Numerical analysis of the electric vehicle battery was performed for the optimization of the thermal management under various operating conditions. For the analysis of internal flow and temperature distributions under the different operating conditions of battery, the battery system which was packed 18 battery cell with -25℃∼ 65℃ operating temperature range was considered, and the air flow rate, velocity, and ambient temperature conditions were varied and compared. It was revealed that the cooling system for battery was necessary to maintain its performance for hot ambient conditions. Especially, in this condition, at least 90m3/h of air flow rate are required to maintain the module temperature under 40℃. However, heating system of battery for cold ambient conditions doesn't need.
Aerodynamic coefficients of a reentry bodyin hypersonic flowfiled are calculated by using a three-dimensional flow solver. The high temperature real gas effects, thermal excitations and chemical reactions of air, are accounted for in the calculation. The reasonable agreement between the calculated aerodynamic coefficients and the Apollo AS-202 flight date are obtained. The effects of thermochemical nonequilibrium on the aerodynamic predictions are shown to be non-negligible.
Magnetostrictive actuator is fabricated with epoxy bonding method instead of sputtering method in this study. Fabrication process and experimental measurement method for magneto-mechanical characteristics is proposed. For the design of highly flexible magnetostrictive actuator, TbDyFe epoxy bonding with SU-8 substrate is adopted. The fabrication process for SU-8 substrate and the epoxy bonding is suggested and magnetostrictive behavior is investigated. Variable magnetic field is applied to measure the various magnetostrictive characteristics and magnetostriction is measured with different waves and different magnitude of magnetic field.
In the present numerical study, simple stenotic artery models using pulsatile flow condition were investigated. A reversing sinusoidal velocity for pulsatile flow was imposed at the flow inlet and the corresponding based on the vessel radius. The stenotic geometries modeled using mechanical 3D CAD. It has been used that consist of 0.2, 0.4, 0.5 0.75 and 0.8 stenotic rate in a cylindrical tube. In this paper, numerical solutions are presented for a second harmonic oscillatory flow using commercial code CFX 14. As stenosis rate increases, the maximum wall shear stress(WSS) increases while the minimum WSS decreases. As the stenotic rate increases, the pressure drop at the throat severely decreases to collapse the artery and plaque. It is found that the fluid mechanical disturbances due to the constriction were highly sensitive with rate of stenosis. When stenosis rate increases, the recirculation region exists. In this recirculation region the possibility of plaque attachment is increasingly higher. The present results enhance our understanding of the hemodynamics of a stenotic artery.
Injection rate characteristics of biodesel fuels according to the blending ratio was described in this work. The injection rate measuring system based on the Bosch's method was utilized to measure and compare the fuel injection rate characteristics. Three different types of biodiesel which were derived from seed, unpolished-rice, and soybean were blended with the diesel fuel in 20% and 40% of volumetric ratio. The fuel properties, injection mass, and injection rate characteristics were obtained and compared in various injection conditions. It is expected that this observations provide important insights into the effect of fuel properties on the biodiesel fuel injection rate performance in a CI engine
Numerical analysis of a Ni-PZT stacked piezoelectric micro actuator is investigated for the prediction of mechanical behavior as a preceding research for the manufacturing of three dimensional micro structures. Finite element method is adopted to examine the simulation of a piezoelectric actuator according to applied direction of voltage, by researching displacement characterization of piezoelectric material through piezoelectric theory. PZT-4 is selected as a piezoelectric material. And bimorph finite element modeling is employed to study the response of Ni-PZT bi-layered micro actuator under the various input voltages. The results are presented as maximum displacement values under each applied voltages. Maximum displacement of 0.71μm at 60V is obtained
This study introduces the web-camera image processing-based natural landmark extraction method for automatic welding using 3-axis stage. The welding is a highly significant process in the industries of shipbuilding, automobile, construction, machinery, and so on. However, it has been avoided due to poor working conditions such as fume, spatter, noise, and so on. For the automatic welding system, the web-camera is used to extract the natural landmarks which can give the relative coordinate to set up the initial position of the stage for the welding process. The Canny edge and Hough transformation have been used to extract the significant points for the natural landmark extraction in this paper.
The experimental study for an operational characteristics and performance of the sodium heat pipe were carried out. For an experiment, the heat pipe which is 1000mm length and 25.4mm diameter of stainless steel container with 50 mesh of screen wick using sodium as a working fluid is manufactured and tested as functions of heat flow rate, inclined angle and operating temperature. The test results are as follows. During the start-up, frontal start up was observed because of the vapor density increasing as increased the hot zone. Also, the heat pipe showed uniform temperature over than 420℃ of the operating temperature. The average heat transfer coefficient increased as the heat flux and the vapor temperature increase, and the range of the total thermal resistance was 0.075～0.04℃/W at the 12～53.55kW/m2 of heat flux and 500～750℃ of operating temperature. The maximum heat flow rate was 750W at the 10 degree of top heating mode.
Recently, applied areas of nonferrous materials have been expanded in terms of efficiency of materials used and cost reduction. And, in accordance with compactness and accuracy of parts, the need of joining of dissimilar materials is raised. Accordingly, this study aimed at finding out the optimal welding current value(6.3～6.5kA) considering tensile strength, fracture test and welding residue after joining with various welding conditions by means of copper pipe(Φ7.0 × t0.5) and aluminium pipe(Φ7.0 × t0.7) using an eutectic diffusion bonding machine.
Thermo-mechanical fatigue cracks on the turbine housing of turbochargers are often observed in currently developed gasoline engines for them to adopt lightness and higher performance levels. Maximum gas temperatures of gasoline engines usually exceed 950℃ under engine test conditions. In order to predict thermo-mechanical failures by simulation method, it is essential to consider temperature-dependent inelastic materials and inhomogeneous temperature distributions undergoing thermal cyclic loads. This paper presented the analytical methods to calculate thermal stresses and plastic strain ranges for the prediction of fatigue failures on the basis of motoring test mode, which is commonly used for accelerated engine endurance test. The analysis results showed that the localized critical regions with large plastic strains coincided well with crack locations from a thermal shock test.
In this study, recliner is modelled and compared with 2 types of models as conventional recliner and round recliner by investigating stress and displacement through strength analysis. The maximum deformation of 0.018mm at round recliner is much smaller than that of 0.18mm at conventional recliner. It can be seen that the round recliner has more safety than conventional recliner. Round recliner model has more durability and safety than conventional model by the result of structural and vibration analysis. The model design of automotive recliner can be designed effectively at applying the safe driving of automobile practically by using the result of this study.
Friction welding in dissimilar materials is widely applied in various engineering fields such as automobiles, rolling stocks, machine tools. Since interface edges of Friction-welded materials have stress singularity by differences of mechanical properties and temperature changes, it is necessary to assess stress singularity with the variation of flash shape and length. In this paper, the influences which the flashes created by friction welding concern to the stress singularity at interface edges are investigated. Through stress analysis by the BEM and static experiments, the influences were studied quantitatively, the stress singularity greatly depends on the shape of the flash and its size.
Adhesive joint method has been used instead of welding, reveted joint, bolt and nut in various industry fields recently. Aluminum foam has hole or crack on adhesive interface which is different from common composite material. To investigate shear characteristic of adhesive interface between aluminum foams, double cantilever beams(DCB) with thicknesses of 25mm, 45mm and 65mm bonded with single-lab joints are designed. The relation between nodes at finite element model is important to investigate adhesive strength in this study. All meshes are generated and some nodes are located on adhesive zone along collinear axis. As reaction force obtained by static experiment is applied, fatigue analysis is carried with 10Hz. In advance, adhesive property is obtained by preliminary experiment for applying adhesive strength to input into simulation analysis. With these conditions, the analysis results show that 2.97MPa, 3.10MPa and 4.2MPa of maximum equivalent stresses are shown respectively in case model thicknesses are 25mm, 45mm and 65mm. By use of the simulation result at this study, it is possible to find adhesive behavior of aluminum foam and be applied to real adhesive joint structure without experiment by sparing experimental cost and time
This study presents a structural safety analysis method for a plant annunciator panel under the seismic effect. Seismic qualification analysis for the nuclear plant annunciator panel is carried out to confirm the structural integrity and the results are represented by required response spectra. For the numerical analysis, finite element method is adopted. Mode combinations are also used to obtain the reliability of the spectrum analysis. The analysis results shows that the nuclear plant annunciator panel is designed as a dynamically rigid assembly, without any resonance frequency blow 33Hz. The calculated stress of the nuclear plant annunciator panel is much less than yield stress of used steel.
The supercritical carbon dioxide Brayton cycle(S-CO2) is one of promising alternatives as a power conversion system of the sodium-cooled fast reactor due to higher cycle efficiency and less reactive working fluid to sodium, compared to the steam Rankine cycle. In a S-CO2 Brayton cycle, turbine, compressors and generator are coupled with a same axis and their rotating speeds are variable in accordance with electrical outputs. However, to synchronize the cycle with a electrical grid, the electrical output of the cycle must has the same frequency with the electrical grid regardless of amount of the turbine output. To deal with this problem, several methods were proposed but each method still has their own weaknesses. In this paper, a new idea will be presented. The idea that the generator with the two reverse rotors are introduced into S-CO2 Brayton cycle and it aims to produce a full range of electricity at a fixed frequency with high efficiency.
The bio reactors with high efficiency using ejector are widely used in gas-liquid system, This is also due to the high efficiency in gas dispersion resulting in high mass transfer rate and low power requirements. Thus, the new liquid fertilizer manufacturing equipment composed with aeration tank, cycling tank and circulation pump using an ejector was developed. The aim of this study is to investigate the effect of an ejector on the liquid fertilizer manufacturing equipment and to design the optimal ejector for actual application using CFD analysis and experimental method. The results show that the suction air mass flow rate is increased, as the diameter of driving ejector nozzle is smaller and the position of nozzle is toward the exit of an ejector.
The object of this paper is to examine the noise generating mechanism at manufacturing process of metal material products. To accomplish the object; A noise generating mechanism of high noise machine, which is mounted in the small and medium size enterprise, was investigated. The measurement method of the noise for the machine by manufacturers were investigated. The noise at the 250 points of the manufacturing process machine in the 40 processes of the 3 factories, 3 business fields was measured. The database of the noise was built from the measurement data. The major sound sources and frequency range for the manufacturing process of metal material product machine was investigated.
Instruments for surgical and dental application based on oscillatory mechanics submit unwanted vibrations to the surgeon's and dentist's hands. frequently the weight of the instrument's body is increased to dampen its vibration. Because medical devices to contact with human body directly are sterilized before use, conventional damping method and damper are not good for medical use. For dissipation of vibration, based on recent research regarding the optimization of particle damping, we made a prototype particle damper that dissipate the vibration of oscillatory saw and tested for validation of particle damping. As a result we found that particle damper operate more efficiently than solid mass damper if the geometry of the damper is optimized with respect to the specific amplitude of the vibration.