Direction Of Centrifugal Force Research Articles

Effect of Three Layered Centrifugal Casting on Tribological and Microstructural Characteristics of Mg Based Functionally Graded Material Alloy

Objectives: The aim of this study is to examine the tribological properties and microstructural of functionally graded material (FGM) composites based on magnesium (Mg) base material. Magnesium alloys are commonly employed in the development of biomaterials for implant applications owing to their favorable corrosion properties. The research objective is to produce Zn/Mo reinforced functionally graded magnesium composites using the centrifugal casting. Methods: A centrifugal process was employed to fabricate a functionally graded material (FGM) consisting of three layers with a cylindrical shape. The base material used for this FGM was Magnesium, which was alloyed with 10% of Zn and 10% of Mo. The developed FGMs have been analyzed for their mechanical and microstructural characteristics. The microstructure of the samples were analyzed via the Optical Microscope (OM). It is identified that denser particle molybdenum (Mo) have influenced the mechanical and microstructural characteristics of the FGM composites. Findings: Results recommend that, all the three layered testing’s, Mg (80%) +Zn (10%) + Mo (10%) composite exhibited favorable mechanical and microstructural properties. It is identified that denser particle of Mo which is influenced the microstructural characteristics. The alteration in micro hardness in the direction of centrifugal force is observed, and it is observed that the minimum wear loss for sliding wear samples A, B & C of Mg based FGM alloy were found to be 0.0018 g, 0.028 g and 0.031 g respectively, while the maximum wear loss for sliding wear samples A, B & C of FGM alloy were found to be 0.0021 g, 0.41 g and 0.31 g respectively. Novelty: In this study, a novel three-layered centrifugal casting technique was devised. Owing to its rapid degradability, the anticipated duration of the implants within the human body would be significantly shorter in comparison to alternative biomaterials such as Titanium and Stainless steel. Furthermore, the findings from the conducted tests strongly advocate for the utilization of this technique in biomedical implantations. Keywords: Functionally graded material (FGM), Centrifugal casting, Tribological characteristics, microstructural behavior, and bio­implants

Microstructural and Mechanical Characterization of the Mg Based Functionally Graded Material Fabricated through Centrifugal Casting Process

Objectives: The aim of this study is to examine the mechanical and microstructural properties of functionally graded material (FGM) composites based on magnesium (Mg). Magnesium alloys are commonly employed in the development of biomaterials for implant applications owing to their favorable corrosion properties. The research objective is to study the microstructural and mechanical properties and produce Zn/Mo reinforced functionally graded magnesium composites using the centrifugal casting. Methods: A triple layered cylindrical shaped Mg based functionally graded material (FGM) was fabricated through a centrifugal process from (Mg (80%) +Zn (10%) + Mo (10%) alloy. The developed FGMs have been analyzed for their mechanical and microstructural characteristics. The microstructure was analyzed via the OM AND SEM microscope. It is identified that denser particle molybdenum (Mo) have influenced the mechanical and microstructural characteristics. Findings: Results recommend that, all the three layered testing’s, Mg (80%) +Zn (10%) + Mo (10%) composite exhibited favorable mechanical and microstructural properties. It is identified that denser particle of Mo which is influenced the microstructural characteristics. The alteration in micro hardness in the direction of centrifugal force is observed, and it is perceived that top surface has higher hardness as compared to the middle and bottom region. The flexural strength of top surface sample is 254 MPa, which is 10% greater than middle surface sample and 12.36% greater than bottom surface sample. Compressive strength of 385 MPa, surpassing the middle surface sample by 17.11% and the bottom surface sample by 19.36%. Novelty: In this study, a novel three-layered centrifugal casting technique was devised. Owing to its rapid degradability, the anticipated duration of the implants within the human body is significantly shorter in comparison to alternative biomaterials such as Titanium and Stainless steel. Furthermore, the findings from the conducted tests strongly advocate for the utilization of this technique in biomedical implantations. Keywords: Functionally graded material (FGM), Centrifugal casting, Mechanical properties, Microstructural behavior and bioimplants

Failure mechanism of single-crystal superalloy NiAlReRu components with film cooling holes under the coupling high-speed rotating and high temperature condition

In order to make up for the deficiency that the laboratory testing of standard samples cannot approximately simulate the turbine blade geometry and service environment, the creep experiment of the nickel-based single crystal superalloy NiAlReRu components with film cooling holes (FCHs) is carried out under the coupling high-speed rotating and high temperature condition. The component with the FCHs exposed to the coupling high-speed rotating of 20000 rpm and high temperature of 1000 ℃ continuously lasts 255.92 h until it breaks. The microstructural evolution and fracture process are analyzed. The results indicate that the existence of the FCHs evidently changes the stress distribution of the region with the FCHs, which makes the microstructural evolution of γ′ phase significantly different. The component is fractured along the second row of the FCHs and the normal direction of the fracture surface is basically parallel to the centrifugal force direction. The fracture process can be divided into three typical stages. The coupling effect of temperature and stress on the failure mechanism is discussed.

Polymerization in centrifugally oriented liquid crystal reaction field

Poly(3,4-ethylenedioxythiophene) (PEDOT) film was electrochemically prepared in nematic LC solvent under centrifugal force. Polarized ultraviolet-visible (UV-Vis) absorption spectra and polarizing optical microscopy (POM) images of the polymer film indicate orientation perpendicular to centrifugal force direction. PEDOT alignment was achieved during the polymerization through alignment of the liquid crystal matrix by centrifugal force. The monomer was polymerized along the liquid crystal alignment to form oriented PEDOT. Visualization of LC director was achieved by electrochemical polymerization in the LC.

Investigation of Leakage and Heat Transfer Properties of the Labyrinth Seal on Various Rotation Speed and Geometric Parameters

To investigate the influence of the variation of geometric parameters on the leakage and heat transfer characteristics of labyrinth seals at various rotational speeds, the labyrinth seal models with different geometric parameters were numerically simulated based on the control variable methods. Results show the aerodynamic mechanism of leakage characteristics changing with rotational speed, as well as the leakage characteristics of labyrinth seals under the coupling action of geometric parameters and rotating speeds. When the characteristic scale changes along the direction of centrifugal force, the variation trend of labyrinth seal leakage characteristics is consistent at different rotational speeds. However, the leakage characteristics of labyrinth seals show the difference of rotational speed when the feature scale changes along the axis. At the same time, the laws of convective heat transfer on the surface of the rotor and stator are shown by the results of the studies, which provides reference for the thermodynamic analysis of labyrinth seals.

Wirelessly-controlled electrolysis pumps on lab-on-a-disc for automation of bioanalytical assays

Electrolysis pumping on microfluidic CDs relies on pneumatic pressure to propel liquids against the direction of centrifugal force. This active pumping method operates in a closed fluidic network, which prevents introducing contaminations from the environment to the CD. However, due to two main reasons, the conventional pump has not been suitable for the automation of complex bioanalytical assays. First, the layout of the electrolysis pump requires a large space of the disc. Second, the slip-rings used for pump operation have a short number of connection ports and a short shelf-life due to mechanical wear. To overcome these challenges, we developed a compact 3D and wirelessly-controlled electrolysis pump. Compared to the conventional electrolysis pump, the 3D device allows for better use of the limited disc space, and therefore the integration of more pumping units and/or other fluidic components. Our 3D electrolysis pump is electrically supplied by an “electrified Lab-on-a-Disc” board that enables wireless control of several pumps, as well as other actuators or sensors, on spinning CDs. We developed an android application to control the activation of several electrolysis pumps simultaneously. To evaluate the liquid pumping with the proposed design, we recorded the time required to pump various liquid volumes from 20 to 120 µL. The EL pump showed repetitive behavior in terms of the time needed to displace specific volumes. As a proof of concept of the use of the pump in an application, we developed a centrifugal microfluidic device with several pumps and an active valve to automate the fluidic steps commonly used in an immunoassay with peptide-microarrays.

Production and properties of functionally graded hybrid composites containing Al3Ti and TiB2

AbstractThis study examined the production and properties of functionally graded hybrid composites containing titanium di-boride (TiB2) and titanium tri-aluminate (Al3Ti) particles. The composites were produced by the centrifugal solid particle method at 850 °C. A detailed study of the microstructures, hardness and abrasive wear behavior of the hybrid composites was carried out. The results showed that the produced composites had three different regions along the centrifugal force direction. It was found that there were Al3Ti particles in the outer region, TiB2 particles in the middle region and neither Al3Ti nor TiB2 particles in the inner region of the functionally graded composites. It was determined that the abrasive wear properties of the composites were improved by 5 times with about 33 wt.% Al3Ti and by 3 times with about 7 wt.% TiB2 in comparison to the pure aluminum matrix.

The production and properties of Al3Ti reinforced functionally graded aluminum matrix composites produced by the centrifugal casting method

In this study, the production and properties of titanium tri-aluminide (Al3Ti) particle reinforced functionally graded composites (FGCs) by a centrifugal casting method, are investigated. FGCs were produced by using Al-Ti master alloy which was alloyed with copper and silicon and without alloying to obtain three types of composites, namely Al3Ti/Al, Al3Ti/Al-Si and Al3Ti/Al-Cu FGC. It was observed that produced composites contain two different area: the functionally graded and Al3Ti-free area. The ratio and size of Al3Ti particles were found to change regionally in functionally graded area of each composite type. The effects of the regional change in functionally graded area and both the reinforcement ratio and particle size of composite types were discussed using statistical techniques. In addition, density, Brinell hardness and abrasive wear property of Al3Ti particle reinforced FGCs have been examined inwardly from the outer surface of composites depending on the centrifugal force direction. The results showed an improvement in Brinell hardness value inwardly from the outer surface of composites in each composite type. It was observed that the volumetric wear loss of composites were reduced by increasing the ratio of Al3Ti particles in the matrix.

Electrolysis Pumping on Centrifugal Microfluidic Platforms for Automation of Bioanalytical Assays

One of the advantages of Lab on a Disc (LoD), compared to Lab on a Chip (LoC), is the use of centrifugal forces to move liquids within the chambers and microchannels; eliminating the need of external mechanical pumps (e.g., syringe pump) and piping networks for the automatization of bioanalytical assays. However, the centrifugal force is unidirectional and therefore liquids can only be displaced from the center to the edge of the disc. This prevents the possibility of utilizing all the available space in the disc for the implementation of a complex microfluidic process. To overcome this limitation, we developed an electrolysis system to induce a pneumatic force to move liquids towards the center of a spinning disc or against the direction of centrifugal force. We developed a microfluidic disc that contains a series of electrolysis pumps and peptide microarrays to automate a multiplexed immunoassay for the detection of different antibodies e.g., Ha and anti-flag antibodies. The pumps on this centrifugal microfluidic platform are powered and controlled wirelessly using the electronics-LoD [1]. In general, the develop pumping system allows for the best use of the limited space of microfluidic disc and the automation of complex bioanalytical process for point of care applications. [1] S.M.T. Delgado, D.J. Kinahan, F.S. Sandoval, L.A.N. Julius, N.A. Kilcawley, J. Ducrée, D. Mager, Fully automated chemiluminescence detection using an electrified-Lab-on-a-Disc (eLoaD) platform, Lab Chip. 16 (2016) 4002–4011. doi:10.1039/C6LC00973E.

Numerical investigation of heat transfer and flow characteristics of supercritical CO2 in U-duct

The present study investigated the heat transfer and flow characteristics of supercritical CO2 in U-ducts by numerical simulations. Analyses focused on the effect of the turn geometry and the gravity direction on the flow field and temperature field of supercritical CO2. Results show that, as the radius of the turn geometry increases from 0.5D to 3.0D, the flow and temperature distribution after the turn region changes a lot, due to the flow separation and reattachment. In the turn region for the vertical upward flow, the gravity plays a dominant role in the change of flow field, and a secondary flow structure is induced by gravity, which is completely opposite to the Dean Vortex in conventional fluid flow. The angle between the centrifugal force and gravity direction have a significant influence on the migration and deposition process of the low-temperature and high-density fluid when supercritical CO2 passing through the turn region, making the flow field and temperature distribution after the turn different completely.

The Changes in the Morphology of Bi⁻Sb System under Centrifugal Force at Room Temperature.

In this paper, the morphology evolution in a Bi–Sb system under the centrifugal force at room temperature is discussed. The rotation speed was 35,000 rotations per minute and the length of the arm (radii) was 88 mm. It is shown, that after the centrifugation the phases become oriented in the direction parallel to the direction of the centrifugal force. Moreover, the voids move in the direction opposite to the centrifugal force direction. The movements of such voids result in their coalescence and finally lead to formation of cracks at the interface between ordered and disordered part of the sample.

The transfer behavior in centrifugal casting of SiCp/Al composites

The centrifugal casting of SiCp/Al composite slurry caused an intense segregation of phases, leading to a refined primary α (Al) phase and a modified eutectic silicon. A three stages transfer process was deduced as follows: the relative motion of SiC particles, the segregation of primary phase and the filling of the remaining melt. Most of SiC particles and some primary α (Al) phases migrated to the external region of the castings under the centrifugal force, resulting in a particle free zone in the middle zone of the castings and a macrosegregation along the centrifugal force direction.

Нефропротекторные свойства соединения РУ-63 при экспериментальной острой почечной недостаточности в условиях гипергравитации

В экспериментах на белых крысах найдена диуретическая доза соединения РУ-63, которая составила 1 мг/кг. Выявлено нарастание диуретического и салуретического эффекта данного соединения на фоне воздействия гравитационного фактора. Установлено, что блокатор 5-HT3-рецепторов РУ-63 (1 мг/кг подкожно) при ежедневном введении на фоне ГВ (3 g в направлении вектора центробежного ускорения к почкам животного) в условиях развития ишемической острой почечной недостаточности на 3 сут эксперимента повышал экскреторную функцию почек, скорость клубочковой фильтрации, креатининурез (в среднем на 180 %, p < 0,05), понижал креатининемию, мочевую экскрецию белка, лактатдегидрогеназы, γ-глутамилтрансферазы (в среднем на 49 %, p < 0,05) в сравнении с нелеченым контролем. В аналогичных условиях диуретик гидрохлоротиазид (в дозе 20 мг/кг внутрижелудочно) обладал более выраженным (на 358 %, p < 0,05), чем у РУ-63, креатининуретическим действием.

Laterally stratified flow in a curved microchannel

Laterally stratified fully developed flow in a curved channel is investigated, in this work. Motivated by applications in microchannels, we focus on the limit of small Reynolds numbers. The method of domain perturbation is used to obtain an analytical solution, by considering the curvature ratio of the channel (ratio of the channel’s width to its radius of curvature) to be a small parameter. Centrifugal forces give rise to multiple pairs of Dean vortices in the two fluids. Depending on the properties of the fluids and their holdups (volume fractions), one of the fluids dominates the flow and influences the flow pattern within the other fluid. The multi-dimensional parameter space is divided into five different regions, each characterized by a distinct vortex pattern. Centrifugal forces are shown to deform the interface; it bulges outward, in the direction of centrifugal force, to an extent that increases with the Weber number (ratio of centrifugal forces to interfacial tension forces). The deformation also depends on the flow pattern. Redistribution of the axial velocity profile is analyzed and attributed to geometric and inertial effects. The perturbation solution is compared with numerical simulations and found to be accurate for the range of Reynolds numbers and curvature ratios typically encountered in microchannel applications.

烟草BY-2原生质体定向伸长对离心力响应的相关性研究

本研究以烟草BY-2细胞为材料，在单细胞水平探讨应力条件对植物细胞定向伸长的影响。将烟草原生质体包埋于琼脂糖凝胶块中，通过施加不同大小的离心力和在恒定的施力条件下处理不同时间分析应力与细胞定向伸长的相关性。结果表明，在恒定施力条件下，原生质体的定向伸长与施力时间密切相关，倾向以垂直于应力方向伸长，且细胞的定向伸长与应力强度存在剂量关系。细胞微管骨架与离心力的方向平行。 In this study, the protoplasts from tobacco BY-2 (Nicotiana tabacum) were used to determine whether cells can be induced to expand in a preferential direction in response to an externally applied centrifugal force. Spherical protoplasts were embedded into agarose block. Constant uniaxial pressure released by a centrifugal force was imposed on the block. The results showed that protoplasts elongated with a preferential axis oriented perpendicularly to the applied force direction, according to a certain dose-dependent relation between the intensity of centrifugal force and the stress induced responses. The microtubules with centrifuged protoplasts were found to be oriented parallel to the centrifugal force direction.

Development of functionally graded vapor-grown carbon-fiber/polymer materials

We successfully produced vapor-grown carbon-fiber (VGCF)-incorporated polymer-based functionally graded materials (FGMs) using a centrifugal method. Gradual VGCF incorporation within an epoxy resin effectively produced depth gradients in the fiber distribution, microstructure, mechanical, and electrical conductivities and microwave absorbing properties. This VGCF-grading capability indicated that it is possible to tailor desired gradient filler content distributions by careful selection of the processing parameters to control variations in the property and microstructure precisely. The results confirmed that the volume content of VGCF in the epoxy substrate increased as a function of the normalized thickness along the centrifugal force direction, which caused a gradient. A uniform VGCF gradient in the composite can also be observed using field-emission scanning electron microscopy. In the case of the electrical properties, for example, the volume resistance exhibited a depth-graded distribution in the matrix as the electrical conductivity of the FGM nicely followed the grading direction; this is considered to be ideal for applications demanding an electrically conductive surface and an insulating core for FGMs. The results of microwave absorption behavior of FGMs indicate that the grading structure can lead to a graded absorption ability, which could be a better design for microwave absorption materials. The concept of FGMs bridges conventional materials and nanocomposites and will be effective for wider material applications. POLYM. COMPOS., 34:1774–1781, 2013. © 2013 Society of Plastics Engineers

Investigations on dielectric, DSC and DMA behavior of graphite-filled polyester gradient composites

This article reports the results of dielectric, alternating current (AC) conductivity, differential scanning calorimetry (DSC) and dynamic mechanical analysis of graphite-filled polyester gradient composites. Dielectric, AC conductivity, DSC and dynamical mechanical measurements were performed on these gradient composites. Effects of temperature and frequency variation on dielectric constant ( ε′), dielectric dissipation factor (tan δ) and on AC conductivity ( σAC) were determined. With the increase in graphite content, the dielectric constant increased gradually in the direction of centrifugal force, which confirms the development of a gradient structure. The Linchtenecker model fits well for the dielectric data obtained experimentally for these composites. Conduction occurring in the composites is due to electronic conduction. The activation energy, Ea, varied with frequency and showed a semiconducting behavior of these composite. Cole–Cole plots for the gradient composites between ε′ and ε′ showed a dielectric relaxation for all the samples due to the motion of the dipolar groups of the polyester resin.

Fabrication of Functionally Graded SiO2‐Mo Material by Centrifugation and Floc‐Casting of Highly Concentrated Slurry

To fabricate functionally graded materials, a highly concentrated slurry of SiO2‐Mo system was prepared and centrifugal force was applied in an attempt to achieve a graded composition. Subsequently, we formed a homogeneous green body with compositional gradation by floc‐casting at 80°C, which was then fired at 1750°C for 10 min in Ar. The sintered body had compositional ratios of SiO2 and Mo as well as electrical conductivities that changed gradually along the direction of centrifugal force. The results demonstrate that centrifugation and control of slurry characteristics such as flocculation are effective in fabricating functionally graded SiO2‐Mo materials.

Studies on Dielectric and a.c. Conductivity Behavior of Activated Carbon-Filled Epoxy-Graded Composites

In this study, an activated carbon-filled epoxy resin gradient composite was developed. The dielectric constant increased gradually with the increase of activated carbon content in the direction of centrifugal force, due to gradual increase in carbon concentration. Dielectric constant and a.c. conductivity increased with increase in temperature. Increase of a.c. conductivity with temperature was due to the formation of the polycondensed rings, which allowed charge transport in the composite. By using the power law σa.c. = A ωs, values of constant A and frequency exponent s were calculated. It has been found that a decrease from sample 1 to 4 due to the increased concentration of activated carbon in the composite. Small values of activation energy obtained at higher frequencies suggest that the conduction in the composite is mainly due to hopping of charge carriers.

Study of Boride-Reinforced Aluminum Matrix Composites Produced via Centrifugal Casting

The redistribution of AlB2 and AlB12 reinforcing particles in functionally graded Al–B–Mg composites was investigated as a function of centrifugal casting time, rotational speed, and pouring temperature of the melt. The microstructure was characterized both qualitatively and quantitatively on four different sections along the main axis (centrifugal force direction) of the cylindrical casting. The resulting aluminum matrix composite showed an evident gradient of particles concentration, with more particles at the external zone than at the internal zone of the casting. Processing temperature was found critical for its direct effect on the viscosity of the liquid, which regulates the segregation of the reinforcements. As expected, the higher concentration of particles on the external regions of the castings raised the measured superficial Rockwell hardness and Vickers microhardness of the composite. Finally, complementary energy dispersive spectroscopic analysis indicated that Mg dissolved in the AlB2 dispersoids but not in the AlB12 particles.