Effect of Shear Deflection on Bending Properties of Compressed Wood

We investigated the bending properties of compressed Japanese cedar (Cryptomeria japonica D. Don). The specimens were compressed in the radial direction under 180°C for 5 h. Compression ratios (the ratio of deformation to the initial thickness) were 33% and 67%. Young's modulus was measured by flexural vibration test and static bending test. As a result, the Young's modulus obtained by loading in the radial (R) and tangential (T) directions approached the value without shear influence as the length-to-depth ratio and the span-to-depth ratio increased. In the same compression ratio, the Young's modulus was closer to the value without shear influence in loading in the T-direction than in the R-direction. This is because the Young's modulus to shear modulus ratio of the tangential section was smaller than that of the radial section. In the static bending test, the Young's modulus at the span-to-depth ratio of 14 used in major standards was not appropriate

Real-Time Measurement of the Viscoelasticity of Green Juvenile Wood of Japanese Cedar at High Temperature

Changes in the viscoelasticity of green juvenile and mature wood during high-temperature drying were measured in real time. For each measurement, a 180-mm-long specimen of Japanese cedar (Cryptomeria japonica), its supporting system, a magnetic driver, and a deflection sensor were placed in an electric oven and a free-free flexural vibration test was performed. The temperature was fixed at 120°C. The resonance frequency decreased and the loss tangent increased during heating of the juvenile vs mature wood. These tendencies apparently occurred because the initial moisture content of the juvenile wood was higher than mature wood and because the juvenile wood had the larger number of intercellular layers

Changes in Vibrational Properties of Wetwood of Japanese Fir (Abies Sachalinensis Mast) with Time During Drying

Temporal changes in vibrational properties of wetwood of Japanese fir (Abies sachalinensis Mast.) during a drying process were investigated. Specimens were cut from wetwood defined as heartwood with extremely high moisture content and normal wood whose moisture content was not so high, and matched in the R-direction. Green and water-saturated wood specimens were prepared. The specimens and the vibration testing system were put in an electric drying oven, where a free-free vibration test was conducted at intervals of 5 to 20 minutes. When the green specimens were used, the resonance frequency and loss tangent of both wetwood and normal wood reached the minimum and maximum, respectively, early in the drying. The minimum and maximum of the wetwood were smaller and larger than those of the normal wood. These differences between the wetwood and normal wood were mainly caused by the differences in initial moisture content because such differences, which existed in the green wood, disappeared once a water-saturated condition was reached

EFFECT OF HIGH TEMPERATURE AND HIGH HUMIDITY TREATMENT ON BENDING PROPERTIES OF WOOD

Japanese cedar (Cryptomeria Japonica D. Don) 110 110 1000-mm green boxed-heart timbers were dried under high temperature (110-140C) and high humidity (0.01-0.24 MPa gauge pressure) conditions until the weight remained unchanged. Then strength properties were examined. Wood became brittle because of the high temperature and high humidity treatment. We hypothesize that the wood was seriously damaged by hydrolysis because of the long treatment time used in this study and that the large cross-sectional area and high set gauge pressure lengthened the time of water loss from the wood. We considered viscosity and plasticity, rather than elasticity, to be the main factors that contributed to the decrease of work for rupture

Comparisons of Shear Stress/Shear Strain Relations of Wood Obtained By Iosipescu And Torsion Tests

In this paper, we compared the shear stress/shear strain relations of wood obtained by Iosipescu and torsion tests.Quartersawn boards of Sitka spruce (Picea sitchensis Carr.) and shioji (Japanese ash, Fraxinus spaethiana Lingelsh.) provided the specimens. Iosipescu tests were conducted with specimens loaded in the radial direction, and the shear stress/shear strain relations were obtained. Shear stress/shear strain relations were obtained independently of the Iosipescu tests by torsion tests of rectangular bars. The following results were obtained:(1) The shear moduli, shear yield stresses, and shear strengths obtained from both methods showed good agreement with each other, except for the shear strength of ash.(2) As for spruce, the difference between the shear stress/shear strain relations obtained by Iosipescu and torsion tests was significant in the 5% significance level, whereas that for the ash was not significant.(3) Although the Iosipescu test can derive the shear stress/shear strain relation directly, it has the drawback that failure occurs earlier than with the torsion test. In contrast, the torsion test has the drawback that the procedure for obtaining the stress/strain relation is quite complicated. In determining the shear stress/shear strain relation of wood properly, shear stress/shear strain data should be measured more frequently by these methods

From microscopy data to in silico environments for in vivo-oriented simulations

In our previous study, we introduced a combination methodology of Fluorescence Correlation Spectroscopy (FCS) and Transmission Electron Microscopy (TEM), which is powerful to investigate the effect of intracellular environment to biochemical reaction processes. Now, we developed a reconstruction method of realistic simulation spaces based on our TEM images. Interactive raytracing visualization of this space allows the perception of the overall 3D structure, which is not directly accessible from 2D TEM images. Simulation results show that the diffusion in such generated structures strongly depends on image post-processing. Frayed structures corresponding to noisy images hinder the diffusion much stronger than smooth surfaces from denoised images. This means that the correct identification of noise or structure is significant to reconstruct appropriate reaction environment in silico in order to estimate realistic behaviors of reactants in vivo. Static structures lead to anomalous diffusion due to the partial confinement. In contrast, mobile crowding agents do not lead to anomalous diffusion at moderate crowding levels. By varying the mobility of these non-reactive obstacles (NRO), we estimated the relationship between NRO diffusion coefficient (Dnro) and the anomaly in the tracer diffusion (α). For Dnro=21.96 to 44.49 μ m2/s, the simulation results match the anomaly obtained from FCS measurements. This range of the diffusion coefficient from simulations is compatible with the range of the diffusion coefficient of structural proteins in the cytoplasm. In addition, we investigated the relationship between the radius of NRO and anomalous diffusion coefficient of tracers by the comparison between different simulations. The radius of NRO has to be 58 nm when the polymer moves with the same diffusion speed as a reactant, which is close to the radius of functional protein complexes in a cell.ISSN:1687-4145ISSN:1687-415

Characterisation and categorisation of the diversity in viscoelastic vibrational properties between 98 wood types

International audienceContext Increased knowledge on diversity in wood properties would have implications both for fundamental research and for promoting a diversification of uses as material. *Aims The objective is to contribute to overcoming the critical lack of data on the diversity of wood dynamic mechanical/viscoelastic vibrational properties, by testing lesser-known species and categorizing sources of variability. *Methods Air-dry axial specific dynamic modulus of elasticity (E'/γ) and damping coefficient (tanδ) were measured on a wide sampling (1792 specimens) of 98 wood types from 79 species. An experimental device and protocol was designed for conducting systematic (i.e. rapid and reproducible) characterizations. *Results Diversity at the specimens' level corroborates the "standard" relationship between tanδ and E'/γ, which is discussed in terms of orientation of wood elements and of chemical composition. Diversity at the species level is expressed on the basis of results for normal heartwood, with specific gravity (γ) ranging from 0.2 to 1.3. Axial E'/γ ranges from 9 to 32 GPa and tanδ from 4×10-3 to 19×10-3. Properties distribution follows a continuum, but with group characteristics. The lowest values of tanδ are only found in certain tropical hardwoods. Results can also suggest alternative species for musical instruments making