Woodruff School of Mechanical Engineering
NRE 8011/8012 and MP 6011/6012 Seminar
Nuclear & Radiological Engineering and Medical Physics Programs
Modeling the Mechanical Behavior and Deformed Microstructure of Irradiated bcc Materials Using Continuum Crystal Plasticity
Mr. Anirban Patra
Georgia Tech, MS&E
Thursday, January 31, 2013 at 11:00:00 AM
Boggs Building, Room 3-47
Dr. Chaitanya Deo
The mechanical behavior of structural materials used in nuclear applications is significantly degraded as a result of irradiation. Combined phenomena of increase in yield strength, decrease in ductility, flow localization, and lower strain to fracture are typically observed. The deformed microstructure after tensile loading shows the formation of defect-depleted, dislocation channels which are ~50-200 nm wide, and in which majority of the inelastic strain is localized. Further, creep rates are accelerated under irradiation. These changes in mechanical properties can be traced back to the irradiated microstructure which shows the formation of a large number of material defects, e.g., point defect clusters, dislocation loops, and complex dislocation networks. Interaction of dislocations with the irradiation-induced defects governs the mechanical behavior of irradiated metals.
The present work uses a continuum constitutive crystal plasticity framework to model the mechanical behavior and deformed microstructure of bcc ferritic/martensitic steels exposed to irradiation. Understanding the governing physics of the material at the level of crystal plasticity can lead to an accurate description of the inelastic deformation. In this respect, continuum models for various plasticity-induced dislocation migration processes such as climb and cross-slip are developed. The continuum model is used to simulate the quasi-static and creep response under irradiation environments. Dynamic evolution of the distribution of point defects (generated due to radiation cascade events) is modeled, using a rate theory-based approach, to simulate realistic experiments. This framework represents the state-of-the-art in constitutive modeling of the deformation behavior of irradiated materials.
Anirban Patra is a PhD candidate in the School of Materials Science and Engineering at Georgia Tech working with Prof. David McDowell. He obtained his Bachelorís degree in Metallurgical and Materials Engineering from Indian Institute of Technology Kharagpur. Anirban's research deals with understanding the deformation mechanisms and modeling the mechanical behavior of Fe-Cr alloys subjected to radiation damage.