Can it be measured - Fracture Toughness from Repetitive Nano-impacts Test?

The design of coatings in the field of engineering applications aims at a progressive shift to the development of “hard but tough” coatings. The difficulty in assessing their mechanical behaviour by conventional methods is behind the growing relevance of “in situ” experiments using instrumented microindentation technique. This technique is one of the few able to investigate the mechanical properties along of whatever length range, i.e. from small volume to bulk material. Information from the load-depth curve of indentation has proven to be abundant and varied and it can be used to determine several mechanical properties such as: hardness, Young’s modulus, yield strength, viscoelastic properties, etc [[1]].In fact, from this technique the evaluation of wear-resistance by hardness and/or scratch testing have become in a routine in a multitude of different materials [[2]]. Nevertheless, the results are not always accurate, particularly when the surfaces are subjected to erosive wear during service and fail by a fatigue process. For the purpose of providing a solution, impact technique have been developed to extend the capability of depth-sensing indentation/scratch instrumentation to perform fatigue testing in a wide variety of surfaces, such as DLC and amorphous carbon [[3]], plasma electrolytic oxidation surface[[4]], polymers [[5]] and numerous coatings for cutting tools [[6]]. Along the experiment, this technique produces a repetitive impact with a high stresses and high strain rates, simulating the fatigue conditions under repetitive contact conditions, at the nano or micro-scale. Depending on the material ductility and the load magnitude, fracture of the surface may be achieved. Therefore, the question is whether from these tests it is possible to calculate fracture toughness values, KC, since conventional ways to determine fracture toughness by single edge notched beam (SENB), chevron notched beam (CVNB) and double cantilever beam (DCB) are not applicable for systems whose dimensions are between a few hundreds of nanometers to a few microns. Along this work, it will be studied the feasibility of using impact tests with a cube-corner tip using low loads, assuming that the indented coatings resembles the pattern for the fracture mode type I considered in the classical fracture toughness tests. For this purpose, fracture toughness calculation by impact test will be analysed first in a brittle bulk Al2O3 material, since its mechanical properties are well known. After this, fracture toughness of Al2O3 coating on ductile metallic substrate will be analysed for chequing the substrate contribution and the applicability of the classical indentation models, IM, in case of impact done at low loads. Finally, a novel method to determine the fracture toughness in metallic nanomultillayer coatings by impact test will be show. The design of coatings in the field of engineering applications aims at a progressive shift to the development of “hard but tough” coatings. The difficulty in assessing their mechanical behaviour by conventional methods is behind the growing relevance of “in situ” experiments using instrumented microindentation technique. This technique is one of the few able to investigate the mechanical properties along of whatever length range, i.e. from small volume to bulk material. Information from the load-depth curve of indentation has proven to be abundant and varied and it can be used to determine several mechanical properties such as: hardness, Young’s modulus, yield strength, viscoelastic properties, etc [[1]].In fact, from this technique the evaluation of wear-resistance by hardness and/or scratch testing have become in a routine in a multitude of different materials [[2]]. Nevertheless, the results are not always accurate, particularly when the surfaces are subjected to erosive wear during service and fail by a fatigue process. For the purpose of providing a solution, impact technique have been developed to extend the capability of depth-sensing indentation/scratch instrumentation to perform fatigue testing in a wide variety of surfaces, such as DLC and amorphous carbon [[3]], plasma electrolytic oxidation surface[[4]], polymers [[5]] and numerous coatings for cutting tools [[6]]. Along the experiment, this technique produces a repetitive impact with a high stresses and high strain rates, simulating the fatigue conditions under repetitive contact conditions, at the nano or micro-scale. Depending on the material ductility and the load magnitude, fracture of the surface may be achieved. Therefore, the question is whether from these tests it is possible to calculate fracture toughness values, KC, since conventional ways to determine fracture toughness by single edge notched beam (SENB), chevron notched beam (CVNB) and double cantilever beam (DCB) are not applicable for systems whose dimensions are between a few hundreds of nanometers to a few microns. Along this work, it will be studied the feasibility of using impact tests with a cube-corner tip using low loads, assuming that the indented coatings resembles the pattern for the fracture mode type I considered in the classical fracture toughness tests. For this purpose, fracture toughness calculation by impact test will be analysed first in a brittle bulk Al2O3 material, since its mechanical properties are well known. After this, fracture toughness of Al2O3 coating on ductile metallic substrate will be analysed for chequing the substrate contribution and the applicability of the classical indentation models, IM, in case of impact done at low loads. Finally, a novel method to determine the fracture toughness in metallic nanomultillayer coatings by impact test will be show. [1] W. C. Oliver, G. M. Pharr. J. Mater. Res. 1992;7:1564. [2] J.L. Meneve, J.F. Smith, N.M. Jennett, S.R. Saunders. Appl. Surf. Sci. 1996;100/101:64 [3]B. Beake. Surf. Coat. Technol. 2005:198:90 [4]J.M. Wheeler, C.A. Collier, J.M. Paillard, J.A. Curran. Surf. Coat. Technol. 2010;204:3399. [5]B. Beake, S. Goodes, J. Smith, F. Gao. J. Mater. Res. 2004;19:237. [6]B.D. Beake, V.M. Vishnyakov, J.S. Colligon. J. Phys. D Appl. Phys. 2011;4

Evaluación de la calidad asistencial y funcionalidad en el tratamiento de la artrosis prevalente de mano mediante dos técnicas quirúrgicas: artoplastia total vs tenosuspensión

El objetivo de este trabajo es evaluar la superioridad o no de la Prótesis total trapecio-metacarpiana tipo ARPE® frente a la Tenosuspensión en pacientes con Rizartrosis. Se llevará a cabo un estudio prospectivo protocolizado con 53 pacientes diagnosticados de Rizartrosis con características epidemiológicas y clínicas similares, de los cuales 26 serán candidatos a la prótesis tipo ARPE (Grupo 1) y 27 a la Tenosuspensión (Grupo 2). Realizando un seguimiento durante 1 año de los diferentes parámetros a evaluar. Ambas técnicas consiguen una reducción estadísticamente significativa del dolor (escala EVA), del DASH (afectación en las actividades de la vida diaria); y una mejoría del movimiento de oposición (Kapandji). Sin embargo, solo el Grupo 1 experimenta una mejoría del movimiento de abducción radial del pulgar y de la fuerza de la pinza, estadísticamente significativo. Mientras, que el Grupo 2 incluso experimenta un empeoramiento de la fuerza de la pinza. Así mismo, el Grupo 1 también experimenta mejores resultados en longitud del pulgar (precisión pinza) como en retropulsión. En conclusión, la Artroplastia Total Tipo ARPE ® ofrece unos mejores resultados en el postoperatorio inmediato, tanto en fuerza, como en movilidad y funcionalidad. Asegurando de este modo una rápida inserción laboral y social.Grado en Medicin

Structure and electrical behavior relationship of a magnesium–tellurite glass using Raman and impedance spectroscopy

In this paperwe present the study of the glassy systems of formula: xMgO(1−x)(0.5V2O5·0.5MoO3)2TeO2,with (0 b x b 1). The aim of the work is to understand the relationship between in the induced changes in the glassy matrix by the incorporation of MgO in a vanadium–tellurite glass and the electrical response of the material. It has been found that the incorporation of MgO in the glassy matrix raises the glass transition temperature. The whole system's electrical behavior is explained by the small polaron hopping, in good agreement with the variable range polaron hopping model. In this matrix, an ionic transport by Mg2+ is not allowed. The study gives an opportunity to understand how to tune in the middle-range glassy structural order and, as a direct implication, how to control the electrical conduction process.Instituto de Física La Plat

The fictitious diurnal cycle of aerosol optical depth: A new approach for “in situ” calibration and correction of AOD data series

Aerosol optical depth (AOD) very often shows a distinct diurnal cycle pattern, which seems to be an artifact. This phenomenon is the result of a deficient calibration (or an equivalent effect, as filter degradation). The fictitious sinusoidal shape of the AOD diurnal cycle is a function of the cosine of the solar zenith angle (SZA) and its effect is more accentuated during mid-day. The observation of this effect is not easy at current field stations and only those stations with excellent weather conditions permit an easier detection and correction. By taking advantage of this diurnal cycle behavior because of its dependence on the cosine of the SZA, we propose an improved “in situ” calibration correction procedure. The method is named KCICLO because the determination of a constant K and the behavior of AOD as a cycle (ciclo, in Spanish). It can be seen as a modification of the classical Langley technique (CLT) with the same level of accuracy when CLT is applied at high-altitude stations, and results in an accuracy of 0.2–0.5% for the calibration ratio constant K (or 0.002–0.005 in AOD). The application of this correction method to current and old data series at sunny stations is a significant improvement over “in situ” methods, because no other information beyond the AOD data is necessary

Crested Becard (Pachyramphus validus) in Entre Rios, Argentina

Presentamos el primer registro provincial del Anambé Grande (Pachyramphus validus) en Entre Ríos. Este fue realizado 260 km al sur del registro más cercano.We report the first observation of Crested Becard (Pachyramphus validus) in Entre Ríos Province. It was observed 260 km south from the closest known record.Fil: Jordan, Emilio Ariel. Provincia de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Universidad Autónoma de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción; ArgentinaFil: Reales, César Fabricio. Provincia de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Universidad Autónoma de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción; ArgentinaFil: Frutos, Antonio Esteban. Provincia de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Universidad Autónoma de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción; Argentin

Comparison between measurements and model simulations of solar radiation at a high altitude site: case studies for the Izaña BSRN Station [Póster]

Póster presentado en: International Radiation Symposium, celebrado del 6 al 10 de agosto de 2012 en Berlín, Alemania.Financial supports from the Spanish MICIIN for projects CGL2009-09740, CGL2011-23413 and CGL2010-09480E, CGL2011-13085-E are gratefully acknowledged. We authors to acknowledge the AERONET-PHOTONS-RIMA networks (http://aeronet.gsfc.nasa.gov) and the LibRadtran model (http://www.libradtran.org)

La estación BSRN de Izaña

Financial supports from the Spanish MICIIN (ref. CGL2008‐05939‐CO3‐00/CLI and CGL2009 09740) and from the GR‐220 Project of the Junta de Castilla y León are Gratefully acknowledged

Comparison between measurements and model simulations of solar radiation at a high altitude site: case studies for the Izaña BSRN Station

Financial supports from the Spanish MICIIN for projects CGL2009-09740, CGL2011-23413 and CGL2010-09480E, CGL2011-13085-E are gratefully acknowledged

Comparison of measured and modelled UV spectral irradiance at the Izaña Station based on Libradtran and UVA-GOA models

Póster elaborado para el 37th Annual European Meeting on Atmospheric Studies by Optical Methods celebrado en Valladolid los días 23-26 de agosto de 2010Financial supports from the Spanish MICIIN (ref. CGL2008-05939-CO3-00/CLI and CGL 2009-09740) and from the GR-220 Project of the Junta de Castilla y León are gratefully acknowledge

Comparación entre la irradiancia espectral UV medida experimentalmente en la estación de Izaña y simulada con los modelos de transferencia radiativa LibRadtran y UVA‐GOA

Financial supports from the Spanish MICIIN (projects CGL2008‐05939‐CO3‐00/CLI and CGL200909740) and from the GR‐220 Project of the “Junta de Castilla y León” are gratefully acknowledged