The distribution of rays was traced by placing regular-sized small dots at the center of all rays of tangential sections in sugi (Cryptomeria japonica) and tochinoki (Aesculus turbinata) to produce “dot maps”. These dot maps were set on an optical Fourier transform equipment in such a way that the axial direction of the dot maps corresponded to the vertical line. The diffraction patterns which reflect only the arrangement information of rays were recorded on photographic films. The diffraction patterns of rays showed characteristic spots only on the equator in sugi and on the meridian in tochinoki. For the interpretation of these diffraction patterns some mathematical treatments were introduced. As the result, the arrangement of these rays on an arbitrary direction was shown to be detected by densitometry of the diffraction pattern along the direction through the origin. Ths method is useful to the two-dimensional analysis of the distribution of many tissues or cells of wood.
The change in social needs now imposes the following task for “wood quality” on forestry researchers: the wood quality should be reformed so as to satisfy various current demands and coming timber utilisation. The purpose of the study was to seek for the wood quality indices which contribute closely to the production forestry and the timber utilisation. The experimental results obtained were summarised as follows: (1) There are so many sugi (Cryptomeria) cultivars and their wood quality was so divrse. Consequently, the effect of cultivar species on wood quality can not be neglected. (2) The basic density, obtained from green volume and ovendry weight, and the latewood tracheid length had lower coefficients of variation within each cultivar than those among different cultivars. (3) The growth ring width is not valid as a wood quality index. (4) The latewood tracheid length, which can be easily introduced into the forest industry and timber industry, is expected to be an effective wood quality index of sugi-cultivars. (5) It is questionable to introduce a stress grading machine into the sawn timber grading of a mixture of cultivars.
The force in driving a nail into wood by pressing and the withdrawal resistance were measured. Among the factors affecting the force and resistance against nail of wood at various specific gravities (Hem-Fir) were the diameter of nail, nail point and type of shank. (1) A curve for driving force and moving distance of a nail could be separated into two regions: the I-region as affected by the nail point inserted into wood and separating fibers and the II-region as affected by the friction between shank and fibers. (2) The maximum driving force and withdrawal resistance had a linear relationship to the diameter of nail and the specific gravity of wood. The slope of nail driving force into wood in the II-region was reasonably equal to the slope of withdrawal resistance as affected by friction. (3) The effect of screw-or ring-shank, when compared to that of common smooth-shank was recognized in the shape of curve near the maximum point and the change in residual strength with moisture conditions.
The purpose of this paper was to measure the change of moisture diffusion coefficient with drying and then to investigate the relationship between moisture content and diffusion coefficient. In this research, discussions were limited to the isothermal moisture movement, and also one dimensional diffusion in the direction of the board thickness (tangential direction) of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco.). During conventional kiln-drying, the inner moisture distribution change of the board can be non-destructively detected with the medical X-ray CT Scanner. Therefore, it can been continuously measured at the same part of the same section. This method was developed in this study to obtain more accurate moisture content in wood from CT images. As the noise of images was reduced by employing alternative techniques, the standard error achieved finally was 0.8% MC in the hygroscopic range. The diffusion coefficients were calculated directly from the moisture distribution change, by an appropriating differential equation for non-steady diffusion, as the driving force is MC. This research gave two interesting results. One is that, on the boundary layer between the lumber and the surrounding air, the moisture sorption did not rearch to an equilibrium state. Its MC was higher than EMC, which is being used generally. The maximum difference between them in the first stage of drying, was 6% MC, and in the last stage, it became 3-5% MC at least. Another result was that the diffusion coefficient appeared constant independent of MC. However, the computer simulation of moisture distribution showed that a more appropriate correlation seemed to be “the diffusion coefficient is dependent on MC, a cubic function with the maximum value of about 15% MC”.
Various types of carbon materials are being used as overlays in the manufacture of fire resistive particleboards. The fire endurance of carbon materials overlaid particleboards was evaluated by three different methods, and the results were compared with those of boards without any overlay and of non-combustible commercial boards. The mechanical and dimensional properties of these overlaid particleboards were also examined. The results obtained were as follows: 1) The fire endurance of overlaid boards was improved both in the time delay in temperature rise at unexposed surface (JIS A 1304) and in burn through when exposed in high velocity flame due to low combustibility of carbon. The creep under fire of overlaid boards showed better performance than those of conventional particleboards and non-combustible commercial structural boards due to high heat-resisting property of carbon. Graphite and charcoal from softwoods saw dust and bark were found to be highly effective as the overlay materials in increasing fire resistance of particleboards. 2) The mechanical properties of overlaid boards were lower than those of the control particleboard. However, they could be improved by reinforcing overlaid boards with glass or carbon fiber clothes, or by veneering. 3) Overlaid boards showed great dimensional stability because of high water resisting property of carbon and low compaction of particles.
The superplastic behavior was investigated for 60/40 brass and free cutting brass containing 3% lead. The former alloy was cut off from a large ingot and was grain refined by the low temperature extrusion process after β quenching. The latter alloy was extruded at a low temperature from a 50mm diameter rod on market. Tensile specimens of 8mm diameter and 30mm gauge-length were machined, and tensile tests were carried out between 500-750°C at the initial strain rates from 2.78×10-4 to 2.78×10-2S-1. The following results were obtained: (1) A maximum neck-free total elongation of 640% for 60/40 brass was obtained at 675°C and the strain rate of 2.78×10-4S-1. (2) The volume of cavities increased as the true strain increased, while at the same true strain, the volume of cavities at a small strain rate was smaller than that at a large strain rate for 60/40 brass. (3) The strain enchanced grain growth of α and β phases showed a small increase with increment of true strain at 675°C and 2.22×10-3S-1, but that of soft β phase was considerably larger than that of α phase at 675°C and 5.56×10-4S-1 for 60/40 brass. (4) By refining grain size, superplasticity was recognized even in free cutting brass which has low Pb content and thus essentially shows low ductility at high temperatures.
The injection moulding for sintered products has recently attracted a great deal of interest because the moulding method has a relative freedom to shape intricate geometries. The purpose of this investigation was to clarify the effects of Mn/Si ratio and sintering temperature on the mechanical properties of sintered stainless steel. The materials used were two kinds of stainless steel powder having an approximately equal particle size and a similar chemical composition except Mn. The results obtained are as follows; (1) The tensile strength of the sintered stainless steels was 540MPa regardless of the Mn/Si ratio and was almost equivalent to that of the conventional SUS304. In addition, it was found that the logarithm of the tensile strength was proportional to the volume fraction of pores. (2) The fatigue limit of the specimen having a relatively low Mn/Si ratio was 328MPa, while the specimen having a high Mn/Si ratio exhibited a significantly low fatigue limit, that is, 265MPa. (3) It became clear from these results that the fatigue properties varied considerably with the Mn/Si ratio. The ratio affected the volume fraction, the composition and the shape of the oxides. The high Mn/Si ratio seemed to produce sharp pores from which the fatigue cracks initiated easily.
In this report, we analysed the data of 3-point bending tests on Si3N4 and PSZ rectangular bar specimens and ZrO2 round bar specimens. The strength distributions of Si3N4 and PSZ and that of ZrO2 were representd by the multi-modal Weibull distribution and 2-parameter Weibull distribution (mono-modal), respectively. The parameters of the former were estimated with the multi-step maximum likelihood method, and those of the latter with the least square method. Using these parameters, the true stress (stress at the fracture origin) distributions were calculated on the basis of the statistical theory of stress and fracture location. As a result of comparison of the calculated distributions and experimental data, it was found that the both distributions showed good agreement. Furthermore, on the ZrO2 round bar specimens other bending tests were carried out, varying the specimen size and the loading method. Weibull moduli obtained in the tests were not constant. There was a tendency that they increased as the effective size decreased. We discussed the reason of this change, considering the experimental relationship between the crack size and the fracture strength.
Application of ceramics to mechanical and structural components requires, for a strength design or a quality control, to deal with the strength as a material constant independent of either testing methods or the shapes and sizes of specimens. Therefore, we propose the analysis method for estimating commonly the material intrinsic strength from all the data obtained by tensile, bending, creep and fatigue tests at the same temperature. The fracture strength of commercial engineering ceramics is assumed to be governed by crack growth properties from an initial flaw larger than a grain size by about more than ten times. If the strength data from all the tests are analyzed according to Weibull statistics in considering the effective hold time of applied stress and the effective volume at the same time, the strength can be expressed commonly as follows σf(Nfteff)nf=σf0m√ln(1-Pf)-1/Veff where nf is the strength decrement index and equals to the inverse of crack growth rate index n, and σf0 is the strength normalized for cumulative effective hold time Nfteff=1(sec) and effective volume Veff=1(mm3). The estimating method proposed here is useful for making a reliability design or a quality control for ceramic components requiring lot quality checks.
The effect of precipitation hardening on rotary bending fatigue strength of circumferential V-notched specimens was investigated at room temperature by using two commercial steels, i.e., 18 Ni maraging steel and an austenitic heat resisting steel, JIS SUH38. The rotary bending fatigue tests were carried out on the as solution-treated, peak-aged and over-aged specimens. The fatigue limits of the smooth specimens as well as all of the notched specimens were not influenced by precipitation hardening in 18 Ni maraging steel. Non-propagating cracks were found in all the notched specimens having the stress concerntration factor, α, of 6.2 except the over-aged specimens. It was also found that the stress concentration factor at the branching point, α0, is nearly 4. In SUH38, the fatigue limits of the smooth specimen and the notched specimen with α of 2.1 were found to increase with precipitation hardening, while the fatigue limits for the other notched pecimens having α larger than 2.1 did not change in spite of precipitation hardening. The value of α0 was nearly equal to 2 in the as solution-treated specimens and 4 in the other aged specimens. Furthermore, nonpropagating cracks were easier to be formed in SUH38 than in 18 Ni maraging steel and in the as solution-treated specimens than in the aged specimens. Discussions were finally made on the fatigue limits by dividing them into the fatigue limit for crack initiation, σw1 and the fatigue limit for crack propagation, σw2. Especially the behavior of nonpropagating cracks was discussed on the basis of roughness-induced crack closure.
The behavior of AE total ringdown counts during the stepwise increment of oscillating stress under various conditions (loads, microstructures and materials) was investigated and the following conclusions were obtained. 1) Various factors influencing AE total ringdown counts during the stepwise increment of oscillating stress were clarified. 2) The mean value and standard deviation of stress giving rapid AE increment corresponded to those of the endurance limit given by 14S-N testing method under various conditions (loads, microstructures and materials). Thus, the mean value and standard deviation of the endurance limit can be estimated precisely from the stress giving rapid AE increment. 3) The stress giving rapid AE increment corresponded to generation of slip bands during the stepwise increment of oscillating stress. It was 0.9 times of the endurance limit given by 14S-N testing method.
Crack propagation behavior under creep-fatigue conditions at elevated temparatures was studied with a SUS 304 stainless steel, a quenched 21/4Cr-1Mo steel and a Hastelloy X, and the results were discussed in the light of fractography. The crack propagation rates of the 304 steel and the Hastelloy were correlated linearly with cyclic J integral range ΔJ. In the region of low propagation rate, the crack propagation rates of the 304 steel, the Cr-Mo steel and the Hastelloy were about the same. In the region of high propagation rate, on the other hand, those of the Cr-Mo steel were higher and those of the Hastelloy were slightly lower than those of the 304 steel. This difference in crack propagation rete is probably associated with the difference in creep ductility of these materials. In the case of C-P type loading, in all materials, a transition of fracture morphology from the transgranular fatigue type to the intergranular creep type occurred when the ratio of creep component to fatigue component φ exceeded a critical value of about 1. In the C-C type loading, transgranular fatigue fracture appeared also in the case of φ ratio larger than 1, where the fracture morphology in C-P type loading was intergranular. It is suggested that reversible slip along grain boundaries caused by compressive creep possibly recovers forward slip along the boundaries caused by tensile creep. No appreciable difference was found between crack propagation rates of the 304 steel in air and vacuum, and it was consistent with a small difference observed on fracture surfaces in these environments.
A new life prediction method was proposed for high strength materials under fatigue-creep interaction (FCI) based on their tensile total strain energy behavior. The net tensile hysteresis energy is now being used to evaluate FCI life in the frequency modified damage function rule developed by W.J. Ostergren. For high strength materials, however, this damage rule seems to require some modification to give good life assesment, because the elastic strain range is much larger than the inelastic strain range in the FCI behavior of these materials. In this paper, strain controlled tensile or compressive strain hold tests with F-F, F-S and S-F wave forms were performed for Cast René 80. The total strain energy including a large elastic strain energy was defined, and FCI life was obtained against this strain energy. Multiple regression analysis was carried out to assess the relationship between strain energy and cycles to failure and was expressed numerically to improve life estimation accuracy. Finally, a frequency modified total strain energy parameter was defined to evaluate the failure lives (Nf) of high strength materials such as René 80 under the FCI condition. The total tensile strain energy (ΔWTT) and the time (τTT) under tensile stress loading were used to define this tensile strain energy parameter. Thus, ΔWTT·τnTT·Nmf=C where, n, m and C are constants. A similar relation was also obtained between total strain energy (ΔWTT) and crack initiation life (Nc).
In order to investigate the effect of corrosive environment on fretting fatigue, plane bending fatigue tests were carried out by clamping contact pads to fatigue specimens. The materials for the fatigue specimens were S45C carbon steel and SCM430 (SCM435) alloy steel, and those for the pads were S45C steel for the S45C steel specimens and SUS420J1 steel for the SCM430 (SCM435) steel specimens. The tests were carried out in air and in city water. From the results of the tests in air, it was found that the fatigue limit of the fretting fatigue specimen under plane bending was nearly equal to that of the shrink-fitted specimen under rotating bending. Both S45C+S45C and SCM430+SUS420J1 failed at the slipping region where fretting damage occurred by contacting with the fretting-shoe. S45C+S45C in city water failed at outside of the contact area with the fretting-shoe because the city water did not penetrate into the contact area. In the case of SCM435+SUS420J1 in city water, it was considered that the reduction of its fatigue stength in comparison with the case of S45C+S45C was due to the galvanic corrosion of SCM435 steel and SUS420J1 steel.
Extreme value statistical analysis has been applied for estimating corrosion loss of carbon steel pipes and tanks, in which leakage due to corrosion was found. In the cases of erosion at elbows in sulfuric acid and corrosion at gas cooling tubes used for heat transfer, a good coincidence between the measured and the estimated depth by the extreme value analysis was achieved if the population of samples was divided into the following two groups: the heavily corroded area and the other area before the analysis. For oil tank plates which showed uniform corrosion with a constant corrosion rate, the population of samples could be analyzed as a whole and the return period could be set as large as 10000. A grouping method was proposed for analyzing a large number of point data which were measured according to the Fire Service Act for oil tank base plates corroded by local penetration of rain in the outside boundary.
The chief factors influencing the phenomenon of grinding ceramics are wheel speed, feed, depth of cut, grain size, concentration, etc. One of them is grinding fluid. In this paper, the methodology of ranking the fluids in order of suitability for the grinding, which are of one type of emulsion, two types of soluble and five types of straight oils, is presented, using the experimental results of abrasive cut-off ceramics which are three types of Si3N4, SiC and ZrO2. The performance index is assessed by presence or absence of fume during the abrasive cut-off process. It is difficult to evaluate such index quantatively, since fuming phenomenon in itself is qualitative. So dual scaling was used in ranking fluids quantatively. The result shows that soluble oil is proper for processing ceramics, while emulsion is improper. By testing the correlation between the order of suitability in fluids and the characteristics of the fluids, the characteristics for the suitability are selected. In consequence, viscosity and the amount of sulphur are selected. That is, the higher viscosity and/or the more sulphur in fluid, the worse the suitability is.
Recently, need for excellent bonding between materials such as ceramics and semiconductors has increased remarkably in the fields of electronics and precision machinary. The bonding of glass-to-glass without any binding agent was conducted under an applied dc potential at temperatures well bellow the softening point of glass. The experiments were made in the temperature range of 210-300°C in air, on the specimens with smooth surfaces to mate closely. The experimental results showed that the bonding strength increased with increasing both the applied potential and temperature. The increase of bonded area increased the bonding strength. The bonding of glass/glass may have occurred by the electrostatic attraction associated with the movement of sodium ions in the glass under applied potential.
The X-ray elastic constants of composite ceramics of zirconia mixed with 40wt% alumina were determined by X-ray stress measurements and compared with theoretical predictions. The results obtained are summarized as follows: (1) The X-ray elastic constants were determined for the diffraction from Al2O3 (146) plane by Cu-K α radiation, and for those from Al2O3 (1.0.10) and ZrO2 (133) planes by Cr-K α radiation. The X-ray values of EX'/(1+νX') and EX' (EX'=Young's modulus, νX'=Poisson's ratio) of the composite decreased in the alumina phase and increased in the zirconia phase when compared with those of single-phase ceramics. (2) The values of EX'/(1+νX') for Al2O3 (146), Al2O3 (1.0.10) and ZrO2 (133) planes of the composite calculated from those of single-phase ceramics on the bases of Hauk's model agreed fairly well with the experimental values. The value of EX'/(1+νX') for the alumina phase in the composite calculated from the elastic constants of single crystals on the basis of Eshelby's model was slightly larger than the experimental value. The contribution of pores in the composite should be included in modeling.
The X-ray stress analysis at an arbitrary stress level during cyclic loading is effective to make clear the effect of residual stress on fatigue behavior. The method of sampling the diffracted X-rays at only one applied stress level in a short time during cyclic loading is required to perform such X-ray stress measurement, because the actual stress of specimen always changes during stress measurement. This paper suggests the method of measuring the diffraction profile during cyclic loading by using an X-ray stress analyzer with a position sensitive proportional counter (PSPC) and discusses the accuracy of this X-ray stress measurement. The results obtained are summarized as follows: 1) The method of time-resolved measurement of the diffraction profile by using PSPC was established. X-rays are constantly irradiated on the specimen during cyclic loading, and as soon as the applied stress reaches to a set stress level, the diffracted X-rays are sampled for a minute time, and the profile is determined by integrating the diffracted X-rays for several time-resolved samplings at this applied stress level. 2) The X-ray stresses at various levels of applied stress were measured very accurately. However, when the sampling time per one cycle was very short, the error of the X-ray stress increased. 3) The number of cycles needed for the stress measurement was considerably decreased by using a stress analyzer with PSPC. It was also decreased by decreasing the preset peak counts for measuring diffraction profile as well as the angles of X-ray incidence for the analysis. 4) It was confirmed by the time-resolved X-ray stress measurement that the actual stress during cyclic loading was the algebraic sum of the applied stress and the residual stress.