• Journal of Welding and Joining
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• 제33권6호
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• pp.27-35
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• 2015

Laser welding sector in the automotive industry has been widely recognized as one of the most important bonding processes, such as parts welding. Efforts to improve productivity and weld quality have been progressing steadily. In addition, laser welding is suitable for welding process that can produce high-quality welds suitable for flexible production and small quantity batch productions. In order to ensure the rigidity of the material, high strength material are applied to more than 1 GPa class body parts and automotive bumper beams. However, not only the situation is that the trend of domestic research, but also development is based on product molding considering freedom of shape where reinforcement is applied to meet the safety regulations and high-speed crash performance, despite the use of high strength materials. The tendency for heat-affected zone (HAZ) softening phenomenon common in areas of laser welded high tensile steel welding confirmed the occurrence of weld softening effect according to the process parameters. Based on this, range of process parameters could be selected for ensuring weld quality.

• 한국강구조학회 논문집
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• 제10권2호통권35호
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• pp.303-315
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• 1998

크레인 주행거더에 발생된 피로균열에 대한 보수방법으로 stop-hole(5mm 또는 9mm), stop-hole에 고력볼트 체결, 용접. 첨판과 고력볼트에 의한 4가지 보수방법을 적용하였다. 이중에서 stop-hole로 보수를 한 경우와 용접보수를 한 경우에는 재균열이 발생하였다. 그러나 stop-hole에 고력볼트를 체결한 경우 및 첨판과 고력볼트로 보수한 경우에는 재균열이 발생하지 않았다. 보수전과 보수후 피로강도를 비교해보면 stop-hole 또는 stop-hole과 고력볼트로 보수를 한 경우에는 모두 보수전과 동등한 피로강도를 얻었다. 용접보수를 할 경우에는 정확한 시공이 시행되면 보수전과 동등한 피로강도를 기대할 수 있지만. 시공이 잘못되면 피로강도가 현저하게 저하될 수 있음을 알 수 있었다. 피로균열이 발생된 위치에 첨판과 소요볼트를 시공할 수 있는 조건이라면 첨판과 고력볼트로 보수하는 것이 가장 확실한 보수법임을 알 수 있었다.

• Steel and Composite Structures
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• 제21권5호
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• pp.1017-1029
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• 2016

When a welded circular hollow section (CHS) tubular joint is subjected to brace axial loading, failure position is located usually at the weld toe on the chord surface due to the weak flexural stiffness of the thin-walled chord. The failure mode is local yielding or buckling in most cases for a tubular joint subjected to axial load at the brace end. Especially when a cyclic axial load is applied, fracture failure at the weld toe may occur because both high stress concentration and welding residual stress along the brace/chord intersection cause the material in this region to become brittle. To improve the ductility as well as to increase the static strength, a tubular joint can be reinforced by increasing the chord thickness locally near the brace/chord intersection. Both experimental investigation and finite element analysis have been carried out to study the hysteretic behaviour of the reinforced tubular joint. In the experimental study, the hysteretic performance of two full-scale circular tubular T-joints subjected to cyclic load in the axial direction of the brace was investigated. The two specimens include a reinforced specimen by increasing the wall thickness of the chord locally at the brace/chord intersection and a corresponding un-reinforced specimen. The hysteretic loops are obtained from the measured load-displacement curves. Based on the hysteretic curves, it is found that the reinforced specimen is more ductile than the un-reinforced one because no fracture failure is observed after experiencing similar loading cycles. The area enclosed by the hysteretic curves of the reinforced specimen is much bigger, which shows that more energy can be dissipated by the reinforced specimen to indicate the advantage of the reinforcing method in resisting seismic action. Additionally, finite element analysis is carried out to study the effect of the thickness and the length of the reinforced chord segment on the hysteretic behaviour of CHS tubular T-joints. The optimized reinforcing method is recommended for design purposes.

• 대한기계학회논문집
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• 제8권6호
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• pp.569-575
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• 1984

본 연구에서는 가장 하혹한 부식 환경 분위기에서 널리 사용되는 오오스테나 이트계 스테인레스 강재 용접부에 대해 비등 염화 마그네슘 용액 중에서의 SCC 발생 및 전파특성을 초기 응력강도계수(initial Stress intensity factors) $K_{Ii}$ 값에 대하여 비교, 검토함으로서 모재, 용접열 영향부, 용착금속 및 비이드 형상에 따른 용 접부의 SCC 감수성을 정량적으로 구명하였다. 또한 이상과 같은 각 부분의 SCC 특성 을 용접부의 조직적 및 기계적 특성 변화와 관련시켜 고찰하였다.

• 한국전산구조공학회논문집
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• 제20권4호
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• pp.443-451
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• 2007

강바닥판 피로손상을 억제할 수 있는 유효한 방법의 하나로 데크 플레이트의 판 두께를 증가시키거나 세로리브의 보강 등에 의한 강성 증가를 고려할 수 있는데, 이 강성증가는 일반적으로 윤하중에 의한 강바닥판의 국부변형 억제 등에 효과가 있을 것으로 판단된다. 따라서 본 연구에서는 강바닥판교의 피로균열이 빈번히 발생해 가장 문제가 되는 U-rib와 가로리브 연결 상세부의 발생응력을 최소화할 수 있도록 벌크헤드플레이트나 수직리브와 같은 보강상세의 부착에 따른 변수로 정밀 구조해석을 수행하였다. 그 결과, 벌크헤드플레이트는 전체적으로 연결 상세부의 주응력을 경감시키나, 피로균열이 발생되는 용접 지단부에서는 오히려 응력집중이 커지는 경향을 나타내는 것을 알 수 있었다. 그러나 수직리브는 용접 지단부에서 응력집중을 경감시키는 효과를 나타내어 벌크헤드플레이트의 보강보다는 수직리브의 보강이 더 효율적일 것으로 판단된다.

• 대한토목학회논문집
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• 제2권4호
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• pp.23-32
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• 1982

강구조물(鋼構造物)의 안전유지(安全維持) 및 보수보강(補修補强)에 필요한 자료(資料)를 얻기 위해, 공용이역(供用履歷)을 갖는 강재(鋼材)와 갖지 않는 강재(鋼材)의 기계적(機械的) 성능(性能) 및 인성변화(靭性變化)를 실험적(實驗的) 방법(方法)을 통(通)해 비교검토 하였다. 본(本) 연구(硏究)에서는, 공용중(供用中)에 받은 피로누적(疲勞累積)에 의한 경화(硬化) 및 취화인성저하(脆化靭性低下)등을 검토하였으며, 파악된 사항이 강구조물(鋼構造物) 연결방법(連結方法)에 사용되고 있는 용접(鎔接)에 미치는 영향을 고찰하였다. 그 결과(結果), 경화(硬化) 및 취화(脆化)의 영향은 강도증가(强度增加) 보다 인성저하(靭性低下)에 더 많은 작용을 하였으며, 강구조물(鋼構造物) 연결방법(連結方法)으로 채택한 용접(鎔接)에서도 같은 경향을 보였다. 또한 공용이역(供用履歷)을 갖는 강재(鋼材)와 갖지 않는 강재(鋼材)를 용접(鎔接)하였을 경우에는 상온(常溫)에서도 취성(脆性)을 나타내고 있음을 알 수 있었다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 춘계학술대회 논문집
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• pp.132-137
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• 2012

To enhance the CAE accuracy, the definition of material behavior is one of key influence on the result. In case of plastic material with fiber reinforcement, the anisotropic material behavior should be taken into account to increase of CAE accuracy. BASF has developed an innovative CAE tool, ULTRASIM$^R$, which is capable of generating material models of thermoplastic materials for structural simulation. ULTRASIM$^R$, not only the glass fiber orientation effect, but also the weld line effect, tensile-compression anisotropy, strain rate effect are combined in a non-linear material law, which will be evaluated in a unique failure criterion, thus resulting in an highly accurate CAE approach.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.299-304
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• 2008

This paper presents plastic limit loads of piping branch junctions with local wall thinning under combined pressure and in-plane bending, based on systematic three-dimensional finite element limit analyses using elastic-perfectly plastic materials. An ideal branch junction without weld or reinforcement around the intersection is considered with two locations of wall thinning; one in the run pipe, and the other in the branch pipe. Based on FE results, effects of thinning geometries on plastic limit moments are quantified and simple approximations of plastic limit loads are proposed.

• Journal of Welding and Joining
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• 제15권6호
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• pp.66-77
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• 1997

In the present work, Taguchi method for electron beam welding(EBW) process in AISI 4130 steel plate has been adopted for investigating the contribution of effect of welding variables. $A L_8(2^7)$ orthogonal array is adopted to obtain the effect of adjustment parameters. The adjustment parameters consist of accelerating voltage, beam current, travel speed and focus currrent. And the quality features selected for the EBW process are bead width of weldment, reinforcement, penetration depth, undercut and area of weld metal. Variance analysis is performed in order to check the effect of adjustment parameters on EBW. The mechanical properties of electron beam welded joints for each heat treatment conditions are investigated in comparison with those of base metal, especially from the view point of tensile and impact properties.

• 한국공간구조학회논문집
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• 제22권3호
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• pp.73-80
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• 2022

Unlike the CFT retrofit method, The EPFT retrofit method, which fills the steel tube with engineering plastic, does not require a separate concrete forming work and is a lightweight seismic Retrofit Method. In this study, an prototype model of the EPFT was proposed, and to analyze the seismic performance, an independent specimens and a reinforced concrete column were fabricated to conduct a seismic performance test. As a result of loading test of the independent specimens, the strength was increased compared to the steel tube column without internal filling, and the ductility ratio did not significantly increase due to the falling off of the weld. As a result of loading test of the concrete reinforcement specimen, the strength, ductility ratio, and energy dissipation were increased, and the number of cracks by loading step decreased compared to the non-reinforced specimen.