Online measurement and evaluation of the Er:YAG laser ablation process using an integrated OCT system

Laser surgery has gained clinical importance due to numerous advantages including contact-free processing, arbitrary cutting geometries, and high precision. However, online process control remains a challenge for widespread clinical use. Therefore, we established a combined setup of a pulsed Er:YAG laser ( = 2940 nm) and an optical coherence tomogra-phy (OCT) ( = 930 nm) for in situ monitoring of hard tissue ablation. The optical setup facilitates an interactive control of the laser ablation depth and remaining tissue strength through the depth resolution of OCT. The 3D OCT data-set, which is acquired after ablation, provides contours and layer thicknesses

El arte del bordado en Santiago de Compostela. Nuevos datos sobre bordadores de los siglos XVI y XVII

In this article there is contributed new information from Santiago de Compostela embroiderers of the 16th and 17th century. There includes news related to the life of these makers and to the artistic production of the same ones, that is to say, contracts, concerts, etc. It is the result of a meticulous work of investigation in the file of the Cathedral of Santiago de Compostela and in the Historical University of the same city. With it we try to penetrate into this plot of the Galician history of the art for many forgotten and to mark a point of item to future investigations.En este artículo se aportan nuevos datos de bordadores compostelanos de los siglos XVI y XVII. Se incluyen noticias relacionadas con la vida de estos artífices y con la producción artística de los mismos, es decir, contratos, conciertos, etc. Es el resultado de un minucioso trabajo de investigación en el archivo de la Catedral de Santiago de Compostela y en el Histórico Universitario de la misma ciudad. Con ello pretendemos profundizar en esta parcela de la historia del arte gallega por muchos olvidada y marcar un punto de partida a futuras investigaciones

Agricultura y pobreza en República Dominicana

Este trabajo trata de verificar si la pobreza está vinculada a los modelos productivos agrícolas de las provincias del país relacionando los niveles de pobreza de cada provincia con sus actividades agrarias principales. Como metodología se ha elegido los principales productos agrícolas sembrados y cosechados para correlacionarlos con la pobreza poblacional. Como resultado podemos decir que el mayor nivel de pobreza está en las provincias que se encuentra en la frontera con Haití, lo que es un indicador influyente. Haití tiene fuentes de ingresos restringidas; en cambio las provincias con un nivel de pobreza menor o media están localizadas al Este y al Norte del país, donde están la fuente del turismo y las siembras y cosechas de los principales cultivos. En conclusión, la identificación de los principales productos agrícolas de la República Dominicana es una buena base de partida para disminuir la pobreza con la generación de fuentes de ingresos para el país

Monotone continuous dependence of solutions of singular quenching parabolic problems

CRUE-CSIC (Acuerdos Transformativos 2022)Depto. de Análisis Matemático y Matemática AplicadaInstituto de Matemática Interdisciplinar (IMI)Fac. de Ciencias MatemáticasTRUEMinisterio de Ciencia e Innovación (MICINN)Universidad Complutense de Madridpu

Rate and temperature dependent plasticity and failure of AA7017-T73: experiments and modelling

En esta investigación se presenta el modelo de plasticidad utilizado para describir el comportamiento de la aleación de aluminio 7017-T73 bajo cargas uniaxiales. Para ello, se ha realizado una serie de ensayos de tracción uniaxial a diferentes velocidades de deformación con probetas mecanizadas en varias orientaciones con respecto a la dirección de laminación del material. Los resultados experimentales revelan que la AA7017-T73 presenta un alto grado de anisotropía tanto en el límite elástico como en el flujo plástico. También, cabe destacar que el material presenta muy poca sensibilidad a la velocidad de deformación. Además, la AA7017-T73 presenta deformaciones de rotura muy diferentes para cada orientación de carga. A la vista de los resultados experimentales obtenidos, para describir el comportamiento observado del material se emplea la función de plastificación Yld2000-3d con endurecimiento por deformación tipo Voce. Las simulaciones por elementos finitos muestran que el modelo de plasticidad utilizado es capaz de describir con precisión las respuestas local y global del material bajo cargas uniaxiales. Por último, se presenta el criterio de rotura Cockcroft-Latham para describir el comportamiento a fractura anisótropo de la AA7017-T73. A series of tensile tests on uniaxial specimens machined from different orientations with respect to the rolling direction was carried out at a wide range of loading rates for an aluminium 7017-T73 alloy. The experimental results revealed a high degree of anisotropy on both yield stress and plastic flow. In addition, the material showed very little strain-rate sensitivity. The measured fracture strains for different loading orientations showed large differences. In order to describe the material behaviour, the Yld2000-3d yield criterion and an isotropic Voce hardening model were used to describe the plasticity of the AA7017-T73. Finite element simulations showed that the plasticity model provided accurate predictions of local and global material responses under uniaxial loading. A Cockcroft-Latham failure criterion was presented for describing the anisotropic fracture behaviour of the AA7017-T73

Tenacidad de fractura dinámica de iniciación a diferentes velocidades de solicitación: técnicas experimentales

En esta investigación se presentan diversos dispositivos experimentales diseñados para la realización de ensayos de tenacidad de fractura a diferentes velocidades de solicitación. Se realizan ensayos de flexión en tres puntos de probetas normalizadas (ASTM E399) empleando una máquina servohidráulica, una torre de caída, una barra Hopkinson modificada y un dispositivo especialmente diseñado para trabajar con cargas explosivas. Para poder validar dichos dispositivos experimentales, se realizan estos ensayos sobre un material independiente de la velocidad de deformación; dicho material es la aleación de aluminio 7017-T73. Todos los ensayos realizados sobre dicha aleación dieron el mismo valor de tenacidad de fractura dinámica de iniciación; por lo tanto, los dispositivos experimentales diseñados se consideraron válidos para este fin. Una vez validada la técnica experimental, se llevan a cabo ensayos de flexión en tres puntos en un material dependiente de la velocidad de deformación. Por lo tanto, los dispositivos experimentales diseñados fueron utilizados para determinar la tenacidad de fractura dinámica de iniciación del acero Mars 240. Los resultados obtenidos muestran que, en el caso de este acero, la tenacidad de fractura dinámica de iniciación aumenta con la velocidad de solicitación. ---------- ABSTRACT---------- The design and development of different experimental devices for the purpose of performing fracture toughness tests at different loading-rates are presented. Three-point bending tests of pre-fatigued standard specimens (ASTM E399) were carried out employing a servo-hydraulic universal testing machine, a free-drop tower, a modified Split Hopkinson Pressure Bar and an explosive load transferring device. A rate-independent alloy, a 7017-T73 aluminium alloy, was selected in order to validate such devices. All of the 7017-T73 aluminium alloy experiments provided the same value of the dynamic fracture-initiation toughness. Therefore, the developed devices were validated and considered suitable for such a purpose. Fracture toughness test of a rate-dependent armour steel, a Mars240 steel, employing the developed devices, were performed in order to determine the evolution of the dynamic fracture-initiation toughness with the loading-rate. In this case, the dynamic fracture-initiation toughness values of the Mars 240 steel increased with the velocity of the application of the load

On the loading-rate dependence of the Al 7017-T73 fracture-initiation toughness

While static fracture toughness is a widely studied and standardised parameter, its dynamic counterpart has not been exhaustively examined. Therefore, in this research a series of quasi-static and different loading-rate dynamic tests were carried out to determine the evolution of fracture toughness with the velocity of the application of the load on aluminium 7017-T73 alloy. Three-point bending tests of pre-fatigued standard specimens (ASTM E399) at four loading-rates were carried out. The experiments were conducted by employing the subsequent apparatus ordered from lowest to highest load application velocity: a servo-hydraulic universal testing machine, a free-drop tower, a modified Split Hopkinson Pressure Bar and an explosive load testing device. In order to perform the dynamic fracture toughness tests, it was necessary to design and develop some experimental devices. The fracture-initiation toughness of the aluminium 7017-T73 alloy did not exhibit a significant variation for the studied cases. As a conclusion, the research showed that fracture-initiation toughness remained constant regardless of the velocity at which the load was applied

An experimental and numerical study of ductile failure under quasi-static and impact loadings of Inconel 718 nickel-base superalloy

A numerical and experimental study of ballistic impacts at various temperatures on precipitation hardened Inconel 718 nickel-base superalloy plates has been performed. A coupled elastoplastic-damage constitutive model with Lode angle dependent failure criterion has been implemented in LS-DYNA non-linear finite element code to model the mechanical behaviour of such an alloy. The ballistic impact tests have been carried out at three temperatures: room temperature (25 °C), 400 °C and 700 °C. The numerical study showed that the mesh size is crucial to predict correctly the shear bands detected in the tested plates. Moreover, the mesh size convergence has been achieved for element sizes on the same order that the shear bands. The residual velocity as well as the ballistic limit prediction has been considered excellent for high temperature ballistic tests. Nevertheless, the model has been less accurate for the numerical simulations performed at room temperature, being though in reasonable agreement with the experimental data. Additionally, the influence that the Lode angle had on quasi-static failure patterns such as cup-cone and slanted failure has been studied numerically. The study has revealed that the combined action of weakened constitutive equations and Lode angle dependent failure criterion has been necessary to predict the previously-mentioned failure pattern

Packaging Process Optimization in MultiheadWeighers with Double-Layered Upright and Diagonal Systems

[EN] In multihead weighers, packaging processes seek to find the best combination of passage hoppers whose product content provides a total package weight as close as possible to its (nominal) label weight. The weighing hoppers arranged in these machines dispense the product quantity that each package contains through computer algorithms designed and executed for this purpose. For its part, in the packaging process for double-layered multihead weighers, all hoppers are arranged in two levels. The first layer comprises a group of weighing hoppers, and the second comprises a set of booster hoppers placed uprightly or diagonally to each weighing hopper based on design of the machine. In both processes, the initial machine configuration is the same; however, the hopper selection algorithm works differently. This paper proposes a new packaging process optimization algorithm for double-layer upright and diagonal machines, wherein the hopper subset combined has previously been defined, and the packaging weight is expressed as actual values. As part of its validation, product filling strategies were implemented for weighing hoppers to assess the algorithm in different scenarios. Results from the process performance metrics prove that the new algorithm improves processes by reducing variability. In addition, results reveal that some machine configurations were also able to improve their operation.We express our gratitude for the support from Universidad Simon Bolivar, and Universitat Politecnica de Valencia.Garcia-Jimenez, R.; García-Díaz, JC.; Pulido-Rojano, ADJ. (2021). Packaging Process Optimization in MultiheadWeighers with Double-Layered Upright and Diagonal Systems. Mathematics. 9(9):1-20. https://doi.org/10.3390/math9091039S1209

Vehicle Reference Generator for Collision-Free Trajectories in Hazardous Maneuvers

This paper presents a reference generator for ground vehicles, based on potential fields adapted to the case of vehicular dynamics. The reference generator generates signals to be tracked by the vehicle, corresponding to a trajectory avoiding collisions with obstacles. This generator integrates artificial forces of potential fields of the object surrounding the vehicle. The reference generator is used with a controller to ensure the tracking of the accident-free reference. This approach can be used for vehicle autonomous driving or for active control of manned vehicles. Simulation results, presented for the autonomous driving, consider a scenario inspired by the so-called moose (or elk) test, with the presence of other collaborative vehicles