Papers by Author: Hyun Woo Lee

Abstract: An internal lobe pump is suitable for oil hydraulics of machine tools, automotive engines, compressors, constructions and other other applications. In particular, this type of pump is an essential element of an automotive engine to feed lubricant oil. We perform a theoretical analysis of the internal lobe pump whose main components are rotors. Usually, the outer is characterized by a lobe with elliptical and involute shapes, while the inner rotor profile is determined as the conjugate to the other rotor. Our integrated system, which is composed of three main modules, was developed through AutoLISP using AutoCAD. It generates a new lobe profile, and automatically calculates the flow rate and flow rate irregularity according to the lobe profile generated. Results obtained from the analysis enable the designer and manufacturer of oil pumps to be more efficient.

Abstract: Flexible printed circuit board (PCB), which is used for folder and slide type cellular phones, consists of flexible copper clad laminate (FCCL) and cover layer. Through it an electric current is applied to liquid crystal display (LCD) from the main board of cellular phone. In thin Cu foils of flexible PCB fatigue cracks due to repeated bending motion generate and propagate, and they cause a short circuit. Fatigue behavior of thin Cu foils being used for flexible PCB must be evaluated and confirmed to resolve this problem. It is based on findings by several researches that the mechanical properties of thin film materials differ from those of their bulk counterparts. Thin film properties have been investigated over the last years; however fatigue behavior of thin films has not yet been studied as thoroughly as monotonic behavior. In this study fatigue properties of thin Cu foils for the application in flexible PCB are obtained. Fatigue testing was performed for two kinds of Cu foils that were made by rolling and electrochemical procedures respectively. Differences of fabrications in fatigue behavior of thin foils were distinguished. Especially for rolled Cu foils, effects of rolling directions in fatigue properties were evaluated.

Abstract: Bi-Te-Sb compound material was developed by spark plasma sintering process. The electrical, thermal, thermoelectric and mechanical properties also obtained by the experiments. This paper discusses performance and strength of the thermoelectric cooler made of Bi-Te-Sb compound alloy. The effect of the current has been investigated. The coefficient of performance (COP) is the primary factor to evaluate the performance of the coolers. Using the FEMLAB software package finite element (FE) analysis was carried out with properties of Bi-Te-Sb compound alloy from experiments. The temperature distributions, the stress distributions and the COP in the thermoelectric cooler were obtained.

Abstract: Crack growth behavior of S45C notched tubular specimen was studied to predict fatigue crack initiation and crack propagation under biaxial loading conditions. Stress-strain field near the hole was analyzed by ANSYS. The crack initiation lives and the crack initiation locations were predicted from strain based theories, and the analysis results were compared with the test results. Crack propagation behaviors were studied to understand the reason of crack branching and crack growth rates changing under biaxial loading conditions. Crack growth direction was also observed to find the governing factors of the fatigue damage under biaxial loading conditions.