Poisson's ratio Research Papers - Academia.edu (original) (raw)

This paper summarizes research work related to materials with zero, or negative Poisson's ratio, materials which are also referred to as auxetic materials. This review puts an emphasis on computations and aspects of their mechanics. It... more

This paper summarizes research work related to materials with zero, or negative Poisson's ratio, materials which are also referred to as auxetic materials. This review puts an emphasis on computations and aspects of their mechanics. It also considers diverse examples: from large structural, to biomedical applications. It is concluded that auxetic materials are technologically and theoretically important. While the development of the research has been dominated by periodic/ordered microstructures, the author predicts that future research will be in the direction of disordered microstructures utilizing the homogenization method.

Polydimethylsiloxane (PDMS) is a soft polymer that is primarily used for soft lithography (e.g., microfluidics and labon-chip devices) and also has wide range of applications, such as for thermomechanical actuators. The unique material... more

Polydimethylsiloxane (PDMS) is a soft polymer that is primarily used for soft lithography (e.g., microfluidics and labon-chip devices) and also has wide range of applications, such as for thermomechanical actuators. The unique material properties of PDMS (such as the low values of Young's modulus) renders it to be an attractive material for applications where large range of deformations can be achieved with small variations in the actuating pressure (or actuating forces) thus providing good mechanical advantage. PDMS has been reported in the literature for microfabricating and testing thermally actuated microvalves (for microfluidics applications). These microvalves involve the thermal expansion of a fluid resulting in the deformation of a flexible PDMS membrane. Accurate numerical modeling of such thermo-mechanical actuators made from PDMS necessitates the knowledge of the temperature dependent mechanical properties of PDMS (such as Young's modulus) which is currently lacking in the literature. In this study large deformations were obtained for a thin flexible PDMS membrane (with a square footprint of 7.2 mm and thickness of 200 microns) that was microfabricated on the top of a hermetically sealed cavity (that was 3 mm deep) by subjecting the membrane to thermo-pneumatic pressure arising from the thermal expansion of air trapped in the hermetically sealed cavity and heated from below. This enabled the experimental determination of maximum displacement of the membrane as a function of actuating temperature and therefore the estimation of the temperaturedependent mechanical properties (e.g., Young's Modulus and Poisson's ratio) using parametric simulations using the finite element method (FEM) and based on linear elastic assumption for the deformation of PDMS. Using digital images of the convex shape of the deformed PDMS membrane the maximum deformation was measured as a function of temperature under steady state conditions. Computational Fluid Dynamics (CFD) based commercial solver (Ansys™ 2019R1®) was used to estimate the air pressure inside the hermetically sealed chamber as a function of temperature under steady state conditions (which was verified by analytical calculations). The values of pressure (obtained from CFD simulations) was used as the boundary condition in the FEM model (Ansys™ 2019R1®) for a fixed value of the Young's Modulus and Poisson's ratio to estimate the maximum deformation of the PDMS membrane. By parametric variation of the Young's Modulus and Poisson's ratio (for a particular operating temperature) the actual values were determined based on the computational result that matched the experimental data. The results show that the material

The vast quantity of asphalt concrete being used in the U.S. highway system demands deeper understanding of the material to ensure sustainability of the highway pavement system. Poisson’s ratio, though a vital material property for... more

The vast quantity of asphalt concrete being used in the U.S. highway system demands deeper understanding of the material to ensure sustainability of the highway pavement system. Poisson’s ratio, though a vital material property for elastic materials, does not serve the purpose of material characterization for viscoelastic materials like asphalt concrete. This paper presents a brief review of existing literature on the use of Poisson’s ratios in general and by the asphalt research community in specific. The literature review revealed that the majority of existing studies assumed a constant Poisson’s ratio of 0.3–0.35. Few analytical simulations have been conducted to realize the time and stress dependence of viscoelastic Poisson’s ratios. The errors caused by incorrectly assuming constant Poisson’s ratios and the same moduli relaxation times for viscoelastic materials were quantified. The effect of varying moduli ratios on Poisson’s ratios was also studied. This study concludes that assuming a constant Poisson’s ratios and similar relaxation times can lead to serious errors in characterization of asphalt mixtures.

This study numerically investigates the side resistance of drilled shafts (bored piles) in sand using FLAC 2D computer program. The results of the equations available in the literature are compared with the results of the present... more

This study numerically investigates the side resistance of drilled shafts (bored piles) in sand using FLAC 2D computer program. The results of the equations available in the literature are compared with the results of the present numerical study. A series of analyses is also conducted to assess the effects of various soil and pile parameters on the magnitude of side resistance of bored piles embedded in sand. Furthermore, the coupling (combined) effect of coefficient of lateral earth pressure with friction angle, and the coefficient of lateral earth pressure with a unit weight of soil on side resistance are investigated. The results show that the maximum effect of K 0 on side resistance occurs around the soil friction angle of 40° and 45°. Also, the effect of K 0 on side resistance is approximately constant by increasing the soil unit weight. Finally, a correction factor for coefficient of lateral earth pressure is determined.

This study provides a contribution to the research field of 3D-printed earthen buildings, focusing, for the first time, on the load-bearing capacity of these structures. The study involves the entire production and testing process of the... more

This study provides a contribution to the research field of 3D-printed earthen buildings, focusing, for the first time, on the load-bearing capacity of these structures. The study involves the entire production and testing process of the earthen elements, from the design, to the preparation of the mixture and the 3D printing, up to the uniaxial compression test on a wall segment. The results indicate that 3D-printed earthen elements have a compressive strength of 2.32 MPa, comparable to that of rammed earth structures. The experimental data also made it possible to draw conclusions on the action of the infill, which seems to have the function of stopping the propagation of cracks. This has a positive effect on the overall behavior of 3D-printed earthen elements, since it avoids the onset of dilative behavior in the final stages of the load test and maintains ultimate load values higher than 50% of the maximum load.

Prediction of the mechanical properties of porous materials is crucial for their industrial applications. There are various types of porous materials: natural (bones, wood, coral) or man made (porous ceramics, aluminium foam); porous... more

Prediction of the mechanical properties of porous materials is crucial for their industrial applications. There are various types of porous materials: natural (bones, wood, coral) or man made (porous ceramics, aluminium foam); porous compacts (low or intermediate porosity) or foams (porosity up to 1). This article deals with the porous solids prepared as follows: At the beginning there is certain green density or tap density at which the consolidation of powders starts. Then, the physical bonds begin to create in the regions where powder particles touch each other. When certain number of such bonds is created and the material is able to carry its weight the powder compact starts to exist. This undergoes usually at smaller porosity as was porosity prior densification. Such porosity is called critical porosity or percolation threshold. [1] Further, the interconnected pores close down and disappear as porosity is going to zero. Due to random structure porous materials properties cannot be predicted analytically. On the other hand, prediction by numerical computations requires the knowledge of exact porous materials microstructure. The only practical ways to obtain it are microscopy, X-ray microtomography or models of the structure. However the costs and/or computational time of used method are very high and/or the accuracy of the method is very bad. Especially the models are able to create microstructure only at low porosity. [2] Another problem is 2D modeling of porous material: Garboczi et al. [3] stated that to reproduce 3-D experimental results it is crucial to use 3-D models. Moreover they pointed out that as the percolation threshold is approached during computer modeling, the statistical fluctuation and finite size effect errors grow quickly. The problem is also the variation of porous materials microstructure from sample to sample at constant porosity. Randomness is the result of the preparation method and type of used powders. Using future computers it will be possible to predict the properties more precisely and cheaper. Until that numerical models containing some errors or models that predict effective properties of porous materials on empirical or semi-empirical basis (this is a subject of this article) can be used. Theoretical To obtain the exact prediction of Young's modulus for a porous material at given porosity, various models, such as linear dependence, exponential dependence or quadratic equation, have been extensively used during the past years. [4] Main disadvantage of these models is that they can be used either for low or high porosity range, but not for entire poros-ity range. It seems that some requirements ought to be fulfilled by good model for whole porosity range: It must be as simple as possible, must possess the smallest number of fitting parameters as possible and it is necessary to incorporate the critical porosity (percolation threshold) into the model. For this reason Knudsen and Spriggs exponential model is not suitable as no percolation threshold is taken into account. Moreover, it is also inapplicable for foams as it doesn't satisfy the boundary condition E = 0 for p = 1 (E is Young's modulus and p is porosity). Up to now there are two basic models considering the per-colation threshold. One of them is general form of the Coble-Kingery relation proposed by Pabst and Gregorová [5] (1) where a is the coefficient depending on the matrix Poisson's ratio. It seems that a = 2 is always a reasonable approximation for Young's modulus of porous materials with isometric pores. This equation for p c = 1 reduces to Coble-Kingery relation. The model satisfy the boundary conditions for p = 0 and p = p c. The second one is percolation theory model [6] for almost homogeneous and isotropic porous material in the form of (2) where f E is the characteristic exponent for Young's modulus. It is characteristic exponent instead of universal exponent [1] be

This research work was done by modeling and simulating a four step three dimensionally braided composite micromechanical model using Finite Element Analysis software ANYSYS. Three-dimensionally (3D) braided composites are strong... more

This research work was done by modeling and simulating a four step three dimensionally braided composite micromechanical model using Finite Element Analysis software ANYSYS. Three-dimensionally (3D) braided composites are strong contenders for the structural applications in situation like aerospace, aircraft, building and automobiles industries due to their good mechanical properties, structural layout and strength coupled with their thickness stiffness properties. The mechanical properties of the 3D-braided micromechanical composite model was analyzed, based on the result some relevant conclusion were made. With the assumption that the fiber bundle is transversely isotropic and the matrix is isotropic, the macroscopic elastic constants of 3D-braided composites were simulated, and the elastic constants versus the braiding angles and fiber volume fraction were analyzed. The presence of reinforcement along the thickness direction in three-dimensionally braided composites, increases the through thickness stiffness and strength properties. Based on this research, it was also discovered that FEM technique has the ability to model and study the response of complex shapes subjected to complex load applied at any boundary of the design model.

Ulu Slim hot spring possesses the highest surface temperature with a reported temperature of 104°C. Hence, the site may be suitable for electric power generation from the geothermal aquifer. In the present work, two seismic techniques are... more

Ulu Slim hot spring possesses the highest surface temperature with a reported temperature of 104°C. Hence, the site may be suitable for electric power generation from the geothermal aquifer. In the present work, two seismic techniques are used for shallow structures investigation. The methods are the seismic refraction and the Multi-Channel Analysis of Surface Waves (MASW). The delineation of superficial structures will aid in developing the area without affecting the geothermal system. The instrumentation used for both is similar to a large extent. The main differences are the natural frequencies of geophones used. MASW requires a low natural frequency geophone, whereas seismic refraction uses high-frequency ones. Both techniques are applied at five locations distributed in the 5 km x 5km area. The results obtained from both methods are also tending to confirm with each other. From all profiles, three layers are delineated in the vicinity of the hot spring. The top layer is impermeable clay with an average Vp of 500 m/s and Vs <200 m/s. Underneath this surface layer, the possible aquifer unit characterised by sand, with Vp in the range of 1000 to 2800 m/s and Vs between 200 m/s and 300 m/s. The final layer is the bedrock characterised by a Vp higher than 3700 m/s and Vs greater than 300 m/s. A particularly striking feature of the bedrock structure obtained from our results shows that the bedrock is relatively close to the surface of the vicinity of the hot spring, with a depth of about 5 m. These results confirm the conceptual model proposed for the Ulu Slim hot springs as of granitic origin. Moreover, a plot of the Poisson ratio indicated regions of high water saturation that may represent the hot water pathway to the surface. ARTICLE HISTORY

When subjected to dynamic loading, materials can exhibit a mechanical behaviour quite different from its static counterpart. The evaluation of dynamic properties is thus very useful in the assessment of existing masonry structures. This... more

When subjected to dynamic loading, materials can exhibit a mechanical behaviour quite different from its static counterpart. The evaluation of dynamic properties is thus very useful in the assessment of existing masonry structures. This paper presents results of an experimental campaign to determine both the dynamic Young's modulus and the shear modulus of brick masonry constituents through two non-destructive testing methods. Following a discussion on the reliability of the methods, a robust procedure is described and tested on a variety of samples. The results show that the techniques can be successfully applied to provide reliable estimates of the dynamic elastic properties of brick masonry constituents.

This research uses the Finite Element Analysis software ANYSYS to build a four step 3D-braided composite micromechanical model and analyses its properties. With the assumption that the fibre bundle is transversely isotropic and the matrix... more

This research uses the Finite Element Analysis
software ANYSYS to build a four step 3D-braided composite
micromechanical model and analyses its properties. With the
assumption that the fibre bundle is transversely isotropic and
the matrix is isotropic, the macroscopic elastic constants of 3Dbraided
composites were simulated, and the elastic constants
versus the braiding angles and fibre volume fraction were
analysed. The presence of reinforcement along the thickness
direction in three-dimensionally braided composites, increases
the through thickness stiffness and strength properties, more
so the three-dimensionally preforms can be manufactured with
numerous complex architecture variations to meet the needs of
specific application.
Among the advantages of this technique (FEM) is simplicity
and the ability to model and study the response of complex
shapes subjected to complex

Solids exhibit transverse shrinkage when they are stretched, except auxetics that abnormally demonstrate lateral expansion instead. Graphene possesses the unique normal-auxeticity (NA) transition when it is stretched along the armchair... more

Solids exhibit transverse shrinkage when they are stretched, except auxetics that abnormally demonstrate lateral expansion instead. Graphene possesses the unique normal-auxeticity (NA) transition when it is stretched along the armchair direction but not along the zigzag direction. Here we report on the anisotropic temperature-dependent NA transitions in strained graphene using molecular dynamics simulations. The critical strain where the NA transition occurs increases with respect to an increase in the tilt angle deviating from armchair direction upon uniaxial loading. The magic angle for the NA transition is 10.9 , beyond which the critical strain is close to fracture strain. In addition, the critical strain decreases with an increasing temperature when the tilt angle is smaller than the NA magic angle. Our results shed lights on the unprecedented nonlinear dimensional response of graphene to the large mechanical loading at various temperatures.

Auxetic materials are gaining special interest in technical sectors due to their attractive mechanical behaviour. This paper reports a systematic investigation on missing rib design based auxetic structures produced from braided... more

Auxetic materials are gaining special interest in technical sectors due to their attractive mechanical behaviour. This paper reports a systematic investigation on missing rib design based auxetic structures produced from braided composites for civil engineering applications. The influence of various structural and material parameters on auxetic and mechanical properties was thoroughly investigated. The basic structures were also modified with straight longitudinal rods to enhance their strengthening potential in structural elements. Additionally, a new analytical model was proposed to predict Poisson's ratio through a semi empirical approach. Auxetic and tensile behaviours were also predicted using finite element analysis. The auxetic and tensile behaviours were observed to be more strongly dependent on their structural parameters than the material parameters. The developed analytical models could well predict the auxetic behaviour of these structures except at very low or high strains. Good agreement was also observed between the experimental results and numerical analysis.

Studies of various acoustical and thermodynamical parameters such as pseudo-Gruneisen parameter, Debye temperature, internal pressure, free volume, surface tension, diffusion constant, solubility parameter, refractive index, and thermal... more

Studies of various acoustical and thermodynamical parameters such as pseudo-Gruneisen parameter, Debye temperature, internal pressure, free volume, surface tension, diffusion constant, solubility parameter, refractive index, and thermal conductivity has been made in the temperature range 0-100 degrees Celsius, using ultrasonic velocities taken from literature. The temperature dependence of elastic moduli (E, G, K and Poisson ratio) and ultrasonic absorption in liquid mercury have also been studied. The theory of the flow of liquids has been applied to the system under study and the results obtained have been explained in terms of the interactions present in it. The validity of the Nernst-Lindemann equation has been investigated. It has been shown that the Nernst-Lindemann equation estimates fairly well the dilatational contribution to specific heat and the temperature-independent parameter A does not remain constant in the temperature range under investigation.

A new procedure is proposed for identifying uniaxial stress-strain relationship and Poisson's ratio in compressed plain concrete. The procedure is based on the assumption of an internal core of intact material always present inside a... more

A new procedure is proposed for identifying uniaxial stress-strain relationship and Poisson's ratio in compressed plain concrete. The procedure is based on the assumption of an internal core of intact material always present inside a specimen in uniaxial-compression. This involves a modification of the traditionally identified uniaxial stress-strain relationship and Poisson's ratio, which turns out to be almost independent of the loading step. The main finding concerns the volumetric strain, since it appears to be no real increase in the volume of a concrete solid when the solid is placed under pressure.

We report that carbon honeycomb, a new three-dimension carbon allotrope, exhibits large negative Poisson's ratio, as large as −0.32, in tensile revealed via molecular dynamics simulations. The Poisson's ratio of carbon honeycomb is... more

We report that carbon honeycomb, a new three-dimension carbon allotrope, exhibits large negative Poisson's ratio, as large as −0.32, in tensile revealed via molecular dynamics simulations. The Poisson's ratio of carbon honeycomb is anisotropic, and sensitive to temperature. The carbon honeycomb has phase transformation from normal to auxetic by tensile, along both zigzag and armchair directions. The critical strain for the normal-auxetic transition along the cell-axis direction reduces with respect to an increase in temperature. Combined with high strength of 50 GPa, such a unique and adjustable negative Poisson ratio suggests broad engineering applications of carbon honeycomb.

Study on mechanical properties of graphyne nanostructures by molecular dynamics simulation Bozhao Wu, Xianqiong Tang, Jiuren Yin et al. Tersoff potential with improved accuracy for simulating graphene in molecular dynamics environment G... more

Study on mechanical properties of graphyne nanostructures by molecular dynamics simulation Bozhao Wu, Xianqiong Tang, Jiuren Yin et al. Tersoff potential with improved accuracy for simulating graphene in molecular dynamics environment G Rajasekaran, Rajesh Kumar and Avinash Parashar A structural insight into mechanical strength of graphene-like carbon and carbon nitride networks Obaidur Rahaman, Bohayra Mortazavi, Arezoo Dianat et al.

FOR CITATIONS: SALEM, H.S., 1993. A Preliminary Study of the Physical Properties of the Terra Nova and Hibernia Oil Fields in the Jeanne d'Arc Basin, Offshore Newfoundland, Canada. Geological Survey of Canada, Dossier Public, Halifax,... more