Investigation of Effect of Preliminary Annealing on Superplasticity of Ultrafine-Grained Conductor Aluminum Alloys Al-0.5%Mg-Sc

Effect of preliminary precipitation of Al3Sc particles on the characteristics of superplastic conductor Al-0.5%Mg-X%Sc (X = 0.2, 0.3, 0.4, 0.5 wt.%) alloys with ultrafine-grained (UFG) microstructure has been studied. The precipitation of the Al3Sc particles took place during long-time annealing of the alloys at 300 °C. The preliminary annealing was shown to affect the superplasticity characteristics of the UFG Al-0.5%Mg-X%Sc alloys (the elongation to failure, yield stress, dynamic grain growth rate) weakly but to promote more intensive pore formation and to reduce the volume fraction of the recrystallized microstructure in the deformed and non-deformed parts of the aluminum alloy specimens. The dynamic grain growth was shown to go in the deformed specimen material nonuniformly–the maximum volume fraction of the recrystallized microstructure was observed in the regions of the localization of plastic deformation.

Energy Transfer Enhancement Inside an Annulus Using Gradient Porous Ribs and Nanofluids

Porous media and nanofluid utilization are two passive heat transfer improvement tools, which have been employed extensively in recent years. Porous media with gradient properties result in both a higher effective thermal conductivity and better local convective heat transfer because of conducting the flow to the desired regions. In this study, distinct porous ribs are located on the internal border of an annulus. Four different conditions are considered for permeability change of ribs, including the minimum and maximum Darcy numbers and linearly increasing or decreasing variation in the radial direction, called LIV and LVD, respectively. In the first step, effects of porous rib relative height, porous rib porosity, and flow Reynolds number on the thermal efficiency and pressure drop are investigated. The results show that the configuration with Da = LVD and W/Rh = 0.25 has the maximum performance number PN = 2, that is the Nusselt improvement over pressure drop increment. Porous ribs arrangement with W/Rh = 0.25 and the minimum porosity (ɛ = 0.9) give the best PN. In the next step, the effects of nanoparticle addition with different volume fractions to the base fluid in different Reynolds numbers are investigated. In this step, porous rib relative height is set to W/Rh = 0.25. The results show that the maximum volume fraction has the highest heat transfer enhancement (about 2–2.5 times) but the lower volume fractions have higher PNs (PN ≈ 2.5 at ϕ = 1% and Re = 500).

Microstructure and Mechanical Evolution of Cu-2.7Be Sheets via Annealing

The microstructure and mechanical properties of cold-rolled Cu-2.7Be sheets under various annealing processes and conditions were investigated in this research. The increased beryllium content in the Cu-2.7Be alloy facilitates the formation of brittle secondary phases. Consequently, the study highlights the functionality of annealed Cu-2.7Be alloys as more favorable dynodes than the traditionally used Cu-2.0Be alloys. The mechanism of recrystallization used for the transformation of Cu-2.7Be alloys was that of continuous static recrystallization (cSRX). Moreover, the relationship between the orientation of the β phases and that of the surrounding Cu-matrix was determined to be (111)α∥(110)β and (011)α∥(001)β. The β phase has a body-centered cubic (bcc) structure with a = b = c = 0.281 nm. The β phase undergoes a morphology transformation from primitive lath-shaped β particles to quadrangle-shaped β particles during the annealing process. Such transformations could potentially have an effect on the mechanical properties of Cu-2.7Be sheets. There was a noticeable decline in the yield strength of the Cu-2.7Be after annealing, and the samples annealed at 770 °C for 15 min achieved the elongation with deep and uniform dimples caused by suitable β particle sizes, appropriate grain sizes, and the maximum volume fraction of ∑3 boundaries.

Mechanical and Wear Characterization of Nano Based Calotropis Gigantea Fiber Reinforced Polyester Composites

The growing interest on development of biodegradable materials led to growing concern about bio-based composite materials among the bio fibers applications one of the lightweight materials. Very minor research work is available in the mechanical characterization of CGF composites. In this paper the mechanical properties like tensile strength, flexural strength, impact strength and hardness of the CGF reinforced polymer composites were investigated. Also the impact of naturally modified montmorillonite (MMT).Nano clay on mechanical properties of the CGF composites was studied. The maximum volume fraction of the Specimens is 35%. The results demonstrate that the properties of nano-based CGF composites are better than the non-nano based composites. Tri-biological behavior of the CGF composites also studies and observed that nano CGF composites are having good wear characterization

Mechanical Properties of Al 25 wt.% Cu Functionally Graded Material

The present work refers to describe the effects of Al2Cu variations on various properties of thick-walled functionally graded (FG) cylindrical shell. Al-25 wt.% Cu hypo-eutectic alloy ingot is melted and centrifugally casted to obtain high entropy FG composite. A series of microstructure examinations such as FESEM and EDX analysis were carried out to determine the distributions of constituent phases and elements. It is revealed that the maximum volume fraction of Al2Cu particle is reached near the inner surface with 35.7 Vol.% and then reduces gradually to 32.5 Vol.% at the outer surface of FG cylindrical shell. The effects of the variations Al2Cu along radial direction of FG tube are discussed through Vickers hardness, wear rate, coefficient of thermal expansion and compressive test measurements. The experimental results show that the wear and hardness are varied in graded manner which the highest wear resistance with wear rate of 9.1×10−5g/mm2 and hardness with 153HV are found towards Al2Cu enriched zone or inner periphery. Moreover, the studied FG cylindrical shell shows drop 2.5% in yield stress and 4.5% in elastic modulus from intermediate to inner layers due to Al2Cu particles clustering in metal matrix.

Rheology of dense granular suspensions

Suspensions are composed of mixtures of particles and fluid and are omnipresent in natural phenomena and in industrial processes. The present paper addresses the rheology of concentrated suspensions of non-colloidal particles. While hydrodynamic interactions or lubrication forces between the particles are important in the dilute regime, they become of lesser significance when the concentration is increased, and direct particle contacts become dominant in the rheological response of concentrated suspensions, particularly those close to the maximum volume fraction where the suspension ceases to flow. The rheology of these dense suspensions can be approached via a diversity of approaches that the paper introduces successively. The mixture of particles and fluid can be seen as a fluid with effective rheological properties but also as a two-phase system wherein the fluid and particles can experience relative motion. Rheometry can be undertaken at an imposed volume fraction but also at imposed values of particle normal stress, which is particularly suited to yield examination of the rheology close to the jamming transition. The response of suspensions to unsteady or transient flows provides access to different features of the suspension rheology. Finally, beyond the problem of suspension of rigid, non-colloidal spheres in a Newtonian fluid, there are a great variety of complex mixtures of particles and fluid that remain relatively unexplored.

Rheology of concentrated suspensions of non-colloidal rigid fibres

Pressure- and volume-imposed rheology is used to study suspensions of non-colloidal, rigid fibres in the concentrated regime for aspect ratios ranging from 3 to 15. The suspensions exhibit yield stresses. Subtracting these apparent yield stresses reveals a viscous scaling for both the shear and normal stresses. The variation in aspect ratio does not affect the friction coefficient (ratio of shear and normal stresses), but increasing the aspect ratio lowers the maximum volume fraction at which the suspension flows. Constitutive laws are proposed for the viscosities and the friction coefficient close to the jamming transition.

Imperata cylindrica / Sacred Grass Long Fibre Reinforced Polyester Composites – An Experimental Determination of Properties

In the present work a new natural fibre i.e. sacred grass botanically called Imperata Cylindrica is introduced and it belongs to vedic grass family. The fibre is extracted by splitting method and is reinforced into the polyester matrix by hand lay-up technique for the fabrication of tensile, flexural, impact, dielectric test specimens as per ASTM procedures. Highest values of tensile strength (50.96 MPa), modulus (990.86 MPa) are observed for sacred grass fibre reinforced polyester composites at maximum volume fraction of chemically treated fibre. At 14.75 %, 35.89 % sacred grass fibre volume fraction the composites exhibited flexural strength, modulus of 43.19 MPa, 4.81 GPa respectively. Impact strength of 92.53 kJ/m2 is obtained for the composites reinforced with 34.73 % volume fraction of sacred grass fibres. The dielectric strength of the composites varies from 10 to 6.66 kV/mm for composites reinforced with fibres from minimum (6.26 %) to maximum (32.25 %) fibre content.