Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Matsuno, Takashi*; Fujita, Taiki*; Matsuda, Tomoko*; Shibayama, Yuki; Hojo, Tomohiko*; Watanabe, Ikumu*
Journal of Materials Processing Technology, 322, p.118174_1 - 118174_16, 2023/12
Times Cited Count：8 Percentile：66.71(Engineering, Industrial)The impact of high stress triaxiality on work hardening in transformation-induced plasticity (TRIP) steel has been widely acknowledged, particularly through measurements of the austenite fraction. Understanding this TRIP behavior is crucial for predicting material fracture in press-forming processes. However, the actual flow stresses under high-stress-triaxiality conditions remain largely undetermined. To address this gap, we developed a new tensile testing method using tiny notched round bars to investigate stress-triaxiality-induced work hardening in TRIP steels. The specimens were analyzed using two-dimensional micrometry to allow finite element analyses to identify the flow stress. Additionally, we conducted in situ tensile tests in which their crystal lattice stresses were monitored using synchrotron X-ray diffraction (XRD) to realize mechanism analyses of the unexpected work-hardening behavior identified by the developed tensile testing method. Our combined approach revealed a mutual, unstable increase in the flow stress and stress triaxiality in the TRIP-aided bainitic ferrite steel, which reduced the hardening exponent coefficients and thus induced a higher stress triaxiality. In contrast, the TRIP-aided martensitic steel exhibited a weakening behavior, characterized by a significant decrease in the hardening exponent coefficients in the case of the sharpest notch. XRD analyses showed that microstructural heterogeneity led to an extraordinarily high hydrostatic stress in the austenite phase, accounting for these contrasting behaviors. This finding challenges the established consensus on TRIP steels and suggests the need for a revised framework for their application in press-forming, taking into account stress-triaxiality conditions.
ZnKoizumi, Mitsuo; Seki, Akiyuki*; Toh, Yosuke; Osa, Akihiko; Utsuno, Yutaka; Kimura, Atsushi; Oshima, Masumi; Hayakawa, Takehito; Hatsukawa, Yuichi; Katakura, Junichi; et al.
Nuclear Physics A, 730(1-2), p.46 - 58, 2004/01
Times Cited Count：21 Percentile：73.08(Physics, Nuclear)Coulomb excitation experiment was carried out with a Zn beam bombarding a 
Pb target. Two 
matrix elements and the quadrupole moment of the 2
state were newly derived with the least-squares search code GOSIA. The potential energy surface (PES) was calculated with the Nilsson-Strutinsky model, showing two shallow minima: the first minimum does not contain the 
orbit below the Fermi surface, while the second minimum does. The ground state band and the intruder band seem to be constructed on the first and the second minimum, respectively. As for the ground state band, the asymmetric rotor model and the IBM in O(6) limit reproduced the experimental values rather well. The shallow PES may suggest unstability of the shape. The ground state band structure may be explained assuming a soft triaxial deformation.
ZnKoizumi, Mitsuo; Seki, Akiyuki*; Toh, Yosuke; Oshima, Masumi; Osa, Akihiko; Kimura, Atsushi; Hatsukawa, Yuichi; Shizuma, Toshiyuki; Hayakawa, Takehito; Matsuda, Makoto; et al.
European Physical Journal A, 18(1), p.87 - 92, 2003/10
Times Cited Count：16 Percentile：67.83(Physics, Nuclear)no abstracts in English
