Introduction

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OnScale provides an analyst the ability to model the coupled electro-mechanical behavior of piezoelectric materials.  However, electrostatic forces are not considered within the program's computational algorithms.  Hence, if no piezoelectric materials are present within a computational model, no mechanical forces will develop due to driving the model electrically.

CMUT (capacitive micromachined ultrasonic transducers) models differ from traditional piezoceramic models in that both electrostatic forces must be considered and large deformation effects (geometric nonlinearity) must be considered in both the mechanical and electrical response.  CMUT devices consist of a thin membrane under large membrane stresses that deflect several membrane thicknesses.  The large deformations cause large changes in the capacitance and to a lesser degree, geometrically nonlinear mechanical response.

The capabilities in OnScale include:

  1. The computation of electrostatic forces due to the charge distribution within the electric window of the model.  The piez command group has esta (electrostatic) options to provide this functionality.
  2. The ability to perform 'large deformation' simulations that include the changes in model response due to changing geometry, i.e. geometrical nonlinearity.  The ldef command activates this option.
  3. The shell element (a layered Mindlin plate) allows thin membranes to be modeled without the time step penalties that occur if they are modeled with continuum elements.  The shel command group provides this element type.  However, it should be noted that the shell elements only include the mechanical stiffness of a membrane.  Dielectric properties are not currently assigned to shell elements.  Continuum elements must be used to provide the proper dielectric distribution within the electric window.

Note: These capabilites are available for both 2D models (both axisymmetric and plane strain) and 3D models.




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