Artículos de revista DING - INGS Aldizkari artikuluak

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Open Access
Analysis of thermal stresses in unsymmetric cross-ply composite strips
(SAGE, 2008) Carbajal, N.; Vargas Silva, Gustavo Adolfo; Arrese, A.; Mujika, Faustino; Ingeniería; Ingeniaritza
An approach based on the hypotheses of the classical beam theory for determining thermal stresses in unsymmetric cross-ply strips has been developed. The material behavior is considered linear elastic, and viscoelastic effects are not considered. By supposing linear strain distribution in the cross-sections, the position of the neutral axis, the radius of curvature and the distribution of thermal stresses have been determined. The analysis is valid in the case of large displacements, since the curvature is constant and the deformed shape is an arc of circumference. Five different lay-up configurations of strip geometry specimens have been used for experimental verification. Mid-point deflections have been measured and compared with theoretical values, applying both the proposed approach and the classical laminated plates theory.
Open Access
Analysis of in-plane and out-of-plane thermo-mechanical stresses in un-symmetric cross-ply curved laminated strips
(SAGE, 2009) Vargas Silva, Gustavo Adolfo; Arrese, A.; Carbajal, N.; Mujika, Faustino; Ingeniería; Ingeniaritza
A new approach for determining in-plane and out-of-plane stresses due to thermal and mechanical loading, in un-symmetric [0n/90 m] cross-ply curved laminated strips is presented in this work. This approach can also be applicable to bi-modulus curved laminated strips. Predictions of curvatures, displacements, and stresses based on the superposition principle are carried out. In-plane stresses are calculated considering classical beam theory. In addition, out-of-plane stresses are predicted by using the Airy¿s stress function in polar coordinates. The new approach satisfies the continuity conditions at the interface between 0° and 90° layers. Results show that in-plane and out-of-plane stresses are particularly sensitive to the thickness ratio and to geometric conditions. Finally, thermo-mechanical predictions have revealed that out-of-plane stresses are much lesser than in-plane stresses for initially flat laminates. For laminates with high imposed curvatures out-of-plane stresses are high, leading to delamination failure.
Open Access
Mechanical properties dependency of the pearlite content of ductile iron
(Association for Computational Materials Science and Surface Engineering, 2009) Gonzaga Jarquín, Rafael; Martínez Landa, Paulino; Pérez Ezcurdia, Amaya; Villanueva Roldán, Pedro; Ingeniería; Ingeniaritza
Open Access
An antibacterial surface coating composed of PAH/SiO2 nanostructurated films by layer by layer
(Wiley, 2010) Urrutia Azcona, Aitor; Rivero Fuente, Pedro J.; Ruete Ibarrola, Leyre; Goicoechea Fernández, Javier; Fernández Valdivielso, Carlos; Arregui San Martín, Francisco Javier; Matías Maestro, Ignacio; Ingeniería; Ingeniaritza; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2; Institute of Smart Cities - ISC
In this work we propose a novel antibacterial coating composed of SiO2 and the polymer Poly(allylamine hydrochloride) (PAH). The coating was fabricated by the technique Layer-by-Layer (LbL). This technique has already been used in previous works, and it has the advantage that it allows to control the construction of nanosized and well organized multilayer films. Here, the new nanotexturized LbL SiO2 surface acts as antibacterial agent. The fabricated coatings have been tested in bacterial cultures of genus Lactobacillus to observe their antibacterial properties. It has been demonstrated these PAH/SiO2 coating films have a very good antimicrobial behaviour against this type of bacteria.
Open Access
Conversion of a commercial spark ignition engine to run on hydrogen: performance comparison using hydrogen and gasoline
(Elsevier, 2010) Sopena Serna, Carlos; Diéguez Elizondo, Pedro; Sáinz Casas, David; Urroz Unzueta, José Carlos; Guelbenzu, E.; Gandía Pascual, Luis; Ingeniería; Ingeniaritza
The modifications performed to convert the spark ignition gasoline-fueled internal combustion engine of a Volkswagen Polo 1.4 to run with hydrogen are described. The car is representative of small vehicles widely used for both city and interurban traffic. Main changes included the inlet manifold, gas injectors, oil radiator and the electronic management unit. Injection and ignition advance timing maps were developed for lean mixtures with values of the air to hydrogen equivalence ratio (λ) between 1.6 and 3. The established engine control parameters allowed the safe operation of the hydrogen-fueled engine (H2ICE) free of knock, backfire and pre-ignition as well with reasonably low NOx emissions. The H2ICE reached best brake torque of 63 Nm at 3800 rpm and maximum brake power of 32 kW at 5000 rpm. In general, the brake thermal efficiency of the H2ICE is greater than that of gasoline-fueled engine except for the H2ICE working at very lean conditions (λ = 2.5) and high speeds (above 4000 rpm). A significant effect of the spark advance on the NOx emissions has been found, specially for relatively rich mixtures (λ < 2). Small changes of spark advance with respect to the optimum value for maximum brake torque give rise to an increase of pollutant emissions. It has been estimated that the hydrogen-fueled Volkswagen Polo could reach a maximum speed of 140 km/h with the adapted engine. Moreover, there is enough reserve of power for the vehicle moving on typical urban routes and routes with slopes up to 10%.
Open Access
Determination of in-plane shear strength of unidirectional composite materials using the off-axis three-point flexure and off-axis tensile tests
(SAGE, 2010) Vargas Silva, Gustavo Adolfo; Mujika, Faustino; Ingeniería; Ingeniaritza
The aim of this work is to compare from an experimental point of view the determination of in-plane shear strength of unidirectional composite materials by means of two off-axis tests: three-point flexure and tensile. In the case of the off-axis three-point flexure test, the condition of small displacements and the condition of lift-off between the specimen and the fixture supports have been taken into account. Some considerations regarding stress and displacement fields are presented. The in-plane shear characterization has been performed on a carbon fiber reinforced unidirectional laminate with several fiber orientation angles: 10°, 20°, 30°, and 45°. Test conditions for both off-axis experimental methods, in order to ensure their applicability, are presented. Off-axis flexure test is considered more suitable than off-axis tensile test for the determination of in-plane shear strength.
Open Access
A new method for determining mode II R-curve by the End-Notched Flexure test
(Elsevier, 2010-01-01) Arrese, A.; Carbajal, N.; Vargas Silva, Gustavo Adolfo; Mujika, Faustino; Ingeniería; Ingeniaritza
A new method for obtaining the mode II R-curve in a End-Notched Flexure test is proposed in the present work. New compliance and energy release rate equations have been derived incorporating shear, local deformation and bending rotation effects. Mode II R-curve, which represents energy release rate as a function of crack extension, is obtained without optical determination of crack tip position. Crack length and energy release rate are determined at each point of the test based on experimental compliance until unstable advance occurs. In order to confirm the theoretical models, unidirectional carbon/epoxy specimens have been tested. Experimental data are evaluated by means of two reduction schemes: an existing data method named Corrected Beam Theory with effective crack length and the new method named Beam Theory including Bending Rotation effects. Shear and local deformation effects are included in both reduction schemes. Results concerning the determination of crack length without crack advance and during stable crack propagation are presented. The agreement between experimental values and theoretical results obtained by the new approach is excellent. Based on the accurate crack length determination at each point of the test, energy release rate is determined point to point and therefore R-curve is obtained.
Open Access
Determination of in-plane shear properties by three-point flexure test of ±45° anti-symmetric laminates
(Elsevier, 2011) Vargas Silva, Gustavo Adolfo; Mujika, Faustino; Ingeniería; Ingeniaritza
The aim of this work is to propose a new method for determining both the in-plane shear modulus and the in-plane shear strength of composite materials by using three-point flexure tests on [±45] angle-ply laminates. Symmetric and anti-symmetric configurations have been analysed by Classical Laminated Plate Theory. The anti-symmetric configuration has been considered more suitable than the symmetric one, due to the absence of bending/twisting coupling effects. Three-point bending tests have been performed on [±45] anti-symmetric laminates of AS4/8552 carbon/epoxy material. Experimental results obtained by flexure tests in anti-symmetric laminates agree with the values attained by tensile tests on symmetric laminates, and with values reported in literature. Experimental conditions for determining in-plane shear properties by using the anti-symmetric three-point bending method are recommended.
Open Access
Conversion of a gasoline engine-generator set to a bi-fuel (hydrogen/gasoline) electronic fuel-injected power unit
(Elsevier, 2011) Sáinz Casas, David; Diéguez Elizondo, Pedro; Urroz Unzueta, José Carlos; Sopena Serna, Carlos; Guelbenzu, E.; Pérez Ezcurdia, Amaya; Benito Amurrio, Marta; Marcelino Sádaba, Sara; Arzamendi Manterola, Gurutze; Gandía Pascual, Luis; Ingeniería; Ingeniaritza
The modifications performed to convert a gasoline carbureted engine-generator set to a bi-fuel (hydrogen/gasoline) electronic fuel-injected power unit are described. Main changes affected the gasoline and gas injectors, the injector seats on the existing inlet manifold, camshaft and crankshaft wheels with their corresponding Hall sensors, throttle position and oil temperature sensors as well as the electronic management unit. When working on gasoline, the engine-generator set was able to provide up to 8 kW of continuous electric power (10 kW peak power), whereas working on hydrogen it provided up to 5 kW of electric power at an engine speed of 3000 rpm. The air-to-fuel equivalence ratio (λ) was adjusted to stoichiometric (λ = 1) for gasoline. In contrast, when using hydrogen the engine worked ultra-lean (λ = 3) in the absence of connected electric load and richer as the load increased. Comparisons of the fuel consumptions and pollutant emissions running on gasoline and hydrogen were performed at the same engine speed and electric loads between 1 and 5 kW. The specific fuel consumption was much lower with the engine running on hydrogen than on gasoline. At 5 kW of load up to 26% of thermal efficiency was reached with hydrogen whereas only 20% was achieved with the engine running on gasoline. Regarding the NOx emissions, they were low, of the order of 30 ppm for loads below 4 kW for the engine-generator set working on hydrogen. The bi-fuel engine is very reliable and the required modifications can be performed without excessive difficulties thus allowing taking advantage of the well-established existing fabrication processes of internal combustion engines looking to speed up the implementation of the energetic uses of hydrogen.
Open Access
An antibacterial submicron fiber mat with in situ synthesized silver nanoparticles
(Wiley, 2012) Rivero Fuente, Pedro J.; Urrutia Azcona, Aitor; Goicoechea Fernández, Javier; Rodríguez, Yoany; Corres Sanz, Jesús María; Arregui San Martín, Francisco Javier; Matías Maestro, Ignacio; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute of Smart Cities - ISC; Ingeniería; Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2
This work presents an alternative approachfor fabricating electrospun submicron highly hydrophilicfiber mats loaded with silver nanoparticles. These fiber matsshow a high efficient antibacterial behavior, very attractivefor applications like wound healing and skin regenerationprocesses. The fabrication method is divided in two steps.First, poly(acrylic acid) (PAA) and b-cyclodextrin (b-CD)submicron fibers were electrospun and further stabilizedusing a thermal treatment, yielding stable hydrogel-likefibers with diameters ranging from 100 nm up to severalmicrons. In the second step, silver ions were loaded into thefibers and then reduced to silver nanoparticles in-situ. Theelectrospinning parameters were adjusted to achieve thedesired properties of the fiber mat (density, size) and after-wards, the characteristics of the silver nanoparticles(amount, size, aggregation) were tuned by controlling thesilver ion loading mechanism. Highly biocide surfaces wereachieved showing more than 99.99% of killing efficiency.The two-step process improves the reproducibility and tun-ability of the fiber mats. To our knowledge, this is the firsttime that stable hydrogel fibers with a highly biocide behav-ior have been fabricated using electrospinning.
Open Access
Humidity sensor based on silver nanopartlcles embedded in a polymeric coating
(Sciendo, 2012) Rivero Fuente, Pedro J.; Urrutia Azcona, Aitor; Goicoechea Fernández, Javier; Arregui San Martín, Francisco Javier; Matías Maestro, Ignacio; Ingeniería; Ingeniaritza; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2; Institute of Smart Cities - ISC
In this work, it is presented a novel optical fiber humidity sensor based on silver nanoparticle-loaded polymeric coatings built onto an optical fiber core. The polymeric film was fabricated using the Layer-by-Layer assembly technique. The silver nanoparticles (Ag NPs) were characterized using transmission electron microscopy (TEM and UV-VIS spectroscopy. A Localized Surface Plasmon Resonance (LSPR) attenuation band is observed when the thickness of the coating increases, and showed a very good sensitivity to Relative Humidity (RH) variations, suitable for high performance applications such as human breathing monitoring.
Open Access
Conversion of a commercial gasoline vehicle to run bi-fuel (hydrogen-gasoline)
(Elsevier, 2012) Sáinz Casas, David; Diéguez Elizondo, Pedro; Sopena Serna, Carlos; Urroz Unzueta, José Carlos; Gandía Pascual, Luis; Ingeniería; Ingeniaritza
Bi-fuel internal combustion engine vehicles allowing the operation with gasoline or diesel and hydrogen have great potential for speeding up the introduction of hydrogen in the transport sector. This would also contribute to alleviate the problem of urban air pollution. In this work, the modifications carried out to convert a Volkswagen Polo 1.4 into a bi-fuel (hydrogen-gasoline) car are described. Changes included the incorporation of a storage system based on compressed hydrogen, a machined intake manifold with a low-pressure accumulator where the hydrogen injectors were assembled, a new electronic control unit managing operation on hydrogen and an electrical junction box to control the change from a fuel to another. Change of fuel is very simple and does not require stopping the car. Road tests with hydrogen fuel gave a maximum speed of 125 km/h and an estimated consumption of 1 kg of hydrogen per 100 km at an average speed of 90 km/h. Vehicle conversion to bi-fuel operation is technically feasible and cheap.
Open Access
Single-stage in situ synthesis of silver nanoparticles in antibacterial self-assembled overlays
(Springerlink, 2012) Urrutia Azcona, Aitor; Rivero Fuente, Pedro J.; Ruete Ibarrola, Leyre; Goicoechea Fernández, Javier; Matías Maestro, Ignacio; Arregui San Martín, Francisco Javier; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute of Smart Cities - ISC; Ingeniería; Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2
In this work, a novel single-stage process for in situ synthesis of Ag nanoparticles (NPs) using the layer-bylayer (LbL) technique is presented. The Ag NPs were formed into nanotextured coatings based on sequentially adsorbed poly(allylamine hydrochloride) (PAH) and SiO2 NPs. Such highly porous surfaces have been used in the fabrication of highly efficient ion release films for applications such as antibacterial coatings. In this approach, the amino groups of the PAH acted as reducing agent and made possible the in situ formation of the Ag NPs. This reduction reaction occurred during the LbL process as the coating was assembled, without any further step after the fabrication and stabilization of the multilayer film. Biamminesilver nitrate was used as the Ag+ ion source during the LbL process and it was successfully reduced to Ag NPs. All coatings were tested with gram-positive and gram-negative bacterial cultures of Escherichia coli, Staphylococcus aureus, and Lactobacillus delbrueckii showing an excellent antimicrobial behavior against these types of bacteria (more than 99.9% of killing efficiency in all cases).
Open Access
Electrospun nanofiber mats for evanescent optical fiber sensors
(Elsevier, 2013) Urrutia Azcona, Aitor; Goicoechea Fernández, Javier; Rivero Fuente, Pedro J.; Matías Maestro, Ignacio; Arregui San Martín, Francisco Javier; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute of Smart Cities - ISC; Ingeniería; Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
In this work, a study about the optical response of electrospun nanofiber (ENF) coatings for their use in evanescent optical fiber sensors is presented. Several types of ENF mats composed of poly(acrylic acid) (PAA) were developed with different ENF diameters and densities. These ENF mats were deposited onto an optical fiber core in order to fabricate humidity evanescent optical fiber sensors. The devices were exposed to relative humidity (RH) variations from 30% RH to 95%RH. The transfer functions of the devices (transmitted optical power versus relative humidity) presented two well-differenced behaviors depending on the ENF diameter and the ENF mat density. The devices with lower ENF diameters and higher mat density showed an increase in the transmitted optical power when RH increased. On the contrary, the devices with higher ENF diameters and lower mat density showed a decrease in the transmitted optical power when RH increased. In addition to this, sensors with thinner ENF overlays, showed a higher sensitivity. In order to study the response time of these devices, the ENFs sensors were submitted to human breathing cycles and presented a response time around 340 ms (exhalation). In spite of the high RH conditions of this experiment, the devices showed a recovery time around 210 ms and a negligible hysteresis or drift with respect to the initial condition (inhalation).
Open Access
Project risk management methodology for small firms
(Elsevier, 2014) Marcelino Sádaba, Sara; Pérez Ezcurdia, Amaya; Echeverría Lazcano, Amparo; Villanueva Roldán, Pedro; Ingeniaritza; Institute of Smart Cities - ISC; Ingeniería
Open Access
Experimental study of the performance and emission characteristics of an adapted commercial four-cylinder spark ignition engine running on hydrogen-methane mixtures
(Elsevier, 2014) Diéguez Elizondo, Pedro; Urroz Unzueta, José Carlos; Marcelino Sádaba, Sara; Pérez Ezcurdia, Amaya; Benito Amurrio, Marta; Sáinz Casas, David; Gandía Pascual, Luis; Ingeniería; Ingeniaritza
The use of hydrogen/methane mixtures with low methane contents as fuels for internal combustion engines (ICEs) may help to speed up the development of the hydrogen energy market and contribute to the decarbonization of the transportation sector. In this work, a commercial 1.4 L four-cylinder Volkswagen spark-ignition engine previously adapted to operate on pure hydrogen has been fueled with hydrogen/methane mixtures with 5–20 vol.% methane (29.6–66.7 wt.%). An experimental program has been executed by varying the fuel composition, air-to-fuel ratio (λ), spark advance and engine speed. A discussion of the results regarding the engine performance (brake torque, brake mean effective pressure, thermal efficiency) and emissions (nitrogen oxides, CO and unburned hydrocarbons) is presented. The results reveal that λ is the most influential variable on the engine behavior due to its marked effect on the combustion temperature. As far as relatively high values of λ have to be used to prevent knock, the effect on the engine performance is negative. In contrast, the specific emissions of nitrogen oxides decrease due to a reduced formation of thermal NOx. A clear positive effect of reducing the spark advance on the specific NOx emissions has been observed as well. As concerns CO and unburned hydrocarbons (HCs), their specific emissions increase with the methane content of the fuel mixture, as expected. However, they also increase as λ increases in spite of the lower fuel concentration due to a proportionally higher reduction of the power. Finally, the effect of the increase of the engine speed is positive on the CO and HCs emissions but negative on that of NOx due to improved mixing and higher temperature associated to intensified turbulence in the cylinders.
Open Access
Characterization of the linear viscoelastic region of magnetorheological elastomers
(SAGE, 2014-01-13) Agirre Olabide, Iker; Berasategui, Joanes; Elejabarrieta, María Jesús; Bou-Ali, M. Mounir; Ingeniería; Ingeniaritza
The linear viscoelastic behaviour of magnetorheological elastomers is analysed in this work according to their formulation and working conditions. This study comprised both the synthesis of different magnetorheological elastomers and the strain and frequency sweep characterization under different magnetic fields and temperatures. The characterization was performed by a Physica MCR 501 rheometer from Anton Paar, equipped with a magnetorheologic cell 70/1T MRD. In the synthesis with a given elastomeric matrix, samples with different magnetic particle content are studied with two types of curing conditions: under the action of a magnetic field (anisotropic magnetorheological elastomers) and without a magnetic field (isotropic magnetorheological elastomers). The working conditions are excitation frequency, temperature and the applied external magnetic field. In this work, a new procedure to determine the linear viscoelastic behaviour is proposed; the loss factor is analysed in addition to analysing the storage modulus to determine the linear viscoelastic region of each sample. The results show that high temperatures and magnetorheological elastomers with higher volume fraction of magnetic particles restrict the linear viscoelastic behaviour of magnetorheological elastomers.
Open Access
Design of an electromagnetic servo brake with ABS function
(Trans Tech Publications, 2015) Lostado Lorza, Rubén; Somovilla Gómez, Fatima; Corral Bobadilla, Marina; Villanueva Roldán, Pedro; Fernández Martínez, Roberto; Ingeniería; Ingeniaritza
Open Access
In-plane shear behaviour of multiscale hybrid composites based on multiwall carbon nanotubes and long carbon fibres
(SAGE, 2015) Vargas Silva, Gustavo Adolfo; Ramos, José Ángel; Gracia, Juan de; Ibarretxe, Julen; Mujika, Faustino; Ingeniería; Ingeniaritza
Both in-plane shear modulus and in-plane shear strength of multiscale hybrid composites have been studied. Carbon fibre-based laminates have been fabricated including functionalized multiwall carbon nanotubes by means of solvent spraying method and hot compression process. Mechanical in-plane shear characterization has been carried out using off-axis three-point flexure test. Fibre volume fraction of multiscale hybrid composites has been determined through thermogravimetric analysis and fracture surfaces after testing have been imaged by scanning electron microscopy. Results reveal that the inclusion of functionalized multiwall carbon nanotubes on laminates has a small influence on in-plane shear modulus, although it increases up to 15% of the in-plane shear strength. Multiwall carbon nanotube functionalization improves shear stress transmission between matrix and carbon nanotubes, which represents a reinforcement effect responsible for the increase in in-plane shear strength. Scanning electron micrographs have confirmed in-plane shear tests results.
Open Access
Inertia transfer concept based general method for the determination of the base inertial parameters
(Springer, 2015) Ros Ganuza, Javier; Plaza Puértolas, Aitor; Iriarte Goñi, Xabier; Aginaga García, Jokin; Ingeniería; Ingeniaritza; Institute of Smart Cities - ISC
This paper presents a new algorithm to obtain the symbolic expressions of any of the possible base inertial parameter sets of a multibody system. Based on the ¿inertia transfer concept¿, a procedure is proposed to write a system of equations from which the base parameters are obtained. This leads to an automatizable and general method to obtain these parameters symbolically. The method can also be used to determine base inertial parameters numerically, and it can be even more straightforward to implement and use than the standard numerical methods. An example is presented to illustrate in detail the application of the algorithm, and to compare its results with those of a standard numerical procedure. The symbolic base inertial parameters can be of interest in symbolic simplification of the dynamic equations for real-time applications, design optimization, dynamic parameter identification, model reduction, and in other fields.