The indoor temperature and humidity in an actual wooden house were measured at various places including each room, the places under the floor and above the ceiling, and a closet. The function controlling temperature and humidity at each place was evaluated by the regression analysis between indoor and outdoor temperature or humidity changes in a day. The function was different very much for each place of the house. The indoor temperature was affected by outdoor temperature in the following order: In the ceiling>rooms facing the south>rooms facing the north>under the floor. This suggests that the effect of sunshine acts strongly on indoor temperature. The function of humidity control at each place of the house was similar to that of temperature control. This also means that the control of indoor humidity change depends mainly on the degree of the relaxation of indoor temperature against outdoor. The humidity under the floor was considerably high because it faces to the moist ground, and the pattern of humidity change was more irregular comparing to the other places.
In this study, six species of wood and four wood based materials were tested in bending from -180 to +20°C, and the influence of temperature on bending strength (Fb) and Young's modules (Eb) was discussed. In the case of wood, not only the effect of temperature but also that of specific gravity on Fb and Eb were discussed. The moisture content of specimens was controlled to about 4% at 20°C in a vacuum, and the temperature during bending tests was regulated with liquid nitrogen and nitrogen gas. The results obtained are as follows. (1) In the case of wood, Eb and Fb are representable by the equations (3) and (4) respectively, containing two factors, specific gravity (ρ) and test temperature (θ°C). (2) The effect of temperature on Eb for wood based materials tested is illustrated on Figures 1 to 6. As the results, Eb increases as temperature falls, and their relation can be expressed approximately by a regression straight line for each wood based material. (3) Figure 7 shows the relation between Fb for wood based materials and test temperature.
Natural penetration of water into wood specimens was investigated by using soft X-ray densitometry. This method makes it possible to obtain the continuos moisture distribution within the specimen during water penetration without destruction. Specimens were taken from the sap- and heartwood of Hinoki (Chamaecyparis obtusa Endl.) and the sapwood of Akamatsu (Pinus densiflora Sieb. et Zucc.), and trimmed to the dimension of 10mm (R)×10mm(T)×180mm(L) and 10mm(R)×2mm(T)×180mm(L). One end of each specimen was dipped in distilled water and the water uptake was measured continuously by a load cell. At given time intervals, the specimens were taken out to weigh water uptake and for soft X-ray irradiation. After these measurements, the specimens were put back to continue the water penetration. The X-ray film obtained was scanned both in L- and R-direction of the specimens by a densitometer. Moisture increase within the specimen was calculated from the difference of film densities before and after penetration. As a result, the changes in moisture distribution in L- and R-directions of the specimen and penetration height during the process were clarified. With the aim to make clear the path of water penetration, wood specimens were stained with 1% aqueous solution of acid fuchsine, and the split radial surface was observed under a stereoscopic microscope. It was concluded that the moisture distribution in each direction of the specimen was characteristic of the wood species. This characteristic was considered to be caused by the difference in penetration mechanism due to wood structure.
Axial water permeability was measured on the specimens of coast and mountain types of Douglas-fir (Pseudotsuga menziesii FRANCO) sap- and heartwood, in green and air dried conditions. The measurement was carried out on the water saturated specimens of various lengths from 0.4 to 3.2cm in the fiber direction. Conducting tracheids, which were labeled with 0.5% water solution of Rhodamine B fluorochrome through the wood specimens, were observed with a reflected light fluorescence microscope in order to make clear the path-way, and the conducting area in the cross section of specimen was also measured on the specimens of various lengths. Most of sapwood specimens in green were quite permeable and their permeability was constant in any specimen length. However, the air dried sapwood specimens of coast type showed very low permeability 3.5×10-2 darcy even in the specimen length of 0.4cm, which corresponds to its fiber length. The permeability K in darcy decreased exponentially with increasing specimen length l in cm, as follows. logK=-0.19·l-1.84 R2=0.52 On the other hand, for the air dried sapwood specimens of mountain type, the one with specimen length of 0.4cm gave the same high permeability as that of green condition, and the permeability was expressed by the following equation (see Fig. 2), logK=-0.63·l+0.52 R2=0.87 These results agree with Bramhall's consideration. In green sapwood, water conduction occured in the whole early wood and a part of late wood. In drying, pits in early wood were blocked by aspiration and became to be impermeable. However, conducting tracheids in late wood, which has low permeability even in green, still remained under a air dried condition. Therefore, in air dried sapwood, most of the conducting tracheids were in late wood (see Fig. 5 (a)(b)). The measured values of conducting area for the specimens of various lengths did not correspond to those calculated from the permeability according to Bramhall's equation. The reduction in conducting area e-bl, as Bramhall said, should be understood as the reduction in number of conducting pits, because, for example, air dried sapwood of mountain type had the measured conducting area of 50% against 10% calculated from b vlue of 1.46. The former represented the total area of tracheids labeled with fluorochrome even if their permeability was very low, while the latter corresponded to the conductivity in pits between tracheids.
The characteristics of water absorption of wood-cement composites were investigated, comparing with those of particle board. The results obtained are as follows: (1) The water absorption of wood-cement composites was smaller than that of particle board. But up to about ten hours the water absorption of wood-cement composites was larger than that of particle board. (2) The coefficient of thickness swelling of wood-cement composites was 1/2∼1/3 of particle board. The reasons why that of wood-cement composites was small, are considered as follows: (1) The wood content of wood-cement composites is smaller than that of particle board. (2) The pressure intensity of pressing for making wood-cement composites is lower than that for making particle board. (3) On absorbing water, the recovering force of compressive strain in wood-cement composites is smaller than that of particle board, because the wood moisture content of wood-cement composites is high at the time of making them. (3) On absorbing water, the bond durability between wood and cement is a little smaller than that between wood and synthetic resin adhesive such as phenolic resin adhesive.
The contributions of dipoles and trapping electrons to the thermally stimulated current (TSC) spectra (-170∼130°C) in dry wood electrets were investigated not only by examining the collecting voltage-dependence of the TSC but also by substituting acetyl groups for hydroxyl groups in wood. When the polarizing voltage (VP) and the collecting voltage (VC) were applied, the current (IPC) was proportional to (VP-VC) in the low temperature dispersion. In the high temperature dispersion, the VC-depenence of the current became higher than the VP-dependence with rising temperature and the polarity reverse of the current was observed. When the collecting voltage was applied without the polarizing voltage, the current (IC) showed a high value in the higher temperature region. This phenomenon can be explained by means of the presence of conduction current. The difference between IPC and IC was given by the following equation: IPC-IC=kVP+IT(VP, VC), where IT(VP, VC) is the current due to trapping electrons. When VP was constant and VC was varied, this value (IPC-IC) was held constant in the rising part of the high temperature dispersion as well as in the low temperature dispersion. The value at 80°C tended to decrease with an increase in VC, and so trapping electrons may take part in the current. The current in the high temperature region except near 130°C as well as in the low temperature region markedly decreased with an increase in acetyl value. It is possible to conclude from the above results that the TSC in the rising part of high temperature dispersion as well as in the low temperature dispersion results from the polarization due to dipoles but trapping electrons may take part in the high temperature part of the high temperature dispersion.
In the study of correlation between images and physical characteristics of various interior wall materials, it became necessary to numerize wood grain patterns and other patterns. With consideration of mechanism of seeing, especially mechanism of flicker, pattern numerization formulae were developed as follows; a=4a0/c (1), a0=1/2θ0∫θ0-θ0|Dθ-Dav|dθ (2), Dθ=1/A∫A|Pθ-P0|dA (3), Dav=1/2θ∫θ0-θ0Dθdθ (4), where A: area of pattern P0, c: pattern contrast. The relation between flicker and pattern value a or a0 is formulated as follows; f=abc (8) or f=a0b (9), where b: coefficient of effect of visual angle. By using various patterns generated by computers, the correlation between flicker image and the pattern value was ascertained. The pattern value is not only a good index of flicker but also a good index of regularity in patterns. Therefore, the relation between the pattern value and images of“gorgeousness”and“agreeability”was investigated with various interior wall panels (which include decorative veneer and printed paper overlayed plywood). As the result, it became clear that there exists a considerable correlation between the pattern value and the images.
In this paper, Japanese red pine (Pinus densiflora Sieb. et Zucc.) was blightened by two methods: girdling and inoculation with pine wood nematode (Bursaphelenchus xylophilus). The growth strain on surface, the distribution of moisture content of trees in the blighting processes and the distribution of growth stress within stems after felling sample trees were measured. The results obtained are summarized as follows: (1) At three weeks after inoculation with pine wood nematode, withered leaves started to appear in the lower part of the crown and the exudation of resin on the wounded bark stopped. It was thoght that trees inoculated with pine wood nematode started blighting on this occasion. (2) The moisture content decreased around cambium at the start of blighting of trees treated by girdling and inoculation with pine wood nematode. (3) The growth strain on surface showed a high value at the start of blighting of trees, but it was a passing phenomenon. (4) In the trees treated by girdling and inoculation with pine wood nematode, the distribution of growth stress within stems differed from that of normal wood.
In order to prepare a wood-polymer composite (WPC) having dimensional stability and hygroscopicity similar to wood itself, the radical copolymerization of a hydrophilic oligomer, polyoxy ethylene glycol monomethacrylate (PEGMA), with a hydrophobic monomer, methyl methacrylate (MMA), in the presence of n-dodecyl mercaptan (RSH) as a chain transfer agent, in heartwood of Hinoki (Chamaecyparis obtusa Sieb, et Zucc.) was investigated. The hygroscopicity and dimensional stability were evaluated on the basis of the mole fraction of PEGMA and concentration of RSH in MMA-PEGMA system, bulking effect and the moisture content in the wood part in WPC. The results obtained are as follows: (1) An approximately linear relationship existed between the moisture absorption and the square root of absorption time in the early stage of moisture absorption tests. The retardating efficiency in moisture absorption decreased with increasing mole fraction of PEGMA in MMA-PEGMA system, and above 0.2 of PEGMA mole fraction, the hygroscopicity of WPC was greater than that of untreated wood. The dimensional stability could not be attained for WPC prepared without RSH, while the addition of 1% of RSH in MMA-PEGMA system provided the retardating efficiency in swelling. The anti-swelling efficiency in the equilibrium state at 20°C and 93% relative humidity increased with increasing the concentration of RSH. (2) The dominating factors for dimensional stability were the bulking effect and reduction of hygroscopic sites in wood components due to the impregnation of MMA-PEGMA copolymer, and the tangential swelling (Y) of WPC could be expressed experimentally as Y=1.98-0.67X+0.33Z where X is the bulking effect and Z is the moisture content in the wood part in WPC. (3) The effective surface area that can absorb moisture in WPC did not change during the absorption and desorption cyclic test. The dimensional stability of WPC prepared in the presence of 1% of RSH remained unchanged in the cyclic tests in the range of 0 to 93% relative humidity and 20°C.
Wood panels bow when they are exposed to different conditions on their two sides. Wood panels using plywood, particleboard and semi-hardboard, of which surfaces are untreated, and commercial wood panels for kitchen cabinet, of which surfaces are overlayed or finished for water proof or vapor barrier, are subjected to different humidity conditions on their two sides to measure the bowing. The type of bowing depends on the coating of surface, combination of frame and cyclic humidity change when exposed, especially on thickness, difference of swelling between back and face and interval of humidity change. Wood panels should be selected to meet humidity conditions in use.
Cleavage fatigue tests were carried out on double cantilever type specimens bonded with epoxy resin adhesives containing different amount of flexibilizer (polysulfide). Fatigue strength (σ7) was compared with static strength (σ0), and the effect of flexibility and thickness of glue-line on the fatigue properties of the bond system were discussed. The results obtained were summarized as follows: (1) The cleavage fatigue strength decreased with increasing flexibility of glue-line, while the static strength of the same type specimens increased effectively with it. (2) Both the fatigue and static strengths increased with increasing glue-line thickness, and the effect in the latter was greater than that in the former. (3) The fatigue strength (σ7) of all bonded specimens was lower than that of solid wood specimens, while the specimens bonded with epoxy resin containing 40 or 60phr flexibilizer exceeded the solid wood specimens in static strength. (4) Contrast in fatigue and static properties of bonded specimens in relation to thickness and flexibility of the glue-line could be explained with the complex effects of relaxation of stress concentration at the fracture point with increasing thickness and flexibility of the glue-line (plus effect) and decrease of cohesion of the adhesive polymer with increasing flexibilizer mixed (minus effect).
Mechanical properties of timber joints with metal plate connectors have been empirically estimated for determining the design load. The following variables were included in the test program: plate size, plate angle (angle between directions of force and the principal axis of the plate), grain angle (angle between directions of force and the grain of wood), specific gravity of timber and the effect of long term loading. The results obtained are as follows; (1) The strength of joints at plate angle 90° is the lowest when changing the plate angle, and the modifying factor to that of 0° is about 0.8. (2) The strength of joints at grain angle 90° is the lowest when changing the grain angle, and the modifying factor to that of 0° is about 0.6. (3) The strength of joints is proportional to the specific gravity of timber. (4) The critical load ratio corresponding to the creep limit is about half of the static maximum load. (5) Failure patterns of joints may be classified into five categories; (a) Tension failure of the plate (b) Withdrawal of teeth of the plate (c) Cleavage along the timber grain (d) Shear failure of the plate (e) Break of a wood part into which the teeth have been driven.
The deterioration of preservative treated stakes was followed in aboveground, groundline and belowground zones in order to examine the correlation between their durability and exposure years. Stakes of six wood species were treated with 0.3, 0.4 and 0.5% solutions of di-iodomethyl p-tolyl sulfone (AMICAL 48). They were half buried together with untreated stakes of each species in a graveyard exposure trial. Then, their deterioration by decay and termite attack was inspected every year by visual observation and measurement of compressive strength parallel to the grain. The results obtained were as follows: (1) Even in a belowground zone where the highest deterioration was observed in untreated stakes, the stakes treated with 0.5% AMICAL 48 resisted more than six years with the exception of Beihi sapwood and Oshuakamatsu (Fig. 1, (a)∼(f)). Also, the average ratio of residual compressive strength (σc%) of treated stakes other than Oshuakamatsu was kept over 80% level after six years. (2) The significant correlations between (a) exposure years and grade of damage, and (b) exposure years and σc% were obtained by the regression lines when the deterioration proceeded quickly (Table II). In this case, by examining the regression lines, the durability of stakes could be easily estimated (Fig. 2 (a) (b)). (3) When the deterioration was slow, these correlations were difficult to be obtained by the regression lines. However, it was proved that durability could be estimated from the regression curves based on the results of continuous observations within a six year period (Fig. 3).