Torsion and bending of micron-scaled structures

Typical microelectromechanical systems (MEMS) devices and packages are comp osed of micron-scaled structures. Experimental investigations on the effect of size on the deformation behavior of simple structures have shown that t he deformation behavior of metals and polymers is size dependent, The size dependence in small structures is attributed to the contribution of nonnegl igible strain gradients. In this work, torsion and bending of micron-sized rods and plates were analyzed by using a two-parameter model of strain-grad ient plasticity. Microrod torsion and microplate bending experimental data were analyzed to determine the magnitude of the strain-gradient material pa rameters. The parametric analyses showed that conventional analysis is appl icable only when the size of the structure is significantly larger than the material parameters, which are typically in the micron range, Strain-gradi ent analysis of micron-sized rod revealed that the presence of strain gradi ent increased the torque by three to nine times at the same twist. For MEMS structures with micron-sized features, conventional structural analysis wi thout strain gradient is potentially inadequate, and strain-gradient analys is must be conducted to determine the elastoplastic behavior in the micron scale.