• Journal of Welding and Joining
• /
• 제29권3호
• /
• pp.70-75
• /
• 2011

Welding process generates distortion and residual stress in the weldment due to rapid heating and cooling. Welding distortion and residual stress in the welded structure result in many troubles such as dimensional inaccuracies in assembling and safety problem during service. The accurate prediction of welding residual stress is thus very important to improve the quality of weldment and find the way to reduce itself. This paper presents the simulation of welding-induced residual stress analysis to examine the cause of cracking in the SUS-overlay welding specimen at FPSO Moon Pool structure.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2002년도 추계학술대회 논문집(I)
• /
• pp.225-231
• /
• 2002

The problem of welding stresses and fatigue behavior is the main concerns of welding research fields. The residual stresses and distortion of structures by welding is exert negative effect on the safety of mechanical structures. That is, expansion of material by high temperature and distortion by cooling during welding process is caused of tensile and compressive residual stresses on welding material, and this residual stresses reduce fracture and fatigue strength of welding structures. The accurate prediction of residual stress and redistribution due to fatigue crack propagation of weld zone is very important to improve the quality of weldment. In this study, a finite element modeling technique is developed to simulate the redistribution of residual stresses due to fatigue crack propagation of weld zone.

• 대한용접접합학회:학술대회논문집
• /
• 대한용접접합학회 2004년도 추계학술발표대회 개요집
• /
• pp.254-256
• /
• 2004

The purpose of this study is to establish the control method of angular distortion at the weldment of the pressure hull penetration. In order to do it, comprehensive experiment and FEA were performed to evaluate the distortion behavior for the weldment of HY-100. Based on the results, a proper deposit sequence for the both sides X groove penetration weldment was established. In addition, a proper welding sequence was proposed by evaluation of bending restraint intensity with size and position of pressure hull penetration.

• 한국해양공학회지
• /
• 제22권6호
• /
• pp.100-105
• /
• 2008

The block assembly of ship consists of a series of heat processes such as cutting, bending, welding residual stress relaxation and fairing With the fast development of computers, the thermal elasto-plastic analysis method has become a versatile tool for practical applications in the ship production. If numerical analysis is proved to be an advantageous tool to predict the residual deformation due to various heat processes, the optimum methods which can remove the welding distortion can be presented at each assembly stage, which will result in great progress in improving the accuracy of block assembly. In order to minimize the weld-induced angular distortion in thick weldments, this paper proposes the optimum groove design for various plate thickness as the distortion control method. The validity of this method has been substantiated by a number of numerical simulations and experiments.

• 한국산학기술학회논문지
• /
• 제14권4호
• /
• pp.2021-2026
• /
• 2013

냉각법은 용접과 동시에 용접토치로 부터 일정한 거리 떨어져 있는 용접부를 냉각기체를 이용하여 냉각시켜 용접변형을 최소화시키는 기술이다. 냉각기체에 의해 용접부의 온도를 감소시키면 용접부에 발생하는 열응력이 감소되고 그 결과 소성변형이 최소화되어 최종적으로 용접좌굴과 각변형을 방지할 수 있는 기술이다. 이 방법은 용접부 표면을 냉각시키는 방법으로 용접부를 직접 냉각시킴으로서 현장 적용성 면에서 다른 용접변형 방지법 보다 효율적이다. 본 연구에서는 맞대기용접을 대상으로 용접 후면의 냉각조건(폭, 길이)을 변화시켜 열탄소성해석을 실시하여 해석적방법으로 용접 각변형에 미치는 영향을 검토하였다. 그 결과 용접토치와 냉각 선단과의 거리는 25mm, 냉각 길이는 80mm, 냉각 폭은 30mm의 경우가 각변형 저감에 제일 큰 효과가 있었다. 이때 냉각길이는 길면 길수록 각변형을 감소시킨다.

• 대한용접접합학회:학술대회논문집
• /
• 대한용접접합학회 2000년도 특별강연 및 추계학술발표대회 개요집
• /
• pp.170-172
• /
• 2000

In this research, newly proposed heat source equations were calculated to predict micro distortion of small structure in laser welding and compared with experimental results which were measured using laser speckle metrology. A finite element code, ABAQUS is used for the heat transfer analysis with a three-dimensional plane assumption. The results suggest that weld distortion is varied according to the heat source of the. laser beam.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2004년도 춘계학술대회 논문집
• /
• pp.872-877
• /
• 2004

Welding residual stresses are the main topics of welding research fields. The residual stresses and distortion of structures by welding exert negative effect on the safety of mechanical structures. That is, expansion of material by high temperature and distortion by cooling during welding process are caused by tensile and compressive residual stresses in welding material, and this residual stresses can induce fracture and fatigue problems of welding structures. The accurate prediction of residual stress and relaxation due to mechanical loading of weld zone is very important to improve the quality of weldment. In this study, a finite element modeling technique is developed to simulate the relaxation of residual stresses due to mechanical loading. The effects of load ratio for static and cyclic loading are evaluated based on analytical results.

• 한국레이저가공학회지
• /
• 제11권3호
• /
• pp.21-24
• /
• 2008

Hybrid laser welding technology is a good process to reduce a thermal distortion and increase the productivity. However, it requires a high investment and a massive modification of the fabrication line such as a gantry system, milling machine for the edge preparation, high power laser system and weld machine. Therefore the development of an economical laser welding system is a crucial point to apply this system in shipbuilding yard. In this study, a portable hybrid laser welding carriage was developed for I-butt joint without edge milling. It is expected that the carriage type system could reduce investment cost.

• 대한용접접합학회:학술대회논문집
• /
• 대한용접접합학회 2001년도 추계학술발표대회 개요집
• /
• pp.121-124
• /
• 2001

The main characteristic of the Electron Beam Welding technique is its high energy density which produces thin and deep welds with very little distortion. High accelerated electrons, focused in a beam of 0.5 ∼ 2mm diameter, produce narrow welds with deep penetration. The result is a small HAZ as well as a low and uniform distortion which is predictible within very narrow limits. But the small diameter of the EB increases the requirements for the equipment control system for centering the beam on the welding joint in order to avoid any lack of fusion. Therefore, in this paper, we introduce the system developed at our company and the quality of welding zone, the detail function of system.

• 대한용접접합학회:학술대회논문집
• /
• 대한용접접합학회 2007년 추계학술발표대회 개요집
• /
• pp.14-16
• /
• 2007