A novel phenomenological model for dynamic behavior of magnetorheological elastomers in tension-compression mode

Tension-compression operation in MR elastomers (MREs) offers both the most compact design and superior stiffness in many vertical load-bearing applications, such as MRE bearing isolators in bridges and buildings, suspension systems and engine mounts in cars, and vibration control equipment. It suffers, however, from lack of good computational models to predict device performance, and as a result shear-mode MREs are widely used in the industry, despite their low stiffness and load-bearing capacity. We start with a comprehensive review of modeling of MREs and their dynamic characteristics, showing previous studies have mostly focused on dynamic behavior of MREs in shear mode, though the MRE strength and MR effect are greatly decreased at high strain amplitudes, due to increasing distance between the magnetic particles. Moreover, the characteristic parameters of the current models assume either frequency, or strain, or magnetic field are constant; hence, new model parameters must be recalculated for new loading conditions. This is an experimentally time consuming and computationally expensive task, and no models capture the full dynamic behavior of the MREs at all loading conditions. In this study, we present an experimental setup to test MREs in a coupled tension-compression mode, as well as a novel phenomenological model which fully predicts the stress-strain material behavior as a function of magnetic flux density, loading frequency and strain. We use a training set of experiments to find the experimentally derived model parameters, from which can predict by interpolation the MRE behavior in a relatively large continuous range of frequency, strain and magnetic field. We also challenge the model to make extrapolating predictions and compare to additional experiments outside the training experimental data set with good agreement. Further development of this model would allow design and control of engineering structures equipped with tension-compression MREs and all the advantages they offer.We acknowledge funding from the European Research Council grant EMATTER 280078

Synergy between magneto-rheological fluids and aluminum foams. Prospective alternative for seismic damping

This is the accepted manuscript. Access to the published article can be gained at: http://jim.sagepub.com/cgi/reprint/1045389X15596624v1.pdf?ijkey=SyFHNQwE4XMQqBF&keytype=finiteThis article presents the experimental study of a preliminary investigation of a seismic damper device aimed at improving the behavior of structures when subjected to earthquakes. The damper is the result of a binomial material formed by aluminum foam with pores 1 mm in diameter, wetted by a magnetorheological fluid (MRF). The objective of the present work is to explore the synergy between the two components in a magnetorheological test, and to evaluate the effect of the Al foam pores in the structure buildup of the fluid. The analysis is completed with a compressive test carried out on the MRF-filled foam in the presence of a magnetic field. This kind of test demonstrates that the deformation of the foam for very small loads is limited by the hardening of the fluid because of its MR response. The results of this research suggest that there is a mutual benefit between the components of the device, presumably leading to an enhanced dissipation of vibration energy.Proyectos PE2012-FQM694 (Junta de Andalucía, Spain), FIS2013-47666-C3-1-R (MINECO, Spain), SENER-CONACYT "151496" (UNAM Mexico), CONACYT National Quality Graduate Progra

A new approach for modeling of magnetorheological elastomers

202104 bcvcAccepted ManuscriptSelf-fundedPublishe

Experimental investigation of thermo-physical properties, convective heat transfer and pressure drop of functionalized graphene nanoplatelets aqueous nanofluid in a square heated pipe

In the present study, a facile method is used for preparation of functionalized graphene nanoplatelets (f-GNP) nanofluids. The effective thermal conductivity, density, viscosity, specific heat capacity, overall heat transfer coefficient and friction factor for fully developed turbulent flow of f-GNP/water nanofluids flowing through a square pipe at a constant heat flux were studied. f-GNP uniform nanocomposite was produced from a simple acid treatment reaction procedure. The surface characterization was performed by various techniques such as XRD, FESEM, FTIR and Raman. The f-GNP nanofluids were prepared by dispersing the functionalized nanoparticles in base fluid (water) without the assistance of a surfactant. As made nanofluids were stable for a long time and no sedimentation was observed. The experimental data for f-GNP nanofluids have shown significant enhancement in thermal conductivity and overall heat transfer coefficient in comparison to the corresponding water data. The percentage of enhancement is a function of weight concentration of nanoparticles and temperature. Highest improvement of overall heat transfer coefficient is 19.68% with 9.22% raise in friction factor for the weight concentration of 0.1% at a Reynolds number of 17,500 compared to those data from the base fluid

Effect of intracerebroventricular injection of GABA receptors antagonists on morphine-induced changes in GABA and GLU transmission within the mPFC: An in vivo microdialysis study

Objective(s): Many studies have focused on ventral tegmental area than of other mesocorticolimbic areas, and implicated a key role for the medial prefrontal cortex (mPFC) in the development of addictive behaviors. So far, the role of gamma-aminobutyric acid (GABA) receptors in the discriminative properties of morphine has received little attention and few studies evaluated the role of these receptors in drug dependence. Hence, we investigated the role of this receptor on morphine- induced GABA/ glutamate (GLU) changes in the mPFC following morphine administration using in vivo microdialysis.Materials and Methods: In this study, 60 rats weighing 270-300 g were divided into six groups. First, microdialysis probe was inserted into the mPFC and was perfused with artificial cerebrospinal fluid and collected the baseline samples in all groups. In saline and morphine groups, the saline, in phaclophen and (phaclofen+morphine) groups, phaclofen (100 nmol), and in bicuculline and (bicuculline+morphine) groups, bicuculline (20 nmol) was injected intracerebroventricular. In saline, phaclofen and bicuculline groups 20 min later, animals received saline (0.2 ml, IP) and others groups received morphine (20 mg/kg, IP).Results: Our results showed that morphine increased the average concentration of GABA and decreased the concentration of GLU within mPFC. Pretreatment with phaclofen and bicuculline 20 min before morphine administration had no effect on GABA and GLU release for 100 min.Conclusion: The present study indicated that morphine influence the GABA and GLU transmission in mPFC. Therefore evaluation of neurochemistry changes of this neural circuitry may provide further insight into the mechanisms underlying drug dependence

Study of synthesis, stability and thermo-physical properties of graphene nanoplatelet/platinum hybrid nanofluid

In the present study a new synthesis method has been introduced for the decoration of platinum (Pt) on the functionalized graphene nanoplatelet (GNP) and also highlighted the preparation method of nanofluids. GNP–Pt uniform nanocomposite was produced from a simple chemical reaction procedure, which included acid treatment for functionalization of GNP. The surface characterization was performed by various techniques such as XRD, FESEM and TEM. The effective thermal conductivity, density, viscosity, specific heat capacity and stability of functionalized GNP–Pt water based nanofluids were investigated in different instruments. The GNP–Pt hybrid nanofluids were prepared by dispersing the nanocomposite in base fluid without adding any surfactant. The examined nanofluids were stable and no significant sedimentation was observed for a long time (22 days). Thermal conductivity of GNP–Pt nanocomposite dispersed in distilled water nanofluids shows an enhancement of 17.77% at 40 °C and 0.1% weight concentration

Graphene nanoplatelets–silver hybrid nanofluids for enhanced heat transfer

In the present experimental work, a new synthesis method is introduced for decoration of silver on the functionalized graphene nanoplatelets (GNP-Ag) and preparation of nanofluids is reported. The thermo-physical properties, heat transfer performance and friction factor for fully developed turbulent flow of GNP-Ag/water nanofluids flowing through a circular tube at a constant heat flux were investigated. GNP-Ag uniform nanocomposite was produced from a simple chemical reaction procedure, which includes acid treatment for functionalization of GNP. The surface characterization was performed by various techniques such as XRD, FESEM, TEM and Raman. The GNP-Ag nanofluids were prepared by dispersing the nanocomposite in distilled water without the assistance of a surfactant and/or ultrasonication. The prepared nanofluids were found to be stable and no sedimentation was observed for a long time. The experimental data for GNP-Ag nanofluids were shown improvements of effective thermal conductivity and heat transfer efficiency in comparison with the corresponding to the base-fluid. The amount of enhancement was a function of temperature and weight concentration of nanoparticles. Maximum enhancement of Nusselt number was 32.7% with a penalty of 1.08 times increase in the friction factor for the weight concentration of 0.1% at a Reynolds number of 17,500 compared to distilled water. Improved empirical correlations were proposed based on the experimental data for evaluation of Nusselt number and friction factor