scholarly journals Measurement of elastic properties of materials employing 3-D DIC in a Cornu’s experiment

2021 ◽  
Author(s):  
Digendranath Swain ◽  
Binu P. Thomas ◽  
S Karthigai Selvan ◽  
Jeby Philip
Keyword(s):  
Elastic Properties ◽  
Poisson’S Ratio ◽  
Large Strain ◽  
Image Correlation ◽  
Poisson's Ratio ◽  
Difficulty Level ◽  
Single Test ◽  
The Poor ◽  
Properties Of Materials ◽  
Tensile Experiment

Abstract Measurement of elastic properties, especially the Poisson's ratio, utilizing non-contact techniques in a tensile experiment is very challenging. This is primarily due to the poor spatial resolution and the large strain noise inherent to these techniques. The difficulty level increases many folds when Poisson's ratio of less elongating, stiffer, and/or brittle materials, like ceramics and ablatives, is measured. This paper reports a newer approach that employs 3-D digital image correlation (3-D DIC) in a Cornu's experiment to enable accurate measurement of elastic properties in a single test. The deflection field obtained from 3-D DIC in the form of anticlastic surfaces during Cornu's experiment is utilized for determining Poisson's ratio. In the same experiment, the elastic modulus is estimated using the center point deflection method. The proposed methods are validated with standard materials and extended to newly developed materials. Cornu's method with 3-D DIC can provide the elastic properties with ease and has many advantages over other conventional techniques.

scholarly journals Measurement of Nonlinear Poisson’s Ratio of Thermoplastic Polyurethanes under Cyclic Softening Using 2D Digital Image Correlation

Polymers ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1498
Author(s):  
Yi-Xian Xu ◽  
Jia-Yang Juang
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Poisson’S Ratio ◽  
Measurement Errors ◽  
Large Strain ◽  
Reference Sample ◽  
Cyclic Softening ◽  
Image Correlation ◽  
Poisson's Ratio ◽  
Thermoplastic Polyurethanes

Thermoplastic polyurethanes (TPUs) and other elastomers are widely used in many applications for the advantages they provide in terms of high elasticity, lightness, resistance to breakage, and impact resistance. These materials exhibit strong hysteresis in the large strain stress-strain behavior, known as cyclic softening or the Mullins effect. Despite the extensive studies on this phenomenon and the importance of Poisson’s ratio, how the Poisson’s ratio of these materials changes during cyclic uniaxial tests is still unclear. Here, we measure the nonlinear Poisson’s ratio of TPU and investigate its correlation with cyclic softening using two-dimensional digital image correlation (2D-DIC) combined with the reference sample compensation (RSC) method. This accuracy-enhanced method can effectively eliminate the measurement errors induced by the unavoidable out-of-plane displacements and lens distortion. We find that the Poisson’s ratio of TPUs also exhibits large hysteresis in the first cycle and then approaches a steady state in subsequent cycles. Specifically, it starts from a relatively low value of 0.45 ± 0.005 in the first loading, then increases to 0.48 ± 0.005 in the first unloading, and remains largely constant afterward. Such a change in the Poisson’s ratio results in a slight volume increase (≈1%) at a maximum strain of 17.5%. Our findings are useful for those who use finite element method to analyze the mechanical behavior of TPU, and shed new light on understanding the physical origin of cyclic softening.

scholarly journals Modelling the elastic mechanical properties of bioactive glass-derived scaffolds

2020 ◽  
Vol 6 (1) ◽  
pp. 50-56
Author(s):  
Francesco Baino ◽  
Elisa Fiume
Keyword(s):  
Elastic Properties ◽  
Poisson’S Ratio ◽  
Mechanical Performance ◽  
Solid Material ◽  
Poisson's Ratio ◽  
Predictive Capability ◽  
Shear Moduli ◽  
Wide Range ◽  
Constitutive Parameters ◽  
The Relationship

AbstractPorosity is known to play a pivotal role in dictating the functional properties of biomedical scaffolds, with special reference to mechanical performance. While compressive strength is relatively easy to be experimentally assessed even for brittle ceramic and glass foams, elastic properties are much more difficult to be reliably estimated. Therefore, describing and, hence, predicting the relationship between porosity and elastic properties based only on the constitutive parameters of the solid material is still a challenge. In this work, we quantitatively compare the predictive capability of a set of different models in describing, over a wide range of porosity, the elastic modulus (7 models), shear modulus (3 models) and Poisson’s ratio (7 models) of bioactive silicate glass-derived scaffolds produced by foam replication. For these types of biomedical materials, the porosity dependence of elastic and shear moduli follows a second-order power-law approximation, whereas the relationship between porosity and Poisson’s ratio is well fitted by a linear equation.

Low-Cost Measurement Technique of Poisson’s Ratio of Thin, Solvent-Sensitive Polymer Membranes

2019 ◽  
Author(s):  
Lara L. Dienemann ◽  
Anil Saigal ◽  
Michael A. Zimmerman
Keyword(s):  
Poisson’S Ratio ◽  
Low Cost ◽  
Speckle Pattern ◽  
Polymer Membranes ◽  
Polyimide Film ◽  
Fused Silica ◽  
Solvent Free ◽  
Image Correlation ◽  
Poisson's Ratio ◽  
Thin Membranes

Abstract This paper investigates a low-cost testing procedure that measures Poisson’s ratio of thin membranes whose properties may be affected by traditional speckle patterns which are solvent-based. The shear modulus, a key indicator of how materials will fail — especially for thin membranes subjected to interfacial stresses — is a function of Young’s modulus and Poisson’s ratio, which can be determined by tensile testing. The precision of using Digital Image Correlation (DIC) to measure Poisson’s ratio coupled with a solvent-free speckle pattern of fused silica on polyimide film specimen is investigated. DIC processes for thin membranes are currently under development. As such, spraying a conventional speckle pattern may be unfeasible for thin polymer membranes whose properties are a function of solvent content. Experimental factors’ effects, such as vibration and area to which DIC is applied, were also studied in a design of experiments. It was determined that using fused silica as a solvent-free speckle pattern, as opposed to a traditional solvent pattern, does not significantly affect the measurements of Poisson’s Ratio of the polyimide film. Furthermore, it was found that the experimental factors noted above can play a significant role in fused silica-speckled Poisson’s ratio specimen.

Elastic impedance inversion of multichannel seismic data from unconsolidated sediments containing gas hydrate and free gas

Geophysics ◽  
2004 ◽  
Vol 69 (1) ◽  
pp. 164-179 ◽  
Author(s):  
Shaoming Lu ◽  
George A. McMechan
Keyword(s):  
Elastic Properties ◽  
Gas Hydrate ◽  
Poisson’S Ratio ◽  
P Wave ◽  
Poisson's Ratio ◽  
Unconsolidated Sediments ◽  
Free Gas ◽  
Impedance Inversion ◽  
Elastic Impedance ◽  
New Algorithms

The elastic properties of hydrated sediments are not well‐known, which leads to inaccuracy in the evaluation of the amount of gas hydrate worldwide. Elastic impedance inversion is useful in estimating the elastic properties of sediments containing gas hydrate, or free gas trapped beneath the gas hydrate, from angle‐dependent P‐wave reflections. We reprocess the multichannel U.S. Geological Survey seismic line BT‐1 from the Blake Ridge off the east coast of North America to obtain migrated common‐angle aperture data sets, which are then inverted for elastic impedance. Two new algorithms to estimate P‐impedance and S‐impedance from the elastic impedance are developed and evaluated using well‐log data from Ocean Drilling Program (ODP) Leg 164; these new algorithms are stable, even in the presence of modest noise in the data. The Vs/Vp ratio, Poisson's ratio, and Lamé parameter terms λρ and λ/μ are estimated from the P‐impedance and S‐impedance. The hydrated sediments have high elastic impedance, high P‐impedance, high S‐impedance, high λρ, slightly higher Vs/Vp ratio, slightly lower Poisson's ratio, and slightly lower λ/μ values compared to those of the surrounding unhydrated sediments. The sediments containing free gas have low elastic impedance, low P‐impedance, nonanomalous background S‐impedance, high Vs/Vp ratio, low Poisson's ratio, low λρ, and low λ/μ values. We conclude that some parameters such as Vs/Vp ratio, Poisson's ratio, and λ/μ, although they help identify the free‐gas charged layers, cannot differentiate between the hydrated sediments and nonhydrated sediments when gas hydrate concentration is low, and cannot differentiate between the hydrated sediments and free‐gas charged sediments when the gas hydrate concentration is high. Three distinct layers of gas hydrate are interpreted as being caused by gas hydrates with gas of different molecular weights, with correspondingly different stability zones in depth. Free gas appears to be present below the two deeper gas‐hydrate layers, but not below the shallowest one because the lack of a trapping structure. The gas hydrate has an average concentration of ∼3–5.5% by volume, and is highest (9%) at the base of the lower gas hydrate stability zone. The free‐gas concentration ranges from 1 to 8% by volume, and is most developed beneath the local topographic high of the ocean bottom.

On the analysis and prediction of elastic properties in alkali Na2O–B2O3–V2O5 glasses under the substitution of V2O5 by Na2O

2019 ◽  
Vol 60 (6) ◽  
pp. 213-221
Author(s):  
Amin Abd El-Moneim ◽  
Hassan Y. Alfifi
Keyword(s):  
Elastic Properties ◽  
Dissociation Energy ◽  
Packing Density ◽  
Poisson’S Ratio ◽  
Elastic Moduli ◽  
Unit Volume ◽  
Dominant Role ◽  
Glass Network ◽  
Poisson's Ratio ◽  
Structural Units

In this article, we have continued our recent work(30,42) on the prediction of elastic properties in alkali borovanadate glasses. Changes in the elastic moduli and Poisson’s ratio due to the substitution of V2O5 by Na2O in the ternary alkali Na2O–B2O3–V2O5 glasses have been analysed and predicted on the basis of the theories and approaches that existing in the field. Both the packing density and dissociation energy per unit volume of the glass were evaluated in terms of the basic structural units that constitute the glass network. In addition to this, the theoretical values of elastic moduli and Poisson’s ratio were calculated from the Makishima–Mackenzie’s model and compared with the corresponding experimental values. The results revealed that the concentrations of the basic structural units BO3, BO4, VO5 and VO4 play a dominant role in correcting the anomalous behaviour between experimental elastic moduli and calculated dissociation energy per unit volume. An excellent agreement between the theoretical and experimental elastic moduli was achieved for majority of the samples. The correlation between bulk modulus and the ratio between packing density and mean atomic volume has also been achieved on the basis of Abd El-Moneim and Alfifi’s approaches.

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 On the identification of the eggshell elastic properties under quasistatic compression

2004 ◽  
Vol 52 (5) ◽  
pp. 73-82 ◽  
Author(s):  
Jana Simeonovová ◽  
Jaroslav Buchar
Keyword(s):  
Young’S Modulus ◽  
Elastic Properties ◽  
Elastic Constants ◽  
Poisson’S Ratio ◽  
Young's Modulus ◽  
Poisson's Ratio ◽  
Rotational Shell ◽  
Mutual Comparison ◽  
Quasistatic Loading

The problem of the identification of the elastic properties of eggshell, i.e. the evaluation of the Young's modulus and Poisson's ratio is solved. The eggshell is considered as a rotational shell. The experiments on the egg compression under quasistatic loading have been conducted. During these experiments a strain on the eggshell surface has been recorded. By the mutual comparison between experimental and theoretical values of strains the influence of the elastic constants has been demonstrated.

scholarly journals Promising Bialkali Bismuthides Cs(Na, K)2Bi for High-Performance Nanoscale Electromechanical Devices: Prediction of Mechanical and Anisotropic Elastic Properties under Hydrostatic Tension and Compression and Tunable Auxetic Properties

Nanomaterials ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 2739
Author(s):  
Shahram Yalameha ◽  
Zahra Nourbakhsh ◽  
Ali Ramazani ◽  
Daryoosh Vashaee
Keyword(s):  
Elastic Properties ◽  
Poisson’S Ratio ◽  
High Performance ◽  
Hydrostatic Compression ◽  
Poisson's Ratio ◽  
Elastic Behavior ◽  
Hydrostatic Tension ◽  
Tension And Compression ◽  
Electromechanical Devices ◽  
Anisotropic Elastic

Using first-principles calculations, we predict highly stable cubic bialkali bismuthides Cs(Na, K)2Bi with several technologically important mechanical and anisotropic elastic properties. We investigate the mechanical and anisotropic elastic properties under hydrostatic tension and compression. At zero pressure, CsK2Bi is characterized by elastic anisotropy with maximum and minimum stiffness along the directions of [111] and [100], respectively. Unlike CsK2Bi, CsNa2Bi exhibits almost isotropic elastic behavior at zero pressure. We found that hydrostatic tension and compression change the isotropic and anisotropic mechanical responses of these compounds. Moreover, the auxetic nature of the CsK2Bi compound is tunable under pressure. This compound transforms into a material with a positive Poisson’s ratio under hydrostatic compression, while it holds a large negative Poisson’s ratio of about −0.45 along the [111] direction under hydrostatic tension. An auxetic nature is not observed in CsNa2Bi, and Poisson’s ratio shows completely isotropic behavior under hydrostatic compression. A directional elastic wave velocity analysis shows that hydrostatic pressure effectively changes the propagation pattern of the elastic waves of both compounds and switches the directions of propagation. Cohesive energy, phonon dispersion, and Born–Huang conditions show that these compounds are thermodynamically, mechanically, and dynamically stable, confirming the practical feasibility of their synthesis. The identified mechanisms for controlling the auxetic and anisotropic elastic behavior of these compounds offer a vital feature for designing and developing high-performance nanoscale electromechanical devices.

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