Engineering Framework to Transfer the Lower Bound Fracture Toughness between Different Temperatures in the DBTT Region

AbstractIn this paper, an engineering framework to transfer the lower bound fracture toughness between different temperatures in the ductile–to–brittle (DBTT) temperature region is proposed and validated for 0.55% carbon steel using 0.5TSE(B) specimens. The framework requires only stress–strain curve for different temperatures as experimental data. The approach was based on the authors’ finding that the critical stress σ22c of the modified Ritchie–Knott–Rice criterion (the criterion predicts onset of cleavage fracture of a material in the DBTT transition temperature region, when the mid-plane crack-opening stress σ22 measured at a distance from the crack-tip equal to four times the crack-tip opening displacement δt, denoted as σ22d, exceeds a critical value σ22c) seems to be correlated with the lower bound fracture toughness for a specific specimen configuration. The proposed approach is expected to overcome some inconveniences which recent studies have reported to the Master Curve Local approaches to cleavage fracture that the Weibull parameters vary with size and temperature and are different from those stated in the Master Curve

Applicability of the Modified Ritchie-Knott-Rice Failure Criterion to Examine the Feasibility of Miniaturized Charpy Type SE(B) Specimens

This paper examined whether the modified Ritchie-Knott-Rice (RKR) failure criterion can be applied to examine the feasibility of miniaturized Charpy type SE(B) specimens of thickness-to-width ratio B/W=1. The modified RKR failure criterion considered in this paper is the (4δt,σ22c) criterion which predicts the onset of cleavage fracture when the midplane crack-opening stress measured at a distance equal to four times the crack-tip opening displacement, denoted as σ22d, exceeds a critical stress σ22c. Specimens with B values of 25, 10, 3, and 2 mm (denoted as 25t, 10t, 3t, and 2t specimens, resp.) manufactured with 0.55% carbon steel were tested at 20°C. The results showed that the modified RKR criterion could appropriately predict the occurrence of cleavage fracture accompanied by negligibly small stable crack extension (denoted as KJc fracture) naturally for the 25t and 10t specimens. The modified RKR criterion could also predict that KJc fracture does not occur for the 2t specimen. The σ22c obtained from specimens for the 25t and 10t specimens exhibited only a small difference, indicating that the Jc obtained from the 10t specimens can be used to predict the Jc that will be obtained with the 25t specimens

Volcanic strain change prior to an earthquake swarm observed by groundwater level sensors in Meakan-dake, Hokkaido, Japan

We installed and operated a low-cost groundwater level observation system at intermittent hot spring wells in order to monitor volcanic strain signals from the active Meakan-dake volcano in eastern Hokkaido, Japan. Data are sampled at 1 Hz and are transmitted to the data center in real time. Evaluation of the water level time series with theoretical predictive tidal strain and coseismic static strain changes has suggested that the wells penetrate to the artesian aquifer and act as a volumetric strain sensor. An active earthquake swarm with more than 400 events occurred at the shallower part of the volcano from January 9 to 11, 2008. Three independent wells recorded pre- to co-swarm groundwater drops simultaneously, which represented a decrease in volumetric strain. The total volumetric strain change during the three active days was estimated to be from 6 to 7 x 10^[-7]. The observed data, including changes in volumetric strain, absence of deformation in the GPS coordinates, and activation of deep low-frequency earthquakes, might imply possible deflation of a source deeper than 10 km, and these preceding deeper activities might induce an earthquake swarm in a shallower part of the Meakan-dake volcano

The Use of Oral Herbal Medicine (Hange-Shashin-To) in Patients with Pouchitis: A Pilot Study

Objectives: Hange-Shashin-To (HST), which is a combination of seven herbs, has previously been used in the treatment of inflammatory or ulcerative gut disease. The aim of this study was to evaluate the safety and efficacy of HST for the treatment of chronic pouchitis. Methods: Nineteen patients with chronic pouchitis, defined as either frequent episodes ( three episodes per six months) of pouchitis or persistent symptoms that required continuous antibiotic therapies, were selected and treated with ciprofloxacin (CPFX) 600 mg/day for 2 weeks (week 0~2) and HST 3,750 mg/day for 32 weeks (week 0~32). The Pouchitis Disease Activity Index (PDAI) score was measured at week 0 and 6 for short-term evaluation. For long-term evaluation, total CPFX dose in the 26-week period prior to study entry (from 30 weeks before study entry to 5 weeks before study entry) was compared with the total CPFX dose during the 26-week study period (week 7~32). Although no concomitant administration of CPFX was permitted from week 2-6, patients whose condition deteriorated were prescribed CPFX from week 7 to week 32. Results: Fourteen patients completed this 32-week study. The PDAI scores of eight patients decreased below seven. The mean total PDAI scores decreased significantly from 11 ± 2.5 to 6.5 ± 2.5 (P < 0.001). The mean value of total CPFX dose decreased significantly from 491.6 ± 182.4 mg/kg to 392.5 ± 184.0 mg/kg (P < 0.05). No severe adverse events were noted. Conclusions: Our data suggest that HST has a positive effect on chronic pouchitis with no adverse effects

The 2018 Hokkaido Eastern Iburi earthquake (M-JMA=6.7) was triggered by a strike-slip faulting in a stepover segment: insights from the aftershock distribution and the focal mechanism solution of the main shock

The Hokkaido Eastern Iburi earthquake (MJMA = 6.7) occurred on September 6, 2018, in the Hokkaido corner region where the Kurile and northeastern Japan island arcs meet. We relocated aftershocks of this intraplate earthquake immediately after the main shock by using data from a permanent local seismic network and found that aftershock depths were concentrated from 20 to 40 km, which is extraordinarily deep compared with other shallow intraplate earthquakes in the inland area of Honshu and Kyushu, Japan. Further, we found that the aftershock area consists of three segments. The first segment is located in the northern part of the aftershock area, the second segment lies in the southern part, and the third segment forms a stepover between the other two segments. The hypocenter of the main shock, from which the rupture initiated, is located on the stepover segment. The centroid moment tensor solution for the main shock indicates a reverse faulting, whereas the focal mechanism solution determined by using the first-motion polarity of the P wave indicates strike-slip faulting. To explain this discrepancy qualitatively, we present a model in which the rupture started as a small strike-slip fault in the stepover segment of the aftershock area, followed by two large reverse faulting ruptures in the northern and southern segments