The miniaturization of micro-electro-mechanical system incorporating the sensors, actuators, and electronic circuitry for signal processing and control feedback have made possible by advances in technologies originating in the semiconductor industry. The integration of the micro-electro-mechanical system, inter-digital transducers, and conformal antenna in the multifunctional smart materials results in a intelligent system suitable for sensing and control of a variety of functions in automobile, aerospace, marine, medical and civil structures. A good understanding and prediction of the performance of the smart materials plays a critical role in the developments of such intelligent systems. This requires an accurate modeling of smart material behaviors at nano/microscales.

Multiscale modeling of thermo-electro-mechanical material behavior

Piezoelectricity refers to the property of producing an electric field when the material subjected to an external force. A ferroelectrics is a piezoelectric material in which a spontaneous polarization can be reoriented. Piezoelectric or ferroelectric materials are widely used in engineering applications, including sensors and actuators, capacitors and memory applications. They are the most popular smart materials.

We have developed a multiscale model of ferroelectrics, which can describe the effect of atomic displacement at sub-nano scale, domain motion from nano- to microscale, and simulate a fully coupled thermo-electro-mechanical response of the material. Shown in Fig.1 and Fig.2 is a PZT four-layer cantilever-resonator after simulation-based structural optimization.

Fig. 1: Deformation of the four-layer (SiO2, Pt, PZT, Pt) resonator under electric field	Fig. 2: Stress distribution of the four-layer (SiO2, Pt, PZT, Pt) resonator under electric field

Multiscale modeling of polycrystalline material

Most industrial materials are polycrystalline materials, which are composed of randomly oriented crystallites, and a critical role is often played by the grain boundaries. The effect of grain size and grain boundaries on the material response become significant as the size of device goes to microscale or nanoscale.

We have been developing a multiscale model of polycrystalline material to simulate the material behavior that incorporates all the relevant length and time scales ranging from the atomic-level, via the microstructural length and time scale, to the continuum level. Fig.3 and Fig.4 are the computer results of thermal stress distribution due to initial process temperature and due to temperature gradient, respectively. Those results indicate the inhomogeneous material response and are very close to microscopic experimental observations on polycrystalline materials.

Fig. 3: Thermal Stress distribution in polysilicon due to initial process temperature	Fig. 4: Thermal Stress distribution in polysilicon due to temperature gradient

 

Related Recent Publications

Chen Y., Eskandarian A., Oskard M.S. and Lee J. D. (2004) “Meshless Analysis of Crack Propagation in Multiphase Micromorphic Solids”, World Congress of Computational Mechanics VII, Beijing, China, September 5-10, 2004, Tsinghua University Press & Springer-Verlag.

Chen Y., Lee J. D., and Eskandarian A., “Field Representation of Atomic N-body Problem”, World Congress of Computational Mechanics VII, Beijing, China, September 5-10, 2004, Tsinghua University Press & Springer-Verlag.

Chen, Y., Lee, J.D. and Eskandarian, A. (2003) “Micropolar theory and its applications to mesoscopic and microscopic problems”, Computer Modeling in Engineering & Sciences, in press.

Lee, J.D., Chen, Y. and Eskandarian, A. (2003) “A Micromorphic Electromagnetic Theory”, International Journal of Solids and Structures, accepted for publication.

Chen, Y., Eskandarian, A., Oscard, M.S. and Lee, J.D. (2003) “Meshless analysis of plasticity with application to crack growth problems”, Theoretical and Applied Fracture Mechanics, in press.

Chen, Y., Lee, J.D., and Eskandarian, A. (2003) “Atomistic counterpart of Micromorphic theory”, Acta Mechanica, 161, 81-102.

Eskandarian, A., Chen, Y., Oskard, M. and Lee, J.D. (2003) “Meshless Analyses of Fracture, Plasticity and Impact”, Proceedings of IMECE’03 2003 ASME International Mechanical Engineering Congress & Exposition, Washington, D.C., November 16-21.

Chen, Y., Lee, J.D. and Eskandarian, A. (2003) “Atomistic Formulation of A Multiscale Theory for Nano/Micro Physics”, IMECE’03 2003 ASME International Mechanical Engineering Congress & Exposition, Washington, D.C., November 16-21.

Lee, J.D., Chen, Y. and Eskandarian, A. (2003) “Wave Propagation in Micromorphic Ferroelectric Solids”, Proceedings of IMECE’03 2003 ASME International Mechanical Engineering Congress & Exposition, Washington, D.C., November 16-21.

Chen, Y., Lee, J.D. and Eskandarian, A. (2003) “Multiscale Modeling of Polycrystalline Silicon”, Proceedings of IMECE’03 2003 ASME International Mechanical Engineering Congress & Exposition, Washington, D.C., November 16-21.

Chen, Y., Lee, J.D. and Eskandarian A. (2003) “Atomistic Viewpoint of the Applicability of Microcontinuum Theories”, International Journal of Solids and Structures, accepted for publication.

Lee, J.D., Chen, Y. and Eskandarian, A. (2003) “A Micromorphic Electromagnetic Theory”, International Journal of Solids and Structures, accepted for publication.

Chen, Y., Eskandarian, A., Oscard, M.S. and Lee, J.D. (2003) “Meshless analysis of plasticity with application to crack growth problems”, Theoretical and Applied Fracture Mechanics, in press.

Chen, Y., Lee, J.D., and Eskandarian, A. (2003) “Examining the physical foundation of continuum theories from viewpoint of phonon dispersion relations”, International Journal of Engineering Science, 41, pp61-83.

Chen, Y., Lee, J.D., and Eskandarian, A. (2003) “Atomistic counterpart of Micromorphic theory”, Acta Mechanica, 161, 81-102.

Chen, Y., Lee, J.D. and Eskandarian, A. (2002) “Local and Nonlocal Meshless Method of Fracture Mechanics”, Proceedings of International Conference of Computational Engineering and Science, July 29 –Aug. 2, Reno, Nevada.

Chen, Y., Lee, J.D. and Eskandarian, A. (2002) “Applicability analysis of continuum theories from viewpoint of phonon dispersion relations”, US 14th Congress of Theoretical and Applied Mechanics, June 22-27, Blacksburg, Virginia, USA.

Chen, Y., Lee, J.D. and Eskandarian, A. (2002) “Connecting Discrete Atomic Model to Microcontinuum Field Theories”, 39th Annual Conference of the Society of Engineering Science, October 13-16, Pennsylvania.

Chen, Y., Lee, J.D. and Eskandarian, A. (2002) “Finding Material Constants in Micromorphic Theory through Phonon Dispersion Relations”, Proceedings of International Conference of Computational Engineering and Science, July 29 –Aug. 2, Reno, Nevada.

Chen, Y., Lee, J.D., and Eskandarian, A. (2002) “Dynamic meshless method applied to nonlocal cracked problems”, Theoretical and Applied Fracture Mechanics, 38, 293-300.

Chen, Y., Lee, J.D., and Eskandarian, A. (2001) “Meshless Particle Methods for Nonlocal Continua,” published in Advances in Computational Engineering & Sciences (edited by Atluri, Nishioka and Kikuchi), Tech Science Press, presented at Proceedings of the International Conference on Computational Engineering and Science, 19-25 August 2001, Puerto Vallerta, Mexico, on CD-ROM.

Chen, Y., Lee, J.D., and Eskandarian, A. (2001) “On Micropolar Field Theory and Its Applications”, in Advances in Computational Engineering & Sciences (edited by Atluri, Nishioka and Kikuchi), Tech Science Press.