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Title: Bifurcation of thick-walled electroelastic cylindrical and spherical shells at finite deformation
Author: Melnikov, Andrey
ISNI:       0000 0004 6057 5033
Awarding Body: University of Glasgow
Current Institution: University of Glasgow
Date of Award: 2017
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In this dissertation we consider some boundary value and stability problems for electro-active soft rubberlike materials which withstand finite deformations elastically. In the beginning we consider in detail the problem of finite deformation of a pressurized electroelastic circular cylindrical tube with closed ends with compliant electrodes at its curved boundaries. Expressions for the dependence of the pressure and reduced axial load on the deformation and a potential difference between the electrodes, or uniform surface charge distributions, are obtained in respect of a general isotropic electroelastic energy function. To illustrate the behaviour of the tube specific forms of energy functions accounting for different mechanical properties coupled with a deformation independent quadratic dependence on the electric field are used for numerical purposes, for a given potential difference and separately for a given charge distribution. Numerical dependences of the non-dimensional pressure and reduced axial load on the deformation are obtained for the considered energy functions. Results are then given for the thin-walled approximation as a limiting case of a thick-walled cylindrical tube without restriction on the energy function. The theory provides a general basis for the detailed analysis of the electroelastic response of tubular dielectric elastomer actuators, which is illustrated for a fixed axial load in the absence of internal pressure and fixed internal pressure in the absence of an applied axial load. Using the theory of small incremental electroelastic deformations superimposed on an electroelastic finitely deformed body, we then look for solutions of underlying configurations which are different from perfect cylindrical shape of the tube. First, we consider prismatic bifurcations. We obtain the solutions which show that for neo-Hookean electroelastic material prismatic modes of bifurcation become possible under inflation. This result is different from the pure mechanical case considered previously in Haughton and Ogden (1979), because in Haughton and Ogden (1979) prismatic bifurcation modes were found only for an externally pressurised tube. Second, we consider axisymmetric bifurcations, and we obtain results for neo-Hookean and Mooney-Rivlin electroelastic energy functions. Our solutions show that in the presence of an electric field the electroelastic tube become more unstable: axisymmetric bifurcations become possible at lower values of circumferential stretches as compared with the values of circumferential stretches found for analogous problems solved for electromechanically indifferent materials, or equivalently, when electric field is not present. Within similar lines we consider the bifurcation of a thick-walled electroelastic spherical shell with compliant electrodes at its curved boundaries under internal and external pressure. The solutions obtained for neo-Hookean electroelastic energy function show that in some cases axisymmetric modes of bifurcation become possible under inflation in the presence of electric field.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QA Mathematics ; QC Physics