• 소성∙가공
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• 제8권4호
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• pp.393-398
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• 1999

The plastic instable flow phenomenon happens in practical forming process, I. e. upsetting, backward extrusion, piercing, indentation. And also, it is difficult to control precisely the shape and dimensions of forming process. It is found that instabilities of the process are mainly connected with imperfections in the lubrication, billet eccentricity, inclined punch alignment. In view of the direct relationship between instable material flow and quality defects of the products and for better control of forming operation, we should necessarily find out their phenomena. In this study, we introduced the friction disturbance due to inclined punch angle. Analysis of upset forging is carried out using the rigid plastic FEM and slab method with eccentricity. Also, we considered the buckling parameters of billet with the large aspect ratio in upset forging.

• 한국지능시스템학회논문지
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• 제26권4호
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• pp.279-285
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• 2016

본 논문에서는 전기구동방식 궤도차량로봇의 플랫폼을 제안한다. 궤도형 이동로봇은 사람의 접근이 어려운 험지나 장비를 운반하는 등의 목적으로 군사목적, 탐사목적, 재해재난, 농업분야 등 다양한 분야에서 사용되고 있다. 주행 안정각, 측면 전복각 등의 설계조건을 반영하여 전기구동 궤도차량로봇을 설계하였다. 궤도차량로봇을 제작하고 구동시스템 제어기를 제작하였다. 제작한 궤도차량로봇을 $15^{\circ}$ 경사의 실내와 $40^{\circ}$ 경사의 실외 주행 실험을 실시하였다. 실험을 통하여 개발한 전기구동방식 궤도차량로봇의 주행이 가능함을 확인하였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 춘계학술대회논문집
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• pp.98-101
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• 1999

The plastic instable flow phenomenon happens in practical forming process I. e. upsetting backward extrusion piercing indentation. And also it is difficult to control precisely the shape and dimensions of forming process. It is found that instabilities of the process are mainly connected with imperfection in the lubrication billet eccentricity inclined punch alignment. In view of the direct relationship between instable material flow and quality defects of the products and it is for better control of forming operation we should necessarily find out their phenomena. In this study we used the friction disturbance due to inclined punch angle and introduced the method considering kinematic hardening effect Analysis of upset forging is carried out using the rigid plastic FEM and slab method with eccentricity.

• 한국항공우주학회지
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• 제50권2호
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• pp.93-101
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• 2022

실속, 결빙, 센서 이상 등으로 인해 일어나는 제어불능 또는 비정상 비행 상황은 항공기의 추락으로 이어지기 때문에 필수적으로 대비해야 한다. 이와 관련해 비정상 비행 상황에서 항공기의 동적 특성을 정확하게 파악하는 것은 매우 중요하다. 본 논문에서는 일시적인 센서 이상이 발생한 고받음각의 비정상 비행상태 항공기에 대해서 기존의 칼만 필터 기반의 시스템 식별법 대비 보다 효과적인 적응 차수 조노토픽 칼만 필터와 이동창-최소자승법을 활용한 시스템 식별법을 제시하였다. 제안한 방법을 실제 비행 데이터에 적용하고 그 성능을 기존 연구 결과와 비교하였다.

• Journal of Welding and Joining
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• 제16권2호
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• pp.57-63
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• 1998

This study deals with the friction weldability of machine structural carbon steel (SM45C) to Al-Mg-Si aluminium alloy (A6063). The bonding strength of friction welded joints, from all mechanical test, exceeded that of A6063 base metal, under the condition of friction time 1.5 sec, upset pressure 80MPa. The friction welded joints under these conditions exhibited tensile strength of 262MPa, bending angle of 90$^{\circ}$ without crack at weld interface and shear strength of 113MPa. Consequently, the friction weldability of SM4C to A6063 was very excellent, and that was possible without special preparation of weld surfaces.

• Journal of Welding and Joining
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• 제3권2호
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• pp.1-9
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• 1985

In this study, the influence of carbon equivalents on friction welds of similar steels was investigated. Four types of steels with 15mm diameter tested in the wide range of carbon equivalents from 0.3 to 1.1 Main experimental results are summarized as follows : (1) Under the constant burn-off length, the friction time becomes longer with the increasing carbon equivalent, but the upset length shows no consistent tendencies. (2) Due to the recrystallization in the contact area, the maximum hardness occurs some away from the contact surface. And it increases almost linearly with the increasing carbon equivalent. (3) Even a steel with 1.1 C.E. can be friction welded to make defect-free welds. (4) With the increasing carbon equivalent, the bend angle and charpy impact value decrease very rapidly in the range from 0.3 C. E., but remain nearly unchanged for C. E. higher than 0.6. (5) Heat treatment of the base metals before welding has very little influence on the mechanical properties of welds. On the other hand, normalizing of the welds improves the bend angle and charpy impact value, but its effect becomes almost negligible, when the carbon equivalents are higher than 0.6.

• 한국주거학회논문집
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• 제8권3호
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• pp.219-230
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• 1997

Lack of technical standards, specification and inadequate execution in masonry wall construction in Korea lead to produce serious flaw problems such as crack, efflorescene, and upset etc.. The purpose of this paper is to present the practical details for Masonry cavity wall construction to prevent rain penetration and to accommodate differential movement between the inner and outer wythes of cavity walls. Considering rain penetration and differential movement of both wythes of cavity walls, provision of an adequate air space, an airtight back-up wall, clean cavity with weepholes and vents, properly positioned flashing, tie and shelf angle etc. depend on the cavity wall types will help ensure good performance. The present details included noncorrosive hot dip galvanized steel or stainless steel for metal components, plastic and ultra violet resistant polypropylene Copolymer for other components was taken into account the construction method and several types of cavity walls in Korea

• 소성∙가공
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• 제33권3호
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• pp.193-199
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• 2024

The friction welding characteristics of stainless steels, mainly used in energy and chemical plant industries due to its excellent corrosion resistance and high strength, was evaluated in this study. Friction welding was introduced and conducted at a rotation speed of 2,000 RPM, friction pressure of 30 MPa, burn-off length of 5 mm and upset pressure of 110 ~ 200 MPa on rod typed specimens. The grain boundary characteristics distributions such a grain size, shape, misorientation angle and kernel average misorientation of the welds were clarified by electron backscattering diffraction method. The application of friction welding on SUS304 alloy resulted in a significant refinement of the grain size in the weld zone (5.11 mm) compared to that of the base material (48.09 mm). The mechanical properties of the welds, on the other hand, appeared to be relatively low or similar to those of the base material, which were mainly caused by dislocation density in the initial material and grain refinement in the welds.

• 소성∙가공
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• 제27권4호
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• pp.250-256
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• 2018

Oxygen-free copper (OFC) was prepared as a 90 mm cube and then processed with Multi-Axial Diagonal Forging - Initialization of Prior manufacturing History (MADF). The MADF process has been newly developed as a severe plastic deformation method. The MADF process consists of upset forging with a thickness reduction of 30% and diagonal forging with a diagonal angle of $135^{\circ}$. 1 cycle process consists of a 12 passes forging process. In order to analyze the characteristic changes according to the number of iterations, 1, 2, and 3 cycles of the MADF process were performed. The OFC specimens were MADF processed without surface cracks up to 3 cycles. The microstructure, hardness and tensile test of processed materials were analyzed to study the change of material properties according to the amount of MADF process. The results showed that the MADF process effectively refined the microstructure and increased the strength of OFC. In the case of specimens processed for more than 2 cycles, the grains of all measurement regions were refined to be less than $7{\mu}m$ of grain size. The 1 cycle MADF processed OFC showed the highest mechanical properties with the hardness of 132 HV and tensile strength of 395 MPa. Hardness and strength seemed to be saturated when processed over 2 cycles.

• 한국재료학회지
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• 제27권5호
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• pp.276-280
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• 2017

This study was carried out to evaluate the developed microstructures and mechanical properties of friction welded A6063 alloy. For this work, specimens were prepared at a size of 12 mm ${\O}{\times}80mm$, and friction welding was carried out at a rotation speed of 2,000 RPM, friction pressure of $12kgf/cm^2$ and upset pressure of $25kgf/cm^2$. To perform an analysis of the grain boundary characteristic distributions, such as the grain size, orientation and misorientation angle distributions, the electron back-scattering diffraction method was used. In addition, in order to identify the dispersed intermetallic compounds of the base and welded materials, transmission electron microscopy was used. The experimental results found that the application of friction welding on A6063 led to significant grain refinement of the welded zone relative to that of the base material. Besides this, intermetallic compounds such as AlMnSi and $Al_2Cu$ were found to be dispersed with more refined size relative to that of the base material. This formation retains the mechanical properties of the welds, which results in the fracture aspect at the base material zone. Therefore, based on the developed microstructures and mechanical properties, the application of friction welding on A6063 could be used to obtain a sound weld zone.