Papers by Keyword: Relaxation

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Authors: L.V. Elnikova
Abstract: We propose the Ising-like model treatment for phase transitions in pseudoquaternary solution of SDS (sodium dodecylsulfate), toluene, butanol (cosurfactant) and brine (NaCl), that was investigated by neutron spin echo spectroscopy [1] by Molle and coworkers. We compare the relaxation time and diffusion coefficient in the different kinds of droplet cellular structures in dependence on the correlation length, evaluated by lattice Monte Carlo technique.
Authors: Wu Lian Zhang, Xin Ding, Xu Dong Yang
Abstract: To recognize the interrelationship of plastic deformation with strain and time, uniaxial tension relaxation experiments of PVC coated plain weave membrane were executed along the warp and weft direction, while plastic deformation of the specimen were measured in 1 year. Using multiple functions from the product of both the strain difference (strain- critical strain) power function and the time power function, the experimental data was studied on a multiple regression analysis. It was concluded that the model had better fitting results. At the same time, an instantaneous plastic and a relaxed plastic term of the total plastic deformation were analyzed. It was showed that the instantaneous deformation was the main part of the plastic deformation, that the relaxed plastic deformation was the minor part of the plastic deformation, and the relaxed plastic deformation would become smaller and smaller with time extension.
Authors: Xuan Wang, Valérie Budinger, Yves Gourinat
Abstract: Piezoelectric actuators exhibit creep behavior in open-loop operation, which may lead to unaffordable errors in high precision static positioning systems. An inversion-based compensation strategy by open-loop control is presented for reducing creep effect. The approach utilizes a nonlinear viscoelastic model to portray creep phenomenon, which consists of a linear spring, a nonlinear dashpot and a series of nonlinear Voigt elements. It is shown that for the presented creep model the step responses are very similar to the piezoelectric actuators. In order to compensate creep effect, a concept of voltage relaxation in piezoelectric actuators is proposed. And the voltage relaxation model tantamount to the inverse creep model is derived using a PID closed-loop control system. Experimental results prove that, by insertion of voltage relaxation model in open-loop operation, creep effect is attenuated markedly in piezoelectric actuators.
Authors: O.M. Shabanov, L.A. Kazieva, Sagim I. Suleymanov
Abstract: The electrical conductivity of molten sodium and potassium chloroaluminumates increase with increasing electrical field strength and reach the limiting values. The limiting high-voltage conductivities of the melts surpass their usual values up to 200% in NaAlCl4 and 700% in KAlCl4. These results have been obtained on the base of analysis of the microsecond high-voltage discharges in the melts (the Wien effect). After the high-voltage pulses discharges having been completed in the melts, their conductivity has been found to rise up to 50% (the “memory effect”). The relaxation time of a non-equilibrium state reaches 5 minutes and more.
Authors: Zong De Liu, Xue Ping Mao
Abstract: The creep experiments of 2Cr11NiMoVNbNB steel were carried out at 550oC and 600oC. The creep damage laws of this material are discussed. An increase of the stress exponent with decreasing temperature was found experimentally and a modified secondary creep rate equation including in creep threshold stress was derived. Creep damage analyses are made under constant stress and under relaxed stress with creep threshold stress. The experimental results show that the damage value calculated with creep time is almost equal to that calculated with the creep rate, and an iteration method of calculating is proposed.
Authors: Ch. Cunat, France-Anne Kuhnast, A. Aharoune, M. Fiorani, Z. Ayadi
Authors: Xiao Wei Zhu, Wen Fang Wang
Abstract: In order to explore micro-beam relaxation dynamics of MEMS, the beam deflection relaxation expression considering air slide-film damping effect was educed based on Euler–Bernoulli equation with boundary conditions of two hinged ends. The beam deflection relaxation process under over damping, critical damping and under damping was calculated used Maple. The relaxation simulation data of micro-beam with two hinged ends used ANSYS demonstrate that relaxation process conform to theoretical calculation and relaxation period of under damping relaxation approximate constant when damping coefficient is small, but increase significantly when damping coefficient is large.
Authors: Mohammed Diany, Hicham Aissaoui
Abstract: The like-rubber O-ring gaskets are widely used in hydraulic and pneumatic equipments to ensure the sealing of the shaft, the pistons and the lids. The correct operation is due to the good tightening of the joint that generate a sufficient contact pressure able to confine the fluids inside rooms or to prevent their passage from one compartment to another. Several studies are carried out to model the O-ring behavior but without taking in account the effect of the relaxation and creep phenomena. In this article, an axisymmetric finite element model is proposed to study the O-ring relaxation during the first hours of its installation in the unrestrained axial loading case. The results of the numerical model are compared with an analytical approach results based on the classical Hertzian theory of the contact. The effects of the o-ring mechanical and geometrical characteristics are examined. The contact stress profiles and the peak contact stresses are determined versus the time relaxation in order to specify the working conditions thresholds.
Authors: Carlos Roberto Grandini, R.L.N. Oliveira, Rogério Pinto Mota, F.P. Santos, Élson de Campos
Abstract: Titanium dioxide (rutile) has a lot of interesting and useful features and hence is widely utilized for application. It has been used as white pigment, photocatalyst, biocompatible material and semiconductor material used in solar battery. In semiconducting TiO2 oxygen vacancies are said to play an important role in the electrical conduction. Measurements of the elastic energy loss and modulus (anelastic spectroscopy) as a function of temperature can distinguish among the different atomic jumps, which occur in the various phases or at different local ordering. In this paper, it is reported anelastic relaxation measurements in TiO2 samples using a torsion pendulum operating in frequencies around 40Hz, in the temperature range between -173 oC to 330 oC with heating rate of 1 oC/min. The results shown a reduction in the elasticity modulus with the increase in the corn starch content used for this consolidation.
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