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Hysteresis Effects (hysteresi + effects)

Distribution by Scientific Domains
Engineering50%

Selected Abstracts

A geometrically and materially non-linear piezoelectric three-dimensional-beam finite element formulation including warping effects

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 5 2008
A. Butz
Abstract This paper is concerned with a three-dimensional piezoelectric beam formulation and its finite element implementation. The developed model considers geometrically and materially non-linear effects. An eccentric beam formulation is derived based on the Timoshenko kinematics. The kinematic assumptions are extended by three additional warping functions of the cross section. These functions follow from torsion and piezoelectrically induced shear deformations. The presented beam formulation incorporates large displacements and finite rotations and allows the investigation of stability problems. The finite element model has two nodes with nine mechanical and five electrical degrees of freedom. It provides an accurate approximation of the electric potential, which is assumed to be linear in the direction of the beam axis and quadratic within the cross section. The mechanical degrees of freedom are three displacements, three rotations and three scaling factors for the warping functions. The latter are computed in a preprocess by solving a two-dimensional in-plane equilibrium condition with the finite element method. The gained warping patterns are considered within the integration through the cross section of the beam formulation. With respect to material non-linearities, which arise in ferroelectric materials, the scalar Preisach model is embedded in the formulation. This model is a mathematical model for the general description of hysteresis phenomena. Its application to piezoelectric materials leads to a phenomenological model for ferroelectric hysteresis effects. Here, the polarization direction is assumed to be constant, which leads to unidirectional constitutive equations. Some examples demonstrate the capability of the proposed model. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Phase-field systems for multi-dimensional Prandtl,Ishlinskii operators with non-polyhedral characteristics

MATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 4 2002
Jürgen Sprekels
Abstract Hysteresis operators have recently proved to be a powerful tool in modelling phase transition phenomena which are accompanied by the occurrence of hysteresis effects. In a series of papers, the present authors have proposed phase-field models in which hysteresis non-linearities occur at several places. A very important class of hysteresis operators studied in this connection is formed by the so-called Prandtl,Ishlinskii operators. For these operators, the corresponding phase-field systems are in the multi-dimensional case only known to admit unique solutions if the characteristic convex sets defining the operators are polyhedrons. In this paper, we use approximation techniques to extend the known results to multi-dimensional Prandtl,Ishlinskii operators having non-polyhedral convex characteristicsets. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Testing for Hysteresis in Unemployment in OECD Countries: New Evidence using Stationarity Panel Tests with Breaks,

OXFORD BULLETIN OF ECONOMICS & STATISTICS, Issue 2 2006
Mariam Camarero
Abstract This paper tests hysteresis effects in unemployment using panel data for 19 Organization for Economic Co-operation and Development (OECD) countries covering the period 1956,2001. The tests exploit the cross-sectional variations of the series, and additionally, allow for a different number of endogenous breakpoints in the unemployment series. The critical values are simulated based on our specific panel sizes and time periods. The findings stress the importance of accounting for exogenous shocks in the series and support the natural-rate hypothesis of unemployment for the majority of the countries analysed. [source]

Creep and hysteresis compensation for nanomanipulation using atomic force microscope

ASIAN JOURNAL OF CONTROL, Issue 2 2009
Qinmin Yang
Abstract In this paper, a novel scheme is presented to simultaneously compensate the inherent creep and hysteresis nonlinearities of a piezoelectric actuator while positioning the Atomic Force Microscope (AFM) tip. In order to mitigate these nonlinearities, creep and hysteresis phenomenon are first modeled separately by using the classical Prandtl-Ishlinskii (PI) operator. Then, a linear time-invariant (LTI) representation is obtained to identify the creep uncertainty and subsequently an adaptive control scheme is devised for the piezoelectric actuator to track a desired path in the presence of creep. An additional dynamic inversion loop is utilized by using an online approximator to offset the hysteresis effects without the need of identifying the parameters within the hysteresis model. Rigorous performance analysis is conducted using standard Lyapunov stability approach along with simulation results. Copyright © 2009 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society [source]