Articles de revistahttp://hdl.handle.net/2117/57442019-03-19T04:05:35Z2019-03-19T04:05:35ZLow wear and low friction DLC coating with good adhesion to CoCrMo metal substratesCano Prieto, DavidLousa, ArturoEsteve, JoanFerrer Anglada, Núriahttp://hdl.handle.net/2117/1299892019-03-02T04:49:57Z2019-03-01T11:09:24ZLow wear and low friction DLC coating with good adhesion to CoCrMo metal substrates
Cano Prieto, David; Lousa, Arturo; Esteve, Joan; Ferrer Anglada, Núria
A challenge currently facing the orthopedics sector consists in the durability problems posed by joint prosthesis based on metal-on-metal contacts. While the diamond-like carbon (DLC)-based coating solves the shortcomings of wear and friction found in the uncoated metal parts, they are generally subject to adhesion failures that may prove to be catastrophic. Our coatings were deposited with a specific multilayered composition that changes from highly metallic at the metal interface, up to a DLC at the sliding contact region. These coatings show very good wear performance results when tested in a highly humid air atmosphere as well as when they are tested in water immersion or in bovine serum. The friction coefficients of our DLC-against-DLC tribological pair are found to be always less than 0.1, while wear rates are extremely low, under 2.5¿×¿10-8¿mm3/N¿m, and it produces highly polished surfaces. The compressive stresses of our coatings are always lower than 2.5¿GPa, and when combined with good interface adhesion to the CoCrMo metal substrates, make the coatings highly resistant to delamination even after prolonged test runs. Raman analyses do not reveal any detectable changes even after very long test runs, indicating that no tribochemical reactions occur on the DLC coating.
2019-03-01T11:09:24ZCano Prieto, DavidLousa, ArturoEsteve, JoanFerrer Anglada, NúriaA challenge currently facing the orthopedics sector consists in the durability problems posed by joint prosthesis based on metal-on-metal contacts. While the diamond-like carbon (DLC)-based coating solves the shortcomings of wear and friction found in the uncoated metal parts, they are generally subject to adhesion failures that may prove to be catastrophic. Our coatings were deposited with a specific multilayered composition that changes from highly metallic at the metal interface, up to a DLC at the sliding contact region. These coatings show very good wear performance results when tested in a highly humid air atmosphere as well as when they are tested in water immersion or in bovine serum. The friction coefficients of our DLC-against-DLC tribological pair are found to be always less than 0.1, while wear rates are extremely low, under 2.5¿×¿10-8¿mm3/N¿m, and it produces highly polished surfaces. The compressive stresses of our coatings are always lower than 2.5¿GPa, and when combined with good interface adhesion to the CoCrMo metal substrates, make the coatings highly resistant to delamination even after prolonged test runs. Raman analyses do not reveal any detectable changes even after very long test runs, indicating that no tribochemical reactions occur on the DLC coating.Dielectric and piezoelectric nonlinear properties of slightly textured lead barium niobate ceramicsOchoa Guerrero, Diego A.Casals Mirones, Jorge AlejandroVenet, MichelM'Peko, Jean-ClaudeGarcía García, José Eduardohttp://hdl.handle.net/2117/1281542019-02-02T04:02:37Z2019-02-01T18:17:13ZDielectric and piezoelectric nonlinear properties of slightly textured lead barium niobate ceramics
Ochoa Guerrero, Diego A.; Casals Mirones, Jorge Alejandro; Venet, Michel; M'Peko, Jean-Claude; García García, José Eduardo
Dielectric and piezoelectric responses of slightly textured, lead barium niobate ceramics are studied. The designed morphotropic phase boundary composition (Pb0.63Ba0.37Nb2O6) shows considerable nonlinear dielectric and piezoelectric responses. While these nonlinear behaviors lead to significant instabilities of the functional properties, interesting features are revealed as a consequence of the texturing effect in the composition studied. An improved dielectric performance and a lower nonlinear piezoelectric response are observed when the electric field is applied to the sample in the forging direction. The results are quantitatively discussed in the framework of the Preisach and Rayleigh models. In this context, a decrease in the nonlinear response can be associated with a lower grain size related to the texture. The results of this work show that texturing is an effective route for controlling the undesirable nonlinear behavior of piezoceramics with tetragonal tungsten bronze structure.
2019-02-01T18:17:13ZOchoa Guerrero, Diego A.Casals Mirones, Jorge AlejandroVenet, MichelM'Peko, Jean-ClaudeGarcía García, José EduardoDielectric and piezoelectric responses of slightly textured, lead barium niobate ceramics are studied. The designed morphotropic phase boundary composition (Pb0.63Ba0.37Nb2O6) shows considerable nonlinear dielectric and piezoelectric responses. While these nonlinear behaviors lead to significant instabilities of the functional properties, interesting features are revealed as a consequence of the texturing effect in the composition studied. An improved dielectric performance and a lower nonlinear piezoelectric response are observed when the electric field is applied to the sample in the forging direction. The results are quantitatively discussed in the framework of the Preisach and Rayleigh models. In this context, a decrease in the nonlinear response can be associated with a lower grain size related to the texture. The results of this work show that texturing is an effective route for controlling the undesirable nonlinear behavior of piezoceramics with tetragonal tungsten bronze structure.Assessment of the functional properties stability in (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 piezoceramics: huge dielectric and piezoelectric nonlinearityOchoa Guerrero, Diego A.Reyes Montero, ArmandoSuñol Galofre, Francesc XavierVillafuerte Castrejón, Maria ElenaPardo, LorenaGarcía García, José Eduardohttp://hdl.handle.net/2117/1278392019-01-30T03:11:53Z2019-01-29T17:56:16ZAssessment of the functional properties stability in (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 piezoceramics: huge dielectric and piezoelectric nonlinearity
Ochoa Guerrero, Diego A.; Reyes Montero, Armando; Suñol Galofre, Francesc Xavier; Villafuerte Castrejón, Maria Elena; Pardo, Lorena; García García, José Eduardo
The (Ba,Ca)(Zr,Ti)O3 ceramic system has received special attention in recent years because it may lead to promising lead-free piezoceramics. However, the stability of the functional properties of these materials is an important issue that requires greater attention. In this work, the (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 compound (BCZT) is taken as a reference material for evaluating the variation of the functional properties when an external stimulus (e.g., electric field or dynamical stress) is applied, which may constitute an important drawback of piezoceramics. The results show that BCZT exhibits a huge nonlinear behavior, which notably limits this lead-free material for transfer to applications. The instabilities manifest at considerably low amplitudes of the applied electric field or dynamical stress due to a large extrinsic contribution from the irreversible motion of domain walls. Understanding and controlling the physical phenomena related to the domain wall motion presents a fundamental challenge for achieving an effective enhancement of the functional property stability of this system.
2019-01-29T17:56:16ZOchoa Guerrero, Diego A.Reyes Montero, ArmandoSuñol Galofre, Francesc XavierVillafuerte Castrejón, Maria ElenaPardo, LorenaGarcía García, José EduardoThe (Ba,Ca)(Zr,Ti)O3 ceramic system has received special attention in recent years because it may lead to promising lead-free piezoceramics. However, the stability of the functional properties of these materials is an important issue that requires greater attention. In this work, the (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 compound (BCZT) is taken as a reference material for evaluating the variation of the functional properties when an external stimulus (e.g., electric field or dynamical stress) is applied, which may constitute an important drawback of piezoceramics. The results show that BCZT exhibits a huge nonlinear behavior, which notably limits this lead-free material for transfer to applications. The instabilities manifest at considerably low amplitudes of the applied electric field or dynamical stress due to a large extrinsic contribution from the irreversible motion of domain walls. Understanding and controlling the physical phenomena related to the domain wall motion presents a fundamental challenge for achieving an effective enhancement of the functional property stability of this system.High-precision time-of-flight determination algorithm for ultrasonic flow measurementSuñol Galofre, Francesc XavierOchoa Guerrero, Diego A.García García, José Eduardohttp://hdl.handle.net/2117/1273052019-01-24T11:05:22Z2019-01-22T10:30:21ZHigh-precision time-of-flight determination algorithm for ultrasonic flow measurement
Suñol Galofre, Francesc Xavier; Ochoa Guerrero, Diego A.; García García, José Eduardo
Commercial time-of-flight (TOF) ultrasonic flowme-
ters are rapidly expanding in the general industry. Among the
different techniques that can be applied to determine the TOF of
ultrasonic waves, the cross-correlation method presents numerous
advantages, such as robustness for weak signals and noise
suppression. However, the selection of an appropriate reference
wave is presumably a key element in the precise measurement
of TOF. In the present paper, an algorithm to compute an
accurate TOF is proposed. The form of the electric signal
received by the transducer is obtained from an acoustically-forced
underdamped oscillator model, and the analytical solution of the
model is proposed as a reference wave. In order to validate the
effectiveness of this procedure, an ultrasonic flowmeter system
is designed and tested in a flowmeter calibration test rig. It is
demonstrated that the use of the presented scheme overcome the
average method limitations, and turns out to be a convenient
solution in a wide range of conditions. Robust measurements of
near-zero flow values are acquired, which allow the achievement
of a high dynamic range. The error curve of the proposed system
have been obtained, revealing that the absolute value of the
relative errors are lower than 2% within all the spectrum of
flow rates considered (from 0.2 to 150 m
3
/h). Results demonstrate
that the algorithm provides high-precision measurements within
a wide dynamic range. The algorithm is portable and versatile:
it can be adapted to different types of transducers without the
need of additional measurements, allowing to adjust parameters
on-the-fly for an optimal performance of the ultrasonic flowmeter
system.
2019-01-22T10:30:21ZSuñol Galofre, Francesc XavierOchoa Guerrero, Diego A.García García, José EduardoCommercial time-of-flight (TOF) ultrasonic flowme-
ters are rapidly expanding in the general industry. Among the
different techniques that can be applied to determine the TOF of
ultrasonic waves, the cross-correlation method presents numerous
advantages, such as robustness for weak signals and noise
suppression. However, the selection of an appropriate reference
wave is presumably a key element in the precise measurement
of TOF. In the present paper, an algorithm to compute an
accurate TOF is proposed. The form of the electric signal
received by the transducer is obtained from an acoustically-forced
underdamped oscillator model, and the analytical solution of the
model is proposed as a reference wave. In order to validate the
effectiveness of this procedure, an ultrasonic flowmeter system
is designed and tested in a flowmeter calibration test rig. It is
demonstrated that the use of the presented scheme overcome the
average method limitations, and turns out to be a convenient
solution in a wide range of conditions. Robust measurements of
near-zero flow values are acquired, which allow the achievement
of a high dynamic range. The error curve of the proposed system
have been obtained, revealing that the absolute value of the
relative errors are lower than 2% within all the spectrum of
flow rates considered (from 0.2 to 150 m
3
/h). Results demonstrate
that the algorithm provides high-precision measurements within
a wide dynamic range. The algorithm is portable and versatile:
it can be adapted to different types of transducers without the
need of additional measurements, allowing to adjust parameters
on-the-fly for an optimal performance of the ultrasonic flowmeter
system.Bifurcation patterns in homogeneous area-preserving piecewise-linear mapsBenadero García-Morato, LuisFreire Macías, EmilioPonce Núñez, EnriqueTorres Peral, Franciscohttp://hdl.handle.net/2117/1261082019-01-24T11:48:14Z2018-12-20T18:04:53ZBifurcation patterns in homogeneous area-preserving piecewise-linear maps
Benadero García-Morato, Luis; Freire Macías, Emilio; Ponce Núñez, Enrique; Torres Peral, Francisco
The dynamical behavior of a family of planar continuous piecewise linear maps with two zones is analyzed. Assuming homogeneity and preservation of areas we obtain a canonical form with only two parameters: the traces of the two matrices defining the map. It is shown the existence of sausage-like structures made by lobes linked at the nodes of a nonuniform grid in the parameter plane. In each one of these structures, called resonance regions, the rotation number of the associated circle map is a given rational number. The boundary of the lobes and a significant inner partition line are studied with the help of some Fibonacci polynomials.
2018-12-20T18:04:53ZBenadero García-Morato, LuisFreire Macías, EmilioPonce Núñez, EnriqueTorres Peral, FranciscoThe dynamical behavior of a family of planar continuous piecewise linear maps with two zones is analyzed. Assuming homogeneity and preservation of areas we obtain a canonical form with only two parameters: the traces of the two matrices defining the map. It is shown the existence of sausage-like structures made by lobes linked at the nodes of a nonuniform grid in the parameter plane. In each one of these structures, called resonance regions, the rotation number of the associated circle map is a given rational number. The boundary of the lobes and a significant inner partition line are studied with the help of some Fibonacci polynomials.Suppression of undesired attractors in a self-oscillating H-bridge parallel resonant converters under zero current switching controlEl Aroudi, AbdelaliBenadero García-Morato, LuisPonce, EnriqueOlalla Martinez, CarlosTorres Peral, FranciscoMartínez Salamero, Luishttp://hdl.handle.net/2117/1259592019-01-24T10:54:34Z2018-12-18T19:52:51ZSuppression of undesired attractors in a self-oscillating H-bridge parallel resonant converters under zero current switching control
El Aroudi, Abdelali; Benadero García-Morato, Luis; Ponce, Enrique; Olalla Martinez, Carlos; Torres Peral, Francisco; Martínez Salamero, Luis
Resonant converters under zero current switching control strategy can exhibit coexistence of attractors, making it difficult the startup of the system from zero initial conditions. In this paper, the problem of multiple coexisting attractors in parallel resonant converters is addressed. Appropriate modifications of the switching decision with the aim of converting undesired attractors into virtual ones are proposed. A suitable control signal is generated from the state variables of the system and used to adjust the switching decision. Numerical simulations corroborate the proposed solutions and the simplest one was finally verified by measurements from a laboratory prototype.
2018-12-18T19:52:51ZEl Aroudi, AbdelaliBenadero García-Morato, LuisPonce, EnriqueOlalla Martinez, CarlosTorres Peral, FranciscoMartínez Salamero, LuisResonant converters under zero current switching control strategy can exhibit coexistence of attractors, making it difficult the startup of the system from zero initial conditions. In this paper, the problem of multiple coexisting attractors in parallel resonant converters is addressed. Appropriate modifications of the switching decision with the aim of converting undesired attractors into virtual ones are proposed. A suitable control signal is generated from the state variables of the system and used to adjust the switching decision. Numerical simulations corroborate the proposed solutions and the simplest one was finally verified by measurements from a laboratory prototype.Nonlinear dynamic modeling and analysis of self-oscillating H-bridge parallel resonant converter under zero current switching control: unveiling coexistence of attractorsEl Aroudi, AbdelaliBenadero García-Morato, LuisPonce, EnriqueOlalla Martinez, CarlosTorres Peral, FranciscoMartínez Salamero, Luishttp://hdl.handle.net/2117/1259582019-01-24T11:48:13Z2018-12-18T19:43:24ZNonlinear dynamic modeling and analysis of self-oscillating H-bridge parallel resonant converter under zero current switching control: unveiling coexistence of attractors
El Aroudi, Abdelali; Benadero García-Morato, Luis; Ponce, Enrique; Olalla Martinez, Carlos; Torres Peral, Francisco; Martínez Salamero, Luis
This paper deals with the global dynamical analysis of an H-bridge parallel resonant converter under a zero current switching control. Due to the discontinuity of the vector field in this system, sliding dynamics may take place. Here, the sliding set is found to be an escaping region. Different tools are combined for studying the stability of oscillations of the system. The desired crossing limit cycles are computed by solving their initial value problem and their stability analysis is performed using Floquet theory. The resulting monodromy matrix reveals that these cycles are created according to a smooth cyclic-fold bifurcation. Under parameter variation, an unstable symmetric crossing limit cycle undergoes a crossing-sliding bifurcation leading to the creation of a symmetric unstable sliding limit cycle. Finally, this limit cycle undergoes a double homoclinic connection giving rise to two different unstable asymmetric sliding limit cycles. The analysis is performed using a piecewise-smooth dynamical model of a Filippov type. Sliding limit cycles divide the state plane in three basins of attraction, and hence, different steady-state solutions may coexist which may lead the system to start-up problems. Numerical simulations corroborate the theoretical predictions, which have been experimentally validated.
2018-12-18T19:43:24ZEl Aroudi, AbdelaliBenadero García-Morato, LuisPonce, EnriqueOlalla Martinez, CarlosTorres Peral, FranciscoMartínez Salamero, LuisThis paper deals with the global dynamical analysis of an H-bridge parallel resonant converter under a zero current switching control. Due to the discontinuity of the vector field in this system, sliding dynamics may take place. Here, the sliding set is found to be an escaping region. Different tools are combined for studying the stability of oscillations of the system. The desired crossing limit cycles are computed by solving their initial value problem and their stability analysis is performed using Floquet theory. The resulting monodromy matrix reveals that these cycles are created according to a smooth cyclic-fold bifurcation. Under parameter variation, an unstable symmetric crossing limit cycle undergoes a crossing-sliding bifurcation leading to the creation of a symmetric unstable sliding limit cycle. Finally, this limit cycle undergoes a double homoclinic connection giving rise to two different unstable asymmetric sliding limit cycles. The analysis is performed using a piecewise-smooth dynamical model of a Filippov type. Sliding limit cycles divide the state plane in three basins of attraction, and hence, different steady-state solutions may coexist which may lead the system to start-up problems. Numerical simulations corroborate the theoretical predictions, which have been experimentally validated.Influence of extrinsic contribution on the macroscopic properties of hard and soft lead zirconate titanate ceramicsOchoa Guerrero, Diego A.García García, José EduardoPérez Pérez, RafaelAlbareda Tiana, Alfonsohttp://hdl.handle.net/2117/1212062019-01-24T11:47:25Z2018-09-17T08:18:05ZInfluence of extrinsic contribution on the macroscopic properties of hard and soft lead zirconate titanate ceramics
Ochoa Guerrero, Diego A.; García García, José Eduardo; Pérez Pérez, Rafael; Albareda Tiana, Alfonso
In this work, the contribution of the extrinsic effect to the macroscopic properties in soft and hard lead zirconate titanate ceramics is directly evaluated. Close to the room temperature, poled hard ceramics show an anomalous behavior, which is notably different from that of soft ceramics, not only in dielectric but also in piezoelectric and elastic responses. Hence, at room temperature their properties are thermally stable and the losses are unusually low. It is suggested that two mechanisms are present, with one mechanism inhibiting the other.
2018-09-17T08:18:05ZOchoa Guerrero, Diego A.García García, José EduardoPérez Pérez, RafaelAlbareda Tiana, AlfonsoIn this work, the contribution of the extrinsic effect to the macroscopic properties in soft and hard lead zirconate titanate ceramics is directly evaluated. Close to the room temperature, poled hard ceramics show an anomalous behavior, which is notably different from that of soft ceramics, not only in dielectric but also in piezoelectric and elastic responses. Hence, at room temperature their properties are thermally stable and the losses are unusually low. It is suggested that two mechanisms are present, with one mechanism inhibiting the other.Nonlinear behavior in a piezoelectric resonator: a method of analysisGarcía García, José EduardoPérez Pérez, RafaelAlbareda Tiana, AlfonsoMinguella Blasco, Enrichttp://hdl.handle.net/2117/1212002019-01-24T10:53:36Z2018-09-17T07:53:44ZNonlinear behavior in a piezoelectric resonator: a method of analysis
García García, José Eduardo; Pérez Pérez, Rafael; Albareda Tiana, Alfonso; Minguella Blasco, Enric
Theories used for understanding nonlinear behavior of piezoelectric resonators are usually only valid for a given range of amplitudes. Thus, important discrepancies can sometimes be observed between theory and experiment. In this work, a simplified model of the resonator is assumed in order to extend the analysis of nonlinear behavior to any kind of nonlinear function, without a significant increase of mathematical complexity. Nevertheless, nonlinearities are considered to be weak enough to be taken as perturbations. An asymptotic method is used to obtain the first and second order perturbations of the response to an harmonic excitation applied to the system, and each one is separated into Fourier series. Nonlinearity is described by two functions-/spl Phi/, (S,D,S/spl dot/,D/spl dot/) and /spl Psi/ (S,D,S/spl dot/,D/spl dot/)-that must be added to the constitutive equations that give T and E as functions of S and D. These functions can be split into their symmetrical and antisymmetrical parts, which have different incidence over the perturbation terms. In order to simplify the problem, no mechanical excitation is considered, the electrical one is taken as strictly harmonic, and the current rather than the e.m.f. is taken as initial data. As an application example, this method is applied in order to find the second harmonic generation for a particular kind of nonlinearity.
2018-09-17T07:53:44ZGarcía García, José EduardoPérez Pérez, RafaelAlbareda Tiana, AlfonsoMinguella Blasco, EnricTheories used for understanding nonlinear behavior of piezoelectric resonators are usually only valid for a given range of amplitudes. Thus, important discrepancies can sometimes be observed between theory and experiment. In this work, a simplified model of the resonator is assumed in order to extend the analysis of nonlinear behavior to any kind of nonlinear function, without a significant increase of mathematical complexity. Nevertheless, nonlinearities are considered to be weak enough to be taken as perturbations. An asymptotic method is used to obtain the first and second order perturbations of the response to an harmonic excitation applied to the system, and each one is separated into Fourier series. Nonlinearity is described by two functions-/spl Phi/, (S,D,S/spl dot/,D/spl dot/) and /spl Psi/ (S,D,S/spl dot/,D/spl dot/)-that must be added to the constitutive equations that give T and E as functions of S and D. These functions can be split into their symmetrical and antisymmetrical parts, which have different incidence over the perturbation terms. In order to simplify the problem, no mechanical excitation is considered, the electrical one is taken as strictly harmonic, and the current rather than the e.m.f. is taken as initial data. As an application example, this method is applied in order to find the second harmonic generation for a particular kind of nonlinearity.Unexpected dielectric response in lead zirconate titanate ceramics: The role of ferroelectric domain wall pinning effectsGarcía García, José EduardoGomis Arbonès, VicentePérez Pérez, RafaelAlbareda Tiana, AlfonsoEiras, Jose A.http://hdl.handle.net/2117/1211992019-01-24T11:47:25Z2018-09-17T07:41:15ZUnexpected dielectric response in lead zirconate titanate ceramics: The role of ferroelectric domain wall pinning effects
García García, José Eduardo; Gomis Arbonès, Vicente; Pérez Pérez, Rafael; Albareda Tiana, Alfonso; Eiras, Jose A.
Temperature dependent dielectric response has been measured in Pb(Zr1-xTix)O-3 ceramics. Samples of different compositions (x=0.40, 0.47, and 0.60), pure and doped with Nb-or Fe, were studied at temperatures between 15 and 700 K and in the frequency range from 100 Hz to 1 MHz. Unexpected dielectric behavior has been found around room temperature. Anomalous temperature dependent permittivity is observed in pure and Fe-doped samples but not in Nb-doped samples. The anomaly appears related to the presence of oxygen vacancies but not on the sample crystallographic phase. The authors suggest that the anomaly may be a manifestation of the domain wall pinning effect. (C) 2007 American Institute of Physics.
2018-09-17T07:41:15ZGarcía García, José EduardoGomis Arbonès, VicentePérez Pérez, RafaelAlbareda Tiana, AlfonsoEiras, Jose A.Temperature dependent dielectric response has been measured in Pb(Zr1-xTix)O-3 ceramics. Samples of different compositions (x=0.40, 0.47, and 0.60), pure and doped with Nb-or Fe, were studied at temperatures between 15 and 700 K and in the frequency range from 100 Hz to 1 MHz. Unexpected dielectric behavior has been found around room temperature. Anomalous temperature dependent permittivity is observed in pure and Fe-doped samples but not in Nb-doped samples. The anomaly appears related to the presence of oxygen vacancies but not on the sample crystallographic phase. The authors suggest that the anomaly may be a manifestation of the domain wall pinning effect. (C) 2007 American Institute of Physics.