• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2000년도 추계학술대회 논문집
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• pp.153-157
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• 2000

This paper presents possible defects when welded blank hydroforming and focus on wrinkling, and the die design to prevent this defect An explicit finite element code, PAM-STAMP, is used to simulate welded blank hydroforming process. The numerical results are compared to the experimental results in the aspect of deformed shape. An automobile subframe is taken as an example to carry out finite element analysis.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2004년도 가을 학술발표회 논문집
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• pp.421-428
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• 2004

Various type of welded joints of the ship structure have been examined numerically and experimentally under bending and tensional cyclic constant-amplitude loading. Cyclic loading on structures can produce failures not readily predicted by conventional static analysis. The aim of a benchmark study is achieved with a generalization of the reference stress concept. Also different methods and procedures exist for the computation of the welded structure hot-spot stress a welded joints. These are either based on the extrapolation of stresses at certain reference points on the plate surface (or edge) close to the weld toe-as known from experimental investigations- or on the linearization of stresses in the through-thickness direction. In the present paper, the different methods are reviewed and applied to four different details in order to compare the methods with each other and to illustrate the differences.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.425-430
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• 2001

The mechanical behavior of two rectangular plates spot-welded under bending is investigated in detail. The focus of the analysis is to evaluate the effect of thickness of reinforced plates with equivalent thickness. The results of this investigation are compared from detailed finite element analysis and experiments of the plates spot-welded for various parameters, such as aspect ratio, area ratio, and distance ratio of spot-welding points. The study is carried out using the equivalent thickness of the reinforced plates spot-welded.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2001년도 추계학술대회 논문집
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• pp.235-239
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• 2001

The bogie of high speed freight car running on conventional line is welded bogie modeled on Y25 bogie developed in Europe. Y25 bogie has speed limit of 110km/h. But it has limiting factors to speed-up as increasing maintenance cost and friction parts pedestal. And also it was reported that cracks are found in the parts where center beam meet bolster and endbeam near bracket for braking part. This study includes stress analysis improved structure of welded bogie for strength evaluation by numerical method and experimental method. According to the study, new configuration bogie shows improvement in strength.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1998년도 제28회 추계학술대회
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• pp.59-66
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• 1998

This paper presents friction and wear related results of thermite and gas pressure welded rails under various environmental contact conditions. A welded rail which is fabricated by thermite welding and gas pressure one has been tested over full range of test conditions in a pin-on-disk wear testing machine. The results show that the friction coefficient and wear rates of a welded rail are heavily dependent on the contact pressures and sliding environments for two welding methods such as thermite and gas pressure weldings.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2004년도 춘계 학술발표대회 개요집
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• pp.249-251
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• 2004

According to our fatigue tests carried out at 20 ㎐, R=0.1 on transversely butt-welded joints, fatigue strengths of as-welded specimens, that is, specimens having residual stress are higher than those of annealed specimens in short hie range, but vice verse in long life range. This behavior seems to be concerned mainly with residual stress relaxation by applied loading. After analyzing the welding process, we conducted finite element analysis to quantify the degree of residual stress relaxation. By taking into account residual stress relaxation, modified Goodman diagram, and nominal stress, we evaluated the fatigue life of the welded joint from the S-N curve for the parent material. The estimated results are in a good agreement with the experimental results.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2003년도 춘계학술발표대회 개요집
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• pp.263-265
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• 2003

The transverse crack, a type of cold crack, occurs perpendicular to the axis of the weld interface, longitudinal residual stresses ($\sigma$k direction) are more important in transverse crack occurrence from my own experience. Specimens were fabricated and welded under actual construction conditions, and then residual stresses of longitudinal stresses were measured for different welding conditions with SAW and FCAW process. The residual stress values for the specimen welded Interpass temperature below 30$^{\circ}C$ was higher than the specimen welded interpass temperature of 100～120$^{\circ}C$. And also the residual stress values for a specimen measured at weld surface, as welded condition, was higher than that of longitudinal residual stresses that was measured from a small test piece, due to the residual stress was relieved in the process of the cutting and machining. Transverse weld cracks were detected in the area of the maximum residual stresses both SAW and FCAW process.

• 한국구조물진단유지관리공학회 논문집
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• 제7권1호
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• pp.251-258
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• 2003

This study is to understand the characteristics of axial force behavior that operates to the part of continuous welded rail and to investigate the basic data for secure the structure's stability and retrofit of the track. To develop the FEM model that type of plate girder which is used in the domestic national railway among servicing railway type. It is to analyze the characteristics of axial force behavior according to equip of the expansion joint and support placing by using the axial force simulation in making the continuous welded rail. As the result of research on the parametric valuables through the analysis, it is investigated that 'FMFM type' is more efficient than the other support type. Also, it conclude that structures are having the expansion joint is the most safe condition.

• 소성∙가공
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• 제18권1호
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• pp.73-79
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• 2009

In order to investigate the formability of friction stir welded(FSW) tailor welded blanks(TWB) with respect to the base material's directional combination, aluminum alloy AA6111-T4 sheets were welded with three different conjoining types: RD-RD, TD-RD and TD-TD. Here, RD and TD represent rolling and transverse directions, respectively. For experimental formability study, three tests with gradual complexity were performed: the simple tension test with various weld line directions for uni-axial elongation, the hemisphere dome stretching test for biaxial stretching and the cylindrical cup deep drawing test. As a result, all three forming tests showed that RD-RD type samples exhibited the best formability, while TD-TD type sheets showed the least formability performance.

• 한국안전학회지
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• 제25권6호
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• pp.161-168
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• 2010

A series of fatigue tests have been performed on the non-load carrying fillet welded joints in order to quantitatively assess the fatigue characteristics due to the grindings and TIG(Tungsten Inert Gas) welding treatments. From the results of fatigue tests, it has been shown that the fatigue strengths at $2{\times}106$ load cycles were improved in the case of the grinding sand TIG welding treatments, and we could know that it is satisfying fatigue strength prescribed in fatigue design standard in general. Besides, from the results of fracture mechanics approaches, the geometric shape correction factors were the most dominant factors in the initial fatigue crack growth, but as the fatigue crack develops, the finite plate correction factor were became the most dominant factor, and the fatigue life on non-load carrying fillet welded joints could be relatively exactly estimated by using the relations between fatigue crack growth rate and stress intensity factor obtained from finite element analysis and existing proposed formulae.