Earticle

In this study, a finite element analysis was used to analyze the stress state and vibration characteristics generated by continuous contact between wheels and rails when driving urban railway vehicles. The rails applied to the analysis were divided into straight and curved shapes, and three-dimensional modeling was performed to analyze the changes in structural characteristics of wheels and rails when driving on straight and curved rails. As a result of the analysis, the stress characteristics were up to 6.5 MPa on a straight rail and 9.81 MPa on a curved rail, and it is believed that this increase in stress will increase noise due to an increase in friction at the interface. The vibration characteristics of the wheels and rails showed similar behavior from the 3rd mode to the 9th mode of the rail to the intrinsic vibration characteristics from the 4th mode to the 6th mode of the wheel.

Noise is a sound that humans do not want. In this study, noise is measured for C172, the most frequently used general aviation trainer in Korea and abroad. In addition, in this study, noise measurement points are selected for Muan Airport, where most of the domestic training aircraft fly under the supervision of the Ministry of Land, Infrastructure and Transport. Based on this, the measured data is scaled and analyzed. In addition, we intend to analyze what characteristics C172 aircraft have unique through frequency analysis of noise of C172. Through this, it is intended to understand what type of noise training aircraft affect in future studies.

Thin-film shape technology is recognized for its core technology to enhance the technology of LCD, PDP, semiconductor manufacturing processes, hard disks and optical disks, and is widely used to form coated thin films of products. In addition, resistance (electron beam filament) technology for heating is used to manufacture filament for ion implants used in semiconductor manufacturing processes. By establishing an electronic beam filament production system and developing seven specifications of electronic beam filament, it is contributing to improving trade dynamics and increasing exports to Japan through localized media of theoretical imports to domestic companies. In this study, CAE analysis was performed after setting electron beam filament specification and development objectives, facilities and fabrication for electron beam filament production, electron beam filament JIG & fixture design and fabrication followed by electron beam filament prototype. Then, the automation and complete inspection equipment of the previously developed electronic beam filament manufacturing facilities was developed and researched to mass-produce them, to analyze and modify prototypes, design and manufacture automation facilities, and finally, to design and manufacture the complete inspection equipment. In this paper, mainly jig & fixture design, production and trial production of electron beam filament were dealted with.

Welding is one of representative manufacturing processes in the industrial field. Cryogenic storage containers are also manufactured through welding, and conversion to laser welding is issue in the field due to many advantages. Since welding causes thermal-elastic deformation, design considering distortion is required. Prediction of distortion through FEM is essential, but laser welding has difficulties in the field because there is no representative heat source model. The author presented the model that can cover various models using a multi-layer heat source model in previous studies. However the previous study has a limitation which is a welding heat source model must be derived after performing bead on plate welding. Thus this study was attempted to estimate the welding heat source parameters by comparing the shape of bead under various conditions. First, the difference between penetration shape and welding heat source parameters according to welding power was analyzed. The radius of the welding heat source increased according to the welding power, and the depth of the welding heat source also increased. The correlation between the penetration shape and the welding heat source parameter appears at a similar rate, however the follow-up research is necessary with more model data.

Seawater flow and turbine torque in a lab-scale tidal power generation system have been analyzed with CFD method. Its power generation is largely influenced by hydraulic flow characteristics of pressure variation and mechanical turbine torque in the system caused by vertical flow field including tangential rotation. Pressure drop through the turbine was gradually increased with flow rate by seawater level difference, and it depends on the turbine blade and system geometry. And curl was severely varied along the flow direction with more than about 8 times increase through the flow system. There was also turbine torque change with pressure inlet due to the water level. Those predicted results can be widely used as basic concept design data for efficient tidal power generation system development.

In this paper, we design a basic algorithm enabling recognition of surrounding environment and collision avoidance among elemental technologies for autonomous driving, also applies sensor theoretical data and actual road performance to robo-racing system based on experimental data obtained through driving tests to enable sophisticated collision avoidance. For this study, a commercial autonomous driving patform(ERP-42), LiDAR and GPS sensors were used to implement efficient comunication systems and autonomous driving algorithms between each module.

Recently, research on MAX phase materials has been actively conducted. M of MAX phase is made of early transition metal element, A is A-group (IIIA or IVA) element, and X is Carbon or Nitrogen. It has the chemical formula of MnAXn-1, and is called the 211, 312, and 413 groups according to the indices(n=1,2,3). MXene material is characterized by having a layered structure of 2D structure like graphene by etching the element corresponding to A-gruop in the MAX phase. So far, MXene materials have been reported to be applied in various fields. In particular, research is being actively conducted as anode material for Li secondary batteries, electromagnetic wave shielding material, and hydrogen storage alloy material. In the pulse energization active sintering method, the surface of the powder particles is cleaned and activated more easily than the conventional electrical sintering process and material transfers at both the macro and micro level, so that a high-quality sintered body can be obtained at low temperature and fast time. In this study, the MAX phase was synthesized in a short time by using a pulse current active sintering apparatus, and the MXene material was prepared from the synthesized MAX phase and the structure was analyzed.

The flange spreader has been used to withdraw butterfly valves during maintenance. The typical flange spreaders required an excessive working space, and the pipe and flange are damaged by the load. In the previous study, the author developed a valve easy out tool with collet, and designed collet shape to ensure structural safety. However, clamping force of the collet had not been checked. In this study, design of collet shape was performed to improve clamping force. Techniques of structural analysis were established and design parameters were selected. Through parametric study, the collet shape with clamping force of 159,748N was suggested. This will contribute to stability and efficiently of valve maintenance.

Environmental noise occurring on ships has various negative impacts on sailors’ health conditions such as hearing loss, sleep disturbance, psychological stress, etc., so regulations on them are required, but the ship noise regulations are usually applied to only large merchant ships. Although regulations on fishing boats with strong fishing and work intensity are determined to be necessary, there has been little relevant research. This study, therefore, attempted to measure the environmental noise of coastal composite fishing vessels less than two tones and provide the results of basic research on the noise regulations for fishing vessels. It measured them by setting the measurement zones as after side, midship and fore side, and based on the criterion of IMO MSC 337(91). The findings showed that the noise of them often exceeded 75dB(A), the criterion of the open deck noise in the zones in which the load of main engines was increased. In particular, the noise of the stern was as high as 92.2dB(A) during the full ahead. Hence, hearing loss may be caused by such a noise, so a variety of regulations on it are determined to be necessary.

In this study, it was investigated about optical simulation in high brightness and high uniformity direct-type backlight design for medical application. Direct-type backlight has been used high-brightness backlight such as Medical LCD application. The key parameter in designing direct-type backlight was consists of three geometrical dimension such as the distance of two lamps, the gap of lamp and reflection plate and the number of lamps. It has many of variations in optical design and it causes the different properties in backlight system. It shows the best values of above parameters; 26mm of the distance of two lamps, 4.5mm of the gap of lamp and reflection plate and 16 lamps. And we produced the specimen as above condition, and acquired good result in backlight such as the value of the brightness is 6423 nit in center of emission area and less than 5% in brightness uniformity. It shows the effective ways of designing backlight system using optical simulation method for medical LCD application.

A theoretical model has been studied to describe the sound radiation analysis for a railway under the action of harmonic moving line point forces. When a railway is analyzed, it had been modeled as curved beams with distributed springs and dash-pots that represent the radial, tangential stiffness and damping of rail, respectively. The reaction due to fluid loading on the vibratory response of the curved beam is taken into account. The curved beam is assumed to occupy the plane y=0 and to be axially infinite. The curved beam material and elastic foundation are assumed to be lossless Bernoulli-Euler beam theory including a tension force(T), damping coefficient(C) and stiffness of foundation(κ2) will be employed. The expression for sound power is integrated numerically and the results examined as a function of Mach number(M), wave-number ratio(γ) and stiffness factor(ψ).

In this paper, the CFRP(Carbon Fiber Reinforced Plastic) parts were printed and cut in a large-scale additive and subtractive hybrid manufacturing system. A method to increase the strength and durability of a product by identifying the interlayer adhesion during the printing process of a large-scale additive manufacturing hybrid system was investigated. According to the printing conditions(CF content, deposition temperature, compaction process), the specimen was printed and cut to determine the tensile strength in the printing direction. As a result of the experiment, the highest tensile strength was shown when ABS-CF 20wt.% Compound was printed at 230℃ extrusion temperature, and the higher the CF content of the material, the lower the tensile strength. As a result of observing the inside of the test piece through an optical microscope, a large number of voids were kept inside the test piece. To remove voids generated inside the test piece, a compaction process was applied to the additive manufacturing hybrid system to prepare a test piece. As a result, void size decreased, and the strength of the part showed a tendency to increase. It is thought that additive manufacturing with high tensile strength can be obtained through studies on the optimization of deposition conditions in additive manufacturing hybrid systems.

Recently, halogen lamps for vehicle exterior lamp systems are being replaced by LEDs (Light Emitting Diode) in consideration of miniaturization, power consumption, life, luminance, and eco-friendliness. Due to regulations on the amount of light required, luminance, light uniformity, and glare prevention, it is required to develop a light guide for controlling a light source of an LED lamp for a vehicle. For the development of the light guides, the development of machining technology that can cut micro patterns of hundreds of micrometers scale into surface roughness of tens of nanometers scale must be preceded. In this study, the effect of variations in cutting conditions on surface roughness was analyzed through experiments. The micro patterns was manufactured by cutting into STAVAX material, and the surface of the micro patterns was super-finished using a ball-shaped PCD (polycrystalline diamond) tool without flutes. In experiments, the cutting conditions of the super-finishing process were varied, and the varied cutting conditions were feed rate, radial depth of cut, and spindle speed.

In this study, a numerical analysis was performed as steady-state analysis to investigate the effect of interference between the propellers of the hexa-copter. As the distance increases, there is little change in thrust, but when a propeller close to the reference propeller rotates, it was confirmed that the thrust decreased due to the interference effect. Unsteady state analysis was performed to confirm the influence of the hexa-copter fuselage. If there is a fuselage, the thrust was predicted to increase by about 4.97% due to the ground effect. If the design parameters are established considering the effect of the fuselage of the hexa-copter, it is expected to be used for basic design and application design in the future.

In this study, in order to review the structural stability of a Sub-frame assembly mounted on a 5-ton dump truck with a telescopic cylinder type that can secure price competitiveness through cost reduction effect and an extended loading box that satisfies automobile safety standards, the 3D shape design technique for a main component parts is presented. In addition, structural analysis based on the finite element method is performed with the load condition applied to a safety factor 3.0 and boundary condition assigned to the lower part of the Sub-frame. By comparing and examining the maximum stress result from the structural analysis of the entire Sub-frame assembly and individual component and a yield strength of each material applied to each component, a design technique that can assure the structural stability of the Sub-frame assembly is presented.

Controller modeling is essential for the design. It allows various control techniques to be simulated in advance, and various interpretations can be performed. If this is not the case, we need to reverse engineering in the real system developed by others. In this paper, controller modeling was reversely designed using the frequency test results of the target system. First, the characteristic equation of the target equipment was based on and a block diagram was assumed. Thereafter, controller variables were estimated using the frequency test results for each of the four control loops. In addition, time response simulations were performed using the estimated controller modeling. This method is thought to be of great help to reverse engineering in situations where there is completed equipment but no controller modeling.

Ion-beam irradiation(IB) on HfO2 surface induced high-performance liquidcrystal(LC) driving at a 1-V threshold with vertical alignment of liquid crystals(LC). The high-k materials Atomic layer deposition was used to obtain LC orientation on ultra thin and high-quality films of HfO2 layers. To analyze surface morphological transition of HfO2 which can act as physic alignment effect of LC, atomic force micro scopy images are employed with various IB intensities. The contact angle was measured to elucidate the mechanism of vertical alignment of LC on HfO2 with IB irradiation. Contact angle measurements show the surface energy changes via IB intensity increasing.

In this paper, we proposed and tested an indoor obstacle recognition and avoidance algorithm using vision and ultrasonic sensors for effective operation of drone with low-power. In this paper, the indoor flight of a drone is mainly composed of two algorithms. First, for the indoor flight of the drone, the vanishing point and the center point of the image were extracted through Hough transform of the input image of the vision sensor. The drone moves along the extracted vanishing point. Second, we set an area of interest so that the drone can avoid obstacles. The area of interest is a space where the drone can fly after recognizing an obstacle at a distance from the ultrasonic sensor. When an obstacle is recognized in the drone's area of ​​interest, the drone performs an obstacle avoidance action. To verify the algorithm proposed in this paper, a simple obstacle was installed in an indoor environment and the drone was flown. From the experimental results, the proposed algorithm confirmed the indoor flight and obstacle avoidance behavior of the drone according to the vanishing point.

Most domestic pilots are trained at local airfields using propeller aircraft. Training aircraft are mainly trained in the airspace around the aerodrome, and mainly take-off and landing exercises that require a lot of practice among flight control skills. Aircraft noise is a sound that humans do not want. In this study, based on the Rotax 914 engine used in Korea, the propeller blade angle was changed by 1 degree for the 3-leaf “K company” propeller and the 3-leaf GSC wooden propeller, and the engine RPM was changed to examine the noise and thrust changes. The purpose of this study is to check whether noise and thrust loss are the least at the engine's maximum RPM, and to propose an aircraft operation plan in the noisy aerodrome area based on the values.

Most of the steam turbine control valves used for the fossil and nuclear power plants operation in South Korea were developed by GE (General Electric) and manufactured by DHIC (Doosan Heavy Industry Company). For may years, DHIC have tried to develop their own technologies related to the power generation. DHIC has launched many R&D projects and ‘Development of a Control Valve Flow Code for Steam Turbine Operation Control of Fossil Power Plant’ was one of the R&D projects. Through our project, we accomplished the experimental method to obtain a steam turbine control valve characteristic curve using the atmospheric air and the reduced model instead using the steam and the real model. Also, we developed the correction method to calculate the real steam mass flow rate from the characteristic curve obtain by the experiment. In this paper, the effectiveness of the correction method was reviewed and it was concluded that the corrected mass flow rate complies well with the real steam mass flow rate.

In this study, to improve the performance of kitchen range hoods, a comparative analysis of air volume and noise is conducted using three ducts by changing shapes. It was found that the difference in air volume was caused by the pressure difference received by each shape. The noise data can be found to be no more than 60dB overall, except for the second tier of A-type. The difference when connecting the circular, square, and flexible ducts was judged to be due to some laboratory noise, and it was found that there was no difference.

In this study, We designated the injection molded plug housing for charging electric vehicles as a research subject. And we analyzed the effect of Rib design on the quality of injection molded products. First, we used the Taguchi method to derive optimal conditions for rib design. The factors were set as the Thickness of the rib, the Height of the rib, and the Radius of the rib. Each factor consisted of 5 levels and generated conditions for a total of 125. We performed an injection molding analysis and confirmed significant factors affecting the deformation of injection molded products through ANOVA. Based on this, the 25th design detail was selected as the optimal condition. In addition, We compared the results of the molding analysis with the molded products that did not design ribs. We confirmed that the molded product designed with ribs under optimal design detail improved the deformation amount by 22.22% and the residual stress by 8.35%, compared to the molded product not designed with ribs.

There is a considerable amount of research on metal material product worker’s hearing loss caused by noise that comes from manufacturing process. A further investigation that characterizes the sound that comes from manufacturing process of metal material products. however. To do this, a noise management plan is needed. It should include a generated sound process from the main sources of disturbance at manufacturing process areas. And a soundproof measurement will identify the amount of noise reduction needed for a hearing-safe working environment. Finally, researchers in this study measured tests on the noise and the vibration process, and the noise caused by operations allowed for an investigation on the suitability of certain environmental conditions. Noise-related programs can be used to predict the noise distribution of the noise level characteristic. This can help identify and reduce the presence of sound interference through sound proofing measures.

Thin-film shape technology is recognized for its core technology to enhance the technology of LCD, PDP, semiconductor manufacturing processes, hard disks and optical disks, and is widely used to form coated thin films of products. In addition, resistance (electron beam filament) technology for heating is used to manufacture filament for ion implants used in semiconductor manufacturing processes. By establishing an electronic beam filament production system and developing seven specifications of electronic beam filament, it is contributing to improving trade dynamics and increasing exports to Japan through localized media of theoretical imports to domestic companies. In this study, CAE analysis was performed after setting electron beam filament specification and development objectives, facilities and fabrication for electron beam filament production, electron beam filament JIG & fixture design and fabrication followed by electron beam filament prototype. Then, the automation and complete inspection equipment of the previously developed electronic beam filament manufacturing facilities was developed and researched to mass-produce them, to analyze and modify prototypes, design and manufacture automation facilities, and finally, to design and manufacture the complete inspection equipment. In this paper, mainly design and manufacturing of facilities for making electron beam filament were dealted with.

In this paper, the effect of a dynamic vibration absorber to suppress the response of a base excitation vibration system composed of a cubic nonlinear spring and a friction damper is investigated. And the dynamic absorber consists of a linear spring and a viscose damper. The mathematical models of these systems are governed by second order nonlinear ordinary differential equations. The response characteristics of the system are analyzed using the slowly changing phase and amplitude(SCPA) method, which is one of the averaging methods. As a function of the friction force ratio, It was obtained the locking frequency at which the relative motion starts was obtained, and the regions where the locking occurred. The displacement transmissibility was investigated according to the change of the design parameter, and the optimal design parameters could be found to minimize the displacement transmissibility.

In this paper, durability verification of forged wheels for automobiles were performed using the finite element method for bending fatigue analysis and impact analysis. In addition, the durability analysis environment of forged wheels was implemented. By analyzing the stress distribution on the surface of the forged wheel, the area with a high possibility of breakage was identified and improved. The durability analysis of the initial model forged wheel was performed by bending fatigue analysis and impact analysis, The stress distribution of the forged wheel surface was analyzed through the analysis results of the initial model. and the spokes, flanges, hubs, and rear parts are less likely to be damaged were cut to reduce the weight by about 10%, and the reliability of the improved model was confirmed.

Screw jet equipment has been developed based on the existing accumulated experimental indicators in the semiconductor industry, and for specific performance development, it is necessary to visually check a process in which a high viscosity solution is discharged to a nozzle through a screw. Since the transparency of the exterior is not guaranteed after design and production due to the characteristics of the equipment, simulation must be performed to confirm the performance data according to the internal shape. Therefore, in this study, the screw jet equipment was simulated using the moving particle system, and through this, all processes of the screw jet internal solution flow were visually checked and computerized data capable of predicting the performance of the equipment was secured.

Submarining is a phenomenon in that the lap belt goes over the pelvis of the occupant during a frontal crash. It is known to be one of the causes of serious abdominal injuries for the belted occupant. The goal of the current study was to investigate the effect of both the belt geometry and dummy variations on the occurrence of submarining. A series of quasi-static belt-pull tests were performed to evaluate the influence of the parameters on the occurrence of the submarining. The main influencing factor of the submarining was the lap belt angle. The tear or wrinkle of the dummy clothing and torso angle relative to the pelvis also affected the propensity of the submarining. Therefore, these parameters need to be closely monitored to obtain repeatable test results.

Welding is a representative processing technology applied in many industrial sites due to its quality and convenience. In particular, fiber laser welding can be welded at a faster speed compared to arc welding, and there is an advantage in welding distortion, which is the most significant disadvantage of welding. In this study, the weldable thickness was predicted, and the optimal welding angle was estimated using simulations during the welding of the T-shape structure. The multi-layer heat source model proposed in the previous author's study was used, and the study was conducted using the proposed welding heat source under specific conditions of 4kw and 1.0m/min. As a result, it was predicted that high-quality welding would be possible when the thickness was 3mm or 4mm, and it was also confirmed that welding should be performed at an angle of 82.5° or more when welding a 3mm thick structure. As a follow-up study, we plan to build a welding heat source model under various conditions and conduct a study to derive welding conditions at various thicknesses.

This study chiefly aims to clarify efficient methods considering behavioral pattern of refugees in multi-use facilities which can be applied to architectural planning. Accordance with COVID-19 situation, it is mandatory to check the temperature of visitors as a measure for the prevention of COVID-19 in multiuser facilities. When disaster occurs, for people in multi-use facilities such as medical facilities, museum, concert hall etc, it is difficult to find out short and right route to outside since the spatial characteristics are not familiar to visitors. If we design floor plans and circulation system considering behavioral pattern of refugees we can prevent the spread of disasters when they happen.