Nonlinear and hysteretic magnetomechanical model for magnetostrictive transducers

The growing interest on magnetostrictive materials for generation of strains and forces in smart structure systems motivates the development of increasingly accurate models of the performance of these materials as used in transducers. The proposed magnetomechanical model provides a characterization of the material magnetization as well as the strain and force output by a transducer in response to quasistatic applied magnetic fields. The model is built in three steps. In the first, the mean field model for ferromagnetic hysteresis originally developed by Jiles and Atherton is used to compute the magnetization arising from the application of magnetic fields. While this model provides an accurate characterization of the field-induced magnetization at constant stress, it is insufficient in cases where the stress state of the magnetostrictive driver varies significantly during operation. To model the stress-induced magnetization changes, or magnetomechanical effect, a \u27law of approach\u27 to the anhysteretic magnetization is considered. The magnetization hysteresis model in combination with this law of approach provides a more realistic representation of the bidirectional energy transduction taking place in magnetostrictive transducers. In the second step, an even-term series expansion posed in terms of the magnetization is employed to calculate the magnetostriction associated with magnetic moment rotations within domains. While the magnetostriction provides a good description of the total material strain at the low field levels where elastic dynamics are of secondary significance, it is highly inaccurate at higher drive levels, in which the elastic response gains significance. This elastic or material response is considered in the third and last step, by means of force balancing in the form of a PDE system with magnetostrictive inputs and boundary conditions consistent with the transducer mechanical design. The solution to this PDE system provides the longitudinal displacements and corresponding strains and forces generated by the magnetostrictive driver. Since the formulation precludes analytic solution, a Galerkin discretization is employed to express the PDE in the form of a temporal system, which is subsequently solved using finite difference approximations. The ability of the model to accurately characterize the magnetomechanical behavior of magnetostrictive transducers is demonstrated via comparison of model simulations with experimental measurements collected from two Terfenol-D transducers

Fatigue Characterization of Ultrasonic Additive Manufactured Aluminum 3003

An aluminum 3003 H-18 block was built using ultrasonic additive manufacturing with process parameters which optimize mechanical strength. Transverse tensile fatigue tests were conducted on samples cut from the block and a stress vs. number of cycles curve was generated. Results show the curve is relatively flat and a stress threshold of 50% of the ultimate transverse tensile strength exists below which failure does not occur within 3.75 × 107 cycles. Optical and scanning electron microscopy conducted on failure surfaces shows no signs of crack initiation or growth typical of fatigue loading, but exhibits areas of no bonding between foil layers. To explain the failure, a model was developed based on the probabilistic failure of bonded areas in tension. The model uses a Frechet distribution to describe the probability of failure at each individual bonded area. Discrete bond failure and subsequent redistribution of stress to the surviving areas eventually leads to failure for the entire sample. Predictions from the model show good correlation with the experimental results.Mechanical Engineerin

D-type K+ current rules the function of electrically coupled neurons in a species-specific fashion

Este trabajo es parte de un número especial sobre la Estructura y Función de los Canales Iónicos en Células Nativas y Complejos Macromoleculares.Electrical synapses supported by gap junctions are known to form networks of electrically coupled neurons in many regions of the mammalian brain, where they play relevant functional roles. Yet, how electrical coupling supports sophisticated network operations and the contribution of the intrinsic electrophysiological properties of neurons to these operations remain incompletely understood. Here, a comparative analysis of electrically coupled mesencephalic trigeminal (MesV) neurons uncovered remarkable difference in the operation of these networks in highly related species. While spiking of MesV neurons might support the recruitment of coupled cells in rats, this rarely occurs in mice. Using whole-cell recordings, we determined that the higher efficacy in postsynaptic recruitment in rat’s MesV neurons does not result from coupling strength of larger magnitude, but instead from the higher excitability of coupled neurons. Consistently, MesV neurons from rats present a lower rheobase, more hyperpolarized threshold, as well as a higher ability to generate repetitive discharges, in comparison to their counterparts from mice. This difference in neuronal excitability results from a significantly higher magnitude of the D-type K+ current (ID) in MesV neurons from mice, indicating that the magnitude of this current gates the recruitment of postsynaptic-coupled neurons. Since MesV neurons are primary afferents critically involved in the organization of orofacial behaviors, activation of a coupled partner could support lateral excitation, which by amplifying sensory inputs may significantly contribute to information processing and the organization of motor outputs.Agencia Nacional de Investigación e Innovación FCE_1_2021_1_166745Programa de Desarrollo de las Ciencias BásicasComisión Académica de Posgrado de la Universidad de la República BDMX_2022_1#4871635

Heparin binding analysis of boar sperm and its relation with farrowing capacity

New methods for the evaluation of semen quality according to in vivo reproductive data are useful tools for identifying boars of lower fertility among individuals with standard semen parameters. In this study, indirect fluorescence microscopy was used to evaluate the heparin binding site distribution upon capacitation of sperm from eight boars arbitrarily distributed into Groups I and II according to differential farrowing rates (Group I: ≥ 70%, Group II: < 70%). Additionally, the ability of sperm to bind to solubilised zona pellucida (ZP) was assayed in the presence or absence of heparin. Samples of two individuals of Group II showed lower percentage of B pattern in relation to other individuals (P < 0.001). The number of spermatozoa attached to ZP after 2 h of incubation in capacitating conditions with heparin was significantly lower than in its absence (P < 0.0001). These results suggest that heparin binding site distribution concerning capacitation may be indicative of the availability of proteins involved in the fertilisation process, specifically at the initial sperm—oocyte recognition. Differences in heparin binding site dynamics during capacitation may help identify a subpopulation of individuals with lower fertilising capacity and normal spermiogram, which is particularly useful at high-production establishments

Design and Testing of a Dynamically-Tuned Magnetostrictive Spring with Electrically-Controlled Stiffness

This paper details the development of an electrically-controlled, variable-stiffness spring based on magnetostrictive materials. The device, termed a magnetostrictive Varispring, can be applied as a semi-active vibration isolator or switched stiffness vibration controller for reducing transmitted vibrations. The Varispring is designed using 1D linear models that consider the coupled electrical response, mechanically-induced magnetic diffusion, and the effect of internal mass on dynamic stiffness. Modeling results illustrate that a Terfenol-D-based Varispring has a rise time almost an order of magnitude smaller and a magnetic diffusion cut-off frequency over two orders of magnitude greater than a Galfenol-based Varispring. The results motivate the use of laminated Terfenol-D rods for a greater stiffness tuning range and increased bandwidth. The behavior of a prototype Varispring is examined under vibratory excitation up to 6 MPa and 25 Hz using a dynamic load frame. For this prototype, stiffness is indirectly varied by controlling the excitation current. Preliminary measurements of continuous stiffness tuning via sinusoidal currents up to 1 kHz are presented. The measurements demonstrate that the Young's modulus of the Terfenol-D rod inside the Varispring can be continuously varied by up to 21.9 GPa. The observed stiffness tuning range is relatively constant up to 500 Hz, but significantly decreases thereafter. The stiffness tuning range can be greatly increased by improving the current and force control such that a more consistent current can be applied and the Varispring can be accurately tested at a more optimal bias stress

Dynamic Response in the Low-kHz Range and Delta-E Effect in Ferromagnetic Shape Memory Ni-Mn-Ga

Recent work on ferromagnetic shape memory nickel-manganese-gallium (Ni-Mn-Ga) has demonstrated several characteristics which make this material attractive as an active element for the next generation of intelligent transducers. Alloys of martensitic Ni-Mn-Ga can strain up to 6% as a result of the rotation of twin variants and associated twin boundary motion which occur in these materials in response to magnetic fields. The magnetic actuation holds promise in transducer design because it can lead to enhanced frequency response compared with shape memory alloys with comparable strains. In this paper, we report on experimental measurements collected from a Ni50 Mn28.7 Ga21.3 sample which has been tested in a solenoid transducer by means of a novel drive configuration consisting of a collinear uniaxial field-uniaxial stress pair. We have observed that the elastic modulus of a Ni-Mn-Ga sample driven in these conditions changes substantially in response to varying bias field. In this paper, we further investigate the dependence of the elastic modulus on ac field intensity and mechanical load as well as bias field. Quasistatic, white noise, and swept-sine excitations were employed to examine the behavior of Ni50 Mn28.7 Ga21.3 driven under various combinations of magnetic fields and mechanical loads. Mechanically free quasi-static tests demonstrate reversible strains of 6300 με which are consistent with prior measurements on samples with similar composition near the Heusler stoichiometry. Dynamic measurements reveal a significant stiffness increase, of up to 209%, with dc bias field. This frequency shift or ΔE effect is shown to originate in the Ni-Mn-Ga sample and is believed to stem from the reorientation of twin variants in response to varying dc field. These results might facilitate a new class of solenoid-based Ni-Mn-Ga transducers for tunable vibration absorber applications, and lay the ground work for developing methods and criteria for the implementation of broadband Ni-Mn-Ga transducer technologies

Puntuación: desafíos y posibilidades de trabajo en el aula

El propósito de este trabajo es analizar situaciones donde se intenta enseñar a los niños que la puntuación es un sistema de marcas que ofrece indicaciones al lector sobre cómo interpretar el texto. Lejos de concebir el sistema de puntuación solo como signos que reproducen la entonación y las pausas de la lengua oral, la puntuación es entendida aquí como un sistema que organiza los significados del texto y por tanto orienta su interpretación. Se analizan dos situaciones didácticas desarrolladas con alumnos de tercer año de Educación Básica en el marco de una secuencia didáctica donde los niños leen y escriben para el armado de un álbum de datos personales. Una situación refiere a la corrección colectiva de textos ajenos, producidos ad hoc, que presentan problemas relativos a la posición del enunciador, la puntuación y repeticiones innecesarias. Otra situación consiste en la revisión en parejas del texto producido por los niños que presenta problemas equivalentes.The aim of this article is to analyze situations in which it is intended to teach punctuation as a system of marks that offers guide to reader on how the text should be understood. Instead of conceiving punctuation’s system as signs that reproduce intonation and pauses in oral language, punctuation is understood as a system that organizes the meaning of the text and, therefore, guides its interpretation. We analyzed two situations developed at a third year in Basic education in which students read and write to produce an album of personal data. One situation refers to a discussion with all the class to correct a text written by others, invented ad hoc, which present problems with speaker’s position, punctuation and unnecessary repetitions.Another situation consist in revision in pairs a text written by students who have got equivalent  problems

Dynamic Characterization of Galfenol

A novel and precise characterization of the constitutive behavior of solid and laminated research-grade, polycrystalline Galfenol (Fe81:6Ga18:4) under under quasi-static (1 Hz) and dynamic (4 to 1000 Hz) stress loadings was recently conducted by the authors. This paper summarizes the characterization by focusing on the experimental design and the dynamic sensing response of the solid Galfenol specimen. Mechanical loads are applied using a high frequency load frame. The dynamic stress amplitude for minor and major loops is 2.88 and 31.4 MPa, respectively. Dynamic minor and major loops are measured for the bias condition resulting in maximum, quasi-static sensitivity. Three key sources of error in the dynamic measurements are accounted for: (1) electromagnetic noise in strain signals due to Galfenol's magnetic response, (2) error in load signals due to the inertial force of fixturing, and (3) time delays imposed by conditioning electronics. For dynamic characterization, strain error is kept below 1.2 % of full scale by wiring two collocated gauges in series (noise cancellation) and through lead wire weaving. Inertial force error is kept below 0.41 % by measuring the dynamic force in the specimen using a nearly collocated piezoelectric load washer. The phase response of all conditioning electronics is explicitly measured and corrected for. In general, as frequency increases, the sensing response becomes more linear due to an increase in eddy currents. The location of positive and negative saturation is the same at all frequencies. As frequency increases above about 100 Hz, the elbow in the strain versus stress response disappears as the active (soft) regime stiffens toward the passive (hard) regime

Dynamic Characterization of Galfenol (Fe81.6Ga18.4)

Galfenol has the potential to transform the smart materials industry by allowing for the development of multifunctional, load-bearing devices. One of the primary technical challenges faced by this development is the very limited experimental data on Galfenol's frequency-dependent response to dynamic stress, which is critically important for the design of such devices. This report details a novel and precise characterization of the constitutive behavior of polycrystalline Galfenol (Fe81.6Ga18.4) under quasi-static (1 Hz) and dynamic (4 to 1000 Hz) stress loadings. Mechanical loads are applied using a high-frequency load frame. Quasi-static minor and major hysteresis loop measurements of magnetic flux density and strain are presented for constant electromagnet currents (0 to 1.1 A) and constant magnetic fields 0 to 14 kA/m (0 to 180 Oe). The dynamic stress amplitude for minor and major loops is 2.88 and 31.4 MPa (418 and 4550 psi), respectively. Quasi-static material properties closely match published values for similar Galfenol materials. Quasi-static actuation responses are also measured and compared to quasi-static sensing responses; the high degree of reversibility seen in the comparison is consistent with published measurements and modeling results. Dynamic major and minor loops are measured for dynamic stresses up to 31 MPa (4496 psi) and 1 kHz, and the bias condition resulting in maximum, quasi-static sensitivity. Eddy current effects are quantified by considering solid and laminated Galfenol rods. Three key sources of error in the dynamic measurements are accounted for: (1) electromagnetic noise in strain signals due to Galfenol's magnetic response, (2) error in load signals due to the inertial force of fixturing, and (3) phase misalignment between signals due to conditioning electronics. For dynamic characterization, strain error is kept below 1.2 percent of full scale by wiring two collocated gauges in series (noise cancellation) and through leadwire weaving. Inertial force error is kept below 0.41 percent by measuring the dynamic force in the specimen using a nearly collocated piezoelectric load washer. The phase response of all conditioning electronics is explicitly measured and corrected for. In general, as frequency is increased, the sensing response becomes more linear because of an increase in eddy currents. As frequency increases above approximately 100 Hz, the elbow in the strain-versus-stress response disappears as the active (soft) regime stiffens toward the passive (hard) regime. Under constant-field conditions, the loss factors of the solid rod peak between 200 and 600 Hz, rather than exhibiting a monotonic increase. Compared to the solid rod, the laminated rod exhibits much slower increases in hysteresis with frequency, and its quasi-static behavior extends to higher frequencies. The elastic modulus of the laminated rod decreases between 100 and 300 Hz; this trend is currently unexplained

Factores psicológicos y la intención emprendedora en los estudiantes de la Facultad de Ciencias Empresariales de la Universidad Privada de Tacna, 2020

La presente investigación se ha desarrollado con el fin de determinar la relación de los factores psicológicos con la intención emprendedora de los estudiantes de la Facultad de Ciencias Empresariales de la Universidad Privada de Tacna, teniendo como muestra de estudio a 306 alumnos provenientes de las cinco escuelas que conforman la Facultad. La investigación fue de tipo básico, diseño no experimental y el nivel de la investigación es relacional. El instrumento utilizado fue un cuestionario orientado a medir las variables psicológicas y la intención emprendedora. Se contrastaron hipótesis mediante la medición del coeficiente de correlación Rho de Spearman, obteniéndose evidencia significativa de relación entre variables psicológicas orientadas al emprendimiento y la intención emprendedora de los estudiantes de la Facultad de Ciencias Empresariales, 2020