Applying digital image correlation to wood strands: Influence of loading rate and specimen thickness

Holzforschung ◽  
2010 ◽  
Vol 64 (6) ◽  
Author(s):  
Gi Young Jeong ◽  
Audrey Zink-Sharp ◽  
Daniel P. Hindman
Keyword(s):  
Digital Image Correlation ◽  
Young’S Modulus ◽  
Digital Image ◽  
Poisson’S Ratio ◽  
Loading Rate ◽  
Young's Modulus ◽  
Image Correlation ◽  
Poisson's Ratio ◽  
Specimen Thickness ◽  
Loading Rates

Abstract Previous studies were devoted to various applications of digital image correlation (DIC) to wood and wood-based composites. However, the focus of these studies was qualitative strain distribution. Overall, there is a lack of testing protocols of DIC for quantifying the elastic properties of woody materials. The objective of this study was to investigate the effects of different specimen thicknesses and loading rates on measurement of Young's modulus and Poisson's ratio by DIC. Young's modulus from DIC decreased as thickness increased at a loading rate of 0.254 mm min-1. Comparing the different loading rates at a thickness of 0.794 mm, Young's modulus from DIC was not in agreement with the value obtained by means of the extensometer regardless of loading rate. However, Young's modulus from DIC at a thickness of 0.381 mm and a loading rate of 0.254 mm min-1 was in good agreement with the corresponding Young's modulus obtained by an extensometer. Poisson's ratio measured from different loading rates and specimen thicknesses was not significantly different between the two measurement systems. From the testing arrangement applied for this study, it is recommended that DIC should be applied at a loading rate of 0.254 mm min-1 or slower for strands with a thickness of 0.381 mm or less.

scholarly journals DETERMINATION OF THE POISSON’S RATIO IN CONCRETE BY USING DITIGITAL IMAGE CORRELATION

2021 ◽  
pp. 26-32
Author(s):  
Yaroslav Blikharskyy
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Poisson’S Ratio ◽  
Concrete Strength ◽  
Correlation Method ◽  
Image Correlation ◽  
Poisson's Ratio ◽  
Digital Correlation ◽  
Transverse Stresses

The article presents the results of the experimental investigation of concrete prismsand determination of the Poisson's ratio using the method of digital image correlation (DIC). Toachieve the goals and objectives of the research, a concrete prism measuring 100x100x400 mm ofclass C50 / 60 was formed. The surface of the prism was cleaned and levelled to a smooth surfacewith a mechanical device and grinding stone. The surface of the prism is then cleaned with a solventto remove dust residues. After that, speckles were applied to determine the strain using the DICmethod. For determine the strain, by using digital image correlation, were used Two FlirGrasshopper 3 cameras with a Computar F25 / 2.8 lens and a Sigma 70-200 mm f2.8 APO EX DGHSM Macro II lens. Stains for image correlation were recorded at a speed of 250 ms. 2 LED lampswere used for lighting. Since the press is not able to record the load in time, to record the load useda camera at a speed of 50 frames/sec. The load was applied evenly at the same rate to the physicaldestruction of the test samples. As a result, the images were processed using VIC-2D software toobtain vertical and transverse strains. The advantage of the image correlation method is the abilityto obtain deformations and, accordingly, the stress of the full surface of the sample. Thus, if weanalyse the horizontal (transverse) stresses for a prism with a concrete strength of C50 / 60, it ispossible to see the appearance of internal cracks in the sample before it occurs outside, at a timewhen cracks cannot be visually fixed. As a result of work the technique of testing of concrete sampleswith use of digital correlation of the image is developed and presented. The Poisson's ratio from thebeginning of loading to the destruction of the sample was determined experimentally by the developedmethod.

scholarly journals Testing of Auxetic Materials Using Hopkinson Bar and Digital Image Correlation

2018 ◽  
Vol 183 ◽  
pp. 02045 ◽  
Author(s):  
Tomáš Fíla ◽  
Petr Zlámal ◽  
Jan Falta ◽  
Tomáš Doktor ◽  
Petr Koudelka ◽  
...  
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Poisson’S Ratio ◽  
High Speed ◽  
Split Hopkinson Pressure Bar ◽  
Lattice Structure ◽  
Frame Rate ◽  
Image Correlation ◽  
Poisson's Ratio ◽  
Strain Gauges

In this paper, a split Hopkinson pressure bar (SHPB) was used for impact loading of an auxetic lattice (structure with negative Poisson’s ratio) at a given strain-rate. High strength aluminum and polymethyl methacrylate bars instrumented with foil strain-gauges were used for compression of an additively manufactured missing-rib auxetic lattice. All experiments were observed using a high-speed camera with frame-rate set to approx. 135.000 fps. High-speed images were synchronized with the strain-gauge records. Dynamic equilibrium in the specimen was analyzed and optimized pulse-shaping was introduced in the selected experiments. Longitudinal and lateral in-plane displacements and strains were evaluated using digital image correlation (DIC) technique. DIC results were compared with results obtained from strain-gauges and were found to be in good agreement. Using DIC, it was possible to analyze in-plane strain distribution in the specimens and to evaluate strain dependent Poisson’s ratio of the auxetic structure.

Direct measurement and master curve construction of viscoelastic Poisson's ratio with digital image correlation

Strain ◽  
2018 ◽  
Vol 54 (6) ◽  
pp. e12294 ◽  
Author(s):  
Yusuke Hoshino ◽  
Kazuki Tamai ◽  
Yuelin Zhang ◽  
Satoru Yoneyama
Keyword(s):  
Digital Image Correlation ◽  
Direct Measurement ◽  
Digital Image ◽  
Poisson’S Ratio ◽  
Master Curve ◽  
Image Correlation ◽  
Poisson's Ratio

Determination of creep compliance, recovery and Poisson's ratio of elastomers by means of digital image correlation (DIC)

2017 ◽  
Vol 59 ◽  
pp. 245-252 ◽  
Author(s):  
Leonardo Israel Farfán-Cabrera ◽  
Juan Benito Pascual-Francisco ◽  
Omar Barragán-Pérez ◽  
Ezequiel Alberto Gallardo-Hernández ◽  
Orlando Susarrey-Huerta
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Poisson’S Ratio ◽  
Creep Compliance ◽  
Image Correlation ◽  
Poisson's Ratio

scholarly journals Experimental Characterization and Modeling Multifunctional Properties of Epoxy/Graphene Oxide Nanocomposites

Polymers ◽  
2021 ◽  
Vol 13 (16) ◽  
pp. 2831
Author(s):  
Naresh Kakur ◽  
Kamran A. Khan ◽  
Rehan Umer
Keyword(s):  
Thermal Conductivity ◽  
Graphene Oxide ◽  
Young’S Modulus ◽  
Poisson’S Ratio ◽  
Young's Modulus ◽  
Image Correlation ◽  
Poisson's Ratio ◽  
Mechanical And Thermal Properties ◽  
Temperature Dependent ◽  
Frequency Temperature

Thermomechanical modeling of epoxy/graphene oxide under quasi-static and dynamic loading requires thermo-mechanical properties such as Young’s modulus, Poisson’s ratio, thermal conductivity, and frequency-temperature dependent viscoelastic properties. In this study, the effects of different graphene oxide (GO) concentrations (0.05, 0.1, and 0.2 wt%) within an epoxy matrix on several mechanical and thermal properties were investigated. The distribution of GO fillers in the epoxy was investigated using transmission electron microscopy (TEM). The digital image correlation (DIC) technique was employed during the tensile testing to determine Young’s modulus and Poisson’s ratio. Analytical models were used to predict Young’s modulus and thermal conductivity, with an error of less than 13% and 9%, respectively. Frequency–temperature dependent phenomenological models were proposed to predict the storage moduli and loss tangent, with a reasonable agreement with experimental data. A relatively high storage modulus, heat-resistance index (THRI), and thermal conductivity were observed in 0.2 wt% nanocomposite samples compared with pure epoxy and other lower concentration GO nanocomposites. A high THRI and derivative of thermogravimetric analysis peak temperatures (Tm1 and Tm2) were exhibited by adding nano-fillers in the epoxy, which confirms higher thermal stability of nanocomposites than that of pristine epoxy.

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