scholarly journals Characterization of Engineering Elastic Parameters of Oriented Strand Board (OSB) Manufactured from Poplar (Populus deltoides) Strands Using Ultrasonic Contact Pulse Transmission

2020 ◽  
Vol 71 (3) ◽  
pp. 227-234
Author(s):  
Meysam Zahedi ◽  
Saeed Kazemi Najafi ◽  
Josef Füssl ◽  
Majid Elyasi
Keyword(s):  
Shear Modulus ◽  
Elastic Wave ◽  
Elastic Constants ◽  
Modulus Of Elasticity ◽  
Populus Deltoides ◽  
Oriented Strand Board ◽  
Elastic Wave Velocity ◽  
Elastic Parameters ◽  
Pulse Transmission

When using wood and wood-based composites, it is necessary to determine the elastic constants of these engineered materials. Oriented strand board (OSB), as structural wood based panel, plays a significant role in the building sector, but the accessibility of such elastic constants of OSB is mostly limited. For this purpose, this study aimed at determining the elastic wave velocity, stiffness and all elastic constants of OSB made from Poplar (Populus deltoides) strands using ultrasonic through–transmission technique. Laboratory OSBs with the mean density of 760 kg/m3 were made with the average strand sizes of 0.6 mm in thickness, 120 mm in length and 30 mm in width. 8 % phenol-formaldehyde (PF) resin was used with the pressing conditions of 3.43 N/mm2, 190 °C and 600 s as pressure, temperature and time of pressing, respectively. The OSBs were assumed as an orthotropic model. Three modulus of elasticity (E1, E2, and E3), three shear modulus (G12, G13 and G23), and six Poisson’s ratios (v12, v21, v13, v31, v23, v32) were calculated by longitudinal, transversal and quasi-transversal waves velocities. Ultrasonically determined stiffness coefficients of OSB were investigated by representative volume elements (RVE). Therefore, the separation of scales requirement is satisfied, and the measured velocities can be applied to determine the engineering elastic parameters of the examined OSB. The results indicate that modulus of elasticity and shear modulus are in the same order of magnitude in comparison with other references, and the values of Poisson’s ratios are valid in ultrasonic range measurement. In conclusion, the ultrasonic contact pulse transmission shows great potential to determine the characterization of elastic wave velocity, stiffness and engineering elastic parameters.

scholarly journals Sound velocities and Debye temperature of BeSe under high pressure up to 50 GPa

2016 ◽  
Vol 5 (1) ◽  
pp. 7
Author(s):  
Salah Daoud
Keyword(s):  
High Pressure ◽  
Elastic Wave ◽  
Mechanical Behavior ◽  
Debye Temperature ◽  
Elastic Constants ◽  
Structural Parameters ◽  
Theoretical Data ◽  
Elastic Wave Velocity ◽  
Brittle Behavior ◽  
Sound Velocities

The mechanical behavior, sound velocities and Debye temperature of beryllium-selenide (BeSe) semiconductor under pressure up to 50 GPa have been estimated using the structural parameters and elastic constants of Fanjie Kong and Gang Jiang (Physica B 404 (2009) 3935-3940). The Pugh ratio, the directional dependence of elastic wave velocity, the longitudinal, transverse and average sound velocities, and the Debye temperature are successfully predicted and analyzed in comparison with the available theoretical data. The analysis of the Pugh ratio indicates that this compound is prone to brittle behavior. Our obtained results of the longitudinal, transverse and average sound velocities at high pressure indicate that these of Kong and Jiang (Physica B 404 (2009) 3935-3940) are not correctly predicted.

scholarly journals Variations in Orthotropic Elastic Constants of Green Chinese Larch from Pith to Sapwood

Forests ◽  
2019 ◽  
Vol 10 (5) ◽  
pp. 456 ◽  
Author(s):  
Fenglu Liu ◽  
Houjiang Zhang ◽  
Fang Jiang ◽  
Xiping Wang ◽  
Cheng Guan
Keyword(s):  
Shear Modulus ◽  
Elastic Constants ◽  
Coefficient Of Variation ◽  
Modulus Of Elasticity ◽  
Poisson’S Ratio ◽  
Poisson's Ratio ◽  
Stress Wave Propagation ◽  
Sampling Distance ◽  
Poisson's Ratios ◽  
Poisson’S Ratios

Full sets of elastic constants of green Chinese larch (Larix principis-rupprechtii Mayr) with 95% moisture content at four different cross-section sampling positions (from pith to sapwood) were determined in this work using three-point bending and compression tests. Variations in the material constants of green Chinese larch from pith to sapwood were investigated and analyzed. The results showed that the sensitivity of each elastic constant to the sampling position was different, and the coefficient of variation ranged from 4.3% to 48.7%. The Poisson’s ratios νRT measured at four different sampling positions were similar and the differences between them were not significant. The coefficient of variation for Poisson’s ratio νRT was only 4.3%. The four sampling positions had similar Poisson’s ratios νTL, though the coefficient of variation was 11.7%. The Poisson’s ratio νLT had the greatest variation in all elastic constants with a 48.7% coefficient of variation. A good linear relationship was observed between the longitudinal modulus of elastic EL, shear modulus of elasticity GRT, Poisson’s ratio νRT, and sampling distance. EL, GRT, and νRT all increased with sampling distance R. However, a quadratic relationship existed with the tangential modulus of elasticity ET, radial modulus of elasticity ER, shear modulus of elasticity GLT, and shear modulus of elasticity GLR. A discrete relationship was found in the other five Poisson’s ratios. The results of this study provide the factual changes in the elastic constants of green wood from pith to sapwood for numerical modelling of stress wave propagation in trees or logs.

On the method of ultrasonic control of mechanical stresses

2018 ◽  
Vol 84 (7) ◽  
pp. 62-66
Author(s):  
K. V. Kurashkin
Keyword(s):  
Elastic Wave ◽  
Orientation Distribution ◽  
Elastic Wave Velocity ◽  
Mechanical Stresses ◽  
Material Structure ◽  
Stress Determination ◽  
Welded Steel ◽  
Ultrasonic Control ◽  
Cubic Crystallites ◽  
Proportional Relationship

A method of ultrasonic control of the mechanical stresses which takes into account the heterogeneity of the material structure and does not require unloading of the structure or using reference samples is considered. The procedure is based on echo-method of measuring time of the bulk elastic wave propagation and determination of the relative values ν31 and ν32 related to the material structure and mechanical stresses. It is shown that stresses violate the linearity of the relationship observed between the parameters in the absence of the mechanical stresses in the rolled material. This effect formed a basis for developing a method of the deviator stress determination. The purpose of the study is to demonstrate the main advantages of the developed method against the known ultrasonic techniques used for evaluation of the mechanical stresses, give theoretical grounds to the effect which allows taking into account the heterogeneity of the material structure, and also to exemplify the procedure. An analytical expression is derived using bulk elastic wave velocity in an orthotropic material composed of cubic crystallites and an assumption on the existence of simple proportional relationship between the coefficients of the orientation distribution function in rolled metal. Presented results of the mathematical modeling confirm the experimentally observed linear dependence between the parameters ν31 and ν32 in the absence of mechanical stresses. The results of evaluating residual stresses in a welded steel plate are presented as an example of the applicability of the developed procedure. Data of ultrasonic technique and data of strain gage measurements are compared. The features of the described method of stress determination are marked and the applicability limits are specified.

On the Transition from Homogeneous to Bubbling Fluidization

1997 ◽  
Vol 62 (11) ◽  
pp. 1698-1709
Author(s):  
Miloslav Hartman ◽  
Zdeněk Beran ◽  
Václav Veselý ◽  
Karel Svoboda
Keyword(s):  
Elastic Wave ◽  
Froude Number ◽  
Wave Velocity ◽  
Density Ratio ◽  
Elastic Wave Velocity ◽  
Solid Density ◽  
Archimedes Number ◽  
Group A ◽  
Experimental Findings

The onset of the aggregative mode of liquid-solid fluidization was explored. The experimental findings were interpreted by means of the dynamic (elastic) wave velocity and the voidage propagation (continuity) wave velocity. For widely different systems, the mapping of regimes has been presented in terms of the Archimedes number, the Froude number and the fluid-solid density ratio. The proposed diagram also depicts the typical Geldart's Group A particles fluidized with air.

scholarly journals Generalization of intrinsic ductile-to-brittle criteria by Pugh and Pettifor for materials with a cubic crystal structure

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
O. N. Senkov ◽  
D. B. Miracle
Keyword(s):  
Crystal Structure ◽  
Shear Modulus ◽  
Bulk Modulus ◽  
Single Crystal ◽  
Elastic Constants ◽  
Mechanical Analysis ◽  
Quantum Mechanical ◽  
Modulus Ratio ◽  
Cubic Crystal ◽  
The Difference

AbstractTwo classical criteria, by Pugh and Pettifor, have been widely used by metallurgists to predict whether a material will be brittle or ductile. A phenomenological correlation by Pugh between metal brittleness and its shear modulus to bulk modulus ratio was established more than 60 years ago. Nearly four decades later Pettifor conducted a quantum mechanical analysis of bond hybridization in a series of intermetallics and derived a separate ductility criterion based on the difference between two single-crystal elastic constants, C12–C44. In this paper, we discover the link between these two criteria and show that they are identical for materials with cubic crystal structures.

scholarly journals Elastic wave velocity and electrical conductivity in a brine-saturated rock and microstructure of pores

2019 ◽  
Vol 71 (1) ◽  
Author(s):  
Tohru Watanabe ◽  
Miho Makimura ◽  
Yohei Kaiwa ◽  
Guillaume Desbois ◽  
Kenta Yoshida ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Elastic Wave ◽  
Wave Velocity ◽  
High Pressures ◽  
Seismic Velocity ◽  
Volume Fraction ◽  
Elastic Wave Velocity ◽  
Fluid Volume ◽  
Sem Observation ◽  
Wide Aperture

AbstractElastic wave velocity and electrical conductivity in a brine-saturated granitic rock were measured under confining pressures of up to 150 MPa and microstructure of pores was examined with SEM on ion-milled surfaces to understand the pores that govern electrical conduction at high pressures. The closure of cracks under pressure causes the increase in velocity and decrease in conductivity. Conductivity decreases steeply below 10 MPa and then gradually at higher pressures. Though cracks are mostly closed at the confining pressure of 150 MPa, brine must be still interconnected to show observed conductivity. SEM observation shows that some cracks have remarkable variation in aperture. The aperture varies from ~ 100 nm to ~ 3 μm along a crack. FIB–SEM observation suggests that wide aperture parts are interconnected in a crack. Both wide and narrow aperture parts work parallel as conduction paths at low pressures. At high pressures, narrow aperture parts are closed but wide aperture parts are still open to maintain conduction paths. The closure of narrow aperture parts leads to a steep decrease in conductivity, since narrow aperture parts dominate cracks. There should be cracks in various sizes in the crust: from grain boundaries to large faults. A crack must have a variation in aperture, and wide aperture parts must govern the conduction paths at depths. A simple tube model was employed to estimate the fluid volume fraction. The fluid volume fraction of 10−4–10−3 is estimated for the conductivity of 10−2 S/m. Conduction paths composed of wide aperture parts are consistent with observed moderate fluctuations (< 10%) in seismic velocity in the crust.

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