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Eibar, Spain

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Kronberger M.,University of Ljubljana | Pagano F.,Tekniker IK4 | Pejakovi V.,Tekniker IK4 | Pejakovi V.,ACT Research GmbH | And 3 more authors.
Lubrication Science | Year: 2014

The structural impact of ionic liquids was systematically investigated by assessing their behaviour as lubricant additives in two different biodegradable esters (refined rapeseed oil and synthetic ester). Cations were mainly based on derivatives of the tetraalkyl ammonium structure; the anions were alkyl sulfate, methyl sulfonate or bis(trifluoromethylsulfonyl)imide. Miscibility experiments showed that ultrasound treatment yielded the most stable emulsions. X-ray fluorescence was employed to determine maximum concentrations, at which ionic liquids formed stable mixtures in the base oil, either dissolved or as self-stabilized emulsions. Steel/steel contacts lubricated with such saturated rapeseed oil blends were investigated in a reciprocating sliding tester at room temperature and at 100° C. For most anions, a significant reduction of friction and wear was found at ionic liquid concentrations of less than 0.1 weight%. At substantially higher concentrations, a destabilisation of the ionic liquid-ester mixtures was observed, which was accompanied by a loss of wearpreventive properties. © 2014 John Wiley & Sons, Ltd.


Coto B.,Tekniker IK4 | Antia I.,Tekniker IK4 | Blanco M.,Tekniker IK4 | Martinez-De-Arenaza I.,University of the Basque Country | And 3 more authors.
Computational Materials Science | Year: 2011

The effect of carboxylation on axial Young's modulus of carbon nanotubes is investigated using a molecular dynamics (MD) approach. COMPASS force field is used to model the interatomic interactions in single wall (SWCNT) and multiwall carbon (MWCNT) with different amounts of -COOH groups attached to their surfaces. The results of the MD simulations show how an increase of the number of carboxylic groups on the CNT surface leads to a decrease on the Young moduli of the CNTs. The decrease of MWCNT Young's modulus is found to be lower than in the case of SWCNT. © 2011 Elsevier B.V. All rights reserved.


Barrenetxea D.,Ideko IK4 S. Coop. | Alvarez J.,Ideko IK4 S. Coop. | Marquinez J.I.,Ideko IK4 S. Coop. | Madariaga J.,Tekniker IK4 | And 3 more authors.
Journal of Manufacturing Science and Engineering, Transactions of the ASME | Year: 2010

This paper presents new simulation models and global stability charts that have been developed to analyze the principal instabilities and constraints involved in the throughfeed centerless grinding process. In addition to a frequency domain stability analysis of the three characteristic instabilities of the process (geometric lobing, chatter and spinning), new models have been developed and implemented to analyze the other main restrictions, namely, process power, temperature and burning power, roughness, and final part geometrical tolerance due to machine compliance. As a result, new global stability charts have been devised where instabilities are plotted against different productivity rates by combining the two principal variables in the throughfeed process: Regulating wheel speed and feed angle. The use of such charts has led to the development of new optimization strategies for throughfeed operation mode and their implementation in a web based SET-UP ASSISTANT software tool developed to improve machining accuracy and productivity in centerless grinding. Copyright © 2010 by ASME.


Villar A.,Tekniker IK4 | Gorritxategi E.,Tekniker IK4 | Otaduy D.,Tekniker IK4 | Ciria J.I.,Tekniker IK4 | Fernandez L.A.,University of the Basque Country
Analytica Chimica Acta | Year: 2011

This paper describes the calibration process of a Visible-Near Infrared sensor for the condition monitoring of a gas engine's lubricating oil correlating transmittance oil spectra with the degradation of a gas engine's oil via a regression model. Chemometric techniques were applied to determine different parameters: Base Number (BN), Acid Number (AN), insolubles in pentane and viscosity at 40. °C. A Visible-Near Infrared (400-1100 nm) sensor developed in Tekniker research center was used to obtain the spectra of artificial and real gas engine oils.In order to improve sensor's data, different preprocessing methods such as smoothing by Saviztky-Golay, moving average with Multivariate Scatter Correction or Standard Normal Variate to eliminate the scatter effect were applied. A combination of these preprocessing methods was applied to each parameter. The regression models were developed by Partial Least Squares Regression (PLSR). In the end, it was shown that only some models were valid, fulfilling a set of quality requirements. The paper shows which models achieved the established validation requirements and which preprocessing methods perform better. A discussion follows regarding the potential improvement in the robustness of the models. © 2011 Elsevier B.V.


Susperregi L.,TEKNIKER IK4 | Sierra B.,University of the Basque Country | Martinez-Otzeta J.M.,TEKNIKER IK4 | Lazkano E.,University of the Basque Country | Ansuategui A.,TEKNIKER IK4
Advances in Intelligent and Soft Computing | Year: 2012

In this paper we propose a novel approach for low cost multimodal detection of humans with mobile service robots. Detecting people is a key capability for robots that operate in populated environments. The main objective of this article is to illustrate the implementation of machine learning paradigms with computer vision techniques to improve human detection using 3D vision and a thermal sensor. Experimental results carried out in a manufacturing shop-floor show that the percentage of wrong classified using only Kinect is drastically reduced with the classification algorithms and with the combination of the three information sources. © 2012 Springer-Verlag.


Barrenetxea D.,Ideko IK4 | Alvarez J.,Ideko IK4 | Monedero A.,Ideko IK4 | Madariaga J.,Tekniker IK4 | Akorta A.,GOIMEK S. Coop
CIRP Annals - Manufacturing Technology | Year: 2013

Achieving and maintaining geometrical accuracy is nowadays the main limiting factor to accomplish an efficient manufacturing process in the surface grinding of big components. The present paper shows a deep research work carried out by means of experimental measurements of shape deviations, infrared pictures of the temperature field distributions and corresponding FEM simulations that confirm the thermal origin as one of the main limiting factors. A deeper investigation about the influence of the environment and cooling conditions, constraints imposed by part clamping and the grinding conditions reveals that the compensation and even control of thermal effects is possible by combining IR monitoring, modeling and simulation, although still being a challenging methodology. © 2013 CIRP.


Barrenetxea D.,Ideko IK4 | Alvarez J.,Ideko IK4 | Madariaga J.,Tekniker IK4 | Gallego I.,University of Mondragon
CIRP Annals - Manufacturing Technology | Year: 2011

Multiple diameter part applications cope a relevant percentage of infeed centerless grinding operations. Nevertheless, general stability analysis and process optimisation has been mainly investigated for mono-diameter parts. This paper presents a time domain simulation software developed for multiple diameter parts that allows the simulation of average and particular evolution of process forces, power, machine deflections, thermal behaviour, real part diameter and roughness. First, a work rotation stability analysis is carried out. Then, with the use of both the stability analysis and the infeed cycle simulation, optimized process parameters and cycles are defined in order to increase process productivity. © 2011 CIRP.


Tellaeche A.,Tekniker IK4 | Arana R.,Name of Institution 2
IEEE International Conference on Emerging Technologies and Factory Automation, ETFA | Year: 2013

Injection molding is a very complicated process to monitor and control. With its high complexity and many process parameters, the optimization of these systems is a very challenging problem. To meet the requirements and costs demanded by the market, there has been an intense development and research with the aim to maintain the process under control. This paper outlines the latest advances in algorithms for plastic injection process and monitoring, and presents a real case of application that verifies their performance. © 2013 IEEE.


Soriano C.,Tekniker IK4 | Leunda J.,Tekniker IK4 | Lambarri J.,Tekniker IK4 | Garcia Navas V.,Tekniker IK4 | Sanz C.,Tekniker IK4
Applied Surface Science | Year: 2011

A study of the laser surface hardening process of two austempered ductile iron grades, with different austempering treatments has been carried out. Hardening was performed with an infrared continuous wave Nd:YAG laser in cylindrical specimens. The microstructure of the laser hardened samples was investigated using an optical microscope, microhardness profiles were measured and surface and radial residual stresses were studied by an X-ray diffractometer. Similar results were achieved for both materials. A coarse martensite with retained austenite structure was found in the treated area, resulting in a wear resistant effective layer of 0.6 mm to 1 mm with a microhardness between 650 HV and 800 HV. Compressive residual stresses have been found at the hardened area being in agreement with the microhardness and microstructural variations observed. The achieved results point out that the laser surface hardening is a suitable method for improving the mechanical properties of austempered ductile irons. © 2011 Elsevier B.V.


Fernandez I.,Tekniker IK4 | Alegria I.,IXA Group | Ezeiza N.,IXA Group
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2011

Resolving Named Entity Disambiguation task with a small knowledge base makes the task more challenging. Concretely, we present an evaluation of the state-of-the-art methods in this task for Basque NE disambiguation based on the Basque Wikipedia. We have used MFS, VSM, ESA and UKB for linking any ambiguous surface NE form occurrence in a text with its corresponding Wikipedia entry in the Basque Wikipedia version. We have analysed their performance with different corpora and as it was expected, most of them perform worse than when using big Wikipedias such as the English version, but we think these results are more realistic for less-resourced languages. We propose a new normalization factor for ESA to minimise the effect of the knowledge base size. © 2011 Springer-Verlag.

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