The NIR result also shows that the melt pool size is correlated with the energy density; the higher the energy density, the longer the melt pool, though the melt pool width remains similar. The region from which the trees were removed, but also the number of trees from which the sample material has been obtained, must be taken into account since they could have an impact on the material properties. Mechanisms for the observed results are discussed. 1995; Pan et al. Optical Engineering. Lond Edinb Dublin Philos Mag J Sci 41:206–210. Because of the low stiffness in the transverse direction of wood, only low clamping forces act and therefore no slippage was guaranteed. Poisson's ratio for thin Au films using a visual image tracing system." Holzforschung 71:405–414. Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. The model by Hörig (1935) is the basis for the orthotropic description of wood that is used nowadays. By subtracting the new speckle pattern from the reference pattern, an illustration with typical fringe pattern is obtained (Jones and Wykes 1989). The laser and video extensometry measurements were carried out on a universal testing machine Zwick/Roell Z020 (Ulm, Germany), equipped with an optical extensometer system including both gauging techniques. Terms of Use:, parameter of material, which is a fundamental parameter ch, Nowadays, there are a lot of researches focused on evalua, characterizing thin film materials [8-16], where Poisson’s ratio, general, they can be classified into static, dy.

\kern-0pt} {G_{\text{LR}} }}} \\ \end{array} } \right) \cdot \left( {\begin{array}{*{20}c} {\sigma_{\text{L}} } \\ {\sigma_{\text{R}} } \\ {\sigma_{\text{T}} } \\ {\tau_{\text{RT}} } \\ {\tau_{\text{TL}} } \\ {\tau_{\text{LR}} } \\ \end{array} } \right)$$, $$- \frac{{\nu_{\text{RL}} }}{{E_{\text{R}} }} = - \frac{{\nu_{\text{LR}} }}{{E_{\text{L}} }}$$, $$- \frac{{\nu_{\text{TL}} }}{{E_{\text{T}} }} = - \frac{{\nu_{\text{LT}} }}{{E_{\text{L}} }}$$, $$- \frac{{\nu_{\text{TR}} }}{{E_{\text{T}} }} = - \frac{{\nu_{\text{RT}} }}{{E_{\text{R}} }}.$$, $$\varepsilon_{\text{l}} = \frac{\Delta F}{{A*{\text{MOE}}}},$$,,,,,,,,,,,,,,,,,,,-205,558,,,,,,,,,,,,,,, Therefore, the extensometer system contains a gauging sensor, a digital camera and a laser light source. A technique has been developed to measure the longitudinal and lateral displacements under uniaxial loading of the films on a microscale. Wood Sci Technol 40:351–357. 2005; Konnerth et al.

Accessed 30 Aug 2017, Zwick/Roell (2017c) Mechanical-extensometer: makroXtens (Zwick/Roell). The schematic diagram of AIC is shown in figure 3. The Poisson’s ratio. In summary, the study shows that optical gauging techniques are suitable for determining the Poisson’s ratios of (spruce) wood. An original and practical method is demonstrated for determining Poisson’s ratio of thin films by detecting thermal expansion in two directions perpendicular to each other.

deformation distributions as a straight line following the theoretical diffraction model., Crespo J, Aira JR, Vázquez C, Guaita M (2017) Comparative analysis of the elastic constants measured via conventional, ultrasound, and 3-D digital image correlation methods in Eucalyptus globulus labill. Ultramicroscopy. 2011; Bader et al. Reliable FEM is based on a sound data basis of material properties, such as elastic constants, including the Poisson’s ratio (ν). The stiffness or compliance matrix is symmetric due to Betti’s reciprocity theorem [the deflection d (in direction A) due to a unit force p (in direction B) is equal to the deflection d (in direction B) due to a unit force p (in direction A)]. .

Accessed 3 Oct 2017. It should be calculated from the initial portion of the load (or stress) versus strain curve.

For this validation, the axial extension (εl) of the specimens RL and RT has been investigated with the same sample set, because the means of the Poisson’s ratio x̅[νRL] had the biggest discrepancies to the lowest literature reference (Table 2). In this paper, we present a comparative analysis between the cyclic loading tensile behaviour of conventional and auxetic thermoplastic PU foams., Chu TC, Ranson WF, Sutton MA (1985) Applications of digital-image-correlation techniques to experimental mechanics. 2007, 2013; Valla et al. It was assumed that two to three fringes in the y-axis picture would give reliable results per load step. 2016). Compared to that, the Poisson’s ratio of νRL illustrates a good accordance of the means with values of Z (N = 11) = − .533 and p = .594. On the other hand, diverse gauging techniques and apparatuses with different measurement resolutions were used by each researcher. Table 2 gives an overview of the sample’s moisture content (ω), density (ρ) in dependence of the orthogonal directions (ρL, ρR and ρT) and also the summarized test results of the non-contact optical gauging techniques in comparison with the literature references: Hörig (1935), Wommelsdorff (1966), Neuhaus (1981), Niemz and Caduff (2008) and Keunecke et al. The differences to the literature references are open to speculation, because on the one hand, the scattering of the literature data could suggest similar median values compared to the own measurements. 1a) were stressed at maximum with a force of 4000 N and a pre-force of 100 N, and the specimens RL, RT, TL and TR (Fig. The technique uses laser light (coherent light wave) together with a CCD camera to record displacements of the specimen surface. Furthermore, the measurement of the transverse strain of any specimens via laser extensometry was not possible to establish due to the very small transverse contractions of the specimens that led to very small displacements of the measurement zones, which were not exceeding the measurement resolution of the device. Wiley, New York, Forsberg F, Sjödahl M, Mooser R et al (2010) Full three-dimensional strain measurements on wood exposed to three-point bending: analysis by use of digital volume correlation applied to synchrotron radiation micro-computed tomography image data. Springer, Jones R, Wykes C (1989) Holographic and speckle interferometry. As illustrated in Fig. Reference Guide to Evaluating Assembly Failure of Composites and Plastics, G Mark Requirements for Electronics Imported to the Gulf Member States, Testlopedia - The Plastics Testing Encyclopedia, Tensile Testing of Polymers and Composites Materials, Physical and Mechanical Testing of Polymers, Polymer Regulatory and Consulting Services, Polymer Product Processing Development Support, Microbeads and Microplastics Testing and Consultancy, Coatings and Thin Films Analysis and Testing, Adhesives Analysis and Formulation Testing. Wood Fiber Sci 27:346–359, CAS  Poisson’s ratio is a mechanical property often used in Finite Element Analysis (FEA) calculations to predict the stresses a product may see in an end use application. Dissertation, Ruhr-Universität Bochum (in German), Niemz P, Caduff D (2008) Untersuchungen zur Bestimmung der Poissonschen Konstanten an Fichtenholz (Investigations to determine the Poisson’s ratio of spruce wood). It directly provides full-field displacements to sub-pixel accuracy and full-field strains by comparing the digital images of a test object surface acquired before and after deformation. 3. Essentially, it is the measurement of the change in volume of a material during deformation. This phenomenon has also been mentioned in previous studies (Neuhaus 1981; Bodig and Jayne 1982; Garab et al. Young’s modulus and Poisson’s ratio, are permitted to vary in the radial direction. Deformation of the specimen results in a new speckle pattern. The discrepancies with the values found in other studies, though, clearly show the need to characterize and record the morphology of each specimen. In engineering, wood is usually assumed to behave orthotropic. A clear advantage is that all components of the stiffness tensor are established with the same specimen by employing a consistent method. In Fig.

Springer, Wien (in German), Figliola RS, Beasley DE (2001) Theory and design for mechanical measurements, 3rd edn. After that, a complex algorithm runs to find the motion of the defined speckle zone between the initial picture and the following images.

ESPIl, Bader TK, Eberhardsteiner J, de Borst K (2015) Shear stiffness and its relation to the microstructure of 10 European and tropical hardwood species. Wood Sci Technol 42:633–647. Therefore, in this study the optical gauging techniques “Electronic Speckle Pattern Interferometry (ESPI), laser extensometry and video extensometry” are compared head-to-head for establishing the Poisson’s ratio of (spruce) wood. Lond Edinb Dublin Philos Mag J Sci 43:871–878. which are a function of the Young’s moduli (EL, ER, ET), shear moduli (GRT, GTL, GLR) and Poisson’s ratios (νLR, νLT, νRL, νRT, νTL, νTR).

While increasing the fibre volume fraction up to a certain range the composite materials have shown superior amendments in their tensile properties. The specimens LR and LT (Fig. 1b) and 10 N (Fig. In this study, a more accurate 'true' stress-strain curve of human hair was determined by applying optical techniques to the images of the hair deformed under tension. Measuring Poisson’s ratio: mechanical characterization of spruce wood by means of non-contact optical gauging techniques.