It is known that the shear performance of plywood depends on the grain direction of veneer sheets, and if veneer sheets are oriented 45 degree against the lateral sides, it indicates highest shear performance. Authors produced experimentally the diagonal plywood, which were laminated parallelogram veneers oriented diagonally against the lateral sides. The in-plane shear performance of the bearing wall, which joined diagonal plywood to the frame with the nail spaced 50mm to 150mm apart, was evaluated by racking test. When the nail space was shortened, load at yield point increased, but maximum load of diagonal plywood was almost equal to standard plywood. The comparable result was also obtained from the lateral nail resistance test. In conjunction with this, shear strain distribution of panel was measured by digital image correlation (DIC), and approximate shear modulus of panel could be calculated from load-strain curve. Shear strain of diagonal plywood was lower than that of standard plywood. The bearing wall using diagonal plywood indicated large initial stiffness. As a result, it was concluded that bearing wall using diagonal plywood indicates higher reference shear strength. In order to increase the shear strength that is added to diagonal plywood, it is effective if the interval of nail is to some extent shorter than 150mm, which is the specification of wall index 2.5 of bearing wall using standard plywood. Shear modulus of full-sized diagonal plywood was about 4 times as much as that of standard plywood.
The drying stress in a longitudinally hollowed boxed-heart lumber was estimated using a linear finite element method (FEM). The drying stress due to the anisotropic shrinkage of wood was estimated with the aid of thermal stress analysis in orthotropic materials. The tensile drying stress due to the anisotropic shrinkage of wood concentrated at the middle of wider side surface of the hollowed lumber. In the case of the lumber whose pith was set off from the center of the cross section, higher tensile stress was found at the side surface nearer to the pith than at the other surface. This stress concentration was relieved by allocation of the hollow at the position of the pith.
For a study of wood (cellulose) polypropylene composite with high filler content, the effects of resin content and cellulose fiber length on the fluidity of compound and physical properties of mold products were evaluated and discussed. Results are summarized as follows : 1. In the compounding process, void induced by cellulose fiber had influence on the discharge rate, 2. Results of viscoelasiticity and wet strength indicated the effect of tangle of fiber is dependent on resin content and cellulose fiber length. 3. The compound of 300μm fiber length and 20% resin content showed thixotoropic flow and improved the molding characteristics. This paper would contribute for manufacture of high performance composites with high content of cellulose fiber.
Cellulose derived from a kind of algae, Spirogyra sp., was found to have cellulose Iα rich structure by the structural analysis using FT-IR and solid state NMR measurements. The cellulose from the algae was hard to dissolve in the typical cellulose solvent, LiCl/amide system. However, a new technique to promote the dissolution was developed including ethylenediamine treatment, which can dissolve the cellulose from the algae in LiCl/amide solvent within two days. The solution of xylan showed a Newtonian flow in the frequency range of this experiment. Contrary to the previous work that dealt with xylan-added cellulose suspension, the xylan addition did not lower the viscosity of the cellulose solution. From the viscosity measurement of various lignin solutions, it was indicated that the molecular weights of the lignins, even of milled wood lignin, were considerably lowered. Concentration dependence of specific viscosity for various lignin solutions showed that the solution properties of the milled wood lignin and the commercial lignins are almost the same.
It is necessary to properly control humidity in crawl spaces using humidity control materials such as charcoal, sepiolite, zeolite, etc., because the spaces tend to become damp, especially for high airtight and high insulation houses. Furthermore, wood components in crawl spaces are often infested by the subterranean termites (Coptotermes formosanus Shiraki and Reticulitermes speratus (Kolbe)). Recently the more attention is paid to the less- or non-chemical methods for termite control, and as a non-chemical treatment, physical barriers using particulate materials have been practically used in a few countries. In this study, in order to examine the feasibility of pelletized zeolites for a physical termite barrier with the ability to control humidity, moisture adsorption and desorption properties of pelletized zeolites and their penetrability by termites of C. formosanus were investigated. It was found that pelletized zeolites of 1.00 to 4.00mm in diameter showed the same changes in moisture content during adsorption and desorption processes as those for crushed zeolites, which were about four times as large as that for pelletized stones used as a physical termite barrier. In the penetration test of termites, the layer of pelletized zeolites with 1.40 to 3.35mm in diameter prevented termites from penetrating. These findings suggest that it is feasible to use pelletized zeolites as a humidity control material for crawl spaces and a physical termite barrier.
Fatigue crack initiation life (FCI life) of stress concentration can be predicted according to compare between elastic-plastic strain at there and total strain-fatigue life curve (Δεt-Nf curve) of smooth specimen. Elastic-plastic strain is estimated by use of Neuber's rule etc., and Δεt-Nf curve is estimated by use of Manson's universal slope method (US method) etc. At this point, cyclic stress-strain curve (CSS curve) is needed in order to estimate the elastic-plastic strain using Neuber's rule etc. However, CSS curve formulated by Ramberg-Osgood relation can be transform from Δεt-Nf curve formulated by Coffin-Manson & Basquin relation. Consequently, simplified fatigue life prediction methods can be constructed by only mechanical properties (tensile strength, true fracture ductility, Young modulus, etc.), according to combine these estimation methods (Neuber's rule, US method, etc.). In this report, we compared actual fatigue fracture life (FF life) of some stress concentration specimens with predicted FCI life of them obtained by use of simplified methods, and then evaluated about a practical use of simplified methods. The conclusions are obtained as follows : (1) About the precision of predicted fatigue life, modified universal slope method (MUS method) was better for steels, and Median method was better for aluminum alloys and titanium alloys. (2) For steels, the predicted fatigue life using ESED rule was more effective than using Neuber's rule. (3) In case of using elastic stress concentration factor Kt, the ratio of predicted FCI life Np and actual FF life Nf (Np/Nf) was conspicuously decreasing with increasing of Kt. (4) Taking account of decrease of Np/Nf, simplified method can be employed for preliminary fatigue design.
Friction-stir-welding (FSW) was conducted between an aluminum alloy 6061-T6 plate and a cold-rolled steel SPCC plate. Tensile and fatigue strengths of the FSWed material were investigated and its formability was estimated through bending and deep-drawing tests. Furthermore, we investigated effect of aging treatment (18ks, 453K) after FSW. The result showed that the condition of FSW was suitable and no brittle compound and defects were formed at the interface between the 6061 alloy and SPCC steel. However, hardness decreased in the region where the rotating tool passed so that the tensile strength of the FSWed material was slightly lower than that of uniform 6061 alloy. The tensile strength of the FSWed material was recovered by aging treatment and it reached to the same level to the 6061 alloy. The FSWed material and its aged material possessed good bending and deep-drawing formability. However, the fatigue strength was decreased even after aging treatment because an insufficient joining region was inevitably formed by FSW at the opposite side where the rotating tool traveled.
CoNiCrAlY coatings are deposited by the air plasma spraying (APS), the high velocity oxygen fuel spraying (HVOF) and the low pressure plasma spraying (LPPS). Oxides and pores are formed in the coatings during the deposition process, and their content in APS coating is the largest among the three types of coatings while that in LPPS coating is the smallest. In order to estimate the service temperature of a gas turbine component by means of the microstructural change of the coatings, these three types of specimens are exposed to high temperature in air. A diffusion layer grows at the boundary between the coating and the substrate due to the interdiffusion during the exposure. The layer thickness increases in proportion to the square root of the test time. The temperature estimation based on the relation is applicable to HVOF coating as well as to LPPS coating. However, it is difficult to apply the method to APS coating since its layer thickness is much smaller than those in the other coatings. The exposure test is also conducted in air by means of thermal barrier coatings with CoNiCrAlY bond coats prepared by HVOF and LPPS. HVOF bond coat contains larger amount of the oxides and pores than LPPS one. The bond coat is oxidized during the test, and the Al content decreases in the layer at the vicinity of the surface. The layer thickness increases in proportion to the square root of the test time. The applicability of the temperature estimation based on the relation is clarified for HVOF bond coat as well as for LPPS one.
In recent years, deteriorated RC bridges due to chloride-induced corrosion have been generally rehabilitated using Fiber Reinforced Polymers (FRP) sheet. Especially for the bridge, in which the spalling and peeling of covering concrete were occurred, the delaminated covering concrete should be removed and repaired by cross-section patching before bonding FRP sheet. In this paper, the flexural capacity of RC beams with cross-section patching repair and strengthening by CFRP sheet has been studied. The RC beams repaired by four kinds of polymer cement mortar (PCM) and three kinds of polymer cement concrete (PCC) were evaluated for the different rehabilitation. And also the following two points were discussed. In the field, before the cross-section patching repair work, the adhesive was applied at the interface of placing joint (also tensile reinforcement). And the putty was applied before bonding CFRP sheet for enhancing the effect of strengthening. The effects of applying adhesive and applying putty were described in this study. As the results, if the beams were repaired by patch repair material with less 18kN/mm2 of the elastic modulus, the load bearing capability degrades a little compared with the beam without repair. But when CFRP sheet was bonded to, the effect of strengthening degrades greatly compared with the beam without repair. For applying putty, the increase of the effect of strengthening enhanced a little. And for adhesive coating, the initial bond strength between the rebar and PCM increased, but the bond strength decreased after the slip of rebar.
In order to investigate the effects of ball diameters and contact loading rates on ring crack occurrence, static and dynamic contact tests were carried out using ceramic bearing ball. As the results, the scatter of ring crack initiation strength in contact test of same ball diameters is smaller than that of same size. Ring crack occurs at a distance from contact boundary with decreasing ratio of ball diameters. Initiation strength of ring crack is not evaluated by maximum tensile stress on the ball surface, because micro-defects of ball surface doesn't consider. Therefore, the evaluation should apply the stress intensity factor. Since the ring crack occurrences are not dependent on size effect, the scatters of strength are constant even if ball diameters change. In the case of dynamic contact tests, the strengths are increased with decreasing loading time. Then, the scatter is also small. Ring crack strength in dependent loading rates can be evaluated using stress intensity factor and cumulative effective hold time.
The urban landscape is composed of the accumulation of exterior finishing materials used for buildings. In the design of buildings, the exterior finishing materials are selected in consideration of the “performance value” peculiar to each material, the “space value” determined by economic consideration of the building location and the “environment value” based on regional weather conditions and atmospheric environmental conditions. For the purpose of examining the regional characteristics of the performance value of exterior wall finishing materials, an investigation into the quality, texture, geometry, color coordination and finishing cost of exterior finishing materials was conducted in the principal central business districts in Japan. From the investigation results, the factors determining the selection of exterior wall finishing materials in Japan and the similarity between the districts in terms of the degree of agreement are made clear.