A "quick look" at ultrafast ablation using fs-resolved phase-change microscopy

A pump-probe phase-change microscope with fs temporal resolution has been used to understand the transformation induced in the sample surface as a consequence of laser-matter interaction.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Equivalent Conicity and Curve Radius Influence on Dynamical Performance of Unconventional Bogies. Comparison Analysis

In this paper the dynamic behaviour of several unconventional bogies is compared. The study takes into account the radius of the curve and the maximum level of wear allowed to the wheels. Ranges of conicities and curve radius in which each bogie is advantageous are studied, for both high-speed and urban transit vehicles. Simulations have been carried out using an in house software that makes it possible to solve the wheel-rail contact problem in 3D, and to simulate accurately the negotiation of very sharp curves

Femtosecond time-resolved phase-change microscopy and ablation threshold calculations to understand ultrafast laser ablation

El trabajo recoge experimentos realizados en una configuración sonda-prueba haciendo uso de un láser de femtosegundos, con el objetivo de comprender los fenómenos de ablación de materiales sólidos ras irradiación con láseres de pulso ultracorto.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Optimización del proceso productivo de una nueva levadura osmotolerante y validación del sistema de limpieza CIP en las instalaciones de la planta industrial

Hoy en díael objetivo principal de cualquier industriaalimentaria es fabricarproductos seguros y de alta calidad al mínimo coste posible. Para ello,es necesario optimizarlos procesos productivosaprovechando al máximo los recursos disponibles,y mejorarlosprocesos de limpiezagarantizando la inocuidad de las instalaciones. Los objetivos delpresente trabajo sonoptimizar el proceso productivo de una levadura osmotolerante de panadería y validar el sistemade limpieza CIP. En primer lugar, se realizarontres pruebas de fermentación de lanueva levadura en distintas condiciones y se estudiarondiferentes parámetros esenciales para suposiblecomercialización. Por otro lado, fue necesario realizarunavalidación del sistema de limpieza CIP, ya que en los protocolos de limpieza se hicieronuna serie de modificaciones con el fin de mejorar la eficacia del proceso y conseguir un ahorro económico. La conductividad de la sosa utilizadaen la limpieza alcalina se bajó a 70 miliSiemens (mS)yse añadióun nuevo aditivo detergente llamado DEPTA+ con propiedades antiespumantes, mojantes y complejantes. Para la validación, se realizaronanálisis fisicoquímicos y microbiológicos con el objetivode demostrar que los parámetros del sistema de limpieza CIP son capaces de lograr el propósito establecido.Departamento de Ingeniería Agrícola y ForestalMáster en Calidad, Desarrollo e Innovación de Alimentos2022202

Design of an optimised wheel profile for rail vehicles operating on two track gauges

This paper sets out an optimum synthesis methodology for wheel profiles of railway vehicles in order to secure good dynamic behaviour with different track configurations. Specifically, the optimisation process has been applied to the case of rail wheelsets mounted on double gauge bogies, that move over two different gauges, which also have different types of rail: the Iberian gauge (1668 mm) and the UIC gauge (1435 mm). Optimisation is performed using Genetic Algorithms and traditional optimisation methods in a complementary way. The objective function used is based on an ideal equivalent conicity curve which ensures good stability on straight sections and also proper negotiation of curves. To this end the curve is constructed in such a way that it is constant with a low value for small lateral wheelset displacements (with regard to stability), and increases as the displacements increase (to facilitate negotiation of curved sections). Using this kind of ideal conicity curve also enables a wheel profile to be secured where the contact points have a larger distribution over the active contact areas, making wear more homogeneous and reducing stresses. The result is a wheel profile with a conicity that is closer to the target conicity for both gauges studied, producing better curve negotiation while maintaining good stability on straight sections of track. The paper shows the resultant wheel profile, the contact curves it produces, and a number of dynamic analyses demonstrating better dynamic behaviour of the synthesised wheel on curved sections with respect to the original wheel.Spanish Research Ministry MICINN through contract TRA2010-18386 including the FEDER funds of the European Union. The Basque Government through IT-453-10 and Research Grant BFI08.172. UPV/EHU through the training and research unit UFI11/29

On the influence of conformity on wheel–rail rolling contact mechanics

The aim of this work is to assess the effects of conformity on local contact related quantities at the wheel–rail interface such as traction distributions, subsurface stresses and frictional work distributions. For this purpose conformal contact analyses are carried out by means of Finite Element (FE) models, and also with the exact rolling contact theory approach developed by Kalker, which has been appropriately adapted by the authors in order to take into account some of the effects of conformity. On the other hand, equivalent cases are analysed without taking into account the effects of conformity. In this way, the validity of the hypothesis of non-conformity is evaluated in different cases with varying degrees of conformity.Spanish Research Ministry MICINN/Economy and Competitiveness Ministry MINECO through contracts TRA2014-59599-R, including funding by the FEDER-ERDF European Regional Development Fund. Basque Government through IT.691-13-IT.919-16. The financial assistance received from UPV/ EHU through training and research unit UFI-11/29

On the non-proportionality between wheel/rail contact forces and speed during wheelset passage over specific welds

This study investigates the influence on the wheel-rail contact forces of the running speed and the shape and position of weld defects along the track. For this purpose, a vertical dynamic model in the space domain is used. The model is obtained from the transformation between the domains of frequency and space using a Rational Fraction Polynomials (RFP) method, which is modified with multiobjective genetic algorithms in order to improve the fitting of track receptance and to assist integration during simulations. This produces a precise model with short calculation times, which is essential to this study. The wheel-rail contact is modelled using a non-linear Hertz spring. The contact forces are studied for several types of characteristic welds. The way in which forces vary as a function of weld position and running speed is studied for each type of weld. This paper studies some of the factors that affect the maximum forces when the vehicle moves over a rail weld, such as weld geometry, parametric excitation and contact stiffness. It is found that the maximum force in the wheel-rail contact when the vehicle moves over a weld is not always proportional to the running speed. The paper explains why it is not proportional in specific welds.This work was partly financed by the European Horizon 2020 Joint Technology Initiative Shift2Rail through contract No 730841. The authors also wish to thank the Spanish Research Ministry MICINN/Economy and Competitiveness Ministry MINECO for their funding through contract TRA2014-59599-R, including funding by the FEDER-ERDF European Regional Development Fund, and also the Basque Government for financial assistance through IT919-16. The financial assistance received from UPV/EHU through the training and research unit UFI11/29 is likewise gratefully acknowledged

On the study of train-track dynamic interactions caused by rail welds on discrete supported rails

The paper studies the influence of rail weld dip on wheel-rail contact dynamics, with particular reference to freight trains where it is important to increase the operating speed and also the load transported. This has produced a very precise model, albeit simple and cost-effective, which has enabled train-track dynamic interactions over rail welds to be studied to make it possible to quantify the influence on dynamic forces and displacements of the welding geometry; of the position of the weld relative to the sleeper; of the vehicle's speed; and of the axle load and wheelset unsprung mass. It is a vertical model on the spatial domain and is drawn up in a simple fashion from vertical track receptances. For the type of track and vehicle used, the results obtained enable the quantification of increases in wheel-rail contact forces due to the new speed and load conditions.Spanish Research Ministry MICINN/Economy and Competitiveness Ministry MINECO through contract TRA2010-18386, including funding by the FEDER-ERDF European Regional Development Fund. Basque Government for financial assistance through IT-453-10 and IT-691-13 as well as for Research Grant BFI08.172. UPV/EHU through the training and research unit UFI11/29

Predicting rail corrugation in a real line by means of a fast non-linear vertical and lateral model

This work is the result of a problem of premature development of rail corrugation found on a new metro line. As urgent solutions, a rail grinding was carried out and friction modifier started to be applied. Experimental corrugation measurements have been taken periodically in this line at 60 control points since 2018, and an extensive database has been collected since then. As a second stage, a computationally efficient new model has been developed to predict corrugation growth under different running conditions. The aim of this work has been to obtain feasible solutions to delay corrugation growth in metro type lines.The authors gratefully acknowledge financial support from the European Horizon 2020 Joint Technology Initiative Shift2Rail (IN2TRACK3) [101012456], from the Spanish Research Ministry MICINN/Economy and Competitiveness Ministry MINECO and MCI/AEI [PID2019-109483RB-I00], including funding by the FEDER-ERDF European Regional Development Fund, and from the Basque Government [IT1764-22, PRE_2021_2_0047, KK-2023/00029]