Coupled electro-mechanical

Electromechanical Controls. Electro-mechanical control devices are typically used for load control (lighting, ventilation, and heating) in buildings with no feedback signal. The most common device is the electromechanical timer, in which a small motor coupled to a gearbox is able to switch electrical contacts according to a predefined time schedule. They are still in use today, applied to loads with simple scheduling requirements. 

Even for poly(y-methyl L-glutamate) with a high piezoelectric constant (d= 10 7 cgsesu), the electro-mechanical coupling constant k defined by... 

Abstract A general theoretical and finite element model (FEM) for soft tissue structures is described including arbitrary constitutive laws based upon a continuum view of the material as a mixture or porous medium saturated by an incompressible fluid and containing charged mobile species. Example problems demonstrate coupled electro-mechano-chemical transport and deformations in FEMs of layered materials subjected to mechanical, electrical and chemical loading while undergoing small or large strains. 

This scattering mode occurs only in piezoelectric materials, i.e., in crystals without inversion symmetry, and is caused by the electric field associated with acoustical phonons. Zinc oxide exhibits very high electro-mechanical coupling coefficients P (see later), exceeding that of quartz [42,59], which is one of the mostly used piezoelectric materials. Zook [60] has calculated the piezoelectrically limited mobility on the basis of the elastic and piezoelectric constants as (see also Rode [54]) ... 

In the last couple of decades, both Micro-electro-mechanical systems (MEMS) and microbiology achieved remarkable progress. MEMS provide very small systems, made of very small electrical and mechanical components. These systems range in size from sub micrometer level to millimeter level, and can include any component number, from a few to millions, in a particular system. MEMS extend the fabrication... 

To gain a more precise insight into the phenomena occurring in gels, the Theory of Porous Media (TPM), or the coupled chemo-electro-mechanical formulation is a good choice. Normally, the TPM is applied for the gel only, while the coupled multi-field formulation incorporates the gel and the surrounding solution. 

The coupled chemo-electro-mechanical multi-field formulation is a model on the micro-mesoscopic scale. It has been developed to gain a more precise insight into... 

Fig. 7 Unidirectional chemo-electro-mechanical coupling scheme (chemical field, (19) electrical field, (20) mechanical field, (22))...

In Fig. 8, the chemo-electro-mechanical coupling scheme is shown. For one time step, all the involved fields are used in iteration loops until a converged solution is obtained. Then, the same procedure for the next time step will be applied. 

In this test case, the chemical stimulation of the gel film placed in the solution bath is investigated by the fuUy coupled chemo-electro-mechanical formulation. That is additionally, the mechanical deformation of the gel domain is considered and the chemo-electro-mechanical field is directly solved on the deformed domain. 

Fig. 16 Coupled chemo-electro-mechanical simulation Steady-state results (a) of the mobile concentrations and c and (b) of the electric potential after chemical stimulation...

Summarizing, a change of the concentration in the solution by a chemical stimulation provokes a change of the concentration, of the electric potential, and of the gel domain. This fully chemo-electro-mechanical coupling is quite robust and works as a kind of limiter for the change of the chemical, electrical and mechanical unknowns compared to the unidirectional chemo-electrical to mechanical coupling. 

The coupled chemo-electro-mechanical formulation is a quite powerful tool for capturing the behaviour of the chemical, electrical and mechanical unknowns. In order to compare numerical results with experimental results, the numerically obtained relative swelling ratio q versus the prescribed concentration in the solution is depicted in Fig. 17. The initial state of the test cases discussed in Sect 2 has been taken as reference value. 

In this chapter numerical simulations by applying the coupled chemo-electro-mechanical multi-field formulation on a deforming mesh have been performed. It has been shown that this formulation is an excellent method for describing the coupled behaviour of polymer gels in a solution. This method is capable to explain the mechanisms of the behaviour of polyelectrolyte gels under chemical and electrical stimulation, the ion distributions as well as the swelling and bending behaviour. 

Wallmersperger T, Ballhause D (2008) Coupled chemo-electro-mechanical FE-simulation of hydrogels-part II electrical stimulation. Smart Mater Struct 17 045012... 

In the 1950s, Hansell observed the production of drops by electro-mechanically induced pressure waves [8]. In this type of system, a voltage pulse applied to a piezoelectric material that is directly or indirectly coupled to the fluid, at ambient pressure, induces a volumetric change in the fluid. This volumetric change creates pressure/velocity transients within the fluid that are directed so as to produce a drop from an orifice [9-11]. Since the voltage is applied only when the drop is needed, these types of systems are called drop-on-demand or demand mode. ... 

WaUmersperger, T., KropUn, B. Gulch, R.W. 2004, Coupled chemo-electro-mechanical formulation for ionic polymer gels - numerical and experimental investigations . Mechanics of Materials, vol. 36, no. 5-6, pp. 411-420. 

Electrospinning technique has been used not only for the deposition of polymeric nanofibres but also for the production of ceramic nanofibres of PZT. PZT is commonly used in micro- and macro-scale piezoelectric energy harvesting devices due to its high electro-mechanical coupling coefficient of -500-600pC ) as compared... 

A. On reduction by the chemical dithionite, the temperature interval for thermally driven contraction lowers to a temperature interval a and thereby moves the elastic band through the transition zone c. Contraction results when the operating temperature is in zone c. Oxidation by the chemical ferricyanide relaxes the elastic band and completes the reduction-oxidation cycle to return the band and the attached weight to its original state. With the proper mediator molecules to diffuse between electrode and redox couple in the cross-linked matrix, the reduction and oxidation can be carried out electrically thus this may correctly be called electro-mechanical transduction. 

This provides us the electro-mechanical coupling coefficient d for the measured tip displacement (F = 0 in Fig. 2.36) ... 

Electro-mechanical model of IPMC can be represented by a transformer circuit [Newbury and Leo (2003a)] as shown in Fig. 9.6. It is assumed that the electrical and the mechanical component of the systems are coupled... 

Soh, A.K., Song, Y.C., and Ni, Y. 2006. Phase field simulations of hysteresis and butterfly loops in ferroelectrics subjected to electro-mechanical coupled loading. Journal of the American Ceramic Society 89[2] 652-661. 

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