Joint Institute for Computational Sciences (JICS)

Materials Science

Yanfei Gao

Assistant Professor, Department of Materials Science and Engineering, UT
Joint Faculty, Computer Science and Mathematics Division, ORNL

Research

My current research focuses on theoretical and computational mechanics of crystal plasticity at small length scales, microstructural evolution, and the constitutive behavior of amorphous alloys.

Small-scale mechanical behavior

Small-scale Mechanical Behavior

Small scale mechanical experiments have motivated the development of a number of mesoscale plasticity theories, but efforts to compare theoretical predictions to experiments have generally been limited to qualitative features such as the macroscopic hardening behavior. In collaboration with Dr. B.C. Larson’s group in the Materials Science and Technology Division (MSTD) of the American Nuclear Society, we are developing mechanism- and defect-microstructure-based crystal plasticity, in comparison to their quantitative measurements of dislocation microstructure by the x-ray structural microscopy technique (Larson et al., Nature 2002).

Novel Self-assembly Process for Nanostructure Fabrication

Novel self-assembly process for nanostructure fabricationThrough collaborations with Drs. Amit Goyal, Malcolm Stocks, and Jianxin Zhong at MSTD, this project aims to establish a fundamental understanding of the nanoscale self-assembly process of BaZrO3 (BZO) patterns in the YBa2Cu3O7-δ (YBCO) superconducting ceramic thin film using the pulsed laser deposition (PLD) method. We will explore how the the formation and evolution of the nanostructures are affected by various experimental parameters, such as lattice mismatch strain, volume fraction of BZO phase, surface diffusivity, deposition rate, and spacer layer thickness.

Constitutive behavior of amorphous alloys

Recent experiments have shown that inhomogeneous deformation in amorphous alloys critically depends on the environmental temperature and the applied strain rate. Based on a free-volume-based, thermo-viscoplastic constitutive law, a linear stability analysis is carried out to examine the conditions for the unstable growth of temperature fluctuations. A deformation mechanism map is constructed to delineate this transition of inhomogeneous deformation from coarse to fine shear-band arrangements. Connecting the shear banding behavior to the fracture mechanism is a direction for future research.

Practical Importance

Understanding the constitutive response and failure behavior of advanced materials is an issue of fundamental importance for applications not only in the traditional aerospace and automotive industries, but also in modern electronic and energy applications. ORNL has a wide range of user facilities and research programs that offer multi-length-scale and multi-time-scale experimental capabilities, which are commensurate with the microstructural length scales in many advanced materials of interest to the DOE. Theoretical and computational modeling of these experiments will enable the development of mechanism-based material theory with which materials scientists and engineers can have direct design and predictive capabilities.

Benefits of the UT-ORNL Collaboration

The Joint Institute of Computer Science offers indispensable opportunities for the synergistic efforts between theory, simulation, and experiments. This allows a greater flexibility than could be achieved working solely at either a university or government lab.

The Role of High-Performance Computing

The access to the unique computational facilities in JICS enables the development of terascale and petascale computer simulation codes that can be projected to the future machines. On the other hand, the computational capabilities in these leadership computing facilities allow us to explore and extrapolate the predictive capabilities of molecular and other first-principle simulations to the modern experimental resolutions. Along these lines, working in the intimate collaboration between domain scientists, computational material scientists, computer scientists and architects, as provided in JICS, will help achieve goals that would be very difficult to reach separately.

Representative Publications (PDF Format)