In order to make clear the mechanism of the dielectric relaxation processes in MWL (milled wood lignin), the dielectric loss factors of HINOKI MWL, acetylated HINOKI MWL and three kinds of DHP (dehydrogenation polymer) prepared from p-coumaryl alcohol, p-coumaric acid and isoeugenol, respectively, were measured over the frequency range of 3×102 to 1×106Hz and the temperature range of -70°C to room temperature. The results show that two relaxation processes exist in MWL: one is observed in high frequency range below room temperature and the other in low frequency range at room temperature. The activation energy for the relaxation process in high frequency range is about 10kcal/mole and this relaxation process is almost eliminated by acetylation. Furthermore, the same ralaxation process is observed in DHP from p-coumaryl alcohol in which CH2OH group is present. From these results it is considered that the relaxation process in high frequency range is associated with the reorientation of CH2OH dipoles. On the other hand, the activation energy for the relaxation process in low frequency range is about 14kcal/mole and the relaxation process is eliminated by drying and is not observed in acetylated MWL. Consequently, it is considered that the relaxation process in low frequency range is due to the reorientation of water molecules adsorbed to OH group.
Computer simulation was conducted to assess the effect of the rate of drying on stress in wood during drying. Numerical calculations for the simulation were carried out with an electronic computer FACOM 270-20/30. Examples of the flow chart and FORTRAN programs used are shown in the text where we assumed that the stress follows the integro-differential equation derived previously, and that the unknown factors in the equation can be decided as before2). However, six different levels in the rate of drying were assumed in this report. The results obtained are summarized as follows: (1) The increase in the rate of drying promotes the stress development. (2) The relation between the stress development and the moisture content does not depend so much on the rate of drying. (3) The maximum stress decreases nearly inversely with the increase of necessary drying time. (4) The maximum tensile stress appears somewhat earlier than the maximum moisture gradient. (5) The inelastic strain due to creep has a tendency to restrict the stress development and this tendency increases with decreasing the rate of drying. From these results, it is clear that the computer simulation provides many useful informations on the stress in wood during drying.
The purpose of this paper is to investigate the piezoelectric anisotropy of wood. It had been considered that the cellulose micelle in wood are oriented in the same direction of fiber axis and consequently wood belongs to the symmetry class ∞2. And so d14 and d25 had been measured as the piezoelectric moduli of wood. However, we have found that there is a difference in the absolute value between d14 and d25 determined experimentally; that is, |d14|>|d25|. Therefore, it seems that wood belongs not to the symmetry class ∞2 but to the symmetry class 222. The piezoelectric tensor of the class 222 has three independent piezoelectric moduli d14, d25 and d36. In this study, we measured the piezoelectric moduli d14, d25 and d36 as the symmetry class 222, and found that the modulus of d36 exists apparently in our measurement, although it is small compared with d14 and d25. Thus, it is reasonable to consider d14, d25 and d36 as the piezoelectric moduli for wood. The piezoelectric moduli along different directions were also measured by rotating measuring axes, and they were expressed by the components of d14, d25 and d36. The causes for the existence of d36 and the difference between d14 and d25 were also examined. The polarization associated with d36 is considered to arise from the polarization of ray structure, the components of d14 and d25, and d36cell of cellulose crystallites. The difference between d14 and d25 agrees with that of the moduli of rigidity GLT and GLR, suggesting that the magnitude of piezoelectric polarization depends on that of shearing strain in cellulose crystallites. A correlation is found between the magnitudes of d36 and |d25/d14|, and, therefore, the degree of anisotropy of wood can be characterized by either the ratio of |d25/d14| or the magnitude of d36 from the viewpoint of piezoelectricity in wood.
Polarization curves of a platinum rotating disk electrode in acidic solutions containing Fe2+ and Fe3+ showed typical shapes of the diffusion-controlled process in both anodic and catholic directions. The process is governed by the diffusion of Fe3+ when the catholic reduction of Fe3+ couples the anodic dissolution of Fe because the anodic process is relatively fast under the given condition of the experiment. The corrosion test on iron rotating disks was carried out under various conditions. Some discussions on aqueous corrosion of iron in acidic solution containing Fe3+ as well as dissolved oxygen have been made.
Since it is difficult to separate the contribution of residual stress to the fatigue strength from those of other factors such as work-hardening or size effect, no ultimate conclusion has yet been drawn on the effect of residual stress on the fatigue strength. So, the present investigation was designed to clarify the effects of longitudinal residual stress and work-hardening produced by drawing or surface rolling on the fatigue limit and life under rotating bending of carbon steel wire. Two kinds of testing material were used in this study. One is 0.8% carbon piano wire drawn at various additional reduction, and the other is carbon tool steel surface-rolled after annealing. The distributions of longitudinal residual stress and hardness over the cross section were measured. And the tensile test and the fatigue test under rotating bending were carried out for each specimen. From these experiments, the following conclusions were obtained: (1) The relationship between the numder of cycles to failure N and the stress amplitude σ can be expressed as N=C/A-e-Bσ+mΔσB-nΔσr where ΔσB and Δσr are the changes in tensile strength and maximum longitudinal residual stress at outer layer of the specimen due to drawing or surface-rolling, respectively, and A, B, G, m and n are constants dependent upon the material and working conditions. The fatigue strength of a material received cold working can be calculated accurately by this equation. (2) The residual stress influences the fatigue limit and life considerably but its influence is in a much less degree than that of work-hardening, and their ratio is about 1:3.
The distributed-element model is applied to the analysis of the cyclic stress-strain relation. The model regards a material as the aggregate consisting of a number of elastic-plastic elements with different yield strains. The values of the rate of hardening are the same for all of the elements, but they vary only with the number of cycles. The stress-strain behavior of a material can be obtained from summing statistically the strss-strain responses of all the elements. In order to examine the suitability of the model, the cyclic bending test was performed on plate specimens under a constant strain amplitude. From the comparison between the experiment and the theory, it is clear that the behavior of a material under cyclic stress can be predicted well by the present distributed-element model. Furthermore, this analysis is found to be useful to estimate fatigue life.