http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
유한요소법에 의한 PREFLEX BEAM의 용접열분포 특성에 관한 연구
방한서(HAN-SUR BANG),주성민(SUNG-MIN JOO),김하식(HA-SIG KIM) 한국해양공학회 2004 韓國海洋工學會誌 Vol.18 No.2
Preflex beam is a method of construction designed to hold the pre-compressive stresses over the concrete pier by the preflexion load. During the fabrication of the girder, welding causes residual stresses. The welding residual stresses must be relieved in order to generate the accurate compressive pre-stresses. In this study, to determine the thermal distribution characteristics on the girder by welding, both three-dimensional finite element analysis and two-dimensional finite element analysis, in a quasi-steady state, is carried out. After comparing each result between the three-dimensional analysis and the two-dimensional analysis, finite element analysis is carried out against the actual girder, and the welding thermal distribution characteristic over the preflex beam is analyzed. It is possible to provide the input data for the analysis of the welding residual stresses.
신경회로망을 이용한 용접잔류응력 예측 및 최적의 용접조건 선정에 관한 연구
차용훈,김하식,이연신,김덕중,성백섭 朝鮮大學校 機械技術硏究所 2000 機械技術硏究 Vol.3 No.1
The objective of the study is the development of the system for effective prediction of residual stresses using the back propagation algorithm from the neural network. The achieve of this goal, the series experiment were carried out and measured the residual stresses using sectional method. Using the experimental results, the optional control algorithms using a neural network should be developed in order to reduce than the effect of the external distribution during GMA welding processes. Also, comparison with the measured and the calculated results from the FEM(finite element method) and verification of the developed system was carried out. This system can not only help to understand the interaction between the process parameters and residual stress, but also, improve the quantity control for welded structures. Then the results obtained from this study are as follows. Through comparison between the measured and calculated results, the neural network based on back propagation algorithm is the best techniques to predict the process parameter. A new techniques which predict the process parameter such as welding voltage, arc current, welding speed using the training the raw dates, will be proposed.
용접구조물 용접토우부의 잔류응력이 피로강도에 미치는 영향 평가
차용훈,김하식,김일수,성백섭 한국공작기계학회 2001 한국생산제조학회지 Vol.10 No.4
This study is to investigate the influence of weld residual stresses on the fatigue crack growth behaviors in pressure ves-sel reinforcement. In order to perform this study, the automatically welded specimens are prepared. The material is ASTM A516 grade 60 steel used in pressure vessel mainly. For pad-on-plate of skip welding, continuous welding and PWHT specimen, fatigue crack initiation is generally initiat-ed at weld starting and end toe zone, and ruptured at weld starting toe zone. Fatigue life of pad-on-plate continuous specimen is increased more than that of pad-on-plate skip fillet welding specimen about 85% under low load, about 20% under high load, and decreased than that of two-pad continuous welding specimen about 85%. In da dNΔK curve under low load, pad-on-plate skip fillet welding specimen showed retardation on the initial crack, and the fatigue crack growth rate at the low region of ΔK greater specimen E(3.8 × l0 ^6mm/cycle). And the fatigue life of welding specimen was smaller than that of PWHT specimen.
알루미늄 合金 熔接材의 疲勞破壞에 미치는 殘留應力의 影響에 關한 硏究
차용훈,김하식,김덕중 한국공작기계학회 1995 한국생산제조학회지 Vol.4 No.4
This study is to inspect the influence of the initial residual stress on fatigue crack growth behavior after the distribution of the initial residual stress is measured when the crack is growing from the compressive residual stress field to the tensile residual stress field. Also, the influence of the variation of residual stress distribution on fatigue crack growth behavior at the crack tip is studied when the initial crack occurs on weld metal, bead interface and HAZ (Heat Affected Zone), respectively. For this purpose, CT-type specimen that crack parallel to the welding bead were manufactured by butt welding on the Al. Alloy 1100-O plate.
차용훈,김일수,김하식,이연신,김덕중,성백섭,서준열 韓國工作機械學會 2000 한국생산제조학회지 Vol.9 No.6
In order to achieve effective prediction of residual stresses, the series experiment were carried out and the residual stress-es were measured using the backpropagation algorithm from the neural network and the sectional method. Using the experimental results, the optiomal control algorithms using a neural network should be developed in order to reduce the effect of the external disturbances on residual stresses during GMA welding processes. The results obtained from the comparison between the measured and calculated results, showed that the neural network based on backpropagation algorithm can be used in order to control weld quality. This system can not only help to under-stand the interaction between the process parameters and residual stress, but also, improve the quantity control for welded structures. The development of the system is goal in this study.
STS304와 S15C 이종마찰압접부의 접합계면 응력해석
오정국,차용훈,성백섭,박창언,김하식,김충환 한국공작기계학회 2002 한국생산제조학회지 Vol.11 No.3
Friction welding has many merits such as energy efficiency, simple processing, etc. but it is difficult to obtain good welding at the welded interfaces and heat affected zone. It is discovered that stress singularity exists at the interfaces and heat affected zone. The computer program based on boundary element method is utilized in this study. A mathematical model is implemented based on results from several experiments performed at and around the welded interfaces and heat affected zone of disimilar metal under static and dynamic loadings. This study is to investigate the characteristics of the deformation and fracture behavior around interfaces for friction welded materials under static tensile load. Also, the stress distribution at the tip of crack is analyzed by using BEM based on Kelvin's solution of 2-dimensional binding zone. The results of BEM are identical with those in case of considering interfaces of both heat affected zone. Also, stress singularity at the tip of interfaces appears when the elastic modulus ration is 1.07.
차용훈,김하식 한국산업안전학회 1996 한국안전학회지 Vol.11 No.4
In studying the fatigue strength of fillet welded the section of pressure vessel pad, this study was to evaluate the effect of weld toe notch and to compare the results of numerical analysis with the results of fatigue experiments of fillet welded A516 grade 60 steel specimens. The fatigue life for the Bead welded specimen was about 1.4 times as much it as the Wad welded specimen. Also, The fatigue life for the 2Pad welded specimen was about 1.5 times as much it as the 1ad welded specimen. In da/dN-ΔK curve, the fatigue crack growth rate for the lead welded specimen appeared higher than that of the 2Pad welded specimen in the same initial region of ΔK, had a similar inclination in the stabled region.