Scale Effect Of The Mechanical Properties Of Mems Micro-structure

There are extensive applications of micro-structures, along with the development of science and technology. Meantime, people focus their attentions on the design and manufacturing of micro-structures. A number of experiments are demonstrated that the mechanical properties of metal materials have intense size effects, when the length scale parameters of materials are at the level of micron dimension. The phenomenon can't explain by the traditional continuous medium theory. So, the research on mechanical properties of materials will accelerate the development of MEMS.The traditional elastic theory, based on the hypothesis of material's continuity and uniformity, neglect the influence of inner micro-structure of the material. In this paper, the couple stress and rotation gradient are introduced, the mechanical model of micro-structure in MEMS is rebuild, the equilibrium equation and boundary condition are derived, the new constitutive relation based on the couple stress theory and elasticity theory is given. The size effect behaviors of thin brass-wire torsion, ultra-thin plate bending and plate-capacitive accelerometer are analyzed.Using the high-order strain gradient theory, the stress concentration around a hole has been analyzed. The high-order stress and its constitutive relations are introduced, the stress fields of the stress and high-order stress are obtained. The size effect behavior of the stress concentration problem is investigated.The results of this paper can provide a favorable referenced value for the design and manufacturing of micro-structure in MEMS.