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

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

Servicio de Control Microbiológico (SCM), como Estrategia Didáctica para el laboratorio de Tecnología de Alimentos [Microbiological Control Service, as Didactic Strategy for Food Technology Lab]

Servicio de Control Microbiológico (SCM) es una Estrategia Didáctica dirigida a alumnos de Laboratorios de: Tecnología de Alimentos (LABTEC) y Microbiología de Alimentos (LMA), en la Facultad de Química (FQ) de la Universidad Nacional Autónoma de México (UNAM). Se basa en el desempeño de roles profesionales, donde alumnos de LABTEC que elaboran alimentos actúan como productores que requieren análisis microbiológicos; los alumnos de LMA actúan como proveedores del servicio de control microbiológico. Se elaboran solicitudes y reportes formales, basados en normas de referencia, para que se pueda concluir sobre la calidad higiénica del alimento. La estrategia ha permitido a los participantes, una experiencia muy cercana al ejercicio profesional, para evaluar buenas prácticas de manufactura, trabajo individual y en equipo. Todos desarrollaron habilidades de comunicación profesional, solución de problemas y conciencia sobre la importancia de la calidad higiénica de los alimentos. El control microbiológico en LABTEC se ha realizado sin recursos adicionales, pues se aplican aquellos destinados a las prácticas de LMA. Además de la experiencia de aprendizaje, se está generando mejora continua en ambas asignaturas. [Microbiological control service (SCM) as a didactic strategy is aimed to those students in laboratories of food technology (LABTEC) and food microbiology (LMA), at the Universidad Nacional Autónoma de México’s School of Chemistry (FQ). It is based in professional role playing; LABTEC students elaborate the products and act as food producers in need of microbiological analysis; LMA students perform as service providers, for microbiological control. They elaborate formal requests and microbiological analysis report, based on mandatory standards, which can lead to conclusions about product’s hygienic quality. The strategy has given students an experience close to professional practice, to evaluate good manufacturing practices, individual and team work. All developed professional communication skills, problems identification and proposals for solving them, as well as consciousness about the importance of hygienic quality of food. The microbiological control in LABTEC has been carried out without the need for additional resources, since those intended for LMA practices are applied to these real samples. The experience is generating continuous improvement in both courses.