Elastic response in wood under moisture content variations: analytic development

Husson, Jean-Marie; Dubois, Frédéric; Sauvat, Nicolas

doi:10.1007/s11043-009-9104-y

Cited by 16 publications

(5 citation statements)

References 15 publications

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“…A temporary stress locking effect occurs upon drying, which is recovered upon moistening. In analogy with the concept of hygrolock strain previously introduced by other authors (Gril 1988;Husson et al 2010), this stress locking effect will be analysed in the following under the hypothesis of the existence of a hygrolock stress.…”

Section: Discussionmentioning

confidence: 99%

“…Based on this assumption, a model was developed where this effect is coupled with creep (Dubois et al 2005). Later on, this effect was represented by means of a 'hygrolock spring' connected to a Kelvin generalized model (Husson et al 2010;Dubois et al 2012). Besides, an alternative model was developed where the mechanism of creation of the hygrolock strain is represented by an 'active box' in which the elastic behaviour of wood is progressively tuned during a drying-moistening cycle (Colmars et al 2009).…”

Section: Introductionmentioning

confidence: 99%

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Experimental study of the mechanosorptive behaviour of softwood in relaxation

et al. 2016

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In softwood material, the coupling between mechanical loading and hydric state is known as the mechanosorptive effect. However, the coupling with viscoelastic effect remains unclear so far, especially when the loading is controlled by strain. In this context, the present paper is focused on the process of creation and recovery of 'hygrolock' behaviour, i.e. a stress locking effect which occurs in a phase of drying under load. For this purpose, several relaxation tests were first performed on small-scale silver fir specimens in order to express the relaxation function in terms of the ambient humidity. Then, two mechanosorptive tests were carried out in order to induce hygrolock stresses in the same sample loaded in sustained strain condition, and subjected to cyclically varying humidity. Based on the assumption of stress partition, the analysis of the test results clearly shows the existence of a hygrolock stress. From these experimental evidences, a law is finally proposed to describe the evolution of the hygrolock stress in terms of the hydric state of the softwood material.Electronic supplementary material The online version of this article (

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Experimental study of the mechanosorptive behaviour of softwood in relaxation

et al. 2016

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“…Later Husson et al (2009) developed a second version of hygrolock models involving the principle of internal (or fixed) stresses proposed by Liu (2006). In this case total stress on the material is the sum of mechanical stress (that induces deformation) and fixed stresses (due to rigidity variation during drying) which are stored temporary within the material and show no effect on deformation.…”

Section: Hygrolock Modelsmentioning

confidence: 99%

One-dimensional discrete formulation of a hygrolock model for wood hygromechanics

Colmars

Dubois

Gril

2013

Mech Time-Depend Mater

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International audiencea new 1D discrete formulation of hygrolock models is proposed for modeling wood time-dependent behavior. This discrete formulation is compared to an integral formulation presented in a previously published paper. Simulations with various humidity cycles are performed under constant stress (creep) or constant strain (relaxation) using first a hygrolock spring and then a generalized Kelvin-Voigt model with a time-spectral distribution of hygrolocks springs. The discrete formulation presented here, based on original idea of mixed series/parallel rheological model, is shown to be very practical for implementation in scientific numerical codes. In order to compensate a lack of complete data-set on wood material, a generic time and moisture-dependent material is proposed to compare the various models: this dataset could be re-used in other studies. Finally the relevance of hygrolock models for wood time-dependent behavior is discussed: it appears that hygrolock models suits well to the upper part of wood hygroscopic domain, whereas further hypothesis should be tested for dry domain. A judicious choice in moisture activation of material parameters, combined with the blocking effect of hygrolock, agree with recent experimental results on simplifying the description of so-called ++ effect

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“…These works are generally based on complex analytical approaches solved by finite element models taking into account the changes of the mechanical properties of wood during the drying phase [2,3]. In addition, several authors have presented drying models that can assess the distribution of moisture inside the wood during the shrinkage with moisture content near the fiber saturation point (FSP) [4]. Also, the mechanical behaviour of wood and tree has been proposed in order to know the impact of the biomechanical and the microstructures parameters in the old history [5].…”

Section: Introductionmentioning

confidence: 99%

Determination of Stresses in Drying Wood by Means of a Viscoelastic Relaxation Model

Saifouni

Pitti

Destrebecq

2013

Challenges in Mechanics of Time-Dependent Materials and Processes in Conventional and Multifunctional Materials, Volume 2

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ABSTRACT. Stress states caused in wood by drying periods are often the source of considerable structural disorders, when this material is used as structural material. The origin of these stresses is generally due to the viscoelastic behaviour of the wood combined with the dimensional variations (shrinkage) related to the moisture content. In order to better understand this phenomenon, a slice of green wood is submitted to natural drying in stable environmental conditions. The wood slice is placed on an electronic balance so as so to measure the moisture content variation during the drying period. Simultaneously, the displacements caused in the slice by the drying are captured by a video camera. An incremental relaxation model based on the generalized Maxwell's chain is used to analyze the evolution of the stresses induced by the drying process within the wood slice. Numerical results show the development of tensile stresses in the material. Analyzing these results leads to the conclusion that the stresses are due to the orthotropic behaviour of the wood material combined with anisotropic drying shrinkage. A tensile stress concentration is evidenced in a zone where a crack was finally observed during the test.

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Elastic response in wood under moisture content variations: analytic development

Cited by 16 publications

References 15 publications

Experimental study of the mechanosorptive behaviour of softwood in relaxation

Experimental study of the mechanosorptive behaviour of softwood in relaxation

One-dimensional discrete formulation of a hygrolock model for wood hygromechanics

Determination of Stresses in Drying Wood by Means of a Viscoelastic Relaxation Model

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