Because rock masses serve as natural barriers for geological disposal of radioactive waste, information about rock permeability is essential. An understanding of the influence of the surrounding environment temperature on the results is necessary for highly accurate permeability measurements. Herein we describe how to perform precise permeability measurements. Then, to investigate the influence of the surrounding environment temperature, we show the results of permeability measurements under conditions with dramatic changes using the transient pulse method and a Toki granite sample obtained from Gifu Prefecture in central Japan. The measured permeability without a temperature change is used as a reference. A change in the surrounding environment temperature remarkably affects the pressure in the upstream and downstream reservoirs, their pressure difference, and the confining pressure. An increase in the experimental system temperature increases the pressure. This difference is directly related to the estimated permeability. To accurately measure the rock permeability, it is essential to minimize changes in the surrounding environment temperature because they significantly affect the pressure difference.
An advanced deep hole drilling (DHD) technique is developed considering three-dimensional elastic–plastic behavior of materials during drilling and trepanning processes. The conventional, incremental and newly–developed DHD techniques and inherent strain method (strain gauge method) are applied, respectively, to measure through–thickness residual stress in thick-section weldment. Meanwhile, an advanced computational welding mechanics with integrated process–mechanics modeling for welding, which was proposed by authors in previous study, is applied to calculate through-thickness residual stress in the thick-section weldment. The calculated weld bead configuration and thermal cycles were compared with those obtained by experiment to validate the advanced computational simulation technique. Compared with conventional and incremental DHD techniques, newly–developed DHD technique showed a comparatively good agreement with those obtained by inherent strain method and calculated with the simulation technique. It is thus concluded that an advanced DHD technique developed considering three-dimensional elastic–plastic behavior of materials is expected to become available in more accurately measuring through–thickness residual stress in thick-section weldment.
Low cycle fatigue life of Ti and Ti alloys decreases due to tensile stress dwell even at ambient temperature. This phenomenon is called Cold Dwell Fatigue (CDF). CDF properties are affected by dwell time, test stress, and microstructure. In our previous study, the effects of dwell time and the life assessment by linear cumulative damage rule were reported. The effects of test stress and microstructure for CDF properties and life assessment are discussed in this study. Test stress was from 0.85 to 0.955 σ0.2 and influenced fatigue life. As for strain accumulation during stress dwell, rupture time was affected by both test stress and microstructure. On the other hand, rupture elongation was affected by only test stress. Considering stress dependence on rupture elongation was important for ductility exhaustion rule in linear cumulative damage rule and lead to calculation of creep-fatigue damage as DF+DC~1 (DF: fatigue damage, DC: creep damage).
Spatially localized vibration modes in bcc model crystals are investigated numerically. Spatially discreteness of crystal and nonlinearity of atomic interaction support the existence of these localized modes. We construct a hybrid computation method of the molecular dynamics simulation and the iteration method for finding periodic orbit in the phase space. Using the constructed method, we find two types of stationary localized modes in the bcc model crystal: bond-center modes and site-center modes. Frequency of these mode is out of the dispersion band. Structure of these modes in 3D crystal is investigated in detail.
Appropriate ceramics with strong adhesion to single-stranded ribonucleic acids (RNAs), which are used in biomedical and electronics devices, was selected by using an efficient materials-informatics technology based on a combination of an orthogonal array and a response-surface method. In this technology, at the first stage, important factors that significantly influence the adhesion strength were selected from various factors that characterize ceramic materials by using an orthogonal array with molecular simulations. As a result, the short-side and long-side lattice constants a and b were selected from four ceramic-material factors (a, b, the surface energy density, S, and the cohesive energy, C). At the second stage, the adhesion strength was described as a function of the selected important factors by using a response-surface method. From this function, the optimal solution (the best values for a and b) that made the adhesion strength maximum were obtained. The best values for a and b were obtained as 0.338 nm and 0.585 nm, respectively. At the third stage, the best ceramic material whose lattice constants were equal to the best values (a =0.338 nm and b=0.585 nm), which are the lattice constants of single-stranded RNA, was selected by use of the simulation results of lattice constants. As a result, CaO-5%MgO, ZrO2-37%MgO and HfO2-28%MgO, whose lattice constants were a =0.338 nm and b=0.585 nm, were selected as the best ceramic materials with the strongest adhesion to RNA. By applying the same technology to another application (the design of the ceramic material with strongest adhesion to a peptide that is a small part of proteins), CaO-9%NiO, ZrO2-34%NiO, and HfO2-26%NiO, whose lattice constants were close to peptide’s values (a =0.336 nm and b=0.582 nm), were selected.