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Featured researches published by Sang-Hyong Lee.


International Journal of Modern Physics B | 2006

A STUDY ON HYSTERETIC MODEL FOR WELD METAL AND ITS EFFECT ON BEHAVIOR OF STEEL PIPES WITH A WELDED JOINT

Kyong-Ho Chang; Gab-Chul Jang; Sang-Hyong Lee

The weld metals used in welding process influences on behavior of steel structures under monotonic and cyclic loading. Because weld metals have different characteristics than structional steels for stress-strain relationship and mechanical properties. Therefore, to predict behavior of steel structure manufactured by welding process, a hysteretic model for weld metal is necessary. In this paper, to formulate the hysteretic model for E71T-1 weld metal, tensile tests and low cycle fatigue tests were carried out. A formulated hysteretic model applied to 3-dimensional elastic-plastic finite element analysis was proposed by the authors. To investigate the effect of weld metal on behavior of steel pipe members, numerical analyses of steel pipe with a welded joint were carried out under monotonic and cyclic loading. The effect of weld metal was clarified by comparing analytical results both steel pipe with consideration of weld metal and without consideration of weld metal.


Welding International | 2015

Effects of static loads on weldability repair/reinforcement by welding for steel bridges in service

Yasuo Agano; Sang-Hyong Lee; Shouichiro Fujihira; You-Chul Kim

Experiments under static loads were carried out in order to investigate the possibility of repair/reinforcement by welding. Preventing the influence on the experimental devices due to the welding current by isolating between the jigs and the experimental devices, the stable experiments could be carried out. For the cruciform joints and I-shape joints, semi-auto CO2 gas welding was carried out under compressive static loads on the assumption of the dead load. As the experimental results, any cracks were not found. In the cruciform joints with multi-pass welding, there was a tendency that the longer the weld length became, the larger the magnitude of out-of-plane displacement became. In the actual construction, it was verified that repair welding under static loads could be carried out without welding defects by confirming repair weld length, heat input, inter-pass temperature and so on.


Materials at High Temperatures | 2006

Features of thermal stress generated by welding and cutting of dissimilar steels

Sang-Hyong Lee; K.H. Chang; G.C. Jang

Abstract Bridges that are damaged by an increase of vehicle load, corrosion and earthquake need repair or strengthening. Repair procedures of steel bridge generally include cutting, bolting and welding, which occasionally bring in a stress concentration within limit range. Therefore, a chain of confirmation about the safety of the structure is necessary. A safety evaluation method that considers heat effect is necessary to repair damaged structure by welding. Generalized welding and cutting residual stress is employed to estimate the safety of structure during the welding repair work. This research investigates the features of thermal stress generated by welding and cutting. The pattern of cutting residual stress distribution is classified with respect to the ratio between length and width of plate. The features of residual stress generated by welding or cutting are reported.


Welding International | 2015

Verification of weldability under cyclic loads repair/reinforcement by welding for steel bridges in service

Yasuo Agano; Sang-Hyong Lee; Shouichiro Fujihira; You-Chul Kim

In welded structures, it is thought that the crack in welds may be related to collapse of structure. So, the investigation on the relation between weld crack and acting loads in repair/reinforcement work by welding is performed. There are three kinds of load conditions in welding of the site: no loads, static loads and fluctuated loads. In the previous paper, welding under static loads was carried out, it was confirmed that weld crack was not generated. In this case, installation of bents and traffic control were required. So, concerning the social and economical situation, welding under fluctuated loads without traffic control was desirable. In this paper, we performed CO2 arc welding under cyclic loads on the assumption that fluctuated loads, examinations for detection of the crack were carried out. The hot cracks were observed at I-type joints. From the results of fractography, projections of cellular dendrite and striations were observed. And it was known that the magnitude of root gap opening displacement (Δδ) and heat input (Q) was induced the hot crack in the weld metal.


International Journal of Modern Physics B | 2006

EFFECT OF THE DEGREE OF RESTRAINT AGAINST THERMAL EXPANSION AND CONTRACTION ON WELDING RESIDUAL STRESS

Sang-Hyong Lee; Kyong-Ho Chang; Gab-Chul Jang

Steel bridges increased considerably since 1960s in Japan. That is due to the lightness and long trend in bridge construction. Bridges, which are damaged by an increase in vehicle load, corrosion, earthquake, and so on, need repairing or strengthening. Repair procedures of steel bridge generally include cutting, bolting and welding procedures. These procedures, cutting, bolting and welding, occasionally bring about a stress concentration within the limit range. So, a chain of confirmation against the safety of structure is necessary. A safety evaluation method, which has regard to heat effect, is necessary to repair damaged structure with welding. Generalized welding residual stress is useful employ, to estimate the safety of structure during the repair work with welding. This research investigates the features of thermal stress generated by welding. The pattern of welding residual stress distribution was classified according to the ratio between length and width of plate. With those results, the features of residual stress generated by welding were generalized.


Transactions of JWRI | 2007

Mechanical Characteristics of Welds Joined by Newly Developed Welding Wire with a Phase Transformation at Low Temperature (II)

You-Chul Kim; Sang-Hyong Lee


Quarterly Journal of The Japan Welding Society | 2010

Effects of Static Loads on Weldability

Yasuo Agano; Sang-Hyong Lee; Shouichiro Fujihira; You-Chul Kim


Quarterly Journal of The Japan Welding Society | 2011

A Proposal of Repair Procedure by Welding under Cyclic Loads

Yasuo Agano; Sang-Hyong Lee; Shouichiro Fujihira; You-Chul Kim


Quarterly Journal of The Japan Welding Society | 2010

Verification of Weldability under Cyclic Loads

Yasuo Agano; Sang-Hyong Lee; Shouichiro Fujihira; You-Chul Kim


Transactions of JWRI | 2004

Features of Thermal Stress Generated by Welding & Cutting under Loading(Mechanics, Strength & Structure Design)

Sang-Hyong Lee; Kyong-Ho Chang; You-Chul Kim

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