Topic:Microstructural analyses and mechanical simulation for understanding crack generation in high-cycle fatigue of titanium alloys and steels
Speaker: Dr.Osamu Umezawa, Yokohama National University, Japan
Time: 9:30am, (Thursday) Sept. 23, 2010
Venue:Room 356, Lee Hsun Building, IMR CAS
Welcome to attend!
Abstract
Firstly I would like to introduce you the outline of Physical Metallurgy Group, YNU. This group has been launched in 2002. We work on microstructural design and the relationship between structure and deformation or fracture behavior. Our mission is to conceive novel materials or processes using critical experiments tawards low environmental load, high strength and long life in products. The patterns in which atoms, defects and grain structures are arranged in the solid state determine properties of polycrystalline. These arrangements can be designed by altering parameters such as the chemical compositions, phase transformations and deformations.
The subject on subsurface crack generation in high-cycle fatigue of titanium alloys and steels will be presented. Novel systems have employed to clarify the substance crack generation and growth mechanisms of high strength alloys. In the very low plastic strain regime, the impeded glide of the screw dislocations in high strength alloys makes dislocation multiplication by irreversible bowing a difficult process. The fatigue limit is intrinsically related to the movement of a screw dislocation brought up thermally or by a mechanical stress. These conditions result in only a very small fraction of plastically deformed grains. The very localized deformation processes have been found to be decisive for subsurface fatigue crack generation at the lower stress level such as the elastic incompatibility at boundaries. The initial crack size highly depends on the maximum cyclic stress range, which implies a threshold of stress intensity range controlling mechanism. Heterogeneous microplasticity due to planar slip and restricted system is considered to play an important role on making the subsurface crack. Then, it should be progressed in the understanding of damage stage in high-cycle fatigue fracture process.
CURRICULUM VITAE
Name: Osamu UMEZAWA
Nationality: Japanese
Office Address: Department of Materials Science and Engineering
Yokohama National University
79-5 Tokiwadai, Hodogaya, Yokohama, 245-8501, Japan
Telephone: +81-45-339-3871
Fax: +81-45-331-6593
Education
(1) Waseda University (Japan), 1982 - 1986
Bachelor of Engineering Degree in Metallurgy (1986)
Awarded a degree of Doctor of Engineering by Waseda University for a thesis entitled:
"Cryogenic High Cycle Fatigue Failure of High Strength and Non-magnetic Alloys" (1992)
Served in
(1) National Research Institute for Metals (Japan), 1986 (April) - 1996 (March)
Researcher
Awarded the "Tawara Thesis Prize" by the Iron and Steel Institute of Japan for a publication on "Internal crack initiation in high cycle fatigue for Ti-5Al-2.5Sn ELI alloy at cryogenic temperatures", Tetsu-to-Hagane, September 1990.
Awarded the "Oshima Memorial Thesis Prize" by the Cryogenic Society of Japan for a publication on "High cycle fatigue properties of cryogenic structural alloys", Cryogenic Engineering, May 1992.
Awarded the "Honda Research Promotive Prize" by the Honda Memorial Foundation for achievements on "Cryogenic high cycle fatigue failure of high strength alloys", May 1993.
Awarded the "Best Structural Materials Paper" by the International Cryogenic Materials Conference for a publication on "High-cycle fatigue properties of titanium alloys at cryogenic temperatures", Advances in Cryogenic Engineering - Materials, July 1993.
(2) University of Cambridge, Department of Materials Science & Metallurgy, 1993 (October) - 1995 (March)
Visiting Fellow
(3) National Research Institute for Metals (Japan), 1996 (April) - 2001 (Octorber)
Senior Researcher
Awarded the "Tawara Thesis Prize" by the Iron and Steel Institute of Japan for a publication on "Shape, size and crystallographic orientation of the ferrite grains formed at grain boundaries of deformed austenite in a low carbon steel", Tetsu-to-Hagane, March 2001.
(4) Yokohama National University, Department of Mechanical Engineering and Materials Science (Japan), 2001 (November) – 2006 (March)
Associate Professor
Awarded the "Sawamura Thesis Prize" by the Iron and Steel Institute of Japan for a publication on "Influence of phosphorus on solidification structure in continuously cast 0.1 mass% carbon steel", ISIJ International, March 2004.
Awarded the "Academic Prize" by the Japan Institute of Metals for achievements on "Crack generation by heterogeneous deformation and microstructural control for high strength", March 2005.
Awarded the "Academic Prize" by the Iron and Steel Institute of Japan for achievements on "Deformation and fracture with heterogeneous microstructure", March 2006.
(5) Yokohama National University, Department of Mechanical Engineering and Materials Science (Japan), 2006 (April) - now
Professor
(6) Science and Technology Agency, Committee of safety technology for transport nuclear fuel, 1999 (April) – 2000 (December)
Adviser
(7) Tokyo Institute of Technology, Department of Materials Science and Engineering (Japan), 2000
Part-time lecturer
(8) Nuclear Safety Commission of Japan, 2001 (January) – 2003 (December)
Professional member of committee
(9) Yokohama City University, International College of Arts and Sciences (Japan), 2006
Part-time lecturer
Professional Qualifications
Member of the Japan Institute of Metals
Member of the Iron and Steel Institute of Japan
Member of the Japan Institute of Light Metals
Member of the Japan Foundry Engineering Society
Member of the Ecomaterials Forum
Member of the Minerals, Metals and Materials Society
Member of the Japan Society for Heat Treatment