Native celluloses from different origins show variant solubility in lithium chloride/amide solvent system. The solubility of some of native cellulose is enhanced by solvent exchange procedure, namely sequential immersion in water, acetone, and amide solvents. In order to investigate the effect of the solvent exchange on the solubility and the solid structure of native celluloses, small angle X-ray scattering (SAXS), cross-polarized/magic angle spinning (CP/MAS) 13C solid-state NMR, and X-ray photoelectron spectroscopy (XPS) measurements were performed. It was revealed from SAXS and solid-state NMR that the solvent exchange significantly affects the submicron-scale solid structure of wood and cotton celluloses. On the other hand, that of microbial and tunicate celluloses is less affected by the solvent exchange. The structural change induced by the solvent exchange is relevant to the enhancement of the solubility, which is supported by the fact that the XPS detected a vestige of dimethylacetamide (DMAc) molecules strongly absorbed on the surface of the cellulose sample even under an extreme vacuum condition.
The high-temperature setting method, which enables rapid kiln-drying for square timber with pith, has spread in many saw mills in Japan. It has been supposed that obvious drying tension set, which is formed at the shell of timber without back-splitting, results in generation of sufficient compressive stress at the shell, and reducing surface checks significantly. In the paper, we investigated the differences in internal stress between indoor and outdoor storage with sugi (Cryptomeria japonica D. Don) square timber kiln-dried by the method. The compressive stress was expressed as released strain measured by the slicing technique. Main results were shown below.
Strong compressive stress was observed at the shell of the timber which was stored indoor for five years.
On the other hand, the compressive stress obviously decreased at the shell of the timber which was stacked outdoor and covered with a corrugated panel for six years.
The compressive stress might be reduced by loss of tension set which was caused by moisture variation during long outdoor storage.
The hygro-thermal recoverable component of set seemed to be melted, which had been assumed to be recovered only by boiling.
From the above results, the indoor storage had little effect on the compressive stress at the shell of timber kiln-dried by the method, but the outdoor storage decreased the surface stress. Further research is needed for explanation of the time-dependent change for practical uses. For practical outdoor uses, the risk of occurrence of surface checks might increase as time passes.
For the purpose of obtaining shear modulus, axial, transverse and 45 degree off-axis compression test for wood specimen were performed to measure Young's modulus and Poisson's ratio. Strain was measured using a strain gauge and an extensometer, and deformation of specimens was observed using a digital image correlation (DIC) technique. The precision of the test was determined by the finite element method. The following conclusions were made. The nominal Young's modulus obtained from the distance between compression jigs was estimated to be smaller than that obtained using the strain gauge and extensometer. This was because large compression deformations occurred in the local area in contact with the jigs. The Poisson's ratio obtained for the off-axis specimen was negative. The Poisson's ratio obtained by Cauchy's transformation rule and the finite element method using mechanical properties cited in literature was also negative. Off-axis specimens were observed to undergo arc-shaped or S-shaped deformation by compression. Constraint on the jigs probably affected the deformation and resulted in the generation of improper shear stress in the specimen. This constraint was thought to be related to the compliance component C16 of Cauchy's transformation. The component of the cited properties has the maximum value under an off-axis compression of approximately 45°, and the value of the component under an off-axis compression of 15° is 22~69% of the maximum value. We propose that the optimum off-axis angle for obtaining the desired shear modulus probably is approximately 15° for the cited three species.
Asymmetric four-point bending and uniaxial-tension tests of notched specimen were conducted using 5-plywood of Lauan in order to obtain the edgewise shear properties such as shear modulus, proportional limit stress in shearing, and shear strength of this representative material. In addition to the experiments, finite element simulations were performed and the validity of the measurement methods was examined. The experimental and numerical analyses reveal that the asymmetric four-point bending test method is more reliable method available for measuring the edgewise shear properties of this material.
To evaluate a decrease in strength of wooden members and wood-based materials attacked by termites or wood-destroying fungi is important for long-term maintaining of wooden constructions. The relationships between strength and degree of biodeterioration of wooden members and wood-based materials were not evaluated properly, though there were few techniques for evaluating the degree of biodeterioration in wooden constructions using screwdriver, palpation or other apparatus. In this study, the strengths of three species of wood attacked by termites were evaluated using bending test and compression test of perpendicular to the grain, and the relationships between the strength and the density or the velocity of ultrasonic in the attacked wood were also investigated. As the results, European spruce specimens had large damage comparison with other species. Thus the density of attacked wood was positively correlated with the bending strength and young's modulus. The velocity of ultrasonic in attacked wood was loosely correlated with the bending strength and young's modulus. In the case of picking up the European spruce material, between the velocity of ultrasonic and bending strength or young's modulus showed good correlation. On the other hand, it was not found that the density and the velocity of ultrasonic were positively correlated with the compression strength and young's modulus.
This paper aims to discuss the chloride threshold value for the initiation of steel corrosion and the influence of chloride content at the rebar on corrosion progress in marine RC structures. The site investigation of reinforced concrete of seven existing dolphins was conducted in order to examine the influence of cover thickness and chloride content at the rebar on chloride induced corrosion. These dolphins were constructed in Tokyo bay and have been in service for around 30 years. In addition, the laboratory test was carried out by using reinforced concrete specimens with various chloride content and cover thickness in order to prove the results obtained from the site investigation. As the results, the chloride threshold value for the initiation of steel corrosion has been ranged within 2.0 and 2.4kg/m3. Moreover the speed of corrosion progress of rebars has been increased rapidly when chloride content at the rebar exceeded around 4.0kg/m3. Also, no serious corrosion of rebars with cover thickness over 70mm has been confirmed in around 30 years old concrete of dolphins.
Liquid mercury target system for spallation neutron source is installed at Materials and Life Science Experimental Facility in Japan Proton Accelerator Research Complex (J-PARC), which will promote innovative science. Austenitic stainless steel SUS316 for a structural material of the target vessel is contact with mercury, and imposed by cyclic pressure that is induced by pulsed proton beam injection at 25Hz. Therefore, it is important from the viewpoint of the structural integrity to investigate the effect of mercury on fatigue behavior of the structural material. Bending fatigue tests in mercury and air were performed to evaluate the effect of mercury on fatigue behavior. FRActure Surface Topography Analyses (FRASTA) were carried out to evaluate the change in fracture morphology with mercury. It was confirmed that the fatigue strength was decreased by mercury immersion in low cycle region less than 105 cycles and intergranular fracture surface was observed, while in high cycle region the mercury immersion effect was hardly recognized.
Nickel nanocrystalline thin films were produced by electrodeposition using sulfamate solution. Three types of thin films with different grain sizes were produced : CC films were made under constant current, PC films under pulse current, and CC-ally films under constant current with grain refinement additive. The grain size gets smaller in the order of CC, PC, and CC-ally films down to nanometers. The fracture strength and yield strength in tension tests follows the Hall-Petch relation, and the elongation was largest for CC-ally films. The fatigue strength increased with decreasing grain size, following the Hall-Petch relation down to about 10nm. The resistance to fatigue crack propagation decreased for nano grain-sized films. The threshold stress intensity factor was the smallest for PC and CC-ally films. In the intermediate-rate range, the propagation rate increased with decreasing grain size when compared at the same stress intensity factor. The fatigue fracture surface near the threshold consisted of granular features whose size decreased with decreasing grain size. At high stress intensity factors, striations were observed on the fracture surface of CC films, while only fine granular feature was observed for CC-ally films. On the specimen surface near the fatigue fracture surface of CP and CC-ally films, the small grain boundary fracture facets were observed at high stress intensity factors, while not observed near the threshold. For CC films, slip bands were seen together with the grain boundary fracture facets.