This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).
This research project integrates experiments and modeling to develop physics-based predictive models for the problem of room temperature creep in nanocrystalline metallic films. The novel experiments aim at extracting directly the grain-boundary (GB) sliding viscosity and the GB diffusivity. Model experiments augmented with atomic force microscopy measurements will obtain the displacement jumps as a function of time. The measured local GB parameters will be incorporated in cohesive models for the GBs in a multiscale model for polycrystalline Au to quantify the effect of inelastic GB mechanisms on the creep response of nanocrystalline Au films. While other homogenization schemes use the macroscale material behavior to fit microscale parameters, the proposed multiscale experimental/modeling protocol employs macroscale experiments to validate the multiscale modeling predictions.
This project can have significant technological and educational impacts. Several thin film applications, such as radio frequency microelectromechanical systems, variable capacitors and tunable filters involve fixed-fixed metal structures that suffer from loss of mechanical stiffness due to creep at room temperature. Quantification of the GB mechanisms in nanocrystalline metals will allow for mitigating strategies to prevent room temperature creep but maintain the high yield strength that is controlled by dislocation crystal plasticity. Once perfected, the experiments will be integrated in the PI's experimental course "Nanoscale Contact Mechanics" that provides theoretical and experimental education and training to graduate students by following a "bottom-up" methodology in mechanics.
