Electromechanical hysteresis

Zhao X, Hong W, Suo Z (2007) Electromechanical hysteresis and coexistent states in dielectric elastomers. Phys Rev B 76 134113... 

Kamlah, M. 2001. Ferroelectric and ferroeleastic piezoceramics-modeling of electromechanical hysteresis phenomena. Continuum Mech. Thermody. 13 219-268. 

M. Kamlah, Ferroelectric and ferroelastic piezoceramics—modeling of electromechanical hysteresis phenomena. Contin. Mech. Thermodyn. 13(4), 219-268... 

The second category of actuators is based on electrostriction as exhibited by PMN [Pb(Mg 3Nb2/3)03] based ceramics. Although it is a second-order phenomenon of electromechanical coupling (x = ME, where M is called the electrostrictive coefficient), the induced strain can be extraordinarily large (more than 0.1%) [33], An attractive feature of these materials is the near absence of hysteresis (Fig. 4.1.19b). The superiority of PMN to PZT was demonstrated in a scanning tunneling microscope (STM) [34]. The STM probe was... 

In this eontext, ferroelectrets actually represent a third elass of piezoelectric polymers in the sense that these cellular materials share features of charge electrets (real eharges) with those of ferroelectric polymers (hysteresis-type ED characteristics) (Bauer et al. 2004 Lekkala et al. 1996). Moreover, ferroelectrets are characterized by extremely high piezoelectric 33 coefficients as well as an extreme anisotropy in their mechanical and electromechanical properties, which partially require speeifie characterization techniques (Dansachmiiller et al. 2005). 

Answer It is possible to extrapolate part of the way toward an understanding of what might be expected from a glassy phase by consideration of the behavior of very fine polycrystalline materials. The properties tend toward a limit as the particle size reduces. For example, the electromechanical properties tend toward a truly parabolic stress/strain relation and hysteresis due to domain wall movement decreases, as the latter cannot be maintained in ultrafine particles. However, such materials are still polycrystalline in that the majority of atoms have ordered neighbors, and reasonable diffraction patterns are obtainable therefrom. 

The reading on an instrument will be affected by imperfections in components in the instrument. If it is an electromechanical device, these errors will be due to magnetic hysteresis, friction, and tolerances on the sizes, assembly, and purity of the components. Likewise, for an electronic instrument, tolerances on components, assembly, and hysteresis of operation of the various circuits will affect the operation. In both types of instrument, ai r changes in the environment (temperature, humidity, and possibly pressure) will have an effect on the performance. Since many materials change their properties slightly with age (and continual use), it is necessary to consider the effect of age on the performance of an instrument. Since this is difficult to predict, it is essential that instruments be checked (calibrated) at regular intervals, for example, once a year, but preferably every 6 months. From the records (history) of instruments, confidence in the performance of a particular instrument is maintained. 

As hierarchical, multiscale and complex properties in nature, as shown inO Fig. 52.1, adhesion is an interdisciplinary subject, which undergoes vast experimental, numerical and theoretical investigations from microscopic to macroscopic levels. As an example, adhesion in micro- and nano-electromechanical systems (MEMS/NEMS) is one of the outstanding issues in this field including the micromechanical process of making and breaking of adhesion contact, the coupling of physical interactions, the trans-scale (nano-micro-macro) mechanisms of adhesion contact, adhesion hysteresis, and new effective ways of adhesion control (Zhao et al. 2003). 

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