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THE SCHOOL OF MATERIALS SCIENCE AND ENGINEERING
GEORGIA INSTITUTE OF TECHNOLOGY
Under the provisions of the regulations for the degree
DOCTOR OF PHILOSOPHY
on Tuesday, February 21, 2017
8:30 AM
in LOVE 295
will be held the
DISSERTATION PROPOSAL DEFENSE
for
Sukanya M. Sharma
"Effects of Strain Rate on Mechanical Properties and Fracture Mechanisms in Dual Phase Steels"
Committee Members:
Prof. Naresh N. Thadhani, Advisor, MSE
Prof. Arun M. Gokhale, Advisor, MSE
Dr. Shrikant P. Bhat, ArcelorMittal
Prof. Preet M. Singh, MSE
Prof. Kimberly E. Kurtis, CEE
Abstract:
Dual Phase (DP) Steels are a class of Advanced High Strength Sheet (AHSS) Steels used as the structural components of an automobile owing to their good combination of strength to weight
ratio, formability and crashworthiness. The microstructure of DP steels consists mostly of ferrite and martensite. In order to provide corrosion protection, DP steels may also have a
galvannealed layer. Additionally, to improve the bendability of galvannealed DP steels, some commercial grades may also contain a ”decarburized” surface layer. This leads to a gradient in the carbon content and in turn in the microstructure along the thickness direction. Thus, mechanical properties of these steels depend on the geometric attributes of the bulk microstructure and
the chemistry, and the thickness and microstructure of the decarburized layer and the protective galvannealed coating.
DP steels are exposed to strain rates of the order of 10 − 102/s during sheet metal forming operations, and strain rates of the order of 102 − 104/s can be reached under an automotive crash
condition. The intellectual merit of the proposed research is that it will lead to the scientific understanding of how microstructure, microstructural gradients, and surface coatings affect
strain rate dependence of fracture path, fracture micromechanisms and mechanical response of DP steels. The results of this work will be useful for design and development of DP steels
with superior formability and crashworthiness.
