A positive temperature coefficient is the term which has been used to indicate that an increase in solubility occurs as the temperature is raised, whereas a negative coefficient indicates a decrease in solubility with rise in temperature.

Effect of Temperature

Adhesion and Adhesives Edited by Dr. R. Houwink and Dr. G. Salomon. Vol. 1: Adhesives. Second, completely revised edition. Pp. xvi + 548. (Amsterdam, London and New York: Elsevier Publishing Company, 1965.) 135s.

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Adhesion and Adhesives

The grid method is a technique suitable for the measurement of in-plane displacement and strain components on specimens undergoing a small deformation. It relies on a regular marking of the surfaces under investigation. Various techniques are proposed in the literature to retrieve these sought quantities from images of regular markings, but recent advances show that techniques developed initially to process fringe patterns lead to the best results. The grid method features a good compromise between measurement resolution and spatial resolution, thus making it an efficient tool to characterise strain gradients. Another advantage of this technique is the ability to establish closed-form expressions between its main metrological characteristics, thus enabling to predict them within certain limits. In this context, the objective of this paper is to give the state of the art in the grid method, the information being currently spread out in the literature. We propose first to recall various techniques that were used in the past to process grid images, to focus progressively on the one that is the most used in recent examples: the windowed Fourier transform. From a practical point of view, surfaces under investigation must be marked with grids, so the techniques available to mark specimens with grids are presented. Then we gather the information available in the recent literature to synthesise the connection between three important characteristics of full-field measurement techniques: the spatial resolution, the measurement resolution and the measurement bias. Some practical information is then offered to help the readers who discover this technique to start using it. In particular, programmes used here to process the grid images are offered to the readers on a dedicated website. We finally present some recent examples available in the literature to highlight the effectiveness of the grid method for in-plane displacement and strain measurement in real situations.

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The Grid Method for In‐plane Displacement and Strain Measurement: A Review and Analysis

Machine Learning-Based Methods in Structural Reliability Analysis: A Review

Machine learning-based methods in structural reliability analysis: A review

Studying the mechanical behavior of notched wood beams using full-field measurements

Reliability assessment and updating of notched timber components subjected to environmental and mechanical loading

The study and identification of the water diffusion properties of Abies alba Mill at the growth ring scale are investigated in this paper. A full-field measurement technique, the grid method, is used in the experimental tests in order to observe heterogeneities and to measure strain fields in the annual growth rings. In this case, the mechanical behaviour of latewood (LW) and earlywood (EW) is studied under the effect of water stress. This technique is coupled to an inverse method for parameter identification. It enables us to assess the diffusivity of EW and LW in the tangential diffusion direction (T) and their expansion coefficients in the radial direction (R) from strain maps obtained using the grid method. Thus the water diffusion phenomenon and its effect on the deformation of wood specimens are studied. A suitable experimental device is designed to provide direct contact with water on one side of the specimen, and strain maps are obtained over time on the other side. During the experiments,...

Inverse identification of early- and latewood hydric properties using full-field measurements

The integrity of timber structures is mainly related to its capacity to resist crack propagation under various load conditions. However, this phenomenon is random by nature, and the need to incorporate statistical information is mandatory for practical use in structures. This paper aims at defining a probabilistic model in order to characterize the scatter of the toughness test results of timber. The instantaneous failure tests are performed using the mixed-mode crack growth specimen. The crack tip growth is recorded by a video camera for mixed-mode ratios of 15°, 30° and 60°, where the relative displacement of loading points is recorded by LVDT sensor. The experimental energy release rate is evaluated by the compliance method. As large scatter of the energy release rate is observed, the statistical analysis is performed by using the bootstrap simulation, in order to characterize the probabilistic models in the opening and shear crack modes. The reliability analysis is then performed in order to underline the impact of the statistical uncertainties on the rupture of wood material.

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Statistical and reliability analysis for mixed-mode fracture tests applied to wood material

The thermo-visco-hydromechanical properties of Abies alba Mills (white fir of Massif Central) are investigated in this paper. These properties are generally complex to study and model because of various couplings that exist between underlying phenomena. In addition, wood is heterogeneous by species, but these properties are generally studied at the macroscopic scale, thus without having the possibility of discerning the contribution of the various levels of organization which exist in wood. In this context, the main contribution of this paper is to experimentally evidence that earlywood and latewood exhibit each a different visco-hydromechanical response and, more specifically, that humidity directly governs their viscoelastic properties. Three suitable experiments were carried out on three different specimens to highlight this phenomenon. These experiments consist of mechanically testing the specimens under natural drying conditions. The difference in response was observed at the scale of the annual ring by using a full-field measurement technique, namely the grid method. This technique provides the strain fields occurring on the surface of the specimens during the different steps of their hydromechanical loading. Its spatial resolution is such that the strain level in latewood and earlywood can be accurately measured, thus evidencing the significant difference in response of the rings. This measurement technique as well as the three experiments carried out during this study is first briefly described in this paper. The obtained results are then presented and discussed, with a special emphasis on the different responses observed in earlywood and latewood.

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R. Moutou Pitti

Papers

Studying the mechanical behavior of notched wood beams using full-field measurements

Reliability assessment and updating of notched timber components subjected to environmental and mechanical loading

Inverse identification of early- and latewood hydric properties using full-field measurements

Statistical and reliability analysis for mixed-mode fracture tests applied to wood material

Investigating wood under thermo-hydromechanical loading at the ring scale using full-field measurements