• Journal of Ocean Engineering and Technology
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• v.13 no.3 s.33
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• pp.49-56
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• 1999

Welding is a reliable process and is mainly adopted for fabricating heavy structures. Recently, transverse cracks in the weld metal is serious problem, and they affect cost, efficiency, safety and joint reliability for various welded structures. In this view of point, this study investigated the potential factors for weld metal transverse crack. The main results obtained are as follows; 1) The content of diffusible hydrogen in the commercial flux cored are welding wire was remarkable change by manufacturer. 2) The diffusible hydrogen content was thd main factor for weld metal transverse cracks. 3) Weld metal was immune to transverse cracking under the condition of low diffusible hydrogen content of high restraint condition. 4) The factors for weld metal transverse crack would be the content of diffusible hydrogen and restraint of weld joint.

• BMB Reports
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• v.38 no.2
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• pp.161-166
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• 2005

Functional protein of MB78 bacteriophage having apparent molecular weight of 22 kDa is expressed from 1.7 kb HindIII G fragment. The nucleotide sequence of this fragment showed two open reading frames of 222 and 196 codons in tail-to-tail orientation separated by a 62-nucleotide intercistronic region. The ORF of 22 kDa protein is present in opposite orientation, i.e. in the complementary strand, preceded by a strong ribosomal binding site and a promoter sequence. Another ORF started from the beginning of the fragment whose promoter region and translational start site lies in the 0.45 kb HincII U fragment which is located next to the HindIII G fragment, that has the sequence for DNA bending. 3' end of the fragment has high sequence homology to the EaA and EaI proteins of bacteriophage P22, a close relative of MB78 phage.

• Proceedings of the KWS Conference
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• v.43
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• pp.150-152
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• 2004

This study was aimed at evaluation of residual stress of steel pipe structures. The production process of pipes was complex (at first bending was done by roll forming or press forming and welding was final process of making of steel pipes). So there could be effected high residual stresses in steel pipes. In order to evaluate the changes of residual stress the locations of measurement were selected carefully. Measurements of residual stress were done for various kinds of pipes (shapes in circular and square). For the evaluation of residual stress, hole-drilling method (ASTM E837 was applied. The results showed that along the weld Eine high tensile stress were measured as effected, and high tensile stresses were measured where large plastic deformation developed. Through these efforts, experimental results could be more effectively assisted by numerical method.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.1003-1008
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• 2001

It is recently reported that bond failure can be initiated in the region where maximum bending moment and shear force is acted by accompanying shear deformation after flexural crack in full-scale RC beams strengthened by CFRP. Such a shear deformation effect causing bond failure is relatively little in the case of small-scale specimens. So, additional reinforcing details to the critical beam section where maximum moment and shear were acted is required to prevent the bond failure caused by the shear deformations. The U-type wrapping methods by CFRP to the critical beam section is proposed and tested in this paper. Also, the applicability of design bond strength derived from the tests of small-scale beam was investigated by the full-scale RC beam strengthened by CFRP.

• Journal of Ocean Engineering and Technology
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• v.5 no.2
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• pp.85-93
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• 1991

피로 파괴연구의 급격한 발전에 따라 최근의 기계나 구조물들은 많은 분야에서 손상허용설계원리에 근거하여 설계되고 있다. 이러한 상황 하에서 피로파손의 정확한 특성을 밝히는 것은 신뢰성을 고려한 기계나 구조물의 설계에 있어 가장 중요한 요인이 된다. 피로파손은 많은 랜덤요소를 내포하고 있으므로 실험결과 분석 및 수명예측을 분석하기 위해서는 통계학적 해석이 요구되고 있다. 본 연구의 목적은 회전굽힘피로시험을 수행하고 피로수명을 분석하는데 정규분포, 대수분포, 지수분포 및 Weibull분포를 이용하여 실험결과와 비교하고 파손확률을 찾는데 있다.

• Journal of Korean Society for Quality Management
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• v.36 no.4
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• pp.29-36
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• 2008

최근 자동차 경량화를 위한 부단한 노력이 진행되고 있다. 이 목적에서, HSS (high strength steel)는 전통적인 연강 (mild steel)의 대안으로 널리 사용되고 있다. 본 연구의 목적은 판금의 형단조에 있어서의 공구와 공정설계를 위하여 HSS의 스프링백(springback)을 정확히 예측하기 위한 성공적인 방법론을 추구하고자 함이다. 연구를 위하여 먼저 스프링백의 개념과 그의 측정치들을 설명했으며 U-draw bending 시험을 수행하였다. 시험 결과 및 선정된 파라메터들 중심의 수행평가기준에 근거하여, 주어진 파라메터 조합들을 중심으로 유한요소 해석을 수행하였다. 직교배열을 통하여 스프링백에 대한 인자 효과들을 포괄적으로 분석하였으며 최적 인자 조합들을 도출하였다. 이 과정에서 직교배열상의 한 조합 전체의 데이터가 가용하지 않는 문제가 수반되었으며, 반복적으로 signal-to-noise 비(ratio)를 개선해가는 기법을 적용하여 해결하였다.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.31B no.9
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• pp.112-123
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• 1994

In this paper, inspection and subpixed alignment algorithms of SMD's (Surface Mounting Devices) using fuzzy morphology are proposed. First, camera calibration is performed and then the inspection algorithm detects defects such as lead bending and breaking using the ruler generated by fuzy morphology. The SMD having no defects is tested whether it is mounted in the specified position or not. The proposed subpixel alignment algorithm detects accurately orientation and position using subpixel interpolation. It consists of two parts: preprocessing and main processing steps, in which corner points and coarse orientation of a SMD are detected, and interpolation is used to obtain final parameters with wubpixel accuracy. The computer simulation shows that the proposed algorithms give more accurate parameters, and they can be applied to fast and accurate automatic surface mounting systems.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.03a
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• pp.188-191
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• 1997

In the recent sheet metal forming simulations, it increases to adopt the dynamic explicit method for an effective computation and the elastic-plastic formulation for stress recovery. It is inevitable in the dynamic explicit method that some noises occur and sometimes partly spoil results of simulations. It is severer when complicated contact conditions are included in simulations. An effective method to control these noises is introduction of damping effects. In this paper, the concept of contact damping is introduced in order to suppress noises due to complicated contact conditions. This is checked by analyzing a simple sheet metal forming process(U-bending). From the computational results, it is shown that the contact damping can effectively control the noises due to contacts and develop more reliable internal stress states.

• Journal of Welding and Joining
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• v.5 no.4
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• pp.12-21
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• 1987

To investigate the suitability of nitrogen gas as an internal purging gas, various properties of GTA welded joints of duplex, 316L stainless steel, Cu-Ni alloy pipe using nitrogen purging gas were evaluated with reference to onew purged with argon gas. Mechanical properties evaluated by the tensile, bending test, and hardness value of welded joints with nitrogen gas purging did not show any difference those with argon gas. General and local corrosion rates of each welded joint prepared by nitrogen gas purging also showed no difference with those prepared by argon gas. Based on the present test results it is confirmed that nitrogen is a suitable purging gas for GTA welding of stainless steels and nonferrous piping systems, which can be used at lower cost instead of argon.

• Journal of Advanced Marine Engineering and Technology
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• v.16 no.3
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• pp.51-57
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• 1992

Authors had analyzed the Press machine's vibrational characteristics by Substructure Synthesis Method. This paper discribes the structural Dynamic Optimization for the machine using Sensitive Analysis Method. The substructure synthesis method and sensitive analysis methods are used for the vibration analysis and structural modification. The results obtained are as follows ; 1. The tooling precision of the press machine is ruled by the bending vibration of the slide. 2. The structural Modification Method for minimizing impact responses is proposed, and modal analysis and sensitive analysis method are introduced to solve it. 3. The impact responses of running machine were reduced to 40% of the unmodified machine by using the proposed method.