Journal of the Society of Materials Science, Japan

Acoustic Emissions from Wood and Wood-Based Materials

Masami NOGUCHI

1985 Volume 34 Issue 383 Pages 896-904
Published: August 15, 1985
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.34.896

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Present Aspects of Commercial Chemical Modifications of Wood and the Related Studies

Nobuo SHIRAISHI, Tokuo YOKOTA

1985 Volume 34 Issue 383 Pages 905-914
Published: August 15, 1985
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.34.905

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Influence of Strain Rate on Tensile and Compressive Strengths of Beech

Kiyoshi SATO

1985 Volume 34 Issue 383 Pages 915-917
Published: August 15, 1985
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.34.915

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The influence of strain rate on tensile and compressive strengths was investigated.
Tensile strength σ_t increased with increasing strain rate, and σ_t was expressed by the following equation: σ_t=a+blogv. Compressive strength σ_c also increased with increasing strain rate, and σ_c was expressed by the following equation: σ_c=A+Blogv, where v is strain rate.
A fractographical study was also carried out. The effect of strain rate was recognized on the fracture surface of the tensile specimen perpendicular to the grain (R direction).

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Transverse Air Permeability in Fifteen Wood Species

Jun-ichi KAWABE, Minoru MORI

1985 Volume 34 Issue 383 Pages 918-924
Published: August 15, 1985
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.34.918

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The transverse flow rate of air through flat- or quarter-sawn boards of fifteen species including domestic and imported woods was measured. The test specimens were disk type and the thickness (d) was 5-20mm, though extreme thin specimens had been used in the past works. The pressure difference between the two faces of the specimen was in the range of 10-70cmHg. The permeability characteristics for each species and the effect of d on the permeability under both unsteady and steady states were discussed. The results obtained were as follows.
(1) The transverse air flow through the specimen took place with a time lag for the start of reducing pressure. The flow rate increased gradually and, after a short or long increasing course, reached a constant value in the steady state. The time required to reach the steady state from the start and the flow rate at the state depended on wood species and d.
(2) The transverse permeability value calculated on the basis of Darcy's law in the steady state (k_g) was extremely different from one species to another. In coniferous trees, the range of k_g at 5mm of d was (0.3-15.2)×10^-5, and in broad leaved trees that of k_g was (0.02-32.0)×10^-5.
(3) In the cases of six species among all species tested, k_g showed nearly a constant value regardless of d. But in the cases of the other species, a linear relationship was found between d and logarithm of k_g as expressed by k_g=k₀exp(b·d), and the sign of b was positive for seven species and negative for two species.
(4) The longitudinal/transverse permeability ratio for the specimens of 20mm along the flow direction was within the range of (1.5-50.2)×10³ in coniferous trees and changed over a wide range of 2.1×10³-6.7×10⁷ in broad leaved trees.

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Evaluation of Ambient-Temperature Setting Properties of Phenol-Resorcinol-Formaldehyde Resin Wood Adhesives by TBA Method

Ryozo HAMADA, Masahiro TAKATANI

1985 Volume 34 Issue 383 Pages 925-929
Published: August 15, 1985
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.34.925

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Four kinds of RF and PRF wood adhesives were prepared and their curing behavior at ambient temperature was evaluated using the TBA method. The TBA curves obtained under isothermal and non-isothermal conditions revealed the difference in curing behaviour among the resins. It was found that curing measurements conducted at a constant heating rate were convinient for the comparison of the curing rate of the resins differing in resorcinol content. On the other hand, measurements carried out at a constant temperature were suitable for the determination of curing characteristics of the resins. It was observed that CH₂O was readily evolved during TBA measurements which affected the curing properties of the resins. Therefore, viscoelastic measurements were carried out for the resin impregnated in glass braid, sealed and cured. The results show clearly that this method is useful for the evaluation of ambient temperature setting properties of the PRF adhesives.

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Studies on Collapse of Wood Cells and Negative Pressure in Cell Lumen

Yoshiaki HATTORI, Yasushi KANAGAWA

1985 Volume 34 Issue 383 Pages 930-936
Published: August 15, 1985
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.34.930

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The negative pressure, that is liquid-tension, to cause cell-collapse was estimated with osmotic pressure at 20°C, and the behavior of cell-collapsing and the radius of opening in the cell wall were discussed.
The concentration dependence of the osmotic pressure of polyethylene glycol (PEG-20000) was determined over a wide range of concentration up to 0.557g/ml. On the basis of this result, the shrinkage behavior of the collapsing samples in the solution was compared with the amount of cell-collapse in air-drying and with the results of compression tests perpendicular to the grain.
The results obtained were summerized as follows. When the negative pressure in the cell lumen exceeded a certain magnitude, the cells deformed and then the sample shrank abruptly, as if the sample yieled to the stress. The limiting magnitude was about 2kg/cm² in the case of Balsa (Ochroma sp., R=60kg/m³), and 35kg/cm² in Almon (Shorea almon Foxw., R=430kg/m³). According to the magnitude of negative pressure to cause cell-collapse and the permeability of the cell wall to PEG, it was considered that the maximum radius of opening in the cells collapsed at normal temperature was order of 10mμ at the utmost.

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Anisotropy of the Creep of Wood during Drying

Variation with the Direction Relative to Annual Ring

Kiyoshi TABUCHI, Morihiko TOKUMOTO

1985 Volume 34 Issue 383 Pages 937-941
Published: August 15, 1985
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.34.937

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In this paper, the effect of the angle of annual ring with respect to the direction of tension upon the tensile creep perpendicular to the grain of wood was investigated.
Specimens (thickness 0.3cm) of Hinoki wood (Chamaecyparis obtusa Endl.) and Buna wood (Fagus crenata Blume) in the water-saturated state were dried under various tensile stresses to about 1% moisture content at 30°C.
The total creep compliance J_t just before unloading was composed of the initial creep compliance J_i occured before the starting of shrinkage of wood and the non-equilibrium creep compliance J_n during drying. The residual creep compliance after unloading was defined as the set compliance J_s.
The results obtained are summarized as follows:
(1) J_t, J_s and J_n varied significantly with the angle θ of annual ring with respect to to the direction of tension, and showed the maxima at θ=45°.
(2) Such significant variations of J_t, J_s and J_n were explained mainly by the variation of the instantaneous compliance J₀ in the water-saturated state with the angle θ of annual ring. So, the anisotropy of creep during drying had no direct connection with the anisotropy shrinkage in the transversal plane of wood.
(3) The ratio of J_i/J_t for Hinoki was larger than that for Buna and the ratio of J_n/J_t for Buna was larger than that for Hinoki wood.
(4) The slope of regression line between J_n and J₀ for Buna wood was larger than that for Hinoki. It was supposed that the difference in slope between Buna and Hinoki was due to that in chemical composition or specific gravity.

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Response of Warp and Internal Stress in Fiberboard to Change of Environmental Conditions

Yoshihiro MATAKI

1985 Volume 34 Issue 383 Pages 942-948
Published: August 15, 1985
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.34.942

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The modulus of elasticity and the dimensional changeability parallel to the plane of fiberboard are known to vary with depth, and furthermore both of the outer layers of board are directly exposed to the atmosphere, while the inner layer is more or less sheathed with the outer layers. Consequently, the internal stress appearing in the direction parallel to the plane of board is distributed well over the cross section, which can be examined by the slicing method.
Under the normal condition of 20°C·RH 60%, the screen back of SIS (wet-process) hardboard was found to be subjected to little internal stress, while the tempered face layer of S2S (wet-forming·dry-pressing) hardboard was exerted by a steeply high stress. However, the distribution of internal stress in the MDF (dry-process, medium density) was found to be reverse to that in the above-mentioned S1S or S2S, being symmetrical with respect to the center line of cross section.
In the case of a board conditioned at 20°C·RH 60%, the moisture absorption at 40°C·RH 90% and the desorption at 40°C·RH 30%, either from the face or from the back, gave so much influence on internal stress, as to cause the undue warp of board as the result of shifting the warp ability of layer within the cross section of board. The internal stress was distributed complicatedly over the cross section when a rapid moisture-absorption was given by spraying water or when a rapid desorption was achieved by the infrared rays radiation. In particular, the warp of the board almost disappeared after the moisture absorption under restraint of distortion.

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Effects of Size, Specific Gravity and Moisture Content on Energy Absorption of Wood during Impact Bending

Hiroyuki URAKAMI, Manjiro FUKUYAMA

1985 Volume 34 Issue 383 Pages 949-954
Published: August 15, 1985
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.34.949

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In order to elucidate the influences of the size of specimen, specific gravity, and moisture content on the work or the absorbed energy in impact bending, experiments were conducted for five species of Sugi (Cryptomeria japonica), Akamatsu (Pinus densiflora), Yachidamo (Fraxinus mandshurica), Tochinoki (Aesculus turbinata) and Makanba (Betula maximowicziana).
The results obtained are as follows;
(1) The work during impact bending (W) was expressed as a linear or exponential function of the breadth of specimen (B) with the exponent not more than 1.0.
(2) The work was expressed as an exponential function of the height of specimen (H) with the exponent more than 1.0.
(3) The work was given by the following equation: W=aB^mHⁿ (a: absorbed energy in impact bending, m, n: constant). So, it is necessary to reconsider the calculation method of the absorbed energy in impact bending which has been used in JIS, because the difference between the value (a) by JIS and that by eq. (6) becomes larger as the specimen size increases.
(4) The absorbed energy increased exponentially with specific gravity (γ) as expressed with the equation of a=kγⁿ(k, n: constant). From this result it is thought that the equation for calculating dynamic specific strength by a/γ² should inspected, because the exponent n was less than 2.0.
(5) The relationship between the absorbed energy in impact bending and the moisture content was different for each species. There existed the minimum near 10% moisture content for Sugi and Akamatsu, and the maximum near 20% moisture content for Yachidamo. In Makanba the value of the absorbed energy decreased with moisture content above 10%, and in Tochinoki it showed a constant value regardless of moisture content.

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On the Temperature Dispersion of Piezoelectric Modulus of Wood

Nobuyuki HIRAI

1985 Volume 34 Issue 383 Pages 955-958
Published: August 15, 1985
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.34.955

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The temperature dispersion of complex piezoelectric modulus of wood occuring at about 100°C was investigated. The results obtained were as follows: (1) The apparent activation energy was about 40-50kcal/mol, suggesting that the origin of the piezoelectric dispersion is caused by molecular motions of considerably large units. The dispersion temperature for each species was different. In the same species the dispersion temperature was low near the pith and high at outer parts. The dispersion temperature increased with the increase of the degree of crystallinity. It is presumed that the dispersion is related to the semicrystalline state in wood. (2) With heat treatment, the dispersion temperature increased initially and then decreased considerably, and the amplitude of the dispersion became smaller gradually. (3) With the increase of water absorption, the imaginary part of the piezoelectric constant became, negative and the dispersion temperature increased. It may be considered that the shift of the dispersion temperature toward higher temperature is related to the formation and modification of semicrystalline state in wood caused by heat treatment and water absorption.

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Effects of Wood Species, Particle Size, Specific Gravity and Thickness of Board, and Fire Retardant Treatments on the Fire Endurance of Particleboards

Shigehisa ISHIHARA

1985 Volume 34 Issue 383 Pages 959-965
Published: August 15, 1985
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.34.959

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Particleboards were manufactured with five species and eleven sized particles, and fire resistant particleboards were also manufactured with phosphoric acid-melamine-formaldehyde condensation products (A) and urea-melamine-formaldehyde resin glue (B) containing H₃BO₃, Na₂B₈O₁₈·4H₂O and NaBr as fire retardants. The effects of species, particle size, specific gravity and thickness of the board, fire retardant treatments and kinds of the fire retardant chemicals on the fire endurance of the boards were investigated by means of the JIS A 1304. The effect of species on the fire endurance of the boards was very slight. Increasing particle size, specific gravity and thickness of the board resulted in an effective increase in the fire endurance of the boards. A and B glue imparted excellent fire resistance to the board. Increase of the fire retardant glue content in the board and of [H₃PO₄]/[M] molar ratio in A glue improved the fire endurance of the boards. Coating of phosphoric acid-melamine-formaldehyde condensation products on the board surface gave the best fire resistance to the boards.

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Fire Performance, Physical and Mechanical Properties of Fire-Resistant Three Layered Particleboards

Shigehisa ISHIHARA, Satoshi KONDO

1985 Volume 34 Issue 383 Pages 966-971
Published: August 15, 1985
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.34.966

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Three layered fire-resistant particleboards were manufactured with adhesives containing fire-retardant chemicals. Fire endurance, physical and mechanical properties of the boards were determined and discussed. The fire-retardant chemicals used were H₃BO₃, KOH, LiOH·H₂O, Na₂B₈O₁₃·4H₂O, NaOH, and NaBr and the adhesive was a commercial urea-melamine-formaldehyde resin. The fire-retardant adhesive containing H₃BO₃ was stabilized by the addition of alkali metal compounds. The fire-retardant adhesives imparted excellent fire resistant to the three layered particleboard. All of the 22mm thick three layered particleboards and the full scale one glued with the fire-retardant adhesives successfully met the acceptance fire penetration criteria under the standard fire test for 30 minutes rating of class B wall of INTERNATIONAL CONFERENCE ON SAFTEY OF LIFE AT SEA 1960. Excepting a few fire-resistant particleboards, the basic engineering properties of the 22mm thick three layered fire-resistant particleboards were better than or equivalant to those of the commercial fire-resistant particleboards and the untreated commercial ones.

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Influence of Color and Glossiness on Image of Wood

Minoru MASUDA

1985 Volume 34 Issue 383 Pages 972-978
Published: August 15, 1985
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.34.972

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In this study, the correlation between image of wood and its color was investigated by using 16 groups of specimens (printed, decorative veneer overlaid and various colored transparent paper overlaid 123 panels). To calculate the correlation factor between hue and image, a new numerization method of hue was proposed, which made it clear that hue of wood especially near 7.5YR gave “warm” image, and clolor of near 10R and 2.5YR with a low brightness value gave “gorgeous” image. Brightness had correlation with “light” and “neat and clear”, and had negative correlation with “profound”, “heavy and thick”, “sober” and “calm”. Chroma had correlation with “showy” and negative with “sober”.
The influence of clear coating on image was investigated on the adjacent sliced specimens of veneer overlaid plywood (8 species) with the same figures. Clear coating gave gloss and also contrast of wood grain figure, and consequently “showy” and “gorgeous” image increased but “elegant” and “fine” image decreased. In the case of species whose brightness value decreased by coating, “calm” image increased. Anisotropy of glossiness based on wood fiber direction was observed and the anisotropy did not disappear even if the specimen was clear-coated.

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Nondestructive Testing Using Frequency Analysis of Sound to Evaluate Degradation of Wooden House

Takanori ARIMA, Noriyoshi MARUYAMA, Shunji HAYAMURA, Hikaru OKAZAKI

1985 Volume 34 Issue 383 Pages 979-984
Published: August 15, 1985
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.34.979

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Lath mortar wall is one of the typical fire proof walls for wooden houses in Japan. But this wall has a lot of problems, such as crack of mortar due to drying shrinkage, separation from sheathing due to lack of fastening, degradation of timbers for sheathing and framing due to immersion of water, which impose possible damage in earthquake. Thus, nondestructive testing to evaluate the degree of degradation for mortar and timber of building elements is needed. So, in this study, a nondestructive testing method and its criteria for field survey using frequency analysis of sound when hitted by steel hammer have been developed. The results obtained are as follows.
(1) The characteristic patterns for mortar were classified into categories A, B and C by the high, medium and low frequency at the peak of sound level and into I, II and III by the shape of distribution. Examinations of defects of mortar and degradation of timber sheathings and framing in actual use indicated that these categories were related to the degree of cracks in mortar or the degree of degradation of timber due to fungi and termites. Category AI was sound and CIII was the lowest. Mortar had higher possibility of defects and degradation, when it was closer to C and III. Simulating tests in which sheathing and frame of timbers were assumed to be lost also led to the same trend.
(2) The characteristic patterns for sill of timber were classfied into categories A, B and C by the shape of distribution although the frequency at the peak of sound pressure level was not so different. The characteristic pattern for non-degradative timber was ranked into category A independent of moisture content although the peak was little bit different. The sill with mortise and joints, which was newly constructed on site, was ranked into category A or B.

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Bending Creep Test of Wood-Based Materials under Fungal Attack

Yuji IMAMURA, Koichi NISHIMOTO

1985 Volume 34 Issue 383 Pages 985-989
Published: August 15, 1985
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.34.985

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A testing method coupled with bending deformation and decay hazard was newly designed to evaluate mechanical performance of wood-based materials under fungal decay, and it was applied to plywood and particleboard as well as solid wood. The test specimens measuring 50×350mm×(thickness) were subjected to bending creep tests under progressive fungal attack with a brown-rot fungus [Tyromyces palustris (Berk. et Curt) Murr.] and a white-rot fungus [Coriolus versicolor (L. ex Fr.) Quél.] in the decay apparatus. After fixation of loading, the deflection at the center of the span length (300mm) was measured regularly as a criterion to determine its expected performance.
The difference in deflection between the inoculated specimen and the sterile sound control one was assumed to be due to strength reduction caused by the action of fungi, and the behavior of bending deformation varied depending on the durability of the specimens.
The method was shown to be particularly useful for the study of particleboard degradation in which high strength loss and large deflection in bending were occasionally observed at slight weight loss. It can be generally applied not only to untreated materials for estimation of their mechanical resistance to decay fungi, but also to treated ones for determination of their preservative efficacy.

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Impact Problem and its Applications

1. Stress Waves

T. Hayashi

1985 Volume 34 Issue 383 Pages 990-997
Published: August 15, 1985
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.34.990

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