Hae-Yong Cho

Dynamic Analysis on the Closing Resistors of Gas Insulated Switchgear

GIS (Gas Insulated Switchgear) is used in electric power system to insure non conductivity, breaking capacity and operating reliability. In the present study, dynamic analysis on the closing resistors of the GIS has bees carried out by the commercial dynamic analysis code COSMOS MOTION and 3-D modeling program SOLID WORKS. In order to find the minimum value of chatter vibration of closing resistors, the motion of moving and fixed resistor parts of closing resistors were simulated by varying the spring constant, the damping coefficient and the mass of moving and fixed resistor parts. The simulated results were compared with experimental results. The application of the results could reduce chatter vibration of closing resistors of the GIS. These data are also useful on the development of future model GIS with minimum chatter vibration for the determinations of the spring constant, the damping coefficient and mass of a moving part.

Finite element analysis for joining glass fiber reinforced plastic and aluminium alloy sheets

Self-piercing rivet(SPR) is mechanical joining methods and which can be joining dissimilar materials. Unlike conventional riveting, SPR also needs no pre-drilled holes. During plastically deformation, SPR pierces upper sheet and joins it to under sheet. SPR has been mainly applied to the joining the automobile body and some materials, such as glass fiber reinforced polymer and aluminum alloy, which represent the sheet-formed materials for lightweight automobile. Glass fiber reinforced plastic(GFRP) has been considered as a partial application of the automobile body which is lighter than steels and stronger than aluminium alloys. It is needed SPR to join Al alloy sheets and GFRP ones. In this paper, in order to design the rivet and anvil, which are suitable for GFRP, the joinability was examined through simulations of SPR joining between GFRP and Al alloy sheets. For this study, AutoCAD was used for the modeling and the simulated using commercial FEM code DEFORM-2D. The simulated results for SPR process joining between GFRP and Al alloys were confirmed by the same conditions as experimental trials.

Design of self-piercing rivet to joint in advanced high strength steel and aluminium alloy sheets

Abstract Self-piercing riveting is an joining method of advanced high strength steels (AHSS) and other dissimilar materials. It has attracted considerable interest from the automotive industry. The SPR has become an interesting alternative joining technique for difficult to weld materials such as steels and aluminium alloys. In this paper, self-piercing rivet and anvil for SPR were designed for the joining conditions with AHSS and aluminium alloy. Various conditions of SPR were simulated for the design of rivets and anvils. The simulated results were in good agreement with experimental ones. As a result, over HV500 rivet is desirable to joint SPFC780 AHSS and aluminum alloy.Key Words : Self-piercing rivet(SPR), Advanced high strength steels(AHSS), SILAFONT, Dissimilar sheet metals, Finite element method(FEM)ISSN 1225-6153Online ISSN 2287-8955 1. 서 론 초고장력강(AHSS)은 열처리에 따른 상변태로 인한 비강도를 갖는 강재로써 마르텐사이트, 베이나이트, 잔류 오스테나이트 등의 미세조직으로 구성될 수 있다. 1) 기계적 물성을 기준으로 항복강도와 인장강도가 각각 300 MPa, 600 MPa 이상인 초고장력강은 망간과 규소가 일반 강보다 많이 함유되어 강도와 인성이 높다.

Finite Element Analysis for Design of Divided Shank of Self-Piercing Rivet

SPR(Self-Piercing rivet) is mechanical element of joining sheet metal components without the need for pre-punched or pre-drilled holes. Newly designed SPR is developed for high joining strength and shearing strength than semi-tubular rivet. In this study, divided shank of self-piercing rivet were designed for joining DP440 and SILAFONT. Newly designed SPR was simulated by using FEM code DEFORM-3D. In simulations of SPR process, various shape of self-piercing rivet were considered for semi-tubular and newly designed SPR. In other to examine the joinability, joining load and lap-shear load of newly designed SPR were compared with semi-tubular by simulated results and experimental ones.

Design of Helical SPR for Joining Advanced High Strength Steel and Aluminum Alloy Sheets

Self-piercing riveting (SPR) is a sheet-joining method that can be used for materials that are difficult or unsuitable for weld, such as aluminum alloys and other steel sheet metals. The increased application of lightweight materials has initiated many investigations into new SPR conditions for riveting dissimilar materials. However, buckling of the semi-tubular rivet occurs during the riveting of AHSS. In this study, a helical SPR was designed for the riveting of AHSS and Al-alloy. In addition, the reinforced helical SPR which has straight parts was designed. The riveting of AHSS and Al-alloy was simulated. Simulated results were verified by comparison with experimental ones.

Prediction of Temperature Distributions of Cold Forging Process for a CamBolt by FEM

Temperature distributions of cold forging process for a cambolt has been predicted by using finite element method in this paper. The cambolt is used as a part in the steering system of a vehicle for the purpose of driving balanced, so some proper mechanical properties such as strength and endurance limit are required for this part. Moreover, temperature is also an important factor to realize mass production and improve efficiency. However, direct measurement of temperature in a forging process is infeasible with existing technology; therefore, there is a critical need for a new technique. In this study, the thermo-coupled finite element method has been presented for predicting the temperature distribution. The rate of the energy conversion to heat for the material of workpiece has been defined and the temperature distribution throughout the forging process of the cambolt has been analyzed. Experimental verification of the technique is presented.