimens with the results obtained on CT specimens. A clamped SENT specimen was chosen for this study. Finite element computations have been made to optimize the specimen shape and to develop the η-factor, the shape factor F (to compute K) and the normalized compliance μ. Preliminary tests have been conducted, showing that some adjustments of the test procedure should be made. Tests on new specimens are on-going.

scholarly journals Tests on SENT Specimens to Study Geometry Effects in the Brittle to Ductile Transition

2014 ◽  
Author(s):  
Patrick Le Delliou ◽  
Samuel Geniaut
Keyword(s):  
Room Temperature ◽  
Structural Integrity ◽  
Test Procedure ◽  
Crack Size ◽  
Engineering Structures ◽  
Brittle To Ductile Transition ◽  
Loading Mode ◽  
Piping Systems ◽  
Carbon Manganese Steels ◽  
Geometry Effects

The accurate prediction of ductile fracture behaviour plays an important role in structural integrity assessments of critical engineering structures under fully plastic regime, including nuclear reactors and piping systems. Many structural steels and aluminium alloys generally exhibit significant increases in fracture toughness, characterized by the J-integral, over the first few mm of stable crack extension (Δa), often accompanied by large increases in background plastic deformation. Conventional testing programs to measure crack growth resistance (J–Δa) curves employ three-point bend, SEN(B), or compact, CT. However, laboratory testing of fracture specimens to measure resistance curves (J–Δa) consistently reveals a marked effect of absolute specimen size, geometry, relative crack size (a/W ratio) and loading mode (tension vs. bending) on R-curves. These effects observed in R-curves have enormous practical implications in defect assessments and repair decisions of in-service structures under low constraint conditions. Structural components falling into this category include pressurized piping systems with surface flaws that form during fabrication or during in-service operation. This paper presents the on-going work to study geometry effects (e.g. triaxiality effects) in the brittle to ductile transition of carbon-manganese steels, the basic idea being to compare the results obtained on these specimens with the results obtained on CT specimens. A preliminary program was previously conducted at room temperature using deeply notched specimens (Le Delliou, 2012). Finite element computations were made to optimize the specimen shape and to develop the η-factor, the shape factor F (to compute K) and the normalized compliance μ. For the present program, new specimens have been machined with shallower notches (a/W = 0.4), to get a0/W = 0.5 after fatigue pre cracking. Fatigue pre cracking was conducted in 4-point bending to avoid damaging the back of the notch. Moreover, the specimens have been cut in the TS (Transverse-Short) direction of the plate to get lower toughness properties, and less plasticity during the tests. Tests at room temperature have been conducted first to validate the revised test procedure. Then, the SENT specimens have been tested at −100°C, −60°C, and −40°C, together with CT specimens.

Tests on SENT and CT Specimens to Study Geometry Effects in the Brittle to Ductile Transition

2016 ◽  
Author(s):  
Patrick Le Delliou ◽  
Samuel Geniaut
Keyword(s):  
Structural Integrity ◽  
Crack Size ◽  
Engineering Structures ◽  
Geometry Effect ◽  
Brittle To Ductile Transition ◽  
Loading Mode ◽  
Piping Systems ◽  
Carbon Manganese Steels ◽  
Geometry Effects ◽  
Low Constraint

The accurate prediction of ductile fracture behaviour plays an important role in structural integrity assessments of critical engineering structures under fully plastic regime, including nuclear reactors and piping systems. Many structural steels and aluminium alloys generally exhibit significant increases in fracture toughness, characterized by the J-integral, over the first few mm of stable crack extension (Δa), often accompanied by large increases in background plastic deformation. Conventional testing programs to measure crack growth resistance (J–Δa) curves employ three-point bend, SEN(B), or compact, CT. However, laboratory testing of fracture specimens to measure resistance curves (J–Δa) consistently reveals a marked effect of absolute specimen size, geometry, relative crack size (a/W ratio) and loading mode (tension vs. bending) on R-curves. These effects observed in R-curves have enormous practical implications in defect assessments and repair decisions of in-service structures under low constraint conditions. Structural components falling into this category include pressurized piping systems with surface flaws that form during fabrication or during in-service operation. A research program was launched by EDF R&D to study geometry effects (e.g. triaxiality effects) in the brittle to ductile transition of carbon-manganese steels using Single-edge notch tension (SENT) specimens, by comparing the results obtained on these specimens with the results obtained on CT specimens. This paper presents the results of the tests conducted between −40°C and −100°C on a large number of specimens of both types. The toughness values of the SENT specimens appear to be included in the scatter of the CT12.5 ones, so the geometry effect between CT and SENT specimens in the brittle to ductile region is not significant. Moreover, the results of the CT12.5 cut in the L-S direction are not very different of those of the specimens cut in the T-S direction. The Master Curve methodology fits rather well the CT12.5 results, whereas the SENT results are not well covered by this methodology. The energetic approach called GP has been applied to the analysis of some tests. This approach shows that the geometry effect between both types of specimens is limited, in agreement with the experimental observations.

The Effect of Piping System Non-Linearity on the Unstable Growth of a Circumferential Through-Wall Crack in a Pipe

2003 ◽  
Author(s):  
E. Smith
Keyword(s):  
Cross Section ◽  
Material Properties ◽  
Structural Integrity ◽  
Crack Size ◽  
Instability Criterion ◽  
Piping System ◽  
Linear Elastic ◽  
Piping Systems ◽  
Simple Model System ◽  
Linear Manner

During the last twenty-five years, considerable attention has been given to the structural integrity of steel piping systems, and in particular to the effect of circumferential cracks on their integrity. From a safety perspective, it is important that any crack, say for example a stress corrosion crack or fatigue crack, will not develop into a through-wall crack which will then propagate unstably, thus leading to a guillotine rupture and possibly a pipe whip scenario. One way of guaranteeing that this does not happen is to ensure that unstable growth of a circumferential through-wall crack is unable to occur. An appropriate methodology is based on tearing modulus concepts with the instability criterion being expressed in the form TAPP > TMAT where TAPP is the applied tearing modulus, a measure of the crack driving force, and TMAT is the material tearing modulus, a measure of the material’s crack growth resistance. With a piping system that behaves in a linear elastic manner, TAPP involves only the system’s geometry parameters and the crack size but not the magnitudes of the applied loadings or the material properties of the cracked cross-section; the behaviours of the cracked cross-section and the remainder of the piping system are therefore decoupled. If, however, the system behaves in a non-linear manner say, for example, as a result of excessive deformation arising as a consequence of large deformations, then TAPP also involves the material properties of the cracked cross-section; material and piping system geometry parameters are then not decoupled in the instability criterion. The paper illustrates this point by analysing a simple model system where the non-linearity arises from excessive deformation at a connection.

Engineering Assessment of Constraint Effects on Cleavage Fracture

2004 ◽  
Author(s):  
Andrew Sherry ◽  
Dennis Hooton ◽  
David Lidbury
Keyword(s):  
Fracture Toughness ◽  
Cleavage Fracture ◽  
Stress Triaxiality ◽  
Crack Size ◽  
Structural Defects ◽  
Loading Mode ◽  
Safety Margins ◽  
Low Constraint ◽  
Specific Material ◽  
Constraint Effects

It is well known that material fracture toughness is influenced by factors including loading mode and crack size that influence the level of stress triaxiality ahead of the crack tip. This so-called “constraint effect” has been demonstrated both experimentally and analytically, with low constraint (low stress triaxiality) conditions leading to enhanced fracture toughness. Two-parameter fracture mechanics has been developed to provide a framework within which to assess the influence of constraint on safety margins for shallow structural defects. However, this requires the availability of a significant amount of plant-specific material with which to measure the materials’ constraint sensitivity experimentally. This paper presents a case study where constraint effects on cleavage fracture toughness of a shallow-cracked biaxially loaded bend specimen are assessed through a combination of modelling and miniaturised testing. The assessment is performed using the Failure Assessment Diagram approach of R6. It is concluded that the approach provides a practical engineering method for assessing the likely magnitude of constraint effects for low constraint configurations.

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 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.

Integrity Assessment of Pressure Components With Local Hot Spots

2005 ◽  
Vol 127 (2) ◽  
pp. 137-142 ◽  
Author(s):  
R. Seshadri
Keyword(s):  
Hot Spots ◽  
Structural Integrity ◽  
Refractory Lining ◽  
Assessment Method ◽  
Pressure Vessels ◽  
Industrial Processes ◽  
Integrity Assessment ◽  
Piping Systems ◽  
Further Development ◽  
Level 2

Local hot spots can occur in some pressure vessels and piping systems used in industrial processes. The hot spots could be a result of, for instance, localized loss of refractory lining on the inside of pressure components or due to a maldistribution of process flow within vessels containing catalysts. The consequences of these hot spots on the structural integrity of pressure components are of considerable importance to plant operators. The paper addresses structural integrity issues in the context of codes and standards design framework. Interaction of hot spots, as is the case when multiple hot spots occur, is addressed. An assessment method, suitable for further development of a Level 2 “Fitness-for-Service” methodology, is discussed and applied to a commonly used pressure component configuration.

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