arXiv subjects

Joseph Gril

Publications and source records attributed to Joseph Gril.

8 recordsLinked to original sources

arXiv2025

Fractional order derivative approach of viscoelastic behavior of tropical wood

For some time now, wood has offered itself as an alternative to other modern construction materials, and has become the material of choice for structures, mainly because of its renewable nature, durability and ease of shaping. However, once in service, even at room temperature and under low stresses, it deforms and faces the problems of creep and recovery. The aims of this work is to model and predict the viscoelastic deformations of tropical wood by a rheological approach based on fractional calculus theory. Frist, Zener fractional model was used to elucidate these phenomena. The simulations show that the proposed model fit the creep experimental data with an average reliability of 96% and the recovery process with a reliability of 99%. The optimal parameters of this model, determined through an optimization algorithm, exhibit sensitivity to the stress level. To address this issue and enhance the predictive capability of the model, nonlinearities are incorporated into the fractional model, resulting in modified versions that remain applicable across various stress levels.

physics.med-ph↗

arXiv2019

Revisiting the notion of "resonance wood" choice: a decompartementalised approach from violin makers' opinion and perception to characterization of material properties' variability

This work aims to improve our understanding of the resonance wood and to investigate the interactions between their physical-mechanical properties, natural variability, and the violin makers' ways of choosing their materials. In order to identify the luthiers' practices and opinions, a socio-technical survey was conducted. Physical, vibrational, and visual/structural characteristics of the resonance wood obtained from several provenances with a variety of quality grades were also determined. Finally, these two approaches were completed by a psychosensory evaluation to compare the measurements that we have conducted with the perception and qualification of wood by the violin makers.

physics.class-ph↗

arXiv2005

Modélisation des déformations de maturation de la fibre

The generation mechanism of growth strains is investigated theoretically by developing an elastic analysis of a wood cell viewed as a composite tube, with layers composed of a ligno-cellulosic material of varying composition and microfibrillar orientation. For each layer, the kinetics of induced strain is assumed synchronous with that of rigidification. In this case, variations of polymer behaviour concomitant with orientation must be invoked to account for observed variations of the growth strain.

physics.class-ph↗

arXiv2005

Role of the Gelatinous Layer (G-Layer) on the Origin of the Physical Properties of the Tension Wood of Acer sieboldianum

The tension wood (TW) properties of a 70 year-old Acer sieboldianum Miq were analyzed by using the G-fiber model which was proposed in our previous paper. The roles of the G-layer on the origins of (1) a high large tensile growth stress, (2) a large longitudinal Young's modulus, and (3) a high longitudinal drying shrinkage in the tension wood xylem were discussed on the basis of the simulations using the G-fiber model. The results suggest that the G-layer generates a high tensile stress in the longitudinal direction during the xylem maturation; the longitudinal Young's modulus of the green G-layer becomes significantly higher than that of the lignified layer; furthermore, the G-layer tends to shrink extraordinarily higher than that of the lignified layer during the moisture desorption.

physics.class-ph↗

arXiv2005

Shrinkage of cane (Arundo donax L.) II Effect of drying condition on the intensity of cell collapse

To improve the drying method in the manufacture of woodwind reeds, green canes (Arundo donax L.) were dried under various humidity-temperature conditions and the intensity of cell collapse was evaluated from the swelling due to steaming involving the recovery of collapse. At 30 C, the intensity of collapse was increased by slower drying. It was considered that: 1) slower drying resulted in higher sample temperature in the early stage of drying to increase the collapse; 2) rapid drying stiffened the surface of sample and such "shell" prohibited the following collapse; 3) slower drying i.e. longer loading of liquid tension caused more remarkable and/or frequent viscoelastic yields of cells. Consequently the intensity of collapse increased when the cane was dried from its waxy outer surface or in the presence of node: both of them retarded the drying. On the other hand, higher drying temperature caused greater intensity of collapse in spite of faster drying. It was suggested that the thermal softening of cane cells leads to easier yield of the cell wall, at the same time the rapid drying does not allow the recovery of collapse after the disappearance of free water. These results indicated that faster drying at lower temperature is preferable for drying cane with less collapse.

cond-mat.mtrl-sci↗

arXiv2005

Swelling of acetylated wood in organic liquids

To investigate the affinity of acetylated wood for organic liquids, Yezo spruce wood specimens were acetylated with acetic anhydride, and their swelling in various liquids were compared to those of untreated specimens. The acetylated wood was rapidly and remarkably swollen in aprotic organic liquids such as benzene and toluene in which the untreated wood was swollen only slightly and/or very slowly. On the other hand, the swelling of wood in water, ethylene glycol and alcohols remained unchanged or decreased by the acetylation. Consequently the maximum volume of wood swollen in organic liquids was always larger than that in water. The effect of acetylation on the maximum swollen volume of wood was greater in liquids having smaller solubility parameters. The easier penetration of aprotic organic liquids into the acetylated wood was considered to be due to the scission of hydrogen bonds among the amorphous wood constituents by the substitution of hydroxyl groups with hydrophobic acetyl groups.

physics.chem-ph↗

arXiv2005

Reduction of wood hygroscopicity and associated dimensional response by repeated humidity cycles

The reduction of wood response to variations of ambient humidity, described as kind of ageing, has been studied from both points of view of moisture uptake and dimensional changes. Clearwood specimens from 3 gymnosperms (Pinus sylvestris L., Pinus pinaster Ait., Pinus insignis Dougl.) and 4 angiosperms (Populus spp., Quercus pyrenaica Willd., Entandrophragma cylindricum Sprague, Chlorophora excelsa Benth. & Hook f.) were subjected to five wet-dry cycles and their moisture content and dimensional changes in radial and tangential direction at three increasing levels of relative humidity (57.6, 84.2 and 90.2%) were measured before and after the treatment. For a given increase of relative humidity, a coefficient of hygroscopic ageing was defined as the relative decrease of moisture uptake, and the coefficient of dimensional ageing as the difference of swelling strain before and after ageing. All species exhibited a clear ageing effect, much stronger in the wet range than in the dry range. Calculation of swelling coefficients suggested that in some cases the relation between swelling strain and moisture content is no longer linear in aged wood.

physics.class-ph↗

arXiv2005

Studies on European beech (Fagus sylvatica L.). Part 1: Variations of wood colour parameters

Colour parameters of European beech were measured using CIELab system. 103 logs from 87 trees in 9 sites were cut into boards to study the variations of wood colour parameters. Both site and tree effect on colour were observed. Patterns of red heartwood occurrence were defined. When excepting red heartwood there was still a highly significant effect of site and tree; differences remained after veneer processing. Axial variations were small, except very near the pith or in red heartwood, suggesting possible early selection at periphery under colour criteria. Red heartwood is darker, redder and more yellow than normal peripheral wood.

q-bio.TO↗