Erin E. Flater

Contact mechanics description of inelastic displacement response of a nano-positioning device

A classical mechanistic model was developed to capture the existence of pre-sliding tangential deflection (PSTD) in contacting polysilicon and coated polysilicon surfaces. For the purposes of modeling asperity friction, experiments have shown, and been supported through detailed finite element analyses, that frictional forces developed through tangential sliding scale linearly through a material parameter known as the junction strength. A junction strength model coupled with a discrete quasi-static contact mechanics analysis, using contacting surface descriptions sampled by AFM from actual polysilicon surfaces, predicts inelastic tangential displacements that are qualitatively consistent with observed PSTD response. The simulations imply that the existence of PSTD depends not only on the spatial characteristics of contacting surfaces, but also on the local loading characteristics.

Multiscale Roughness of MEMS Surfaces

Investigation of contact and friction at multiple length scales is necessary for the design of surfaces in sliding microelectromechanical system (MEMS). A method is developed to investigate the geometry of asperities at different length scales. Analysis of density, height, and curvature of asperities on atomic force microscopy (AFM) images of actual silicon MEMS surfaces show these properties have a power law relationship with the sampling size used to define an asperity. This behavior and its similarity to results for fractal Weierstrass-Mandelbrot (W-M) function approximations indicate that a multiscale model is required to properly describe the surfaces.© 2004 ASME