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We developed a method for evaluating the moisture content of sugi logs using an impedance measurement to categorize the effective wood-drying process. The patterns of moisture content distribution in a trunk were found to affect the impedance frequency dependence. For example, in case of high moisture content of heartwood, we observed that the impedance values are constant with increasing frequencies and the phases are constant at about 0o with increasing frequencies. In contrast, with the high moisture content of heartwood, the case of low moisture content of heartwood showed that the impedance values decreased with increasing frequencies and the phased are constant at about −90o with increasing frequencies. We estimated the distribution of moisture content in a log using an electrical impedance measurement method. Classification of the wood according to its moisture content is important for improving the wood-drying process and for efficient conversion into timber. We suggest that the frequency behavior of impedance and the phase angle could be used to classify the moisture content distribution in a log using three models in a series connected to the two-parameter model based on parallel resistance and capacitance.

New crack length measurement methods using thin metal film were proposed in order to evaluate the crack growth characteristics during static fatigue process of ceramics. Also, the effect of crack length on the crack growth characteristics was investigated using both soda-lime glass and glass ceramics specimens. As the results, it was found that in the soda-lime glass, there is no difference between small- and long-crack growth characteristics. On the other hand, in the glass ceramics, it was found that sub-critical crack growth (SCG) resistance in small-crack propagation test is higher than that in long-crack propagation test. In addition, it is confirmed that the glass ceramics has higher SCG resistance than that in the soda-lime glass. Furthermore, it was confirmed that the proposed crack length measurement method is suitable for crack growth characteristics evaluation on ceramics.

The production of new materials by mixing together more than two raw materials is a useful method from the viewpoint of waste disposal. However, a number of trials and errors are required to produce the desired material. It is therefore important to clarify the target to improve the efficiency of production. In this study, as targets of production, glass-ceramics with anorthite, wollastonite, and gehelenite crystals are used, and inorganic wastes of fly ash, concrete sludge, and glass cullet are used as raw materials. The mixing ratios of these inorganic wastes are determined on the basis of the phase equilibrium diagram of CaO-Al2O3-SiO2. The XRD profiles and SEM observations showed that the crystallized phase of the glass ceramic samples produced were identified as anorthite, wollastonite, and gehelenite, respectively. Moreover, the strength, hardness, Young's modulus, fracture toughness, and acid resistance were measured. From the results, it is considered that glass-ceramics with wollastonite crystals are excellent in terms of mechanical properties, but those with anorthite are excellent in terms of chemical resistance.

A new method to evaluate the relationship between stress intensity factor K I and crack growth rate V of ceramics which is based on the Double-Torsion (DT) technique was proposed. Plate-type DT spe...

Flexural vibrations of rectangular plates and beams which consist of functionally inhomogeneous materials due to cyclic loadings of external force and temperature change are analyzed mathematically. Effects of aspect ratio of rectangular plates and loading frequency on the interference between the flexural vibration due to cyclic loading and that due to cyclic heating are discussed. The amplification factor in the dynamic behavior to the quasi-static one is also studied. Especially, comparing transient responses in flexural vibration of rectangular plates with those of beams, the difference in the amplifications of out-of-plane deflection and stresses between plates and beams is discussed.

This study is concerned with a magneto-thermo-elastic problem of a conducting rectangular cylinder in an external magnetic field which varies sinusoidally in time. Analytical solutions of eddy currents induced in the cylinder are derived on the basis of a theory of the quasi-stationary current. Two-dimensional transient temperature change produced by the eddy current loss is derived by means of the Green’s function method. The stresses in the infinitely long cylinder in a plane state are derived by making use of the Airy’s stress function. The effect of a frequency in a sinusoidal change in time of the external magnetic field on behaviors of eddy current loss, temperature change and stresses in the cylinder is examined by numerical calculation. The skin effect with an increase in a frequency of the external magnetic field on the transient response of temperature change and stresses in the cylinder is discussed.

A plane elastic problem for inhomogeneous and isotropic solids such as functionally graded materials is treated theoretically. An inhomogeneous slab with a Griffith crack subjected to uniformly distributed loading such as internal pressures on the crack surfaces is considered. It is considered that the Griffith crack is located on the middle plane of the slab. It is assumed that inhomogeneous material property such as the shear modulus of elasticity varies in a form of a power of a transverse coordinate, and the material inhomogeneity in the slab is symmetric with respect to the middle plane. The mixed boundary value problem is developed theoretically using a fundamental equation system for such inhomogeneous and isotropic solids derived in our previous paper. Thereafter, considering a variation of inhomogeneity in the shear modulus of elasticity, displacements and stresses in the slab, and a stress intensity factor for the mode I deformation at the tip of a crack are examined numerically. An effect of inhomogeneity in the shear modulus of elasticity on plane elastic behavior and stress intensity factor for the mode I deformation is discussed.

From the viewpoint of the effective utilization of waste wood, the green composite which is produced by solidifying woodchips has been developed [Miki M, Takakura N, Kanayama K, Yamaguchi K, Iizuka T. Effects of forming conditions on compaction characteristics of wood powders. Trans Jpn Soc Mech Eng C 2003;69(678):502–8 [in Japanese]; Miki M, Takakura N, Kanayama K, Yamaguchi K, Iizuka T. Effects of forming conditions on flow characteristics of wood powders. Trans Jpn Soc Mech Eng C 2003;69(679):766–72 [in Japanese]; Miki M, Takakura N, Iizuka T, Yamaguchi K, Kanayama K. Possibility and problems in injection moulding of wood powders. Trans Jpn Soc Mech Eng C 2004;70(698):2966–72 [in Japanese]]. Since the composite was solidified by the compressive load without the binder, it did not have the high strength and was very brittle, and it had no water resistance [Kinoshita H, Kaizu K, Koga K, Tokunaga H, Ikeda K. In: Proceeding of the Japan Society of Mechanical Engineers M& M2007; 2007. CD [in Japanese]]. In this study, to improve these defects, it was proposed that a biodegradable resin as an adhesive and bamboo fibers as reinforced fibers were applied to the woodchip composite. By using woodchips with two kinds of the particle size, bamboo fibers with three kinds of the length and the biodegradable adhesive, several kinds of specimens changed mixing ratio of those materials were produced by compression molding at the appropriate temperature. By examining the bending strength and impact strength of the composites, it was found that the high bending strength was obtained in the case where woodchips with the small particle size and long bamboo fibers were used, and the high impact strength was obtained in the case where woodchips with the large particle size and long bamboo fibers were used.

Ceramics, Composite Material, GFRP, Clay, Recycling, Bending strength Abstract In this study, as the effective recycling technique for the waste GFRP, the process for the producing the porous glass fiber reinforced ceramics by firing the mixture of the clay and the crushed waste GFRP was proposed. The proposed recycling technique for the waste GFRP enables to produce various ceramics parts by effectively reusing the glass fibers included in the waste GFRP as well as to dispose injurious GFRP radically. By changing the mixing ratio of the waste GFRP and clay, and by firing the mixture at some temperatures, several kinds of ceramics specimens (tiles) were produced. The microstructure of each specimen was observed using the SEM and the microscope, and then water absorption and the bending strength of the specimens were examined in detail by comparison with those of specimens without the glass fiber. From those results, it was confirmed that the high-strength porous glass fiber reinforced ceramics could be produced by our proposed process.

From the viewpoint of the effective utilization of natural resources, the green composite which is produced by solidifying woodchips has been developed[1][2][3]. However, since this composite was solidified by the compressive load without the binder, the composite was very brittle and had no water resistance [4]. In this study, to improve these defects, the biodegradable resin is used as an adhesive and bamboo fibers are used as reinforced fibers. By using woodchips with two kinds of the particle size, bamboo fibers with three kinds of the length and a biodegradable adhesive, several kinds of specimens changed those mixing ratio were produced. The composite consists of the ingredients which are friendly to the environment. By the four-point bending test and Charpy impact test, the bending strength and impact strength of the composites were examined. From the experimental results, it was found that the high bending strength and high energy absorption were obtained in case where woodchips with the small particle size and long bamboo fibers were used. The proposed composite has the high strength, and the practical application is also possible.

In riveting, it is very important to make the plate's deformation small as well as to obtain the high joint strength. Therefore, we proposed the new riveting process using the washer in the same way as the bolt joint in order to accomplish both purposes. In this paper, first, by changing the combinations of hardness and flow stresses of the rivet material and the plate, we investigated the deformation and strength of the joints in detail and clarified the characteristics of the joints. Next, by considering these experimental results, the new method using the washer in riveting was proposed and the effectiveness of the proposed method was examined. The obtained results show that the joint strength is improved while the deformation of the joint decreases. The usefulness of the proposed method was confirmed from those results.

This research presents a practicable method to investigate the characteristics of the microcrack growth in brittle materials. The crack length measurement method using an ion-sputtered film was applied to measure the length of the microcrack growing in soda-lime glass and alumina ceramics in four-point bending tests. Since the measurement system can measure the crack length at a sampling frequency of 125 kHz, the crack length was measured almost continually, and the relation-ship between the crack growth rate and the stress intensity factor was obtained in the whole regions from low crack growth rate to brittle fracture. If the relationship between crack growth rate and stress intensity factor follows the Paris law, the n values of the soda-lime glass and alumina ceramics are obtained in the region I and region II that are very important to the fatigue life estimation for these materials.

Recently, in place of the welding, the new rivets such as the self-piercing rivet are noticed in the auto industry. In this paper, the new impact riveting method (Single Impact Riveting Method) in which an aluminum rivet is struck into aluminum sheets by the impulsive force is proposed. Procedures of the joining are as follows : (1) the axis of the impact rivet is struck into sheets by the impulsive force ; (2) the rivet axis penetrates the sheets and collides with the die ; (3) by collision, the tip of the axis forms the other head of the rivet and the axis also becomes thicker ; (4) the sheets are joined tightly by the plastic deformation of the rivet axis. The proposed method does not need prepared holes in sheets and improve the productive efficiency further than the conventional method. From experimental results, it was clarified that the joint strength by the single impact riveting method is higher than that by caulking, and the sheet warp is smaller than that by caulking.

Thermally tempered glass is made by cooling rapidly after heating float glass to near a softening point. The compressive residual stresses generated at the surface layer by thermal expansion make strengthen the material. However, the tensile residual stress layer will be also generated in the interior of the material to compensate for the surface compression residual stress. The presence of these residual stress layers in the thermally tempered glass will play an important role from the viewpoint of crack growth in fatigue. In this study, in order to examine the fatigue crack growth behavior of thermally tempered glass in detail, a simple and straight method suggested by Gupta was applied, where the crack size after indentation is measured by microscope directly. As a result, it was found that the surface compressive residual stress in thermally tempered glass not only strengthen but also restrain the crack growth.

This paper presents the numerical analysis of dynamic thermal stresses by the extended distinct element method (EDEM), which is a kind of the meshless methods. The new technique which radii of the elements of the EDEM are changed with the temperature of each element is proposed. The temperature of the element is calculated on the basis of the heat conduction between elements. By the comparison between the analytical result of Sternberg and Chakravorty and the numerical result obtained by the proposed method, it was confirmed that the method was effective for the dynamic thermal stress analysis. Numerical examples were also presented for the cases of a non-homogeneous plate subjected to the surface heating and a glass block with an initial crack subjected to the surface heating. From these numerical results, it was found that the method based on the EDEM is an efficient tool for analysis of dynamic thermal stresses.

広く信じられていることと異なり, 科学は真理を追求する営為ではなく, 何らかの同一性により, 現象を説明する営為である。この立場から, 現在の遺伝子還元主義的な生物学を批判し, システムを重視する対抗理論について論じた。

Crack length measurement and crack initiation detection in a fatigue process are extremely important techniques in the researches for the investigation of crack growth characteristics and the fatigue strength evaluation of machine elements. The purpose of this research is to show a simple and high precision method to measure the length of a crack as well as a micro crack using an extremely thin ion sputtered film. A grid pattern ion sputtered film was proposed to measure the crack length for a bending test specimen. Based on the comparisons between the measurement results and that by a microscope, it was clarified that the grid pattern ion sputtered film has a very high measurement precision. This method should be invaluable and practicable for the crack length measurement of insulating materials such as ceramics. Meanwhile, a rectangle ion sputtered film was used on a metal bending specimen, the possibility to apply the film in the crack length measurement of a metal machine element was confirmed by the change of the electric resistance of the film with crack growth.

The thermally tempered glass has strong resistance for the surface crack, because the residual compressive stress exists near the surface of the glass. On the other hand, it also has the residual tensile stress in the center of the glass. Fracture behavior of the thermally tempered glass depends on the distribution of the residual stress. However, it is very difficult to clarify those relationships by an experiment. In this paper, a thermally tempered glass model using the Extended Distinct Element Method (EDEM) is proposed. Using our proposed model, the impact fracture behavior and the crack velocity are evaluated. As results for the normal glass and tempered glass, it is confirmed that the distribution of residual stresses can be evaluated by the thermally tempered glass model and the thermally tempered glass model is broken to many pieces by the residual tensile stress as well as experimental results. Furthermore, it is found that residual stresses of tempered glass greatly influence the crack velocity.

Thermal tempered glass is made by rapidly cooling after heating float glass to near the softening point. Compressive residual stresses at the surface layer of thermally tempered glass strengthen the material, and tensile residual stresses are also generated at the same time in the interior of the material to balance with the surface compressive residual stresses. It is considered that the fatigue crack growth characteristics of thermally tempered glass are remarkably different from that of float glass, due to the existence of those residual stresses. In this study, Au film made by ion sputtering method and an optical microscope are used to measure the crack length of the thermally tempered glass and float glass, and these fatigue crack growth characteristics are investigated. As a result, it is confirmed that the crack length measurement with an Au film has high accuracy of measurement. Furthermore, it is found that the higher stress intensity factor is needed to cause the crack growth in thermally tempered glas than in flat glass.

In cold districts, prevention against frost damage of roofing tiles caused by the expansion due to the freezing of water absorbed in the numerous pores in the tile material has becomes a serious problem. It is known that the frost damage is closely connected to the porosity and water absorbing capacity of the roofing tile. Both the porosity and water absorbing capacity of the material can be controlled by the firing temperature. In this work, in order to examine the effect of firing temperature on the frost resistance, tiles fired at different temperatures of 900–1200 °C were fractured by four point bending after applying freezing treatment at low temperatures of −10, −30 and −50 °C. At any firing temperature up to 1100 °C, both fracture stress and fracture toughness increased with the firing temperature, but they dropped above 1100 °C. Furthermore, an obvious decrease in fracture stress with decrease in freezing temperature was observed for the samples fired at 1200 °C. Thus, it was concluded that the roofing tile fired at temperatures of up to 1200 °C forming mullite with a glass phase from the reaction with quartz and feldspar could minimize the frost damage.

This paper presents an impact fracture analysis of a ceramic plate by the extended distinct element method (EDEM). The EDEM model consists of springs, dampers and sliders between two elements in both the normal and tangential directions. This model has the continuity by introducing the pore-springs, which show the effect of the pore material between elements. The medium composed of the EDEM model becomes gradually discontinuous with the destruction of the pore-springs. The purpose of this study is to confirm usefulness of this method for the analysis of the impact fracture and to examine the effect of the impact velocity on the impact fracture behavior. From numerical results, it is shown that the impact velocity greatly influences in the mode of the impact fracture and the genera-tion of the crack is localized at the collision part with the increase in the impact velocity. It is also found the position of fracture is closely related to the position of the high equivalent stress.

This paper presents a method that generates a topological structure under an impulsive load by the extended distinct element method (EDEM). The EDEM model consists of non-linear springs, dampers and sliders between two elements in both the normal and tangential directions. According to the local rule using the calculated equivalent stress, elements are generated or eliminated. From numerical results, it demonstrates that various topological structures are generated by the initial shapes. It is also possible to obtain the design of the structure which is not limited to the design space.

In this paper, the effect of crack size, number and distance between the centers of surface cracks on the fatigue behavior of alumina has been investigated. A single crack and two or three collinear surface cracks were introduced by Vickers indenter. The crack size was changed by several indentation load. The fatigue tests were carried out under static tensile loading (stress ratio R=1) and cyclic loading (R=0 and -1). The main results were as follows. ( 1 ) For any surface crack size, appreciable decrease in fatigue lifetime due to cyclic load was observed, and the degree of the decrease was almost the same for each crack size. ( 2 ) No appreciable effect of stress ratio was observed in the decrease in fatigue lifetime due to cyclic loading. ( 3 ) An interaction of multiple surface cracks, that is to say, the decreasing fatigue lifetime by the interaction with the increase in the nurnber of crack or the decrease of the distance between those cracks was more clearly observed in the case of small crack size, while no interaction was observed In the case of large crack. Such a result seems to be caused by the reason that the interaction of multiple surface cracks may be cancelled by the higher crack propagation resistance owing to bridging effect in crack tip.

The finite difference method based on inteqration along the bicharacteristics is the suitable method for the stress wave propagation. The advantage of this method is attributed to the fact that the characteristic surface coincides with wave front. In this paper, by introducing a laminated composite model and the finite difference method based on integration along the bicharacteristics, propagation of the stress waves in a nonhomogeneous plate is approximately analyzed. The material properties in the plate change continuously in the thickness direction. Numerical calculations are carried out for nonhomogeneous plates composed of alumina and aluminum alloy. From numerical results, it is found that impact damage resistance of the nonhomogeneous plate is improved by controlling the distribution of the components.

In order to examine the effect of crystal grain size on the fatigue behavior of glass ceramics, cyclic fatigue tests were carried out by four-point bending load under both environments in air and water. A single crack and three collinear cracks were introduced on the surface of plate specimens by Vickers micro hardness indentation. The crystal grain size of the glass ceramics in this work was about 1μm, and it was increased from about 0.05μm used in previous work. As a result, the time-to-failure to the cyclic fatigue of the glass ceramics with a large crystal grain size obviously did not decrease by the effects of water environment and the multiple surface cracks, comparing with that of the glass ceramics with a small crystal grain size. Therefore, the interaction between multiple surface cracks may not be effective sufficiently for glass ceramics with a large crystal grain size. In addition, the fatigue strength of the glass ceramics increased with increasing crystal grain size. These facts mean that a dominant crack propagates along crystal grain boundaries.