FE Modeling Methodology for Load Analysis and Preliminary Sizing of Aircraft Wing Structure

It is a critical part at the basic design phase of aircraft structural design to build a finite element model and it will have a direct impact on time and cost for airframe structure development. In addition, the objective of finite element model will be varied depending on each design review phase and the modelling methodology varied accordingly. In order to build an effective and economic finite element model, it is required to develop adequate level of modelling methodology based on each design phase and its objectives. Therefore, in this paper, the finite element modeling methodology was presented for internal load analysis of wing structure of multi-spar type military aircraft, load path evaluation and initial sizing of wing structure. All structures reflected mechanical function and at the same time, idealized to achieve easy and conservative result of internal load evaluation. Through analysis of various loads, it was confirmed that the finite element modeling suggested in this paper and initial sizing method could be applied to internal load analysis of wing structure and initial sizing

A Suspended Nanogap Formed by Field-Induced Atomically Sharp Tips

A sub-nanometer scale suspended gap (nanogap) defined by electric field-induced atomically sharp metallic tips is presented. A strong local electric field (\u3e109 V=m) across micro/nanomachined tips facing each other causes the metal ion migration in the form of dendrite-like growth at the cathode. The nanogap is fully isolated from the substrate eliminating growth mechanisms that involve substrate interactions. The proposed mechanism of ion transportation is verified using real-time imaging of the metal ion transportation using an in situ biasing in transmission electron microscope (TEM). The configuration of the micro/nanomachined suspended tips allows nanostructure growth of a wide variety of materials including metals, metal-oxides, and polymers. VC 2012 American Institute of Physics

Properties of Magnesia Composites According to Replacement Ratio of Perlite

Recently, passive and zero-energy construction has increased in Korea due to the government`s continuous application of budget-conscious policies for establishments. Accordingly, construction materials are being advanced, and the required performance standards for insulation materials are increasing. However, problems such as fire vulnerability and degradation of physical properties for organic and inorganic insulation materials are shown, so it is necessary to solve this problem. The objective of this research is to examine the properties of the composites by analyzing the flexural breaking load, impact resistance, density, VOCs concentration reduction rate, and fine dust concentration reduction rate of the composites manufactured based on the perlite substitution rate of the magnesia composites. The flexural breaking load test of the composites was assessed according to ‘KS F 3504’, a gypsum board standard and the impact resistance was assessed according to ‘KS F 4715’. The performance evaluation of adsorption performance of air pollutants of the VOCs and fine dust in the context of the small chamber technique suggested by Hanbat University. The results of this study are as follows: The flexural breaking load according to the perlite replacement rate tended to decrease as the perlite replacement rate increased. It is determined that the flexural breaking load is reduced by generating a large amount of pores inside due to the perlite porous structure characteristics. In the case of impact resistance, the impact resistance tended to increase as the perlite displacement rate increased. It is determined that the volume of the binder in the board is reduced, and pores inside the board are generated due to perlite, which is a porous material, thereby reducing the overall bonding force of the board. In the case of VOCs and fine dust concentrations, the VOCs and fine dust concentration reduction rates tended to increase as the perlite replacement rate increased. In the case of the perlite displace rate of 30%, the VOCs concentration decreased by 82.6%, and the fine dust concentration decreased by 87.9%. It has been established that the porous properties of perlite used to create a huge number of pores in the hardened body cause the concentration to be lowered physically through adsorption. This study\u27s findings are thought to be fundamental information for securing the engineering properties and air pollution absorption of magnesia composites blended with perlite

A NUMERICAL STUDY ON THE OPEN WATER PERFORMANCE OF A PROPELLER WITH SINUSOIDAL PITCH MOTION

When a ship operates in waves, the ship moves with 6 degrees-of-freedom, and a propeller at the stern of the ship cannot avoid moving due to the ship motion. Therefore, it is important to analyse the propulsion performance while considering the ship motion in waves for efficient ship operation. The pitch motion of the ship has a dominant effect on the variation of the propeller performance and results in sinusoidal pitch motion of the propeller. In this study, a numerical analysis was done using a KP458 model propeller with a diameter of 10 cm, which was designed for the KLVCC2 body plan. The propeller performance was calculated using computational fluid dynamics (CFD) at several constant tilt angles. Numerical simulations were then conducted with sinusoidal pitch motion in several conditions of varying pitch angle. The variations of the thrust and torque of the propeller in sinusoidal pitch motion were compared with the results obtained in constant tilt angles

Thermal plasma flow and equivalent circuit analyses on the electrical coupling of a DC-RF hybrid plasma torch

Numerical analyses on the electrical coupling of a DC-RF (direct current – radio frequency) hybrid plasma torch are conducted on the basis of magneto-hydrodynamic flow and equivalent circuit models to find the dependency of coupling efficiency on RF frequency and confinement tube radius. Computations are also carried out for the inductively coupled RF plasma torch to make a comparison between their calculated results. Numerical results reveal that the electrical coupling efficiencies of the RF and DC-RF hybrid plasma torches have a similar dependency on RF frequency with an almost constant difference of slightly higher efficiencies for the hybrid plasma, due to the relatively linear frequency dependency of equivalent circuit parameters as well as the resultant radially expanded DC-RF hybrid plasma toward the confinement tube wall compared with the RF plasma. But it is found that the reduction in the confinement tube radius less than some critical value, for instance 22 mm in this numerical work, possibly causes the coupling efficiency of the hybrid plasma to drastically deteriorate compared with that of the RF plasma. Such poor efficiency of the hybrid torch with relatively small radius is attributed to a significant diminution of the high temperature region upstream between the DC torch exit and the first induction coil segment, which means that the reduced tube radius may lead to an ineffective superposition of DC arc jet and RF plasma. As a result of the reduced high temperature region, the magnetic flux linkage is decreased for the smaller confinement tube, which leads to a drastic decrease in the electrical coupling. As the confinement tube radius becomes smaller, the re-circulation eddies under the DC torch are almost destroyed by a DC arc jet and a stagnation region formed is contracted to the central region. This contracted stagnation region prohibits the convection heat transfer by re-circulation of sheath gas flow from the coil zone to the upper part of the confinement tube, which ultimately results in a significant diminution of the high temperature region in the upstream. The present numerical analyses indicate that a special focus need to be brought into the influences of the DC arc jet on the electrical and thermal flow characteristics of the DC-RF hybrid plasma in determining the torch dimensions for effective conversion of RF power into plasma

Intermetallic Nanoarchitectures for Efficient Electrocatalysis

Intermetallic structures whose regular atomic arrays of constituent elements present unique catalytic properties have attracted considerable attention as efficient electrocatalysts for energy conversion reactions. Further performance enhancement in intermetallic catalysts hinges on constructing catalytic surfaces possessing high activity, durability, and selectivity. In this Perspective, we introduce recent endeavors to boost the performance of intermetallic catalysts by generating nanoarchitectures, which have well-defined size, shape, and dimension. We discuss the beneficial effects of nanoarchitectures compared with simple nanoparticles in catalysis. We highlight that the nanoarchitectures have high intrinsic activity owing to their inherent structural factors, including controlled facets, surface defects, strained surfaces, nanoscale confinement effects, and a high density of active sites. We next present notable examples of intermetallic nanoarchitectures, namely, facet-controlled intermetallic nanocrystals and multidimensional nanomaterials. Finally, we suggest the future research directions of intermetallic nanoarchitectures

Production of Hydrogen and Carbon Black by Methane Decomposition Using DC-RF Hybrid Thermal Plasmas

A continuous production of carbon black and hydrogen has been investigated by thermal decomposition of methane using a prototype processing system of DC-RF hybrid thermal plasma, which has great advantage over other thermal sources like combustion or DC plasma torches in synthesizing new nanostructured materials by providing high-temperature environment and longer residence time for reactant gases due to its larger hot core region and lower flow velocity. Appropriate operation conditions and reactor geometries for the effective synthesis process are predicted first from the relevant theoretical bases, such as thermodynamic equilibrium calculations, two-dimensional thermal flow analysis, and chemical kinetic simulation. Based on these derived operation and design parameters, a reaction chamber and a DC-RF hybrid torch are fabricated for the processing system, which is followed by methane decomposition experiments with it. The methane injected into the processing system is converted mostly into hydrogen with a small volume fraction of acetylene, and fine carbon particles of 20-50 nm are identified from their TEM images. Material analyses of BET, DBP and XRD indicate that the synthesized carbon black has excellent properties such as large surface area, high electrical conductivity, and highly graphitized structures with good crystallization