This study develops an efficient numerical algorithm to predict wave-resistance performance of a catamaran hull. The developed numerical algorithm is applied to evaluate wave-resistance performance for two different twin hull forms with a asymmetric and a symmetric mono hull. Numerical calculations and model tests are compared to validate a developed numerical algorithm adopted in the current work. Comparisons are carried out through the sinkage at the bow and stern, the trim and the wave-making resistance coefficient. Model test is performed in order to verify the numerical results. The comparative analysis study regarding hydrodynamic characteristic of different twin hull forms is worthy of application in the catamaran hull form development stage.
This paper presents a method of measuring the 6 DOF motion of a micro object using images taken of interference fringes projected onto the object. Information from the fringe patterns allows for extracting the 6 DOF motion of the object in one image, allowing for real time measurement of the object's pose. This measurement technique is applied to a visual servo control scheme where the object's 6 DOF motion is controled. Experimental results of the developed system are presented.
In this paper, the features of fatigue crack growth under ModeⅠ loading are studied. Double cantilever beam specimens were used. The effects of adherend thickness, rubber modification and adhesive thickness on fatigue crack growth were examined. The experimental results show that some of these parameters do apparently affect fatigue crack growth. Resistance to ModeⅠ fatigue crack growth are increased by rubber modification. The effects of adhesive thickness and rubber content on fatigue crack growth were explained by von Mises's equivalent stress using BEM analysis.
The object of this study is to investigate the penetration characteristics according to the change of stacking sequences and curvature radius in the composite laminated shell. They are staked to [02/902]S and [0/902/0]s, their interlaminar number are two and four. We manufactured the composite laminated shells with various curvature radiuses. Curvature radiuses of composite shell are 100, 150, 200mm and ∞ (it's meaning flat-plate). In general, the kinetic energy before and after impact increased linearly in all specimens, and the absorbed energy of the specimen [02/902]S with a small number of the interlaminars was higher than specimen [0/902/0]s.
Recently, the quiet fan development is one of important issues for comfort of railroad car. The purpose of this study is to find the vibration and noise source of the line flow fan for reduction the noise level. For a vibration and noise source identification, experiments with microphone and acceleration were carefully carried out. The noise of line flow fan is caused by various factors, such as turbulent flow noise, blade passing frequence and unbalance. In order to reduce the fan noise, the blade shape, distance and angle of housing guide should be modified.
A computational fluid flow analysis of a car has been accomplished to explain the lift characteristics according to the changes of wiper angle and car speed. The present study established the process to get the lift coefficient distribution on the whole range of a wiper operating angle. From the result of the present research, it could be seen that the lift coefficient of a wiper with the lower wiper angle had relatively smaller magnitude. On the other hand, the lift coefficient with the wiper angle near 45° was relatively larger than that with the other wiper angles. The present study also verified the usefulness of the lift coefficient that the lift distributions of various car speeds could be derived from the result of a lift coefficient distribution for only a car speed.
The main contributors to the friction in modern internal combustion engines were identified at the top ring around the top dead center of the stroke. In this study, variations of the friction force between piston ring and cylinder liner were varied with piston speed, normal load and oil temperature as well as the properties of the ring materials were investigated experimentally. Their frictional behaviors when sliding against the steel cylinder bore materials lubricated with 10W-30 oil for a commercial medium speed diesel engine were investigated using a Pin-On-Disk tribotester. The results show that the hardness of ring has less effect on the friction force in comparison to the piston speed, normal load and oil temperature. And friction force is lower with harder metals.
This paper studies the optimum design of piezo-driven compliant motion stage. The flexure hinge for designing motion amplification structures has been widely used on conventional piezo stages. The novel 'cross hinge' is more flexible than the flexure hinge, allowing for large motion amplification and less resistance to motion which is ideal for a compliant motion stage. As simulation results, the newly designed stage has superior performance over traditionally designed stages in terms of motion amplification, allowing for larger motion ranges.
This research aims to investigate the flow analysis of LNG ship due to the different shapes of the ship front. Velocity and pressure distribution of fluid at the front portion of ship are numerically calculated for the optimum ship design of front with three different ship speeds for two different front shapes of ship. These numerical calculations are only applied for the immersed part of ship at the ocean. In addition, the coefficient of pressure drag and total drag are numerically obtained. Ultimately, the energy-efficient shape of LNG ship are determined through two different body shapes with three different ship speeds.
In this study, the impact properties of aluminum honeycomb core composite are investigated through simulation analysis. The specimens are applied with different impact energies of 50 J, 70 J, and 100 J. The maximum load occurs at 3.7 ms for 50 J, 3.7 ms for 70 J and 2.3 ms for 100 J. The maximum load occurs when the striker is penetrating the upper face sheet in all cases. In case of 50 J impact energy, striker does not penetrate the lower face sheet and honeycomb core sandwich can be stable as the energy of 38 J happens. In case of 70 J impact energy, the striker penetrates into the specimen. The striker then causes the damage to the lower face sheet after penetrating the upper face sheet and the core as the energy of 53 J happens. In case of 100 J impact energy, the striker penetrates through all of the upper face sheet, core and lower face sheet as the energy of 65 J happens. This study can be utilized at the design of aluminum honeycomb core sandwich composite structure by understanding stability through the impact property.
In the present study, numerical algorithms for a high-speed planing ship were taken into account. The Rankine source panel method was applied to predict a flow phenomena around a ship. The Kelvin type free surface boundary condition and the exact nonlinear free surface boundary condition were compared to predict the wave system generated by the ship and the trim and sinkage state of the ship also were introduced. In order to deal with complex geometries of the planing ship the panel cutting method was adopted. The developed numerical analysis algorithm were applied to the R/V Athena ship and the numerical results were compared with the experimental results.
Local Nusselt number and temperature field distribution within the compound duct with gap have been measured. Measurement of air and wall temperature span a range of gap width from 2mm to 6mm. Also, the Reynolds number is variated from 20,000 to 40,0000. In order to observe the correlations between gap width and turbulent heat transfer, the present measurement has tried to verify the enhancement effect of heat transfer when a gap exists within the compound channel. From this measurement, we could see that the pulsating flow has generated a strong turbulent flow mixing within the compound channel. And the turbulent flow mixing in the pulsating flow plays an effective role of enhancing the Nusselt number by making the fluid temperature uniformly within the compound channel.
This paper will argue that tire damping can be critical to modelling of vehicle dynamic. Tire damping is usually skipped in the process of vehicle modelling. There are two reasons for this. The first one is the simplification of the computer simulation. The second is that the effect of tire damping is thought insignificant to vehicle dynamics. But there is support for skipping tire damping. In this paper, the vehicle performances are investigated with and without tire damping force applied in the dynamic modelling of the system. The transient responses in the time domain and the frequence responses in the frequence domain are analysed to see the effects of tire damping qualitatively and quantitatively. It is shown that significant errors can occur when the tire damping force is skipped during the simulation process.
A numerical analysis was performed to study PEMFC characteristics depending on the flow direction of reactant gas in cathode gas channel using the Fluent. As cathode relative humidity increases, water mass fraction increases due to back diffusion from cathode. For the both of co-flow and counter-flow cases, water mass fraction is higher near the hydrogen inlet region where the chemical reaction rate is high. In overall, counter-flow case gives higher current density compared to co-flow case for the same operating conditions. However, the difference in the current density is not high. The temperature is also higher near the hydrogen inlet region due to the chemical reaction rate for the both of co-flow and counter-flow cases.
In this paper, a three dimensional numerical analysis tool was applied to study the PEMFC performance characteristics. The porosity and electrical conductivity of GDL and CL as well as the relative humidity of anode and cathode channel gas were selected as simulation parameters. The porosity of GDL and CL was varied as 0.3, 0.5, and 0.7. The relative humidity of anode and cathode was varied as 0, 20, 40, 60, 80, and 100 percent. The electrical conductivity of GDL and CL was varied as 1, 5, 10, 50, 102, and 104 1/Ω·m. For a constant cell voltage condition, the maximum current density was obtained at GDL porosity of 0.7, anode relative humidity of 100 percent, cathode relative humidity of 60 percent, and electrical conductivity of 104 1/Ω·m for GDL and CL. As the porosity of GDL and CL increases, current density increases because reactant gases diffuse well. As the electrical conductivity of GDL and CL increases, current density increases due to increased electron transfer rate. As anode relative humidity increases, current density increases. Unlike anode, current density increases when cathode relative humidity increases from 0 percent to 60 percent. Then current density decreases when cathode relative humidity increases from 60 percent to 100 percent.
This study shows an application method of Micro Grid integrating Solar Energy Seasonal Storage (SESS) based on the analysis of time-variant load characteristics of electric railway. Micro Grid includes various renewable energy generation plants as like wind farm, photovoltaic, small hydro, fuel cell, etc. and some energy storage systems to meet the balance between generation production and demand. The essential concept of this paper is the connection and integration between electric railway and Micro Grid including SESS which is able to control power system frequency. This new concept for power system stabilization would be tested in an independent Micro Grid site and some detail application methods would be evaluated for the commercialization.
The sound characteristics is changed by the cabin of the car which mount the speaker. Therefore the speaker must be design to consider the cabin of the car. In this study, the mechanical components of the nonlinear speaker model are investigated by measurement. The frequency characteristics of the sound and the sound pressure level for the same size speakers which are adapted to domestic car model(semi-mid size & mid size car) are investigated, too. From the measurement, we can investigate the differences of the sound characteristics and the thiele-small parameter such as force factor, mechanical mass of driver diaphragm, mechanical resistance of driver suspension losses and mechanical stiffness of driver suspension. This means that the speaker design parameters are changed by the car model
This study aims to analyze the structural behavior on TDCB models bonded adhesively with aluminum foam composite. These simulation models are designed on the basis of British industrial and ISO standards. The variable of configuration factor(m) is set up to investigate the fracture toughness of bonded joint due to the volume of material. Equivalent stress, deformation energy, pressure at bonded part, reaction force-crack length, energy release rate-crack length are obtained by this analysis. Through the data of this study, the fracture behavior can be analyzed by applying the practical composite structure bonded with aluminum foam and the mechanical property can be understood.
Excavator working in the quarry and junkyard, is very difficult to move the things in the truck, because the position of the cab is low, eyesight is not visible. The cab visibility, safety and ease of operation is obtained by the development of the cab lifting system moving the position. To apply cab lifting system on the existing excavator, development of new sub-frame is positively necessary. In this study, the sub-frame, which is suitable for its main function, is manufactured and is verified through hardness test, finite element analysis and endurance test.
There are many risks in using grass cutter because of the pebble in grass and high speed rpm when the cutter hits the hard objects in grass. In this study, the existing patents are surveyed and classified for the new mechanism about the bottom safety cover. The new mechanism was modelled and the planetary gear are designed. The power source (engine or motor) will rotate the sun gear and the carrier of planetary gear is fixed into handle frame. The ring gear will drive the final cutter. The carrier fixed the bottom safety cover through the planetary gear hole at the handle bar. In this paper, we develop a new mechanism and analyze the idea for safe grass cutter and investigate the possibility of having patent through patent search.