ABSTRACT
We present a force-displacement contact model for the compressive loading of elastoplastic spheres. This model builds from the well known Hertz contact law for elastic, quasistatic compression to incorporate a material's strain-rate-dependent plasticity in order to describe collisions between particles. In the quasistatic regime, finite-element analysis is used to derive an empirical function of the material properties. A Johnson-Cook strain rate dependence is then included into the model to study dynamic effects. We validate the model using split Hopkinson bar experiments and show that the model can accurately simulate the force-displacement response of strain-rate-dependent elastoplastic spheres during dynamic compression and unloading.
ABSTRACT
A rapid screening method for optimizing electrochemical deposition conditions of polypyrrole (PPy) nanostructures is reported. An electrochemical cell is integrated within a low-cost microfluidic system, in which electrochemical deposition is carried out across a linear concentration gradient of a reaction parameter. The protocol, refered to as the screening of conditions for rationally engineered electrodeposition of nanostructures (SCREEN), allows rapid screening of conditions for the production of specific morphologies by characterizing the electrodeposited samples produced within a chemical gradient. To demonstrate the utility of the SCREEN method, applications in tunable optical coatings and superhydrophobic surfaces are presented.
