Compression tests parallel to grains were made on short column glulams composed of mechanically-graded sugi (Cryptomeria japonica D. Don) laminae. The effect of grade of laminae on the compression strength was studied. In addition, relations among tensile, bending and compression strength properties of the glulams were discussed. The compression strength of the short column glulam was the same as the average compression strength of each lamina. The distribution of the compression strength was represented as a normal distribution function and the coefficient of variation was considerably lower than those of bending or tensile strength. The presence of knots in the laminae did not much affect the compression strength. The coefficient of correlation between the compression strength and specific gravity of the specimens was considerably high. These two results were in contrast to those observed in bending or tensile strength tests for glulams.
The experimental studies were carried out on the effects of heat-treatment and polyethylene glycol (PEG) impregnation upon the fracture of wood under mixed modes I and II. The experimental results were compared with various fracture criteria hitherto proposed in literatures. The fracture criteria experimentally obtained for solid Alaska cedar, solid alder, solid ash, heat-treated Alaska cedar, heat-treated alder, heat-treated ash and PEG impregnated false arbor-vitae follow approximately the energy release rate criterion, but the one obtained for solid false arbor-vitae does not follow any of these criteria. The values of KI at fracture experimentally obtained for PEG impregnated wood of false arbor-vitae are larger than one obtained for solid wood.
By using a PVC (polyvinyl chloride) sheet with micro-embossed lines, it was attempted to imitate the complicated gloss of wood figure which is generated from the three dimensional grain inclination. The results of the measurements of light reflection showed that the micro-embossed surface had extreme anisotropy of light reflection. This suggests that the change of direction of the embossed lines can be used for imitating the anisotropy of gloss figures of wood. As the examples of application of the micro-embossed lines, the glosses of wavy figure of Japanese horse chestnut and bird's eye figures of maple were imitated. The former was well imitated by using the micro-embossed lines of combined sine curves of different wave lengths. The latter was also skillfully imitated by using embossed lines with three different directions which were determined by three photos of a wood sample taken from three different directions of lighting.
Carbonization of Phyllostachys pubescens Mazel ex Houzeau de Lehaile (PP) at several stages was done and the burned-charcoal (BC) obtained was used in this study. The effects of the carbonization temperature of PP on the charcoal yield, amount of charcoal element, oxidation start temperature and specific surface area were discussed. Thermosetting charcoal spheres (CPS) were made by BC and phenol-formaldehyde resin (PF) and they were used in the manufacture of fire resistive and electromagnetic shield composites. The carbonization temperature of BC relative to fire resistivity, electroresistivity and electromagnetic shielding properties of composites were also discussed. The fire resistivity of the carbon composites was tested by a burn-through method and by the oxygen index method in accordance with the Japanese Industrial Standard (JIS) K 7201. Electroresistivity was tested by JIS K 6911 and electromagnetic shielding property by a DUAL chamber method in accordance with ASTM ES 7-83. The fire resistivity and electromagnetic shielding property of the composites were improved by increasing carbonization temperature, while electroresistivity became low.
A possibility was investigated to calculate the surface roughness of woods by band sawing by using the acoustic emission count rate, the cutting force and the specific gravity of woods. Five different softwoods, four different ring-porous woods and eight different radial- and diffuse-porous woods were used as workpieces. Ripsawing was carried out. The acoustic emission count rate was measured by the ring down method using a measuring system with a microphone. The cutting force in the cutting direction was measured using a load cell attached to the feed table. The surface roughness of a wood measured by a contact instrument with a stylus of 0.25mm curvature was described by ten point height of irregularities. The results obtained in this study are summarized as follows: The surface roughness of softwoods and ring-porous woods can be calculated by the multiple regression of the specific gravity of woods, and the AE count-rate or the cutting force. The multiple regression using the AE count-rate is more precise than using cutting force for the calculation of softwoods and ring-porous woods. The surface roughness of radial- and diffuse-porous woods can be calculated by the linear regression of the AE count-rate when they are classed by the similar characteristics of their structures. Moreover, it can be calculated by the multiple regression of the specific gravity of woods and the cutting force.
In order to develop a nondestructive testing method applicable to manufacture more reliable adhesive wood components, fundamental experiments were performed. The strength of adhesive wood joints was evaluated by measuring the time of sound waves (stress waves, ultrasonics) propagating the part involving adhesive joints to guarantee the bonding strength more directly. The three types of experiments employed were as follows: (1) Measuring the propagation time of stress waves for the end joint and lap joint specimens in the curing process. (2) Measuring the propagation time of sound waves for the end joint specimens before and after gluing. (3) Mesuring the propagation time of ultrasonics in both thickness and width directions and the adhesive shear strength for the two-layer specimens. The results are summarized as follows: (1) Curing of adhesive joints could be evaluated by the propagation time of stress waves. (2) The change of propagation time before and after gluing indicates the difference in the state of adhesive joints. (3) The propagation time of ultrasonics in the thickness direction was effective for evaluating the shear strength of adhesive joints, but that in the width direction was not so effective. However, the shear strength can be evaluated more effective by combining the propagation time in these two directions.
In order to clarify the degradation mechanism of gas turbine bucket coating, 25000hr serviced bucket with Pt-Al coating was destructively evaluated. Degraded phase, which is called breaching, was identified in the substrate of the tip section of the bucket and was figured out to be an Al-rich phase. Based on this evaluation result, Monte Carlo simulation analysis was carried out to simulate the formation of breaching by using an Al-cluster diffusion model. The results obtained are as follows: (1) The degradation phenomena in the serviced coated bucket were successfully simulated by using an Al-cluster diffusion model in a simple Ni-Al alloy system. (2) By using this simulation method, inverse problem analyses of actual complex degradation phenomena were performed. The results are as follows; (a) Preferential formation temperature of breaching was identified. (b) Effects of surface temperature and temperature gradient on the formation of breaching were identified. The gradient shifted the peak breaching formation temperature to the higher surface temparature and also increased the amount of breaching. (c) Effect of orientation on the probability of breaching formation was identified. The probability tended to be high at the direction of Al-cluster diffusion.
In order to investigate the key parameter governing the fatigue strength of adhesively bonded CFRP pipe/steel rod joint, a series of rotating bending fatigue tests were carried out on the joints with different lap length and with different pipe thickness. And, the fatigue strength data were discussed on the basis of stress distributions in the adhesive layer determined by FEM analysis. The results indicated that the fatigue strength of this type of joint was mainly governed by the maximum tensile stress normal to the bond interface at the lap end.
Crack propagation tests of polycrystalline alumina with average grain size of 1μm and 19μm were carried out under static and cyclic load. The alumina with 1μm and 19μm are designated as 0D and 5D, respectively. Small specimens with a semi-elliptical surface crack of 200μm or 340μm were used. The results were compared with those obtained using CT specimens. The main results obtained are as follows: (1) Cyclic load enhanced the crack propagation rate as compared with that under static load. (2) The order of the crack propagation resistance under static load is same as that under cyclic load, as shown hereunder. 0D-200>50D-CT>0D-340>5D-340>0D-CT The notation 0D-200 means the specimen of 0D with 200μm crack. It is to be noted that the bridging effect, which varies depending on grain size, brings difference in crack propagation resistance. (3) Crack opening displacement COD increased as the number of stress cycles increased. This means that cyclic load reduced bridging effect. Stress intensity factor at crack tip KItip was calculated in terms of COD. (4) The value KItip was shown to be a good fracture mechanics parameter to describe the crack propagation behavior.
Bending strength and fracture toughness tests were carried out on four kinds of gamma base Titanium Aluminides with different microstructures in the temperature range from room temperature to 1000°C. Both bending strength and fracture toughness at room temperature were highest for the one with lamellar structure and lowest for the one with equiaxed structure. Fracture toughness increased with an increase in temperature up to a critical temperature and then decreased. Chromium addition, which stabilizes ductile β phase, significantly improved high temperature fracture toughness. The critical temperature at the maximum fracture toughness, which corresponds to recrystallization temperature, was around 800°C for binary and chromium added TiAl, while that for niobium added one was about 1000°C.
Fatigue damage evaluation is one of the most important process for the integrity of a machine or a structure. Although many trials have been made for fatigue damage evaluation, few methods can be used to deal with a wide range of stress or strain conditions of fatigue tests. In this study, the fatigue damage evaluation methods were examined with respect to plastic strain ranging from small to large amplitudes of strain repetition for a given stress sequence. Then, a new fatigue damage rule was proposed in terms of strain condition. The new rule showed a good agreement with the theoretical estimations for various experimental conditions. An interporation technique was developed to obtain the stress-strain behavior of a sample material for a given stress sequence. This showed a good applicability for the fatigue damage estimation.
The heating tubes, which operate under most adverse conditions of all boiler components, deserve exceptional care about their remaining service lifetime, with particular regard to accumulation of damage due to creep and progress of corrosion due to oxidation. The current practice of such evaluation is to perform appropriate destructive tests on the tubings sampled out of a bundle concerned, but the creep test does not return accurate enough estimates because the damage that has been accumulated in service is yet too small, giving rise to large scattering of data. In addition, there is a matter of rise of metal temperature due to internal formation of steam-induced oxide film, hence degradation of thermal conduction: since the metal temperature can exceed the initially set design operation temperature as the service is prolonged, this increment will have to be incorporated in the creep damage evaluation. Also, rise of effective stress arising from loss of wall thickness due to external formation of scale has to be considered. This report introduces a comprehensive damage assessment simulation program that takes these changes into account and discusses its authenticity on comparison with damage evaluation conducted by TEM.
Two groups of the extruded high strength Al-Zn-Mg-Cu-La system alloys, including Al-10 wt.%Zn-1 wt.%Mg-1.5 wt.%Cu-3 wt.%La with various Cr and Mn contents and Al-8 wt.%Zn-1.2 wt.%Cu-4.0 wt.%La with various Mg contents, were developed as the mechanical materials with a good stress corrosion cracking (SCC) resistance. In these alloys, the effects of the additional elements were investigated on the mechanical properties and SCC life. The main results are as follows; (1) The second phase particles which contained Zn and La were observed in the matrix, and dispersed homogeneously. The size of the particles was 5 to 10μm. For the alloys with Cr, dispersoids including Cr were also observed in the matrix. Their size was over 10μm. (2) The maximum value of 568MPa in tensile strength was observed in Al-8 wt.%Zn-1.2 wt.%Cu-4.0 wt.%La with 2.5 wt.%Mg, which was nearly equal to the commercial aluminum alloys7075-T73 and 7475-T6. (3) The excellent resistance of SCC was obtained in these alloys. Their SCC lives were over 15 times as long as that of Al-8 wt.%Zn-1 wt.%Mg master alloy. In conclusion, we developed extruded Al-high Zn-low Mg system alloys with high strength and good SCC resistance.
It is generally known that crazing and/or cracking sometimes occurs on the surface of glassy polymers in contact with solvent. In this report, this environmental stress cracking (ESC) in ABS polymer-fron system was studied from the standpoint of sorption-diffusion kinetics. The absorption behavior of fron into ABS polymer was explained by CASE II transport followed by Fickian type diffusion in a short period. The absorption velocity, defined by the slope of weight gain curve in CASE II region, increased with the decrease of AN content, and a clear correlation between the absorption velocity and critical strain in solvent cracking test was observed. The creep test in liquid fron was also carried out to evaluate the resistance against fron. Under constant BR content, lower absorption velocity ABS polymer with higher AN content showed a better resistance. It was estimated that the lower absorption velocity of fron led to a better resistance against the cracking and creep. On the contrary, under constant AN content, higher absorption velocity ABS polymer with higher BR content showed a better creep resistance. This may be due to lower stress concentration in BR-rich ABS polymer.
Al3C2B48 crystals and Si doped Al3C2B48 type crystals were prepared by the reaction between carbon, boron, aluminium and silicon powders as starting materials in an argon atmosphere. The experimental conditions for obtaining these crystals of relatively large size were determined. As-grown Al3C2B48 crystals and Si doped Al3C2B48 type crystals were subjected to chemical analysis and the study of oxidation in air at high temperatures, and also the measurements of crystal size, unit cell dimension, Vickers microhardness and electrical resistivity, respectively. The results obtained are as follows: (1) The suitable conditions for growing Al3C2B48 and Si doped Al3C2B48 type crystals were the atomic ratios of starting materials (C/B=0.056, B/Al=0.10, Si/B=0-0.07), the soaking temperature (1450°C) and the soaking time (10hrs). (2) Al3C2B48 crystals made under the above conditions, were yellowish brown and semitransparent, having a nearly spherical polyhedral shape. The largest crystals prepared had the dimensions of about 1.8mm×1.8mm×1.8mm-2.5mm×2.5mm×2.5mm. (3) The unit cell dimensions, Vickers microhardness (Hv) and electrical resistivity (ρ) of the crystals were a=12.302(1)Å, b=12.621(1)Å, c=10.161(1)Å, V=1577.7(2)Å3, Hv=27GPa, ρ=2.58×10-2Ω·cm for Al3C2B48 crystals (Si/B=0), and a=12.291(2)Å, b=12.620(4)Å, c=10.161(1)Å, V=1576.3(1)Å3, Hv=36GPa, ρ=90.52×10-2Ω·cm for Si doped Al3C2B48 type crystals (Si/B=0.004), respectively. (4) The oxidation reaction of Al3C2B48 crystals and Si doped Al3C2B48 type crystals began to proceed at about 710°C in air, and their oxidation products were found to be 9Al2O3·2B2O3 (orthorhombic system) and B2O3 (hexagonal system) phases.
To improve the performances, influence of surface treatment on impregnating property and mechanical properties of molded composites made by Structural Resin Transfer Molding (SRTM) were investigated. Three types of continuous glass fiber (E-glass) strand mat as reinforcement were used; original mat, heat cleaning and heat cleaning with coupling agent. In the original mat a binder for tightening fiber strands was used whereas in heat cleaned mat the binder and coupling agent were burned out by heat cleaning, so that fiber strands were spread out. Molding composites in flat shape were fabricated. Bending and tensile tests were performed. Nevertheless the impregnating property of the heat cleaning was far superior to that of the original due to spreading out strands, while the mechanical properties of the heat cleaning were far inferior to those of the original. Reduction of fiber strength by heat cleaning was caused. When the heat cleaning was treated with coupling agent, superior mechanical properties could be obtained because of improvement of adhesion at fiber/matrix interface.