Papers by Author: Jae Yeol Kim

Abstract: In this study, piezoelectric actuator, flexure guide, power transmission element and control method are considered for nanopositioning system apparatus. The main objectives of this thesis were to develop 2-axis nanostage which enables 2-axis control with the aid of piezoelectric actuator, and to improve the precision of the ultra-precision lathe (UP2) which is responsible for the ductile mode machining of the hardened-brittle material where the machining uses a the single-crystal diamond. Through simulation and experiments on ultra-precision positioning, stability and priority of the nanopositioning system with 2-axis nanostage and control algorithm are developed using Matlab/Simulink. Then the system, is applied to analyze surface morphology of the titanium alloy (Ti-6Al-4V)

Abstract: Spread of household air conditioning system is continued to be increased. Along with the spread, the acknowledgement on product quality by the customer is increasing. Therefore, not only basic performances like cooling and power consumption but also design and noise level of in-house and external unit become the important factors. Axial fan in the external unit of air conditioning system is for ventilation and air supplying unit, and the related products have been widely adopted as household electronics, automobile engine, big sized blower in factory, tunnel, and subway. In this study, commercial 3-winged propeller fan from S company is modified to 2-winged fan for the cost reduction. Using 3D modelling, the fan shape is modified, and analysis flow is adopted to provide the way to reduce cost while maintaining the same wind capacity.

Abstract: Applied gas turbine blade material(Ni base Super-alloy) for aircraft as principal parts material of existing electricity generating gas turbine blade. Studied microstructure change after do heat treatment, Hot Isostatic Press(HIP) processing to nickel-based super-alloy. Emphasize in properties of matter refreshing effect confirmation by HIP processing, microstructure observed by scanning electron microscope. HIP processing effect caused positive effect in high temperature Creep and low cycle fatigue failure by microscopic air hole exclusion. Sheep of Eutectic region decreased solid solution being done B, and also precipitated size of cuboidal shape great. Heat treatment effect was seen modification by M23C6 carbide creation that Script MC carbide is microscopic and does Discrete through solution treatment in high temperature state. Precipitation that grow after HIP processing over solution processing and aging processing in heat treatment process solid solution after is done again precipitate being done size decrescent.

Abstract: Combustion gas of gas turbine is about 1100 ~ 1300 °C. Is doing TBC(Thermal Barrier Coating) on the base metal surface to protect rotor or blade from high temperature flame. TBC system reduced heat transfer as metal base metal. TBC system is divided by bond coating of prevent oxidation and corrosion and Top coating reduced of heat transfer by high Temperature flame. The objective of this study was to development of an advance TBC system for high Temperature (>1350°C) gas turbine components. Used coating powder developed newly in coating process, and more than 1350°C by parameter control in usable coating method develop. Internal studies looked at the effect of TBC coating thickness, material chemistry, substrate composition, surface temperature and bond coat as-sprayed surface profile/particle size on technical performance.

Abstract: The NAUT technique allows non-contact ultrasonic testing in air. If the NAUT technique can be applied, not only ultrasonic testing in air with no couplant would be possible, but also the stable transmission and reception of ultrasonic waves, which would thus enable ultrasonic testing of hot or cold materials, or rough surfaces of specimens that could not be tested with conventional-contact ultrasonic testing techniques. By trying NAUT for CFRP (carbon fiber-reinforced plastic) specimens, the applicability of NAUT in these areas was observed, and the results from the waveforms of parts of the specimens were analyzed. To verify the usefulness of NAUT, first, artificially defective specimens were tested to investigate the defect detection ability of NAUT; and second, a test was conducted to select the test conditions, the ultrasonic propagation characteristics, and the mode conversion by the material thickness. Both the spot welding and CFRP specimens showed good applicability of NAUT. For the spot welding specimen, the ultrasonic transmittance was highest at the spot-welded part, regardless of the thickness and location of the specimen. For the CFRP specimen, the waveforms of a defective part and a defect-free part were compared, and the existence of delamination was discovered through the increase and decrease in the amplitude. These findings confirmed the practicality (usefulness) of NAUT.

Abstract: The infrared thermography technique is being applied in many areas. Particularly these days, non-destructive inspection and evaluation using the ultrasound-infrared thermography technique are hogging the spotlight in a wide range of study areas. The ultrasound-infrared thermography technique uses the principle that ultrasound waves projected to objects with cracks or defects at connections generate local heat from the defective surface. In this research, introduce nondestructive evaluation method for total inspection of special shoes applying Ultrasound Infrared thermography Technique. Performance of the proposed method are shown by through thermo-Image. The total inspection system using infrared thermal camera for special shoes, its applicability, and system configuration are introduced.

Abstract: Vibrations during lathe machining include vibrations by a sudden clash of a tool against a workpiece as an external excitation, vibrations by irregular tissues of the workpiece, vibrations by regular excitation due to asymmetric torque, and vibrations by bearing defects. Furthermore, machine tools are heated because most of the supplied energy is transformed to heat and becomes the heat source of the machine tool or an internal heat source. In addition, the spindle is one of the largest internal heat sources. The heat distortion of the spindle by this heat source has the most serious effect on the total heat distortion of the machine tool, and the heat distortion of machine tools is the largest cause of the degradation of cutting precision. In order to obtain accurate data about the causes of such vibrations and heat, this study measured the vibrations and thermal changes of each specimen using a vibrometer and an infrared thermography camera.

Abstract: For the analysis of various extruder models are used not only testing, but also diverse simulation techniques. Of them, the three-dimensional technique is widely used recently. In this study, the breaker plate in a polymer resin extruder was analyzed. The breaker plate changes the rotational motion of the polymer resin extruded from the screw barrel into a straight line motion before it passes through the die. Also, the size and number of circular holes in a breaker plate directly affect polymer resin extrusion molding. In this study, a 3-D modeling was used to conduct the structural improvement of breaker plates, and the thermal/flow analysis program CFdesign was used to conduct a dynamic property analysis in a bid to achieve the production stability of extruders.

Abstract: Property of GFRP is naturally dependent on the property of matrix, but receives of temperature effects by external force. Therefore, determination of mechanical property by effect of temperature in GFRP is most crucial factor. In this paper, temperature distribution during crack propagation from temperature change under tensile test was proposed through IR thermography camera. Lock-in thermography method, which is one of technique in IR thermography camera to measure minute change in temperature, was utilized to monitor temperature distribution and change during crack propagation. Method to analyze temperature distribution during crack propagation under tensile test of GFRP via IR thermography camera was suggested. Anisotropy in fiber orientation showed longer fracture time and lower maximum temperature.

Abstract: Importance on the detection of corrosion-related defect is undeniable from the fact that it can prevent significant economic loss and enhanced safety in mechanical equipments, pipes, ships, bridges, and other applications. Conventionally researched measurement methods for defect and thinning from corrosion are acoustic emission, EMAT using ultrasound, laser induced ultrasound, etc. However, these non-destructive testing methods have the shortcoming of accessibility to on-site. For instance, EMAT should be close to several millimeters to generate magnetic field in structure. For laser application, it can be applied to remote non-destructive testing, but some defect might not be possible to be detected by the surface condition of structure. In this study, infrared thermography camera is utilized to determine the degree of corrosion on paint-coated metal. In addition, fundamental researches to develop corrosion detection system for on-site metallic structure are conducted to provide the applicability of IR camera and possibility of thermal analysis method.