Blog posts

      This letter describes a method to analyze electromechanical stability of dielectric elastomer actuators.  We write the free energy of an actuator using stretches and nominal electric displacement as generalized coordinates, and pre-stresses and voltage as control parameters.  When the Hessian of the free-energy function ceases to be positive-definite, the actuator thins down drastically, often resulting in electrical breakdown.  Our calculation shows that stability of the actuator is markedly enhanced by pre-stresses.

 
   This is a stress modeling position in TI's research
organization Silicon Technology Development (SiTD). The opening is
immediate and the position is filling very fast. Minimum requirement:
MS degree in the following fields: Mechanical Engineering, Physics,
Materials Science or Engineering Mechanics. PhD degree is preferred. 
Please email your resume to Jie-Hua (Jeff) Zhao at jhzhao [at] ti.com or

When an electric voltage is applied across the thickness of a thin layer of an dielectric elastomer, the layer reduces its thickness and expands its area. This electrically induced deformation can be rapid and large, and is potentially useful as soft actuators in diverse technologies. Recent experimental and theoretical studies have shown that, when the voltage exceeds some critical value, the homogenous deformation of the layer becomes unstable, and the layer deforms into a mixture of thin and thick regions.

This has reference to (only) the *last paragraph* in Prof. Harry Lewis' recent post, found at: node/1423#comment-2880.

The reason I write the present post is because I always seem to have had a view of inventing, learning, or teaching mathematics that is remarkably at odds with what Prof. Lewis' last paragraph *seems* to imply.

Postdoctoral positions are available in the Micro and Nano Mechanics group led by Prof. Wei Cai in the Mechanical Engineering Department at Stanford University.  [Link]