Kenaf is a fast-growing plant and is noticed as a nonwood fiber resource. There will be significance in the kenaf utilization when the unique characteristics of kenaf will be effective for certain purposes. In this study, pulping and bleaching of kenaf were carried out to examine the usability of kenaf as a fibrous material. We examined a hydrotropic pulping and an enzymatic bleaching, considering the environmental feasibility. Sodium m-xylene sulfonate solution (NaXS) and sodium p-toluene sulfonate solution (NaTS) were used as the hydrotropic regents. The characteristic peaks for lignin were detected by means of UV, 13C-NMR, and FT-IR measurements of the solution after the hydrotropic cooking. The solution after the NaTS cooking produced precipitation when it was stand at room temperature, although the NaXS was stable. This shows that NaXS has higher power of dissolution of lignin. The molecular orbital calculation implied that this difference was originated from the micelle forming ability of the regents. The enzymatic bleaching by manganese peroxidase (MnP) was applied for the obtained pulp. The brightness was increased in 17.4% and the Kappa number was lowered in 9.0 for the bast fibers by the biobleaching.
In Japan, the shapes of traditional wooden joints are based upon carpenters′ experiences. However, in terms of strength, it is not revealed whether these shapes are optimum or not. For dovetail joints (ari-tsugi in Japanese), which have been frequently used in traditional timber constructions, an inclination of 1/6 is empirically and often used. In this paper, we conducted the tension tests with dovetail joint specimens of various inclinations and base widths, and examined whether empirical shape is optimum or not. Then strain distributions were calculated by digital image correlation (DIC). The results were as follows : (1) Joints with the inclination of 1/3 were 25∼35% stronger than that of 1/6, therefore empirical shape was not optimum. In comparison with the inclination, the effect of the base width to tensile strength was not significant. (2) Radial tensile strain concentrated on the corner of notches in the mortise side (female part of joint), where more than 2% of tensile strain was observed just before the fracture occurred. However, there was little difference between radial strain distributions whether inclination and base width were large or small. On the bottom of the mortise, approximately 0.7% of tensile strain observed in early wood just before the fracture occurred, but there was little strain in late wood. (3) On shear strain, concentration on the notch was remarkable with inclination increase. Consequently, the fracture of dovetail joints was caused due to the complex stress state, though the main factor of it can be radial tensile stress or strain.
Various materials are used for the interior space, and therefore various colors of them appear there. To design visually comfortable living space, an examination about the relations between the colors of the interior materials such as wood and the influence of them on our visual impression is very important. In this study colorimetric features of various interior images are evaluated numerically and the relation between those values and our visual impression of “warm” is discussed. Thirty seven of interior images were prepared as specimens, and questionnaires regarding visual warmth of the specimens were performed to 39 subjects in Experiment A, and to 30 subjects in Experiment B, respectively. The specimen set for Experiment A was composed of more colorful interior images than for Experiment B. To calculate the colorimetric features of the interior images, a digital color image processing method according to sRGB system was adopted. The method made possible the transformation from RGB data to L*a*b* values of LAB color system in every one pixel. By the comparison of the result of both experiments, the effective hue index that was based on a modified hue angle weighed by a metric chroma value was devised. The index could express visual warmth of the interior images which accent colors, vivid red, blue, and so on, existed in well.
Elastic calculations were performed for analyzing the elastic strain field in a cell wall and the cellulose microfibril (CMF) when the wood specimen having an inclined grain is subjected to a uniaxial load. Shear strain and shear stress generated in a cell wall and the CMF were finally predicted. In the present case, it is hypothesized that elastic constants E1, E2, G12, and ν21 in Eqs. (6) can be calculated from the simple mixture rule. If we consider that shear strain γ12 in Eq. (10) and γ'12 in Eq. (15) cause the generation of piezoelectric voltage in the CMF, measured piezoelectric voltage must be proportional to the superposition of those shear strains over all tracheid in the wood specimen. Assuming that a wood specimen could be represented by the multi-tracheid model as shown in Fig. 7, we derived the formulas (23) to (26) which should be proportional to piezoelectric voltage generated in the wood specimen having an inclined grain. Based on those ideas, we could explain the experimental result that a plot of the piezoelectric voltage versus the grain angle of the wood specimen gave a convex curve with a peak at 45 degrees.
Block copolymers, Poly (HPMA-b-DMS)-1∼7, were obtained from polymerization of N- (2-hydroxypropyl) methacrylamide (HPMA) initiated with polydimethylsiloxane (PDMS) type of azo-initiator [4,4’-azobis (polydimethylsiloxane)-4-cyanopentanoate (azo-PDMS)]. From XPS measurements of freeze dried samples, the hydrophilic PHPMA segment was found to migrate to the surface of Poly (HPMA-b-DMS) films in water. Poly (HPMA-b-DMS) showed lower contact angle (θ = 54°∼100°) than PDMS itself (θ = 103°). It was also found that the contact angle of block copolymers was changed in response to change in temperature, i.e., θ = 64°∼79° at 40°C and θ = 54°∼69° at 20°C for Poly (HPMA-b-DMS). The amount of adsorption of albumin on the Poly (HPMA-b-DMS) film was depressed at 20°C compared to the case at 40°C. For the purpose of an application to a thermo-responsive drug delivery system, copolymer hydrogel Gel (HPMA-b-DMS) was also prepared by radical copolymerization of HPMA and N,N’-ethylenebisacrylamide initiated with azo-PDMS.
The problem of semi-infinite plane containing a circular hole has been treated using the stress functions in bi-polar coordinate. In these analyses, the boundary conditions have been given by only stresses or displacements on the hole and the straight edge. The aim of this study is that the solutions are presented for the semi-infinite plane containing a circular hole subjected to stresses at infinity. For introducing the solutions, the solution of semi-infinite plane and that of infinite plane with a circular hole are superposed to converge to both boundary conditions. Some numerical results for displacements are shown by graphical representation.
Effects of rolling ratios, microstructures and crystal orientations on the fatigue cracks that grow on the rolling direction as mixed mode I + II cracks in pure aluminum sheets were investigated by conducting fatigue tests. The CCT specimens were used and made from cold-rolled pure aluminum sheets with rolling ratio of 50%, 75%, and 90%. It was found that the cracks grow to the rolling direction as mixed mode I + II cracks in the specimens with rolling ratio above 75%. It was also confirmed that microstructures in the high rolling ratio specimens are smaller and more elongated to the rolling direction than those with lower rolling ratio. However, there was no effect of microstructure size on the fatigue crack path. The crystal planes on the fracture surfaces and the slip plane of aluminum, (111) planes in the sheets were measured using X-ray diffraction. It was found that (111) planes mainly existed on the fracture surface of the crack that grew on the rolling direction. In addition, there were strong textures of (111) planes on the rolling direction of specimens with rolling ratio higher than 75%. It was clarified that the fatigue cracks, which grow to the rolling direction as mixed mode I + II cracks, are caused by strong textures of (111) planes on the rolling direction that exist in the maximum shear-stress region.
This paper studies the relationship between Superficial Rockwell hardness and elastic-plastic material constants by finite element (FE) analysis. Finite element analyses for Superficial Rockwell hardness were carried out to study the effects of elastic-plastic material constants and friction on the hardness. The hardness increased with increasing yield stress and strain hardening coefficient but it decreased with increasing strain hardening exponent. A new equation was proposed for predicting the hardness from yield stress and strain hardening coefficient and exponent. The equation predicted the FE and experimental results within a small scatter. The critical thickness of specimen was discussed based on the extent of plastic deformation and the experimental results. The friction between indenter tip and specimen upper face had almost no influence on the hardness.
Electromagnetic acoustic resonance (EMAR) is a contactless resonant method with an electromagnetic acoustic transducer (EMAT). This method is free from extra energy losses, resulting in the measurement of intrinsic ultrasonic attenuation in solids. In this study, the EMAR was applied to detect the creep damage of a Cr-Mo-V steel, JIS-SNB16 which is used for high temperature bolt. The material was exposed to the temperature of 923K at various stresses. We measured ultrasonic attenuation for 1-7-MHz frequency range as the creep advanced. The attenuation coefficient exhibits much larger sensitivity to the damage accumulation than the velocity. The attenuation experiences a peak at around 30% and a minimum value at 50% of the creep life, being independent of the applied stress. This novel phenomenon is interpreted as resulting from microstructure changes, especially, dislocations’ recovery. This is supported by TEM observations for dislocation structure. EMAR exhibited a potential for the assessment of damage advance and the prediction of the remaining creep life of metals.
For the purpose of contributing to the jointing plan for the apron pavements of Central Japan International Airport, various tests were conducted in regards to concrete mixed with pulverized blast-furnace slag. Relationships between the amount mixture of pulverized blast-furnace slag, and both the mechanical and shrinkage properties were obtained. Further, the resistance of concrete to cracking was reviewed through stress analysis. In addition, we investigated the conditions in which cracking is induced at the joints of concrete slabs at the actual pavement worksites. These results were then verified using stress analysis. From the stress analyses results, it was found that cracking by shrinkage was induced, where joint spacing was equivalent to that of cement without pulverized blast-furnace slag, when using 40% pulverized blast-furnace slag mixed cement. In relation, results from a follow-up survey concerning with induced cracking in actual concrete slabs, demonstrated a consistency with the stress analysis results.
This paper presents the effects of the cross-sectional in-plane crystal orientation (θ) on the structural strength of single crystal turbine vanes using the finite element method (FEM). The material of the turbine vanes is the single crystal superalloy TMS-75. The obtained results show that the elastic constant matrix (c'44) changes were by above 60% due to the orientation variation (0° < θ < 90°). The dependency of the structural strength of the turbine vane on the crystal orientation was calculated using von Mises stress equation. The strength of the turbine vane was strongly related to θ, and also related to the model shape and load. This influence becomes more significant near the leading edge of the turbine vane where it is most likely to fracture.