Papers by Keyword: Poisson’s Ratio

Abstract: The usage of reinforcing fibers extracted from nature is increasing in the present decade due to increasing the demand for biodegradability and environmentally friendly materials. In this paper, biodegradable sisal fiber and corn starch powder mixed thermoset and thermoplastic composite are prepared and tested for Young’s modulus. The effect of sisal fiber weight fraction on the Young’s modulus is identified at constant content of corn starch powder. Later, using Micromechanics approach and Finite Element Method simulation studies are performed to estimate transverse Modulus, Shear modulus, major and minor Poisson’s ratio of the sisal and starch based polymer composites. It is found that the composites prepared with sisal fiber and corn starch powder are a promising replacement for plastic reinforced composite to promote the biodegradability, especially under high weight fraction of sisal fiber

Abstract: Silica borotellurite glasses doped with different molar fraction of V₂O₅ have been prepared by melt quenching technique. The elastic properties of {[(TeO₂)_0.7 (B₂O₃)_0.3]_0.8(SiO₂)_0.2}_(1-x)(V₂O₅)_x glasses are investigated using ultrasonic pulse echo measurements and their elastic properties have been characterized at room temperature. The density of the glasses was measured by Archimedes method using distilled water as buoyant liquid. The ultrasonic wave velocities (longitudinal, v_l and shear, v_S) were recorded at 5 MHz. Elastic moduli, Poisson’s ratio (σ) and microhardness (H) were then calculated to obtain quantitative analysis regarding the structure of these glasses. The results obtained showed that the doping of V₂O₅ with silica borotellurite enhances the strengthening of glass network. Glass with 0.03 molar fraction of V₂0₅ shows low ultrasonic velocities and low elastic moduli. The variation of elastic properties is related to the change of structure in the vanadium doped silica-borotellurite glass system.

Abstract: The paper analyzes Poisson’s ratios μ₀=μ_100,001=-s₁₂/s₁₁ and elastic anisotropy factor A'=s/s₁₁ (s=s₁₁-s₁₂-s₄₄/2) for single crystal materials of binary and three-component TiNi-TiFe alloys with gradually deteriorating resistance first to one B2-R and further to two martensite transformations B2-R-B19'. The study discusses a ratio H/E of TiNi-TiFe alloys both subject and not exposed to martensite transformations. Surprisingly, this ratio exceeds 0.035 for alloys with martensite transformations, being far higher than in the majority of metals and alloys.

Abstract: The paper deals with the influence of the Poisson’s ratio on the calculated modulus of elasticity of a cementitious composite in the early stage of its ageing. The dynamic modulus of elasticity was determined in the first 24 hours of ageing of the material using the Vikasonic ultrasonic device. Within the experiment, two types of cementitious composites were mixed - cement paste and cement mortar, both having the same water/cement ratio. It is presumed that the value of the dynamic modulus of elasticity calculated on the basis of ultrasonic measurement is closely related to the value of the Poisson’s ratio, which is not constant during ageing of the cementitious composite but varies depending on the degree of hydration of the material. The output of the paper is a comparison of the development of the dynamic modulus of elasticity calculated using different values of the Poisson’s ratio.

Abstract: Fe-Ga alloys are used for practical magnetostrictive materials. The understanding of mechanical properties under magnetic field is very important for their application to vibration power generation devices. Especially, Poisson’s ratio is one of key parameters because it is strongly related with the volume change of materials. In the study, we investigated actual behavior of Poisson’s ratio due to magnetostriction, instead of just the mechanical one. The sample was cube-oriented Fe-18mol%Ga single crystal disc. Static magnetic fields were applied in various directions parallel to (001). Strain values in various directions were measured by strain gauge and X-ray diffraction. And then, tri-axial strain analysis for single crystal was carried out. Theoretically, Poisson’s ratio due to magnetostriction is known to be 0.5, (volume conservative), value is close to the mechanical one, 0.45. On the other hand, we found that Poisson’s ratio exhibits anisotropic behavior despite the elastic constants are equivalent in [010] and [001]. This phenomenon is attributable to the magnetic domain structure under zero magnetic field. In this presentation, we will discuss this apparent Poisson’s ratio considering the volume strain and magnetostriction comprehensively.

Abstract: Effects of gamma radiation on the elastic properties of {[(TeO₂)_0.7(B₂O₃)_0.3]_0.7[ZnO]_0.3}_0.99{Tm₂O₃}_0.01 (thulium doped zinc borotellurite glass) were investigated. Glass samples were prepared using the melt-quenching technique. Density and ultrasonic velocity of glasses before and after irradiation process were measured using Electronic Densimeter MD-300S and Ritec Ram-5000 Snap System, respectively. Next, elastic moduli and Poisson’s ratio of the glasses were calculated. Atomic ring size of the glass network was also calculated to support the attained results. Results show that density varied after radiation and maximised at 20 kGy. This is attributed to the breaking and rearrangement of chemical bonding in the glass network due to radiation. Furthermore, all elastic parameters exhibited an increasing trend that indicated the strengthening of the glass samples as well as increment of its rigidity. Besides that, atomic ring size was found to decrease as radiation dose increased. This indicate that compaction of glass network took place as the samples were exposed to gamma rays which in turn contributed to the elevation of elastic moduli of the prepared glass.

Abstract: Pore closure behavior in sintered Al-4Fe₃C and Al-4Fe₃C-2Cu composite preforms were studied under cold and hot deformation conditions. Preforms of 0.2 aspect ratios with 85±1% initial density were prepared through compaction operation using 1 MN hydraulic press. For hot deformation, directly as sintered preforms are subjected to swaging operation to different strain rate. Preforms that are allowed to cool it to room temperature within the furnace after sintering process are subjected to cold upsetting till visible cracks appear on diametrical surface. The comparative analysis on pore closure against stress, strain, Poisson’s ratio and the stress formability index are performed.

Abstract: Ceramsite cellular concrete (CCC for short) is a kind of lightweight aggregate concrete. In this paper, the selection of materials and design of mix proportion have been discussed, and basic property tests has been done. The compressive strength was proved up to the National Standards of P. R. GB50003-2001(code for design of masonry structures), furthermore, elastic modulus and Poisson's ratio were also introduced. Questions remain regarding the quality control of the product, and further work is needed to resolve this contradiction.

Abstract: This work studies the large deformation behaviors of a re-entrant honeycomb subjected to the quasi-static tensile loading by employing the finite element (FE) package ABAQUS 6.11-2. The size effect of FE models is firstly investigated. Then, the deformation mechanism and stress-strain curve of a re-entrant honeycomb are discussed. Finally, the plastic Poisson’s ratio is calculated from the true strain and presented.

Abstract: A series of Tm-doped zinc borotellurite glass have been extracted by conventional melt-quenching method. The density was measured and it had been found that the value is increased by the increment of Tm³⁺ ion. The elastic properties of the sample were determined by measuring longitudinal and shear velocities using an ultrasound technique. Then the values inserted into equations that calculate the elastic moduli of the glass samples. These include longitudinal, shear, bulk, Young’s modulus and also the Poisson’s ratio. The longitudinal and shear velocities show an increment as Tm³⁺ increases from 0.01 to 0.03 mol content. The trend then changes as Tm³⁺ increases from 0.03 to 0.05 mol content. In terms of elastic moduli, it produces a rapid increment with Tm³⁺ until 0.03 mol content. But after that, the increment becomes slow until 0.05 mol of Tm³⁺. The value of Poisson’s ratio decreases with the addition of Tm³⁺ concentration.