損傷力学に基づくニオブ合金材の機械特性モデリングとクリープ疲労解析

学位の種別: 課程博士審査委員会委員 : （主査）東京大学教授 都井 裕, 東京大学教授 栗山 幸久, 東京大学教授 吉川 暢宏, 東京大学准教授 川畑 友弥, 東京大学准教授 岡部 洋二, 東京大学准教授 山田 知典University of Tokyo(東京大学

Characterization of hydrogen peroxide removal reaction by hemoglobin in the presence of reduced pyridine nucleotides

AbstractHydrogen peroxide removal rates by hemoglobin were enhanced in the presence of reduced pyridine nucleotides. The species which had the activity to oxidize pyridine nucleotides was purified from human blood and identified as hemoglobin A. Hydrogen peroxide removal rates by hemoglobin A without reduced pyridine nucleotides at 0.2 mM hydrogen peroxide were 0.87±0.11 μmol/s/g hemoglobin, and the removal rates using 0.2 mM NADH and NADPH were 2.02±0.20 and 1.96±0.31 μmol/s/g hemoglobin, respectively. We deduced that the removal reaction by hemoglobin included formations of methemoglobin and the ferryl radical and reduction of the latter with pyridine nucleotides. The hydrogen peroxide removal ability by hemoglobin was less than that by catalase but was larger than that by glutathione peroxidase-glutathione reductase system at 0.2 mM hydrogen peroxide. Under acatalasemic conditions, it was suggested that NAD(P)H were important factors to prevent the oxidative degradation of hemoglobin

Life evaluation of a combustion chamber by thermomechanical fatigue panel tests based on a creep fatigue and ductile damage model

The inner liner of a combustion chamber of a cryogenic liquid rocket engine is exposed to a high load induced by the high temperature of the hot gas and the low temperature of the coolant. The high load causes some inelastic strain that accumulates with each operational cycle until the fracture or rupture of the inner liner. A model that can reproduce the propagation of damage under a thermally cycled load is essential for precisely predicting the chamber life. However, the damage propagation phenomenon or the quantitative value of the damage was so far not fully discussed using the damage data obtained from basic testing of a rocket chamber material. The purpose of the present study was to investigate a precise prediction model based on damage mechanics for simulating the damage propagation of a rocket chamber material. In this study, low cycle fatigue test data at a high temperature (900 K) were analyzed, and damage models that could reproduce the damage propagation under cyclic load conditions were investigated. Then the parameters were identified to reproduce uniaxial test data. These damage models were also subject to a finite element method analysis of a thermomechanical fatigue panel test in order to quantitatively evaluate the deformation, damage propagation, and life of a chamber wall. The analysis of low cycle fatigue test data at 900 K suggested a specific model that could precisely reproduce the damage propagation phenomenon and the basic material test data. From the results, it was confirmed that the model could predict the location of crack initiation

Visualization of Hydrazine Decomposition in a Catalyst Bed by Using Neutron Radiography

Proceedings of the 10th World Conference on Neutron Radiography (WCNR-10) Grindelwald, Switzerland October 5–10, 2014Most mono-propellant thruster technologies were developed in the 1960s. Those basic principles and fundamental mechanisms, such as the catalyst and propellant, are still in use without major technical innovation. However, much remains to be clarified in terms of the mechanisms and quantitative limitations of the hydrazine decomposition phenomena inside the mono-propellant thruster. Therefore, in order to enhance the reliability of the propulsion systems, it should be promising to perform the direct observation of the physical and chemical phenomena occurring in the catalyst bed of the mono-propellant thruster. For that purpose, a visualization of the mono-propellant thruster was performed by using high frame-rate neutron radiography technique. The experiments were conducted at the Kyoto University Research Reactor and the hydrazine injection behavior to the catalyst bed was visualized clearly