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REPORT DATE (DD-MM-YYYY)
15-
PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)Massachusetts Institute of Technology 77 Massacusetts Avenue Cambridge, MA 02139
145 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)Office of Naval Research, Materials Science Prg ONR Code 331 800 N. Quincy Street, Balston Tower 9 Arlington VA 22217-5000
SPONSOR/MONITOR'S ACRONYM(S)
ONR
SPONSORING/MONITORING AGENCY REPORT NUMBER
99R00006-01
DISTRIBUTION AVAILABILITY STATEMENTONR Program Officer Dr. George Yoder; Administrative Grants Office; Director NRL; DTIC Othrewise Unlimited 13. SUPPLEMENTARY NOTES
ABSTRACTIn this research the mechanisms of the brittle to ductile transition of fracture initiated primarily by crack tip processes under both quasi-static as well as dynamic conditions was studied experimentally, and mechanistically modeled. Additional experiments and modeling included the role of grain boundariesin resisting cleavage cracking among grains in Fe-3%Si alloy, also associated with modeling. Reproduction in whole, or in part, is permitted for any purpose of the United States Government.This document has been approved for public release and sale, its distribution is unlimited.
BRITTLE TO DUCTILE TRANSITION IN CLEAVAGE FRACTURE OF ALPHA-IRON: EXPERIMENTS AND MODELING OF MECHANISMS
I. Summary of Research Carried out under the ProgramThe research results reported here in this final technical report are a continuation of an earlier program supported by the ONR Mechanics Division under Contract #N00014-92-J-4022 where the emphasis was on an experimental study of the brittle-to-ductile transition of fracture in silicon single crystals by thermal crack arrest and on modeling of dislocation emission from crack tips. Similarly, the research initiated under the ONR Program reported here, supported by the Materials Science Division and studying the role of grain boundaries in the crack growth resistance is now being continued under NSF support.The principal thrust in the completed research program under ONR support was on two experimental studies. One thrust was the completion of earlier research on the study of brittle to ductile fracture transition in silicon single crystals as stated above, while the second thrust was on a study of the role of grain boundaries in the enhancement of cleavage crack-gr...