Papers by Keyword: Aspect Ratio

Abstract: This paper describe a numerical analysis of the effects of numerical simulation geometry on fluid solid particles interaction using multi-relaxation time (MRT) lattice Boltzmann method (LBM). A point force scheme was applied for particles-fluid interactionand with MRT-LBM for fluid flow over a cavity to study the effects of various Aspect Ratio (AR) on the efficiency of particles removal. The results show that change in Aspect ratio causes a dramatic different in the flow pattern and particles removal efficiency. +

Abstract: In this paper, we contribute to another record of computational results by lattice Boltzmann on the flow behavior of nanofluid in a differentially heated enclosure. In the present study, numerical prediction of CuO and Al₂O₃ nanofluid, Rayleigh number ranges 10³ - 10⁵, aspect ratios of 0.5, 1.0 and 2.0 and nanoparticle volume fractions of 1, 3, 5 and 10% were performed. The results show that, for both nanofluids, increases the volume fraction lead to increase of the average Nusselt number for the whole range of aspect ratios and Rayleigh numbers.

Abstract: Plate-like Sr₃Ti₂O₇ powders with anisotropy were prepared by KCl molten salt synthesis (MSS) method, the effect of different SrCO₃/TiO₂ ratio and calcination condition on the phase transition, particle size and morphology of powders were investigated. The results show that SrTiO₃ phase coexist with Sr₃Ti₂O₇ phase and SrTiO₃ is the main phase as the SrCO₃/TiO₂ ratio is 1.15~1.25:1. Pure Sr₃Ti₂O₇ phase can be obtained as the SrCO₃/TiO₂ ratio is 1.55~1.65:1. The aspect ratio of plate-like particles increases firstly and then decreases as the SrCO₃/TiO₂ ratio increases. The sealed and unsealed condition has no influence on the phase structure of the powders. But the aspect ratio of unsealed particles is smaller than that of sealed particle. Finally, the formation mechanism for Sr₃Ti₂O₇ particles was discussed.

Abstract: The aim of present work is to further investigate the flexural behavior of FRC with four types of hooked end steel fibers. The flexural toughness of FRC beams was tested under a three point bending system, and the data of experiments were analyzed according to the standard JGJ/T221-2010 and RILEM recommendation. The results showed equal dosage of different aspect ratio fibers didn’t result in the same flexural toughness. It was found that nominal ultimate flexural strength () and equivalent flexural strength () of beams increased as aspect ratio of the steel fiber was increased. However, the highest equivalent flexural strength () was obtained by the fiber with aspect ratio of 67.

Abstract: A hinge bracket is usually produced by bending of a sheet panel or welding of a hollow bar into a sheet panel. The hinge bracket that is made by bending or welding, however, does not have sufficient durability due to the stress concentration on the bended region or low corrosion resistance of the welded region. In order to make hinge bracket with high durability, a bracket is needed to be produced by forming process. In this study, a thickening process of a sheet panel for the hinge bracket is investigated. The maximum thickening limit in one stage was determined for various aspect ratios of specimen. Finally, the optimum multi-stage forming process was designed for hinge bracket forming and the process was verified by numerical experiment.

Abstract: Distribution of residual stress through the thickness of a cold-rolled aluminum sheet is analyzed by the elastic-plastic finite element method under plane strain condition. Single-pass rolling of 2mm-thick aluminum sheet is considered. Influences of roll diameter D, reduction in thickness r, and friction coefficient μ are investigated. When the friction is low (μ = 0.1 and 0.2), and the case with smaller rolls (D = 130 mm) and low reduction (r = 5%), the residual stress in the rolling direction is compressive at surface and tensile around the layer quarter deep from the surface. While in the case with larger rolls (D = 310 mm) and high reduction (r = 30%), the stress is tensile at surface and the stress decreases to compressive with increasing depth from surface. In other words, with low friction, the residual stress distribution strongly depends on the aspect ratio (contact length / mean thickness) of the roll bite. On the other hand, when the friction coefficient is high (μ = 0.4), the residual stress is compressive at surface regardless of roll diameter and reduction. It means that the friction makes the residual stress at surface more compressive. It is found that the relationship between the residual stress at surface and the aspect ratio is almost linear, and that the slope depends on the friction coefficient.

Abstract: The shape of thin film for flapping rotor wing has a significant impact on aerodynamics. To increase lift, we designed 7 different flexible film wings. Then we compared the aerodynamic force of thin film in accordance with the same aspect ratio of different shapes and the same shape of different aspect ratio. The conclusions suitable for the thin film design guide are obtained. The aspect ratio of thin film for flapping rotor wing is inversely proportional to the aerodynamic force. At the same aspect ratio, the film wing designed by bionic is superior to other shapes. With the aspect ratio increases, the thrust of the film wing designed by bionic decreases faster than the lift.

Abstract: This work aimed to obtain microstructural changes due to the springback effect in order to compare two conventional high strength steels: the interstitial free steel (IF) and the bake hardening steel (BH). The mechanical characterization of the springback effect was performed by a mechanical forming testing called as the three-point air bending. The geometric changes resulting from the forming process were measured by calculating the aspect ratio. The results show that the BH steel suffers a greater springback effect rate than the IF steel due to the greater mechanical strength of the BH steel, and to the variation of this steel’s aspect ratio, depending on the combination of elongation and mechanical strength. It was concluded that the heat treatment performed on the BH steel increased the mechanical strength of the material without losing its formability.

Abstract: Microstructured ZnO have been synthesized by a simple hydrothermal approach, using ZnCl₂ as the zinc source and N₂H₄·H₂O as the amine precursor in water-ethylene glycol solution at 120 °C for 8 h. The X-ray diffractrometer pattern indicates the pure phase formation of ZnO. Scanning electron microscope images show that the aspect ratio of the ZnO microrod increases by the amount of N₂H₄·H₂O ranging from 0.5 to 1mL, but continuing to 3ml, the aspect ratio of the ZnO microrods decreases. Moreover, the optical band gaps calculated through UV spectroscopy are found to increase from 2.94 (±0.02) to 3.0 (±0.02) eV for samples synthesized at different amounts of hydrazine hydrate ranging from 0.5 to 1mL, respectively.

Abstract: External surface cracks can occur in cylindrical vessels due to damage and propagate in the manufacturing process and during service life. Most of research focuses on stress intensity factors for surface cracks with low aspect ratios, i.e., a/c ≤1.0. Situation may well arise where the aspect ratio of cracks is larger than one. An external longitudinal surface crack is assumed to be subjected to different types of hoop stress distributions acting perpendicular to the crack faces. The stress intensity factors (SIFs) along the crack front were determined through the three-dimensional finite element method. Then these results are used to compute approximate values of SIFs in the case of complex loadings by employing both the superposition principle and the power series expansions of the actual hoop stresses. It is found that the maximum stress intensity factor for external surface cracks with high aspect ratio occurs at different point to that with low aspect ratio.