Benchmark analysis of ductile fracture simulation for circumferentially cracked pipes subjected to bending

Kumagai, Tomohisa*; Miura, Yasufumi*; Miura, Naoki*; Marie, S.*; Almahdi, R.*; Mano, Akihiro; Li, Y.; Katsuyama, Jinya; Wada, Yoshitaka*; Hwang, J.-H.*; et al.

Journal of Pressure Vessel Technology, 144(1), p.011509_1 - 011509_18, 2022/02

https://doi.org/10.1115/1.4052852

To predict fracture behavior for ductile materials, some ductile fracture simulation methods different from classical approaches have been investigated based on appropriate models of ductile fracture. For the future use of the methods to overcome restrictions of classical approaches, the applicability to the actual components is of concern. In this study, two benchmark problems on the fracture tests supposing actual components were provided to investigate prediction ability of simulation methods containing parameter decisions. One was the circumferentially through-wall and surface cracked pipes subjected to monotonic bending, and the other was the circumferentially through-wall cracked pipes subjected to cyclic bending. Participants predicted the ductile crack propagation behavior by their own approaches, including FEM employed GTN yielding function with void ratio criterion, are FEM employed GTN yielding function, FEM with fracture strain or energy criterion modified by stress triaxiality, XFEM with J or delta J criterion, FEM with stress triaxiality and plastic strain based ductile crack propagation using FEM, and elastic-plastic peridynamics. Both the deformation and the crack propagation behaviors for monotonic bending were well reproduced, while few participants reproduced those for cyclic bending. To reproduce pipe deformation and fracture behaviors, most of groups needed parameters which were determined toreproduce pipe deformation and fracture behaviors in benchmark problems themselves and it is still difficult to reproduce them by using parameters only from basic materials tests.

High energy photon emission from wakefields

Farinella, D. M.*; Lau, C. K.*; Zhang, X. M.*; Koga, J. K.; Taimourzadeh, S.*; Hwang, Y.*; Abazajian, K.*; Canac, N.*; Ebisuzaki, Toshikazu*; Taborek, P.*; et al.

Physics of Plasmas, 23(7), p.073107_1 - 073107_10, 2016/07

https://doi.org/10.1063/1.4956450

Development of a prototype GEM TPC with a gating grid for an H-dibaryon search experiment at J-PARC

Sako, Hiroyuki; Sugimura, Hitoshi; Ahn, J. K.*; Han, Y.*; Hasegawa, Shoichi; Hwang, S. H.*; Ichikawa, Yudai; Imai, Kenichi; Kiuchi, Ryuta*; Ozawa, Kyoichiro; et al.

Nuclear Instruments and Methods in Physics Research A, 763, p.65 - 81, 2014/11

https://doi.org/10.1016/j.nima.2014.06.007

We developed a prototype TPC for an H-dibaryon search experiment at J-PARC. To investigate its performance, we conducted tests with Ar-CH (90:10) and Ar-CF (95:5), where the former is mainly used. The detection efficiency was measured to be 98% at the beam rate up to cps/cm, and 90% at the rate of cps/cm. Based on the measured horizontal resolution of 0.19-0.46 mm at the drift length of 5-20 cm, the position resolution of better than 0.3 mm is estimated in 1 T magnetic field. The ion backflow fraction was measured to be 5% and reduced up to 3% at the gain of . The horizontal position distortion due to ion backflow in the gate operation was suppressed within mm at the beam rates up to cps/cm. On the other hand, the distortion with the gate open was measured to be mm. The distortion in the final experiment is estimated to be mm.

Development of high power long-pulse RF transmitter for ICRF heating in fusion researches and cyclotron accelerator

Kwak, J. G.*; Wang, S. J.*; Bae, Y. D.*; Kim, S. H.*; Hwang, C. K.*; Moriyama, Shinichi

Fusion Engineering and Design, 86(6-8), p.938 - 941, 2011/10

https://doi.org/10.1016/j.fusengdes.2010.10.005

KAERI have been developing the transmitters for ICRF heating for KSTAR and the cyclotron accelerator since 1996. The toroidal magnetic field of KSTAR is nominally 3 T so that 25-60 MHz transmitter is required to cover ICRF heating scenarios of the KSTAR. The first transmitter is operating up to 60 MHz and it succeeded in achieving 2 MW for 300 s in 2008. Up to 300 kW RF power was successfully injected to KSTAR plasmas. The second one is 70 kW/CW transmitter used for the cyclotron accelerator and their frequency range is from 25 to 50 MHz. Its engineering design was finished. The third one is 1 MW/VHF transmitter which was loaned from JAEA. As the operating ICRF frequency of KSTAR is lower, its cavity structure will be modified from 110 MHz to 60 MHz. The test results of 60 MHz and lessons from the high power test of 2 MW transmitter will be introduced and the circuit analysis and engineering design work for the second and third amplifiers will be shown.

Exchange bias and uncompensated spins in a Fe/Cr(100) bilayer

Kim, K. Y.*; Hwang, Y. S.*; Park, J.-G.*; Torikai, Naoya*; Takeda, Masayasu; Han, S. W.*; Shin, S. C.*

Physica Status Solidi (B), 244(12), p.4499 - 4502, 2007/12

https://doi.org/10.1002/pssb.200777317

We have investigated the effect of the field cooling on the exchange bias and the coercivity in an exchange-biased Fe/Cr(100) bilayer using SQUID magnetometer. After the field cooling, magnetization shifted upwards, indicative of surplus magnetic moments, which could be interpreted as an evidence of pinned and uncompensated Cr magnetic moments induced by the cooling field. Interestingly enough, we also discovered that not all the pinned and uncompensated spins seem to be involved in producing the exchange bias, although they contribute to increasing the coercivity and inducing the surplus magnetization.

Development of a time projection chamber for J-PARC experiments

Hosomi, Kenji; Imai, Kenichi; Sako, Hiroyuki; Hasegawa, Shoichi; Sato, Susumu; Hwang, S. H.*; Han, Y.*

no journal, ,