Poisson Coefficient Research Articles

Determination of Noise Caused by Ventilated Brake Disc with Respect to the Rib Shape and Material Properties Using Taguchi Method

Ventilated brake discs may have various configurations of ribs and can be manufactured from different materials. In order to improve the performance in extreme exploitation conditions, it is necessary that they heat up and wear as little as possible, and that they have good heat dissipation capacity and generate low noise. To achieve this, optimization of the influential parameters is required. In this study, the optimization and the analysis of the frequency value were made on the basis of the influential parameters, such as brake disc vane shape, density, Young’s modulus, and Poisson's coefficient. A numerical investigation was conducted using the ANSYS software package in the MODAL module. In order to better understand which parameter has the greatest influence on the noise formation, the Taguchi method was applied. By applying the Analysis of Variance – ANOVA, the influence of each parameter on frequency, expressed as a percentage, was determined. The obtained results show that the most influential parameter is the shape of the ribs (90.82%), followed by Young’s modulus (8.26%) and density (0.89%).

Strain Properties of Multicomponent Nanosize Film Materials

The results of the correlation between the longitudinal strain coefficient (SC) and the values of the Poisson coefficient and Grüneisen parameter for nanosize film multicomponent alloys (d ≅ 30–50 nm, ci ≅ 11–20 at%) are presented. It is established that in the region of elastic or quasi‐elastic deformation (less than or equal to 0.4%), the value of SC is insensitive to changes in the Grüneisen parameter in the range of 1.5–2.5 units during the transition to plastic formation (more than 0.4%). The value of SC decreases from 4–5 units to 3–1 units. Similarly, SC is insensitive to changes in the Poisson coefficient less than or equal 0.4 but decreases sharply in the region of plastic deformation. It is concluded that a sensitive element based on a multicomponent nanoscale film of a solid solution, including a high‐entropy one, has advantages over others due to phase stability in a wide temperature range. These materials may be used to develop the architecture of sensitive elements of sensors for various functional purposes.

Two-dimensional Si2S with a negative Poisson's ratio and promising optoelectronic properties.

Two-dimensional materials with a negative Poisson's ratio, known as auxetic materials, are of great interest owing to their improved mechanical properties, which enable plenty of advanced nanomechanical devices. Here, by first-principles swarm-intelligence structural search methods, we predict a thermodynamically stable Si2S monolayer, which has a puckered 2D lattice in which the S atoms are adsorbed on the top of a distorted tetragonal silicene layer. The puckered 2D lattice makes the Si2S monolayer exhibit in-plane negative Poisson's ratios of -0.05 and -0.069 along the x and y directions, respectively. Moreover, electronic structure calculations reveal that the Si2S monolayer is a semiconductor with a quasi-direct band gap of 1.81 eV, which can be converted into a direct gap semiconductor of 1.43 eV by applying a low tensile strain (∼2%). The Si2S monolayer has a large visible light absorption coefficient of 105 cm-1. The hole (electron) mobility is 200 (81) cm2 V-1 s-1 along the y direction, 3.4 (1.5) times that along the x direction, comparable to MoS2. Moreover, the Si2S monolayer has the good ability of oxidation resistance. We provide a possible route to experimentally grow a Si2S monolayer on a suitable substrate such as the Cu(100) surface. The versatile properties render the Si2S monolayer potential for advanced application in nanodevices.

Impact characterization of bio-based sandwich panels with cork core

Currently, for ecological and economic reasons, cellulosic fibres obtained from plants have enormous advantages for industrial applications. For example, the automotive sector suggests the use of composites reinforced with natural fibres due to their biodegradability, availability, low cost, and non-abrasive properties. However, due to the low resistance to localized impact loads, the use of composite materials is still a problem for many applications. In this context, sandwich composites can be a solution to overcome this problem, especially when they incorporate cork as a core. Cork has an alveolar structure, and it presents high specific strength and stiffness, near zero Poisson coefficient, high tolerance to the impact loads, impervious to liquid and gases, resistance to reactive agents and microorganisms, resistance to wear and fire, very low thermal conductivity, good acoustic insulation capacity and excellent damping characteristics. Therefore, this work intends to produce and characterize a novel bio-sandwich panel with a cork core and a laminate facing reinforced by date palm leaflets and using a green epoxy resin. The benefits of this new bio-sandwich, in terms of impact strength, will be determined by comparison with a bio-composite laminate involving the same resin reinforced with date palm leaflets. It was possible to conclude that the cork core was responsible for lower impact loads and higher restored energy.

Investigation of the mechanical properties of Mn15Si26 via EBSD-nanoindentation coupling and ab-initio calculation

The goal of this study is to investigate the mechanical and elastic characteristics of the Mn15Si26 compound via experimental nanoindentation measurements and ab-initio calculations. The mechanical properties such as Young’s modulus (E) and nanohardness are important inputs for improving the design and mechanical reliability of thermoelectric modules. The high-energy X-ray diffraction pattern of Mn15Si26 has been indexed with the Miller indices of a tetragonal crystalline structure whose cell parameters are the following: a = b = 5.535(3) Å and c = 65.552(4) Å. Nanoindentation measurements, with a Berkovich indenter tip have been performed on higher manganese silicide (HMS) compound mainly composed of Mn15Si26 grains. For the first time ever, it has been evidenced that both elastic modulus and nanohardness of the latter varied significantly depending on their crystallographic orientations provided by electron backscatter diffraction. Nanohardness and Young’s modulus along the< 001 > orientations are higher than the< 100 > ones. The nanohardness value of Mn15Si26 ranges from 16 GPa to 20 GPa and the Young’s modulus measured varies between 234 GPa and 300 GPa. The stiffness tensor (Sij= (Cij)−1) of Mn15Si26 has been deduced from these experimental measurements as well as calculated using Ab-initio calculations. The macroscopic elastic modulus (E, G, Β) and Poisson's coefficient have been examined and discussed and their 3D-representation has been plotted. The mechanical anisotropy hereby evidenced as the existence of anisotropy of the thermoelectric properties could be a significant factor for the mechanical reliability of thermoelectric modules which consisted of Mn15Si26 legs with a possible preferred crystallographic orientation induced during their fabrication.

Cross-Sectional Association of Food Source with Food Insecurity, Dietary Diversity and Body Mass Index in Western Kenya.

The triple burden of malnutrition in many low- and middle-income countries (LMICs) is partly a result of changing food environments and a shift from traditional diets to high-calorie Western-style diets. Exploring the relationship between food sources and food- and nutrition-related outcomes is important to understanding how changes in food environments may affect nutrition in LMICs. This study examined associations of household food source with household food insecurity, individual dietary diversity and individual body mass index in Western Kenya. Interview-administered questionnaire and anthropometric data from 493 adults living in 376 randomly-selected households were collected in 2019. Adjusted regression analyses were used to assess the association of food source with measures of food insecurity, dietary diversity and body mass index. Notably, participants that reported rearing domesticated animals for consumption (‘own livestock’) had lower odds of moderate or severe household food insecurity (odds ratio (OR) = 0.29 (95% CI: 0.09, 0.96)) and those that reported buying food from supermarkets had lower odds of moderate or severe household food insecurity (borderline significant, OR = 0.37 (95% CI: 0.14, 1.00)), increased dietary diversity scores (Poisson coefficient = 0.17 (95% CI: 0.10, 0.24)) and higher odds of achieving minimum dietary diversity (OR = 2.84 (95% CI: 1.79, 4.49)). Our findings provide insight into the relationship between food environments, dietary patterns and nutrition in Kenya, and suggest that interventions that influence household food source may impact the malnutrition burden in this context.

Investigation of structural, electronic and lattice dynamical properties of YMgNi4H4 cubic and orthorhombic for hydrogen storage applications

This work presents the results obtained from ab initio calculations based on Density Functional Theory (DFT), to study the compound YMgNi4H4 in two phases cubic and orthorhombic, two methods were used: Full Potential Linearize Augmented Plane Waves (FP-LAPW) and Plane Waves Pseudo Potential (PW-PP). The obtained structural properties agree well with previous works. The cohesive energy, hydrating enthalpy and the formation enthalpy are negative for both structures, our results predict that the orthorhombic phase is the most stable. The calculated band structure indicates that this material has metallic behavior. The elastic constants were calculated using the Density Functional Perturbation Theory (DFPT) formalism. The two structures are mechanically stable based on their values, and other mechanical properties such as the bulk modulus, Young's modulus, shear modulus, Poisson's coefficient were calculated using these elastic constants. By analyzing the elastic anisotropy, this material has a pronounced anisotropy. Using the DFPT, the dispersion of the phonons has been calculated for the two phases, it indicates the stability of these two phases because we notice the absence of imaginary modes. Finally, in the [0, 1540] K° range, the variations of thermodynamic properties as a function of temperature were measured.

A virtual scale approach to multi-scale calculations and its application in fiber-reinforced composites

With the development of materials science and technology into the nano-/micro-world, multi-scale problems have become a research focus. Multi-scale calculations usually select a periodic structure as a representative unit with a certain physical meaning and can represent the material properties at a given scale. However, due to the large number of representative elements with complex shape and boundary conditions, the workload of multi-scale calculations is normally huge. In the present effort, a novel virtual scale method is proposed for multi-scale calculations. To demonstrate the validity and significance of the new algorithm, multi-scale calculations have been carried out for the prediction of properties of the ever-popular fiber reinforced composite materials. The equivalent elastic modulus, Poisson's ratio and coefficient of thermal expansion (CTEs) of fiber reinforced plastic in different scales predicted by the new method have been compared with those predicted by the well-established finite element method (FEM) and checked against the experimental results. The good agreements offer solid proof in terms of the validity of the newly developed virtual scale method. In principle, the method can be extended to tackle all multi-scale problems.

Drained triaxial testing of shales: insight from the Opalinus Clay

The investigation of the mechanical behaviour of swelling claystones and shales is challenging because of their very low permeability and of their high sensitivity to changes in water content. The former makes it difficult to carry out triaxial tests with controlled homogeneous water pore pressure fields, and the latter results in some possible effects of swelling when unsaturated extracted specimens are re-saturated prior to being tested. This work presents some data from drained triaxial tests performed on specimens of Opalinus Clay, designated as host rock for radioactive waste disposal in Switzerland, extracted at shallow depth close to the city of Lausen. The data are compared to those recently published from undrained triaxial tests on specimens from the same place, and also to two sets of recent data independently obtained on Opalinus Clay specimens sourced from greater depth at the Mt Terri Underground Research Laboratory. By comparing the data of our drained tests on Lausen specimens to those from specific undrained tests in which swelling has been prevented, quite a good comparability in shear strength is observed at confining effective stresses larger than 5–6 MPa. This is related to the small magnitude of the swelling occurring above this stress during the specimen hydration in drained tests. The question of the possible linearity of the shear strength criterion at low stress is also discussed with respect to both our data and other published ones. It is suggested that undrained tests be also carried out at low confining stresses to investigate whether some perturbations due to hydration swelling occur in this area that could result in a nonlinear shape of the criterion. The change in Young modulus and Poisson coefficient with stress is also discussed, and the data on Opalinus Clay are compared to those of the Callovo–Oxfordian claystone from France, evidencing interesting similarities in terms of shear strength properties and Young’s moduli.

A computational estimation on structural, electronic, elastic, optic and dynamic properties of Li2TlA (A=Sb and Bi): First-principles calculations

The structural, electronic, optic, elastic and dynamic properties of Li2TlSb and Li2TlBi full-Heusler structure are studied by first principles calculations. The plane wave pseudo-potential method with a generalized gradient approximation was used to calculate all these properties. Quantum Espresso program was used to examine structural, electronic and dynamic properties, and Abinit program was used to examine optical and elastic properties. The change correlation function chosen is the Perdew - Burke - Ernzerhof function. The currently calculated structural properties are in good agreement with other theoretical results. Based on the linear harmony of the stress-strain relationship, the elastic constants of these structures have been determined. Poisson's coefficients and Zener anisotropy factor, Bulk, Shear and Young Module are computed. With the density functional perturbation theory, the frequencies of the phonon distribution spectra throughout the entire brillouin region were calculated and all values were found to be positive. These results show that the dynamic stabilities of Li2TlBi and Li2TlSb crystals are strong. The results obtained in this study are thought to be useful in future scientific studies to explore the applications of these materials such as optoelectronic devices and sensors.

Evaluation of the significance of the contact model particle parameters in the modelling of wet soils by the discrete element method

Modelling of the tillage process by working tools based on the method of discrete elements is currently the most promising. The results of modelling the processing process obtained by the method of discrete elements adequately describe the behaviour of the soil. Due to the large number of physical and mechanical parameters included in the description of contact models of discrete elements, the calibration process takes a lot of time. Thus, we set a research goal - to evaluate the significance of the parameters of the contact model particles in soil modelling by the discrete element method and to obtain nomograms for selecting the parameters of the Hertz-Mindlin contact model particles depending on the humidity of various types of soils. The article presents the results of calibration of the physical and mechanical parameters of the particles of the soil medium model described by the discrete element method. An improved Hertz-Mindlin JKR model was used as a contact model, the model was implemented in the Rocky DEM programme. The following properties of the modelled particles are taken as the studied factors – Poisson's ratio, static and dynamic friction coefficients, Jung's modulus, surface energy, and particle diameter. The detection of the natural slope angle of the soil was carried out for black soils of clay, light loam and sandy loam mechanical composition. The calibration was performed according to the angle of the natural slope. Comparison of the simulation results with field experiments of typical soils made it possible to establish that the nature of the change in the angle of the natural slope of the simulated soil environment is significantly affected by the surface energy and the diameter of the particles. The obtained dependences of the angle of natural slope on soil moisture and surface energy allow determining the parameters for the Hertz-Mindlin contact model as a function of humidity for Black soil zones of clay, light loam and sandy loam mechanical composition. Based on the results of field and model experiments, a nomogram was obtained that makes it possible to select parameters for the contact model - the diameter of soil particles and the value of surface energy depending on humidity and soil type. The obtained values of the parameters of the particles of the soil medium make it possible to simulate the process of tillage, optimize the design and technical parameters of the newly created working parts of tillage machines.

Correlation between microstructures and macroscopic properties of nickel/yttria-stabilized zirconia (Ni-YSZ) anodes: Meso-scale modeling and deep learning with convolutional neural networks

A deep learning based homogenization framework is proposed to link the microstructures of porous nickel/yttria-stabilized zirconia anodes in solid oxide fuel cells (SOFCs) to their effective macroscopic properties. A variety of microstructures are generated by the discrete element method and the meso‑scale kinetic Monte Carlo method. Then, the finite element method and the homogenization theory are used to calculate the effective elastic modulus (E), Poisson's ratio (υ), shear modulus (G) and coefficient of thermal expansion (CTE) of representative volume elements. In addition, the triple-phase boundary length density (LTPB) is also calculated. The convolutional neural network (CNN) based deep learning model is trained to find the potential relationship between the microstructures and the five effective macroscopic properties. The comparison between the ground truth and the predicted values of the new samples proves that the CNN model has an excellent predictive performance. This indicates that the CNN model could be used as an effective alternative to numerical simulations and homogenization because of its accurate and rapid prediction performance. Hence the deep learning-based homogenization framework could potentially accelerate the continuum modeling of SOFCs for microstructure optimization.

The improvement of mechanical properties of conventional concretes using carbon nanoparticles using molecular dynamics simulation

In the present study, the improvement of mechanical properties of conventional concretes using carbon nanoparticles is investigated. More precisely, carbon nanotubes are added to a pristine concrete matrix, and the mechanical properties of the resulting structure are investigated using the molecular dynamics (MD) method. Some parameters such as the mechanical behavior of the concrete matrix structure, the validation of the computational method, and the mechanical behavior of the concrete matrix structure with carbon nanotube are also examined. Also, physical quantities such as a stress–strain diagram, Poisson's coefficient, Young's modulus, and final strength are calculated and reported for atomic samples under external tension. From a numerical point of view, the quantities of Young's modulus and final strength are converged to 35 GPa and 35.38 MPa after the completion of computer simulations. This indicates the appropriate effect of carbon nanotubes in improving the mechanical behavior of concrete and the efficiency of molecular dynamics method in expressing the mechanical behavior of atomic structures such as concrete, carbon nanotubes and composite structures derived from raw materials is expressed that can be considered in industrial and construction cases.

Engineering performance’s evaluation of integrated backfill materials

In the process of deep geological disposal, bentonite, illite, zeolite, kaolinite, quartz sand and other materials were used as filling materials for filling in waste tin and rock. This paper proposed integrated backfilling materials (ZBP8, ZBP7, ABP8, ABP7 and Xinjiang bentonite Na+) etc and five groups of formula, with a series of geotechnical experiments measured the engineering properties, such as glial price, expansion solution, liquid limit, plastic limit of compacted expansive, unconfined compressive strength, elastic modulus, Poisson's ratio and coefficient of permeability. Compared with the GMZ-1 bentonite, the engineering performance of various proportions meeted the backfill material disposal requirements and could be used as backfill material candidate for the integrated materials, but proportion of zeolite and palygorskite should not be too large, generally better from 20% to 30%. The specific engineering properties were as follows: Under the condition of the same proportion, ABP mixture was higher than the ZBP mixture of liquid limit. In the ABP mixture and the ZBP mixture, dry density at 1.7g/cm3-1.8g/cm3 and moisture content between 15%-20% of the compaction performance were the best. The compaction performance of ZBP mixture was better than that of ABP mixture under the same condition. Different ratio of ZBP and ABP composite minerals under no load condition, it found that ultimately expansion and expansion force with the increase of bentonite. The expansion performance of ABP mixture was better than that of ZBP mixture. Under the same condition, the unconfined compressive strength, elastic modulus and Poisson's ratio increased with the increase of the content of bentonite in the integrated backfill material. Under the condition of 100 MPa compaction, the permeability coefficient of ZBP and ABP mixture was 2 orders of magnitude higher than that of GMZ-1. The permeability coefficient of Xinjiang bentonite under 50MPa was very close to that of GMZ-1 bentonite under 100MPa.

EQUATIONS FOR DETERMINING THE DYNAMIC CHARACTERISTICS OF ELASTIC ELEMENTS

In this article, we consider equations for determining the dynamic characteristics of inhomogeneous elastic elements using refined elastic modulus and Poisson's coefficients depending on the concentration of reinforcing fibers. The dependences of the first three natural frequencies of the seamless bellows on its thickness and depth of corrugation and the first two natural frequencies of the welded bellows on its thickness are identified and analyzed. The frequency response and frequency response of an accelerometer with a UE are obtained depending on its geometric parameters.

Finite element analysis of the tibial component alignment in frontal and sagittal plane in total knee arthroplasty

Background. This study aims to analyze the tibial component using the finite element method by cutting the tibial in frontal and sagittal planes at an angle between 1.5° (valgus and anterior tilt) and -1.5° (varus and posterior tilt). Methods. This experimental study used the finite element method as an useful tool for simulating the positioning of the tibial component in order to create a personal pre-operative planning. For the finite element method analysis, a geometrical model of a tibia from a cadaver was three – dimensionally scanned and the tibial component, polyethylene and cement, were three-dimensionally shaped in Computer-Aided Design program using material data such as Young modulus (gigapascal – GPa) and the Poisson coefficient. The analysis determined the equivalent von Mises stress, the maximum displacement of the components and the equivalent von Mises deformation. The results showed that equivalent tension and deformation have higher values in the tibia and the polyethylene, which deform faster than cement and the tibial component. In our study, we chose to simulate the tibial resection at a cutting angle ± 1.5° from neutral positioning (which is represented in frontal plane by the perpendicular on the mechanical axis and in sagittal plane by the posterior slope of 7 degree) in frontal and sagittal plane in order to find the minimum threshold from which the tibial component malalignment may begin to determine unfavorable effects. Results. Our results have shown detrimental effects begin to appear for the polyethene component at -1.5° in frontal plane, and the rest of the components at 1.5° in sagittal plane. Conclusion. This finding leads us to propose preoperative planning based on personal calculus of predefined angles, which may show the surgeon the optimal implantation position of the tibial component.

Effect of oxygen impurities on the electronic and mechanical properties of penta-graphene sheet

The electronic and mechanical properties of a penta-graphene monolayer (PGM) in attendance and nonattendance of oxygen impurities were investigated using the SIESTA computational code, based on density functional theory calculations. The results of the first-principles (ab-initio) calculations show that PGM in the nonattendance of oxygen atoms is a semiconductor with indirect band gap. By adding the oxygen, the bandgap size of PGM changes. Analyzing the results indicates that oxygen absorption increases the stability of the structure. The results display that, the addition of oxygen atoms affects the electrical and mechanical properties of penta-graphene, such as converting the band structure from semiconductor to insulating, reducing Young’s modulus, and changing the Poisson’s coefficient sign. Penta-graphene has received a lot of attention from researchers as a mechanical metamaterial or auxetic material due to its negative Poisson coefficient.

Structural, electronic, magnetic and mechanical properties of three LaMnO3 phases: Theoretical investigations

First principles density functional theory is used to study the physical properties of LaMnO3 in its orthorhombic (Pnma), cubic (Pm-3m) and rhombohedral (R-3c) phases, using Full Potential Linearized Augmented Plane Wave (FP-LAPW) method implemented in the WIEN2k code. The exchange-correlation potential was treated with the WC-GGA + U approximation (where U is the Hubbard Coulomb energy term) for the calculation of the structural, electronic and magnetic properties, whereas the Tran-Blaha modified Beck-Johnson (TB-mBJ) potential is applied for the calculation of the electronic properties. We also used the ABINIT code to calculate mechanical properties. Our structural, electronic and magnetic calculations obtained are in good agreement with experimental ones. At equilibrium, spin polarization of the orthorhombic phase of LaMnO3 compound is antiferromagnetic (AFM) and we predict the ferromagnetic phase of the compound LaMnO3 to be half-metal with spin polarization of 100%. In addition, the bonding nature reveals a mixture of covalent and ionic bonding character. The ductility and brittleness are explored from mechanical properties, such as elastic constants, bulk modulus, shear modulus, Young's modulus, Poisson coefficient, B/G ratio and anisotropy ratio, and our obtained values indicate that LaMnO3 is a ductile and anisotropic material in the three phases. We have also investigated the elastic wave velocity and Debye temperature to collect more information on mechanical stability.

Stone Pavement Analysis using Building Information Modeling

The growing need to recover and digitally represent heritage infrastructure has led to the challenge of choosing different Building Information Modeling (BIM) platforms that will be used to manage the implementation of the semi-automatic design and reconstruction processes of reverse engineering modeling. The approach to the integrated management of information derived through Heritage-BIM (H-BIM) has been applied to Via del Duomo, one of the main roads in the old town of Naples, Italy. During preliminary inspections of the construction site it was possible to acquire geometric features and pavement/subgrade information, as well as to conduct a photographic survey, with 1,618 photographs collected. Subsequently, the acquired data were processed, using different BIM-based tools, to obtain the 3D mesh; objects were then converted from pure graphic solids into parametric entities by proposing a specific algorithm. Then a library, with the inclusion of all the possible stone paving package alternatives, including all the structural and stress-deforming characteristics such as Young Modulus (E), Poisson coefficient (n), and Safety factor (SF), was created. In this way, it is possible to associate to the generic element the optimal pavement package solution, depending on different construction contexts. As preliminary result, a dynamic model that updates its information package and modifies the output of the analysis every time the data worksheet is integrated with new collected results is proposed for further pavement management operations evaluation.

Multi-material 3D double-V metastructures with tailorable Poisson's ratio and thermal expansion

Natural materials have achieved excellent comprehensive mechanical properties and fascinating synergistic functionalities through composite architectures and optimum materials distribution within a single tissue during natural selection/adaptation. Producing three-dimensional (3D) architectures with multi-materials has been a major challenge in artificial materials. Herein, 3D double-V hierarchical (DVH) lattices with multi-materials were designed and fabricated using interlocking assembly strategy. Theoretical analysis, numerical simulation and experimental verification were conducted to investigate the mechanical response of the multi-material metastructures, especially effective Poisson's ratio and coefficient of thermal expansion (CTE). The results revealed that the equivalent Poisson's ratio of the 3D DVH lattices can be tuned by changing not only the geometric parameters but also the relative stiffness of the two V segments. Poisson's ratio of the multi-material metamaterials has the minimum/maximum value at transition point and tends to zero with the increase or decrease of the relative stiffness. The equivalent CTE of concave 3D DVH lattices can be tuned by changing not only the geometric parameters but also the relative CTE and relative stiffness of the two V segments from magnified positive to near zero or large negative. Coupled negative Poisson's ratio and CTE, which are hardly found in natural materials, are easily achieved by the architected DVH composite lattices. This work provides an innovative approach for the design, fabrication and characterization of 3D architected cellular materials with simultaneously tailorable auxetic behavior and thermal expansion, which are promising in advanced engineering applications.