The Notch Master Curve: A proposal of Master Curve for ferritic–pearlitic steels in notched conditions

This paper presents a model for the prediction of the apparent fracture toughness of ferritic–pearlitic steels in notched conditions and operating at temperatures corresponding to their ductile-to-brittle transition zone. The model, here named the Notch-Master Curve, is based on the combination of the Master Curve of the material in cracked conditions and the notch corrections provided by the Theory of Critical Distances. In order to validate the model, the fracture resistance results obtained in 168 tests performed on CT specimens (84 for each material) are presented. These tests were carried out, for each material, in specimens with six different notch radii, from 0 mm up to 2.0 mm, and at three different temperatures within their corresponding ductile-to-brittle transition zone. It has been observed that the model provides good predictions of the fracture resistance in notched conditions for the two materials analysed

Un procedimiento básico de evaluación de integridad estructural de componentes entallados

Este trabajo presenta un procedimiento básico de evaluación de integridad estructural de componentes entallados basado en los trabajos realizados por los autores en los últimos 5 años, en los cuales se ha analizado el efecto entalla en materiales tan diversos como el PMMA, la Al7075-T651, rocas como el granito y la caliza y diversos aceros estructurales (S275JR, S355J2, S460M y S690Q). En todos ellos el marco teórico de trabajo ha sido la denominada Teoría de las Distancias Críticas. El procedimiento propuesto combina las correcciones por efecto entalla de dicha teoría con un Diagrama de Fallo básico, único para todos los materiales, y queda validado por su aplicación a 232 ensayos de fractura realizados sobre probetas entalladas.This paper presents a basic procedure for the integrity assessment of structural components containing notches. It is based on the works developed by the authors in the last five years analysing the notch effect in a wide range of materials, including PMMA, Al7075-T651, rocks such as granite and limestone and four structural steels (S275JR, S355J2, S460M and S690Q). In all cases the theoretical framework has been the Theory of Critical Distances. The procedure combines the notch effect corrections provided by such theory with a basic Failure Assessment Diagram, and has been successfully validated through its application to 232 fracture tests performed on notched specimens.Los autores de este trabajo desean agradecer al MINECO del Gobierno de España la financiación de los proyectos MAT2010-15721 y MAT2014-58443-P, de cuyos resultados se deriva este artículo

On the Line Method apparent fracture toughness evaluations: experimental overview, validation and some consequences on fracture assessments

This paper analyses the capacity of the Line Method to provide evaluations of the apparent fracture toughness, which is the fracture resistance exhibited by materials in notched conditions. With this aim, the experimental results obtained in 555 fracture tests are homogeneously presented and compared to the Line Method evaluations. It is remarked that the Line Method provides adequate estimates of the apparent fracture toughness, and also that it conveniently addresses the physics of the notch effect. All this makes the Line Method a valuable scientific and engineering tool for the fracture assessment of materials containing notches

Structural integrity analysis of notched ferritic steels operating within their ductile-to-brittle transition zone: An approach from Failure Assessment Diagrams and the Notch Master Curve

This paper provides a structural integrity assessment methodology for the analysis of ferritic steels containing notch-type defects and operating within their ductile-to-brittle transition zone. The methodology, based on the use of Failure Assessment Diagrams and the novel concept of the Notch Master Curve, has been applied to 323 experimental results performed on four different steels (S275JR, S355J2, S460M and S690Q), six different notch radii (from 0 mm up to 2.0 mm), two different types of specimens (CT and SENB), and three different temperatures within the corresponding ductile-to-brittle transition zone. The results validate the proposed assessment methodology

Assessment of notched structural steel components using failure assessment diagrams and the theory of critical distances

When the structural integrity of notched components is analysed, it is generally assumed that notches behave as cracks, something which generally provides overconservative results. The proposal of this paper consists, on the one hand, in the application of the theory of critical distances for the estimation of the notch fracture toughness and, therefore, for the conversion of the notched situation into an equivalent cracked situation in which the material develops a higher fracture resistance. On the other hand, once the notch fracture toughness has been defined, the assessment is performed using the failure assessment diagram methodology, and assuming that the notch effect on the limit load is negligible. The methodology has been applied to 336 CT notched fracture specimens made of two different structural steels, covering temperatures from the corresponding lower shelf up to the upper shelf, providing satisfactory results and a noticeable reduction in the overconservatism derived from the analyses in which the notch effect is not considered

Light emission from a scanning tunneling microscope: Fully retarded calculation

The light emission rate from a scanning tunneling microscope (STM) scanning a noble metal surface is calculated taking retardation effects into account. As in our previous, non-retarded theory [Johansson, Monreal, and Apell, Phys. Rev. B 42, 9210 (1990)], the STM tip is modeled by a sphere, and the dielectric properties of tip and sample are described by experimentally measured dielectric functions. The calculations are based on exact diffraction theory through the vector equivalent of the Kirchoff integral. The present results are qualitatively similar to those of the non-retarded calculations. The light emission spectra have pronounced resonance peaks due to the formation of a tip-induced plasmon mode localized to the cavity between the tip and the sample. At a quantitative level, the effects of retardation are rather small as long as the sample material is Au or Cu, and the tip consists of W or Ir. However, for Ag samples, in which the resistive losses are smaller, the inclusion of retardation effects in the calculation leads to larger changes: the resonance energy decreases by 0.2-0.3 eV, and the resonance broadens. These changes improve the agreement with experiment. For a Ag sample and an Ir tip, the quantum efficiency is $\approx$ 10$^{-4}$ emitted photons in the visible frequency range per tunneling electron. A study of the energy dissipation into the tip and sample shows that in total about 1 % of the electrons undergo inelastic processes while tunneling.Comment: 16 pages, 10 figures (1 ps, 9 tex, automatically included); To appear in Phys. Rev. B (15 October 1998

Application and validation of the notch master curve in medium and high strength structural steels

This paper applies and validates the Notch master curve in two ferritic steels with medium (steel S460M) and high (steel S690Q) strength. The Notch master curve is an engineering tool that allows the fracture resistance of notched ferritic steels operating within their corresponding ductile-to-brittle transition zone to be estimated. It combines the Master curve and the Theory of critical distances in order to take into account the temperature and the notch effect respectively, assuming that both effects are independent. The results, derived from 168 fracture tests on notched specimens, demonstrate the capability of the Notch master curve for the prediction of the fracture resistance of medium and high strength ferritic steels operating within their ductile-to-brittle transition zone and containing notches

Esomeprazole for the treatment of erosive esophagitis in children: an international, multicenter, randomized, parallel-group, double-blind (for dose) study

<p>Abstract</p> <p>Background</p> <p>Acid suppression with a proton pump inhibitor is standard treatment for gastroesophageal reflux disease and erosive esophagitis in adults and increasingly is becoming first-line therapy for children aged 1-17 years. We evaluated endoscopic healing of erosive esophagitis with esomeprazole in young children with gastroesophageal reflux disease and described esophageal histology.</p> <p>Methods</p> <p>Children aged 1-11 years with endoscopically or histologically confirmed gastroesophageal reflux disease were randomized to esomeprazole 5 or 10 mg daily (< 20 kg) or 10 or 20 mg daily (≥ 20 kg) for 8 weeks. Patients with erosive esophagitis underwent an endoscopy after 8 weeks to assess healing of erosions.</p> <p>Results</p> <p>Of 109 patients, 49% had erosive esophagitis and 51% had histologic evidence of reflux esophagitis without erosive esophagitis. Of the 45 patients who had erosive esophagitis and underwent follow-up endoscopy, 89% experienced erosion resolution. Dilation of intercellular space was reported in 24% of patients with histologic examination.</p> <p>Conclusions</p> <p>Esomeprazole (0.2-1.0 mg/kg) effectively heals macroscopic and microscopic erosive esophagitis in this pediatric population with gastroesophageal reflux disease. Dilation of intercellular space may be an important histologic marker of erosive esophagitis in children.</p> <p>Trial Registration</p> <p>D9614C00097; ClinicalTrials.gov identifier NCT00228527.</p

Analysis of notch effect on the fracture behaviour of granite and limestone: An approach from the Theory of Critical Distances

This paper presents the analysis of the notch effect on granite and limestone fracture specimens. The research is based on the results obtained in an experimental programme composed of 84 fracture specimens, combining the two materials and 7 different notch radii varying from 0.15 mm up to 10 mm. The notch effect is analysed through the evolution of the apparent fracture toughness and the application of the Theory of the Critical Distances. The results reveal a significant notch effect in the limestone, whereas the notch effect in the granite is negligible for the range of notch radii analysed. Both observations are justified by the corresponding critical distance of the material

Pairwise maximum entropy models for studying large biological systems: when they can and when they can't work

One of the most critical problems we face in the study of biological systems is building accurate statistical descriptions of them. This problem has been particularly challenging because biological systems typically contain large numbers of interacting elements, which precludes the use of standard brute force approaches. Recently, though, several groups have reported that there may be an alternate strategy. The reports show that reliable statistical models can be built without knowledge of all the interactions in a system; instead, pairwise interactions can suffice. These findings, however, are based on the analysis of small subsystems. Here we ask whether the observations will generalize to systems of realistic size, that is, whether pairwise models will provide reliable descriptions of true biological systems. Our results show that, in most cases, they will not. The reason is that there is a crossover in the predictive power of pairwise models: If the size of the subsystem is below the crossover point, then the results have no predictive power for large systems. If the size is above the crossover point, the results do have predictive power. This work thus provides a general framework for determining the extent to which pairwise models can be used to predict the behavior of whole biological systems. Applied to neural data, the size of most systems studied so far is below the crossover point