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2012 年 11 月 15 日
Seminar - Effects of time scales on spatiotemporal evolution of thermomechanical fields during cyclic phase transition by Prof. Qingping SUN

Date:   15 November 2012 (Thursday)

Time:   11:00 am – 12:00 pm

Venue:  EF305, The Hong Kong Polytechnic University

Abstract:

Cyclic phase transitions phenomena are widely observed in materials and systems, from biomedical human artificial joints and small-scale sensors and actuators in MEMS to vibration and damping control devices in large scale engineering structures. This talk reports recent advances in the research of the solid–solid cyclic phase transition in NiTi polycrystalline shape memory alloys. In the first part, we report the experiment and modeling of the cyclic phase transition phenomenon, focusing on the macroscopic (average/lumped) level distinctive transient and steady-state temperature and stress oscillations under cyclic phase transition. In the second part, going one level down in more detail, we show how an initially macroscopic homogeneous material state becomes unstable and transforms into a new phase under external driving, leading to the emergence of spatial periodicity in the self-organized domain patterns and their loading rate dependence. Scaling law for such rate-dependant internal length scale is established. We elucidate the multi-physical coupling and multi-scaled nature of the spatiotemporal evolution of thermomechanical fields and emphasize and examine the important role of time scales in the coupling and the response of the material.

Biosketch:

Prof. Qingping SUN got his PhD in solid mechanics from Tsinghua Univ., Beijing, China in 1989. He is now the Professor and the Associate Head of the Mechanical Engineering Department and the Director of Institute of Integrated Microsystems at the Hong Kong University of Science and Technology. His research interests include experiment and modeling of phase transition processes in ceramics, metals and biological systems; bio-materials and medical devices; material instability and pattern evolution; hysteresis phenomena and multi-scale mechanics modelling; phase transition in micro-/nano- scale tribology of materials. He has over 100 publications in international journals, and serves as editorial board for Int. J. Solid Struct., Arch. of Appl. Mech. and Acta Mecanica Solida Sinica, etc.. He delivered over 30 invited key-note lectures in international conferences. His research-related awards and recognitions include the “Citation Classic Award by the Institute for Scientific Information (ISI, USA, 2000)” and “the National Natural Science Award of China (1995)”. He was a visiting professor at many French universities and (CNRS) national labs, including the Universite de Metz (1996), Ecole Normale Superieure de Cachan, Paris (2005) and Ecole Polytechnique, Paris (2007). He also served as the President of the Hong Kong Society of Theoretical and Applied Mechanics (HKSTAM) during 2006-2008.