Search results

The purpose of this paper is to investigate the effect of anisotropy in terms of a single parameter indicating strengthening or weakening in the tangential direction in composite disc with hyperbolically varying thickness introduced presumably by processing or due to alignment of dispersed reinforcements during flow of the matrix.

Mathematical model to describe steady-state creep behavior in an anisotropic rotating disc made of Al-SiCp composite containing 30 vol% of SiC particles. The creep behavior of the composite has been described by Sherby's law. The creep parameters in the law have been determined using the regression equations developed on the basis of available experimental results in the literature. Stress and strain rate distributions for isotropic disc (a=1) have been compared with those obtained for anisotropic composites with characteristic parameters a=0.7 and 1.3.

The study revealed that the change in the stresses by anisotropy in composite disc is relatively small while anisotropy introduces significant change in the strain rates. It is concluded that the radial strain rate always remained compressive for the isotropic composite as well as the anisotropic disc with a greater than unity (a=1.3). However, it becomes tensile in the middle region of the disc when it is less than unity (a=0.7). If a is reduced from 1.3 to 0.7, the variation of tensile strain rate in the tangential direction remains similar, but the magnitude reduces, i.e. the strength in tangential direction is enhanced.

This study puts forward an analytical framework for the analysis of creep stresses and creep rates in an anisotropic rotating disc with hyperbolically varying thickness.

THE work described in this paper is part of a programme concerned with the plastic, creep, and relaxation properties of metals under complex stress systems at elevated temperatures.which is being carried out in the Engineering Division of the N.P.L. It comprises data on the criterion of departure from elastic behaviour, of a low carbon steel over the temperature range 20–550 deg. C, and of an aluminium alloy over the temperature range 20–200 deg. C, and the creep properties under complex stress systems of the low carbon steel at 350 deg. C, and of the aluminium alloy at 150 and 200 deg. C.

This paper aims to establish a mathematical model for water-flooding considering the impact of fluid–solid coupling to describe the process of development for a low-permeability reservoir. The numerical simulation method was used to analyze the process of injected water channeling into the interlayer.

Some typical cores including the sandstone and the mudstone were selected to test the permeability and the stress sensitivity, and some curves of the permeability varying with the stress for the cores were obtained to demonstrate the sensitivity of the formation. Based on the experimental results and the software Eclipse and Abaqus, the main injection parameters to reduce the amount of the injected water in flowing into the interlayer were simulated.

The results indicate that the permeability of the mudstone is more sensitive to the stress than sandstone. The injection rate can be as high as possible on the condition that no crack is activated or a new fracture is created in the development. For the B82 block of Daqing oilfield, the suggested pressure of the production pressure should be around 1–3MPa, this pressure must be gradually reached to get a higher efficiency of water injection and avoid damaging the casing.

This work is beneficial to ensure stable production and provide technical support to the production of low permeability reservoirs containing an interlayer.

Human aging is becoming a common issue these days as it results in orthopaedic-related issues such as joints disorderness, bone-fracture. People with age = 60 years suffer more from these aforesaid issues. It is expected that these issues in human beings will ultimately reach 2.1 billion by 2050 worldwide. Furthermore, the increase in traffic accidents in young people throughout the world has significantly emerged the need for artificial implants. Their implantation can act as a substitute for fractured bones or disordered joints. Therefore, this study aims to focus on electron beam melted titanium (Ti)-based orthopaedic implants along with their recent trends in the field.

The main contents of this work include the basic theme and background of the metal-based additive manufacturing, different implant materials specifically Ti alloys and their classification based on crystallographic transus temperature (including α, metastable β, β and α + β phases), details of electron beam melting (EBM) concerning its process physics, various control variables and performance characteristics of EBMed Ti alloys in orthopaedic and orthodontic implants, applications of EBMed Ti alloys in various load-bearing implants, different challenges associated with the EBMed Ti-based implants along with their possible solutions. Recent trends and shortfalls have also been described at the end.

EBM is getting significant attention in medical implants because of its minor issues as compared to conventional fabrication practices such as Ti casting and possesses a significant research potential to fabricate various medical implants. The elastic modulus and strength of EBMed ß Ti-alloys such as 24Nb-4Zr-8Sn and Ti-33Nb-4Sn are superior compared to conventional Ti for orthopaedic implants. Beta Ti alloys processed by EBM have near bone elastic modulus (approximately 35–50 GPa) along with improved tribo-mechanical performance involving mechanical strength, wear and corrosion resistance, along with biocompatibility for implants.

Advances in EBM have opened the gateway Ti alloys in the biomedical field explicitly ß-alloys because of their unique biocompatibility, bioactivity along with improved tribo-mechanical performance. Less significant work is available on the EBM of Ti alloys in orthopaedic and orthodontic implants. This study is directed solely on the EBM of medical Ti alloys in medical sectors to explore their different aspects for future research opportunities.

The main aim of this work is to evaluate upholstery deformation by using resonant vibrations of separate zones of the soft part.

Provided methodology allows assessing the upholstery deformation of separate parts of soft furniture by exciting resonant vibrations in it.

By recording the value of resonant frequency at separate points of the plane, it becomes possible to obtain the graph of deformation distribution. It is compared to the graph that demonstrates how rigidity distributes itself in different directions within the upholstery fabric. This enables the authors to evaluate the unevenness of upholstery deformation that is present in different directions.

Provided methodology allows assessing the quality of soft furniture assembly and predicting the exploitation time for its upholstery.

Two anisotropic yield criteria, that employ quadratic stress functions and have been extensively used for the elastoplastic analysis of composite materials, are considered. Proposed by Hoffman and by Sun, both these criteria have been formulated using nine parameters. With appropriate choice of parameters they reduce to the well‐known isotropic von Mises criterion and the anisotropic Hill criterion. This paper investigates the convexity, which is an essential condition for any plasticity model, for these criteria in the principal stress space. In each case two orthogonal sections ‐ deviatoric and volumetric ‐ are used to study the shapes of the ensuing curves. Illustrative three‐dimensional plots are included. It is concluded that, while simple interrelationships between the parameters ensure convexity of the Hoffman criterion, conditions for the Sun criterion are quite stringent.

Microribbon with meander type based on giant magnetoimpedance (GMI) effect has become a research hot spot due to their higher sensitivity and spatial resolution. The purpose of this paper is to further optimize the line spacing to improve the performance of meanders for sensor application.

The model of GMI effect of microribbon with meander type is established. The effect of line spacing (Ls) on GMI behavior in meanders is analyzed systematically.

Comparison of theory and experiment indicates that decreasing the line spacing increases the negative mutual inductance and a consequent increase in the GMI effect. The maximum value of the GMI ratio increases from 69% to 91.8% (simulation results) and 16.9% to 51.4% (experimental results) when the line spacing is reduced from 400 to 50 µm. The contribution of line spacing versus line width to the GMI ratio of microribbon with meander type was contrasted. This behavior of the GMI ratio is dominated by the overall negative contribution of the mutual inductance.

This paper explores the effect of line spacing on the GMI ratio of meander type by comparing the simulation results with the experimental results. The superior line spacing is found in the identical sensing area. The findings will contribute to the design of high-performance micropatterned ribbon with meander-type GMI sensors and the establishment of a ribbon-based magnetic-sensitive biosensing system.

The effects of anisotropy and radiation cannot be considered negligible while investigating the stability of the fluid in convection. Hence, the purpose of this paper is to analyze how these effects could affect the system while considering a couple-stress dielectric fluid. Therefore, the study establishes the effect of thermal radiation in a couple-stress dielectric fluid with an anisotropic porous medium using Goody's approach (Goody, 1956).

To analyze the effect of radiation on the onset of convection, the Milne–Eddington approximation is employed to convert radiative heat flux to thermal heat flux. The equations are further developed to approximate for transparent and opaque medium. Stability of the quiescent state within the framework of linear theory is performed. The principle of exchange of stabilities is shown to be valid by means of single-term Galerkin method. Large values of conduction–radiation and absorptivity parameters are avoided as fluid is considered as liquid rather than gas.

The radiative heat transfer effect on a couple-stress dielectric fluid saturated anisotropic porous medium is examined in terms of Milne–Eddington approximation. The effect of couple-stress, dielectric, anisotropy and radiation parameters are analyzed graphically for both transparent and opaque medium. It is observed that the conduction–radiation parameter stabilizes the system; in addition, the critical Darcy–Rayleigh number also shows a stabilizing effect in the absence of couple-stress, dielectric and anisotropy parameters, for both transparent and opaque medium. Furthermore, the absorptivity parameter stabilizes the system in the transparent medium, whereas it exhibits a dual effect in the case of an opaque medium. It was also found that an increase in thermal and mechanical anisotropy parameters shows an increase in the cell size, whereas the increase in Darcy–Roberts number and conduction–radiation parameter decreases the cell size. The validity of principle of exchange of stability is performed and concluded that marginal stability is the preferred mode than oscillatory.

The effects of anisotropy and radiation on Rayleigh–Bénard convection by considering a couple-stress dielectric fluid has been analyzed for the first time.

The purpose of the present paper is to quantify and analyze the strain-rate dependence of the yield stress for both unfilled acrylonitrile-butadiene-styrene (ABS) and short carbon fiber-reinforced ABS (CF-ABS) materials, fabricated via material extrusion additive manufacturing (ME-AM). Two distinct and opposite infill orientation angles were used to attain anisotropy effects.

Tensile test samples were printed with two different infill orientation angles. Uniaxial tensile tests were performed at five different constant linear strain rates. Apparent densities were measured to compensate for the voided structure. Scanning electron microscope fractography images were analyzed. An Eyring-type flow rule was evaluated for predicting the strain-rate-dependent yield stress.

Anisotropy was detected not only for the yield stresses but also for its strain-rate dependence. The short carbon fiber-filled material exhibited higher anisotropy than neat ABS material using the same ME-AM processing parameters. It seems that fiber and molecular orientation influence the strain-rate dependence. The Eyring-type flow rule can adequately describe the yield kinetics of ME-AM components, showing thermorheologically simple behavior.

A polymer’s viscoelastic behavior is paramount to be able to predict a component’s ultimate failure behavior. The results in this manuscript are important initial findings that can help to further develop predictive numerical tools for ME-AM technology. This is especially relevant because of the inherent anisotropy that ME-AM polymer components show. Furthermore, short carbon fiber-filled ABS enhanced anisotropy effects during ME-AM, which have not been measured previously.

DURING the last few years a programme of creep tests under general stress systems at high temperatures has been carried out at the N.P.L., using four metallic alloys which were chosen as being representative of basic groups of materials used in practice in machinery operating at high temperatures. This work, it was hoped, would fulfil, at least partly, the great need for experimental data in this field, as opposed to the comparative abundance of theoretical work available, and also enable a critical examination of the merits of this theoretical work to be made. The materials chosen in order of examination were a cast 0–17 per cent carbon steel, an aluminium alloy (R.R. 59), a magnesium alloy (containing 2 per cent aluminium), and a nickel‐chromium alloy (Nimonic 75). Each material was tested at temperatures lying within the normal working range of the material in question. Thus the 0–17 per cent carbon steel was tested at 350, 450 and 550 dcg. C. (662, 842 and 1,022 deg. F.), the aluminium alloy at 150 and 200 deg. C. (302 and 392 dcg. F.), the magnesium alloy at 20 and 50 deg. C. (68 and 122 dcg. F.), and the nickel‐chromium alloy at 550 and 650 dcg. C. (1,022 and 1,202 deg. F.).