Semi-strand (22.8mm×2.6mm×0.5mm) particles were prepared from small-diameter sugi (Cryptomeria japonica) logs obtained by thinning operations. The particles were treated with saturated steam for various preselected times. The saturated steam pressures used were 3.6, 6.2, 10.5, and 16.5kgf/cm2. The treated and untreated particles were then used to produce boards using urea-melamine formaldehyde resin as a binder. On the other hand, the chemical change of wood after steam pretreatment was investigated. The amount of water solubles and alcohol-benzene extractives increased with increasing treatment time and steam pressure. The pH of the treated wood decreased from 5.80 to 3.91. When the relative humidity was increased from 65% to 96%, the thickness swelling of the boards was reduced drastically by a high temperature steam pretreatment for a short period of time. The control board showed a linear expansion of 0.37% compared with a linear expansion of 0.25% for the boards made of the particles steam-treated 16.5kgf/cm2 for 1 minute. The modulus of elasticity of the boards increased with steam treatment time. Modulus of rupture and internal bond strength was affected adversely by the steam treatment.
The effect of temperature (20-80°C) on the bending creep of wood during moisture adsorption (7%→16%) and desorption (16%→7%) was investigated by using small beams of buna (Fague crenata Blume) and hinoki (Chamaecyparis obtusa Endl.) wood. The test specimens were 120mm radially, 3mm tangentially and 10mm longitudinally. The span was 100mm and the prescribed bending loads fitting to the test temperature were applied at the center of span. The final equilibrium moisture contents were attained in one step (fast) and in 7-8 steps (slow) by suitable humidity schedules in a testing chamber. Creep during moisture desorption was not dependent on temperature between 20°C and 80°C. On the other hand, creep during moisture adsorption was dependent not only on temperature but also on time and the range of moisture content. The difference in temperature dependence of creep between the adsorption and desorption period may be explained based on the behaviour of the amorphous region composed of molecular network. Some possible explanations are given in terms of the response of the molecular network structure in the amorphous region during desorption and adsorption.
The viscosity of wood during water desorption is formulated by the use of Doolittle's viscosity equation. On the basis of the equation, the creep compliance during water desorption is derived and approximately represented by J(t)=J0(t)+KM(t), where J(t) is the compliance during water desorption, J0(t) is the compliance in a steady state of moisture, K is constant, and M(t) is the change of moisture content during water desorption. This equation is equivalent to the equations which have satisfied the empirical results so far. By comparing both the water desorption process and the steady state of moisture, the decrease in excess entropy during water desorption is found to be one of the factors contributing the deflection recovery in the cyclic water adsorption-desorption process except first water adsorption process.
The pretreatment of moist wood by local steam explosion was attempted to improve the permeability of wood, and its effect on drying rate was investigated. In a convective kiln drying of the specimens having low initial moisture content, the drying rate was not improved by local steam explosion. On the contrary, for the specimens having high initial moisture content, the drying rate was increased by this pretreatment. The increase of drying rate by local steam explosion was observed in the whole range of moisture content under the radio-frequency/vacuum drying process even if the specimens have low moisture content. The impregnation of dye solution was also improved by the pretreatment regardless of initial moisture content. From these results, it is clear that the local steam explosion is effective in improving the permeability of wood and the occurrence of the treatment effect is dependent on drying process. The effectiveness of pretreatment in convective kiln drying was assumed to be affected by the initial condition of moisture because free water can not move to the surface by capillary tension force in the case that free water is not continuous in wood. The permeability is easily improved in the RF/vacuum drying process where the transport water through wood is done in the form of vapor by pressure differential.
For the purpose of enhancing dimensional stabilization of wood, Hinoki (Chamaecyparis obtusa Endl.) sapwood specimens were treated with the mixtures of cyclic methylolurea-formaldehyde compounds, called “glyoxal resins”, and dipropylene glycol (DPG). In this paper, the dimensional stability of the specimens was evaluated, and the mechanism of the dimensional stabilization was discussed. The information obtained was as follows; (1) Both of the bulking coefficient (B) and antiswelling efficiency (ASE) of the specimens increased with increasing mixing ratio of DPG in mixture. Them maximal ASE endowed by the treatment was more than 70%. (2) For the specimens treated with the mixtures having costant concentrations, an approximately linear relationship existed between B and ASE, with a high correlation coefficient. (3) For the specimens treated with the mixtures having a constant ratio of glyoxal resin and DPG, the relationship between weight increase (W.I.) and ASE was similar to the relationship between W.I. and moisture excluding efficiency (MEE). Consequently, it is suggested that the improvement of dimensional stability is also dependent on the decrease of hygroscopicity. (4) The specimens treated with the dilute mixtures revealed the dimensional stability that was considered to be caused by cross-linking.
In order to clarify the effect of odors of seven coniferous woods on human, contingent negative variation (CNV) and electroencephalogram (EEG) were measured. Four of the species used, hinoki (Chamaecyparis obtusa), sugi (Cryptomeria japonica), akamatsu (Pinus densiflora), and hiba (Thujopsis dolabrata var. hondai), were grown in Japan, and three of them, Alaska cedar (Chamaecyparis nootkatensis), Douglas fir (Pseudotsuga menziesii), and western red cedar (Thuja plicata), were grown in the United States. The concentrations of their wood odors were analysed by gas-liquid chromatography. The total concentration of monoterpene hydrocarbon in the wood odors was held to less than 3ppb. The amplitudes of early components of CNV and the α/β wave ratio of EEG at the frontal (Fz) and central (Cz) regions between in the presence and absence of wood odors were compared. 5 male and 5 female volunteers ranging in age from 20 to 26 were examinated. The result obtained are summerized as follows: (1) In the presence of wood odors, the early CNV amplitudes at Fz decreased at a statistical level of significance of 5% or better. (2) The α/β wave ratio of EEG increased significantly at Cz with hiba wood odor (p<0.01). (3) The decrease of the early CNV amplitude at Fz is related to the concentration of α-pinene in the wood odors.
This work is a part of the study that will establish the feasibility and limitation of using acoustic emission (AE) to monitor the peripheral cutting process of wood, and discusses the effects of wood fiber direction and tool wear on the acoustic emission signals, surface finish roughness and cutting force for routing. For sensing of AE signals, a non-contact technique with a transducer was used. The results obtained can be summarized as follows: (1) The AE count rate slightly decreased from 0° grain angle to about 15-30° grain angle taking the lowest value, and then increased to reach maximum at the grain angle of 135-150°. At the grain angle of 165°, the AE count rate showed a little lower value than that of 150°. The edge recession affected the AE count rate. The greater the edge wear, the greater the AE count rate. However, there was no significant change in AE count rate at the grain angles of 15° and 30°. Moreover, even though the tool became severely worn, an increase in feed speed gave little effect on the AE count rate while cutting with the grain. (2) The cutting force-grain angle relationship was almost steady at the initial stage of cutting edge. As the bit became severely worn, the relationship dramatically changed and a parabolic relation between two variables with an extreme at the grain angle of 60° became evident, and in a addition, an increase in feed speed did not affect the cutting force. For every cutting condition, the greater the edge recession, the greater the cutting force. (3) The surface roughness, lowest at the grain angle of 0°, slightly increased till 120° and then rapidly became rough reaching maximum at the grain angle of 150°. At the 165° grain angle the surface finish showed a lower value than of 150°. An increase in feed speed did not affect the change in Rz value while cutting with the grain. However, the greater the cutting wear, the worse the surface finish quality.
Localized deformation of Ti-50.6at. pct Ni shape memory alloy subjected to tensile loading at different temperatures (_??_Af) was studied by means of the observation of internal structure. The rolled sheet specimens were subjected to three types of heat treatments, i.e. annealing at 673K (AC), solution-treatment at 1173K (AQ), and aging at 873K after solution-treatment (AS). It was found AQ and AS specimens that the deformation after the yielding in tensile test was caused by the stress-induced martensite (SIM) transformation, and also by the movement of dislocations which was restricted in martensite bands. The deformation in AQ and AS specimens, therefore, were more localized than in AC specimen where the dislocations were introduced both in the matrix and martensite.
A quantitative metallographic study was performed on JIS SS400 steel to estimate the fracture strain from the measurement of aspect ratio for ferrite grains. The circumferentially notched round bar tensile specimens with the notch root radius of 6, 3, 1, 0.5mm were employed to obtain a wide range of fracture strain. The relationship between plastic strain and aspect ratio for ferrite grains was obtained from the detailed metallographic observations on the polished and etched longitudinal midsection through the fractured half of smooth round bar tensile specimen. A large number of ferrite grains, plastically deformed to various strains, were examined carefully to determine the dependence of aspect ratio on plastic strain. The aspect ratio was well expressed by an exponential equation as a function of plastic strain. It was then possible to provide an appropriate estimate of the fracture strain of notched specimens from the above relation. The average aspect ratio of 9 views immediately underneath the fracture surface was used to deduce the fracture strain. The estimated values were found to be in reasonably good agreement with the measured values within an error of about 1 to 8pct.
The objective of this paper is to evaluate the dynamic strength of model columns under biaxial bending. Dynamic and static tests were conducted on reinforced concrete square columns. Dynamic tests were carried out by shaking table test method and static tests were carried out by actuater test method under repeated loading with the same maximum displacement corresponding to each dynamic test. From the test results, the ratio of dynamic maximum strength to static strength at strain rate of 0.1/sec is about 1.12-1.17. It is shown that the proposed analytical method is applicable to estimating dynamic maximum strength of columns by using the enhanced stress-strain curves.
This paper reports the investigation of creep-rupture properties of welded joints of 2.25Cr-1Mo steel. Both small round bar and full-thickness (50mm) specimens were prepared from the joints fabricated by multi-layer welding. The creep-rupture testing was conducted at 550°C, using stresses in the range of 78-159MPa. Detailed observation was made to identify the location and mode of fracture in the specimens with different geometries of the welded joint. The major conclusions are: (1) For both small and large welded joint specimens, the location of fracture is at the fine grained region toward the base metal in the HAZ. In the small specimens fracture is transgranular with local necking, but in the large specimens fracture is intergranular without necking. (2) The fracture location in the small joint specimen that failed after 40980h was in the weld metal.This is because softening is more predominant in the weld metal than in the HAZ. (3) The HAZ structure of the multi-layer welded plate contains a special region with fine grains (6μm) where face and back beads meet. The crack initiates in the fine grained region rather than in the coarse (40μm) and/or mixed grains as traditionally reported. (4) It is necessary to evaluate the creep damage mechanism of welded joints by use of large specimens so that the location of cracking can be identified, whether at the surface or in the interior of the joint.
Recently, a new super rapid heating induction hardening technique which uses MICROPULSE SYSTEM has been developed. The new induction hardening technique differs from the former induction hardning in that the new technique is very useful for controlling case-hardened depth exactly, and is attendant on little deformation after hardening. In this study, in order to clarify the fatigue strength of the notched specimens of carbon steel (S45C, α=1.6) whose effective case-hardened depth are about 0.70mm and 0.45mm, uniaxial loading fatigue tests were conducted. It was found that the fatigue strength of the hardened specimens was 670MPa for the hardning depth 0.70mm and 630MPa for the hardening depth 0.45mm. Micro pulse induction hardening improved the fatigue strength about two times higher than that of the S45C base metal. The “Fish-eye” which indicates that fatigue cracks initiated from the inside of a specimen appeared on many fracture surfaces. And the position of the “Fish-eye” coincided nearly with that of the case-hardened depth.
Reversed plane bending fatigue tests were conducted on SiC particle reinforced aluminum composite which was consolidated by Powder Metallurgy (P/M) process. The initiation and growth of small surface cracks were monitored by a plastic replica technique and investigated in detail. A fatigue crack initiated in matrix in the vicinity of SiC particle by cyclic slip deformation. It was found that the fatigue crack deflected along SiC particles and grew in a zig-zag manner microscopically, although the crack propagated straigth in the direction normal to the loading axis macroscopically. Micro subcracks frequently initiated in the front of main crack and coalesced. The fatigue crack growth rate was found faster in small crack than that in long crack.
By considering the compatibilizing effect for polymer alloy, two kinds of polymer type silane coupling agents, poly (methyl methacrylate) type (MacTMS-Ia-e) with Mn=1000-9800 and poly (styrene) type (MacTMS-IIa-e) with Mn=8300-11700 were prepared from the reaction of corresponding ω-allyl macromonomers and trimethoxysilane using H2PtCl6 as a catalyst, where ω-allyl macromonomers with a different molecular weight were prepared by radical polymerization of methyl methacrylate (or styrene) initiated with 2, 2'-azobisisobutyronitrile, varying the concentration of allyl mercaptan as a chain transfer agent. From the reaction of MacTMS and glass beads, the grafting efficiency (GE) of polymer onto glass beads was found to be 6.14-15.45%. A series of glass fiber reinforced plastics (GFRP-Ia-e, GFRP-IIa-e) were fabricated from GF cloth modified with MacTMS and bisphenolic epoxy acrylate resin oligomer as a matrix resin. It was found that the mechanical properties, such as flexural strength, flexural modulus, and ILSS, were affected by both the degree of polymerization and grafting efficiency of MacTMS.
Hydroxyapatite (HAp) was separated from scales of fish by two different methods, i.e., calcining and treating with hot potassium hydroxide aqueous solution. The thermal change of the powders obtained by the two methods was investigated by thermo-gravimetry, differential thermal analysis and X-ray diffraction, and the Ca/P molar ratio was determined by chelatometry. HAp contained in the scales showed diffuse X-ray diffraction patterns due to low crystallinity and/or micro-crystallinity as well as existence of bone minerals. The values of Ca/P molar ratio of HAp obtained by calcining and by treating with alkaline solution were 1.57 and 1.63, respectively. The former decomposed into stoichiometric HAp (Ca10(PO4)6(OH2) and β-calcium orthophosphate (β-Ca3(PO4)2) at 800°C. The latter was stable up to 900°C and converted to well-crystallized HAp.
Joint performance of two types of friction welded butt joints, A2017/S45C and A6061/S45C, fabricated under several welding conditions was investigated. In the case of A2017/S45C joint, the joint strength decreased with an increase in forging pressure, and the intermetallic compounds of Al7Cu2Fe and iron-aluminum alloy were observed at the weld interface. On the other hand, in the case of A6061/S45C joint, the joint strength increased with an increase in forging pressure, and iron-aluminum alloy was observed at the weld interface. Such a difference in the effect of forging pressure on microstructure at the weld interface depends on the deformation property of each aluminum alloy at elevated temperature. And the thinner was the intermetallic compound or the iron-aluminum alloy, the higher was the joint strength.