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Thermocoupled flow localization of plane strain blocks, obeying the elasto-viscoplastic constitutive equation with straingradient-dependent flow stress, has been analyzed. The effects of the strain gradient, finite element mesh size and the size of the specimen on flow localization have been clarified.

The deformation behavior of the material is modeled by a thermoelasto viscoplastic version of the strain-gradient-dependent constitutive equation. Full plane strain thermocoupled finite-element analysis clarifies the effect of the gradient term added to the constitutive equation, deformation rate and heat conduction on the shear localization. Furthermore, the critical dependence of finite-element simulation with classical continuum theories in shear localization behavior on the employed finite-element mesh size and its partial solution are discussed.

Wood plastic plywood (WPPW), composed of veneer and styrofoam, was manufactured without special adhesives such as urea–formaldehyde or phenol–formaldehyde resins, and its vibrational properties were investigated. WPPW can be produced at 1 MPa and 160°C for 9 min (three-ply) and 12 min (five-ply). The dynamic Young’s modulus reached its highest value when the styrofoam thickness was 30 mm. The sound velocity and dynamic Young’s modulus had minimum values at a grain angle of 45°. The results for dynamic Young’s moduli measured by a longitudinal vibration method and an in-plane flexural vibration method were almost the same. Dynamic shear moduli were measured by an in-plane surface wave propagation test and an in-plane flexural vibration method. From the experimental results, the dynamic shear moduli at 0° and 90° by the two methods were relatively close, although the surface wave propagation test results were higher than those from the flexural vibration method. Dynamic shear moduli at a grain angle of 45° measured by the in-plane surface wave propagation test and calculated from theory were relatively close. The surface wave propagation test results were smaller than the results calculated from theory. The shear stress distribution factors were about 1.000–1.189 for WPPW.

The diffusion model based on Fick's second law has been used to predict the moisture movement in nonsteady state. However, the diffusion coefficient generally is not a constant. The diffusion equation origins from well-known heat transfer theory. In the case of moisture movement, moisture below fiber saturation point should be considered to have some interaction with wood substances. Therefore some additional friction seems to be added to the diffusion process.

The acoustic emission (AE) source wave analysis was applied to the breaking of the wood with a glue line. Tapered double-cantilever beams were used as the test specimens. In the case of solid wood, the value of critical energy release rate obtained from the released energy in the source wave analysis was in good agreement with that from the fracture load. In the breaking of the glue lines, the ratio of the critical energy release rate from the fracture load to the released energy in the source wave analysis decreased with decreasing the wood failure. On the other hand, the decrease of the ratio can be attributed to the decrease of the fracture strain of glue lines. The above results show that the fracture pattern of the breaking of the glue lines is the interfacial failure in the category for the glue line failure.

The flexural vibration of wooden plates is analyzed by using orthotropic, viscoelastic plate theory. The case in which two modes interact with each other and the case in which the plate is influenced by an out-of-plane shear effect are considered. In both cases the calculated values of resonant frequency and internal friction are found to be in satisfactory agreement with experimental values. The plate theory proposed can be applied to more complicated cases.

Young's modulus from a conventional elongation test of paper is usually underestimated, mainly because slippage occurs between the specimen and the grips during loading. A more accurate Young's modulus is sometimes required for a precise discussion of paper science or the suitable material design of paper. Although the vibrating reed method and the ultrasonic method have both been proposed for determining Young's modulus of paper, these techniques are limited by the requirement of special devices and a complicated measurement procedure. Therefore, a modified calculation method for Young's modulus from the elongation test is discussed in this study.The apparent deformation (Δd) of paper in a conventional elongation test can be divided into two parts, a real sheet deformation (Δf) and a false deformation which includes the slippage (Δs). The percentage of Δs of the apparent strain becomes larger as span 1 decreases, because for a certain kind of paper at a certain external loading level Δs is considered to be the same regardless of test span. The amount of Δs at a given load can be obtained by extrapolating the relationship between apparent deformation at the load level and test span to zero span. Thus, Young's modulus can be calculated after the correction of sheet strain by the value of Δs.The effect of restraint of lateral contraction near the grips on extensional rigidity was found to be small when calculated by the finite element method, provided that the span is more than twice the sample width. The results suggest that the specimen span should be more than 30 mm.Young's modulus corrected in this way was fairly close to that obtained from the vibrating reed method.

Etude theorique et experimentale de la vibration forcee d'une poutre de Timoshenko anisotrope et viscoelastique, aux extremites libres. Les experiences sont faites sur des poutres de bois. Calcul et mesure du module de Young dynamique et de la tangente de perte en fonction de la forme de la poutre et de la frequence

On discute des variations du degre de cristallinite de la cellulose et de la rigidite du bois sur des periodes de plusieurs centaines d'annees