• Journal of Welding and Joining
• /
• 제24권3호
• /
• pp.34-41
• /
• 2006

The CD (Capacitor Discharge) stud welding utilizes the arc heat and pressure to attach the stud to the workpiece, which consists of the arc. ignition, arcing and pressure welding stages. In order to predict the dynamic behavior of the CD stud welding process, mechanical and electrical models are employed in this work. While the mechanical model estimates the duration of each stage, the electrical model predicts the voltage and current waveforms using the RLC circuit. Effects of process parameters such as the electric components and spring force are analyzed through simulation. It is found that the contact resistance and gap between the stud and base metal influence the tip fusing and arcing duration. The calculated results showed reasonably good agreements with the experiment results.

• 수산해양기술연구
• /
• 제36권4호
• /
• pp.322-328
• /
• 2000

남해안 연근해에서 조업하는 정치망 어선에 양망작업시 보조기계로 사용되는 캡스턴의 드럼에서 용접부 온도분포 및 구배를 해석한 결과의 주요 사항은 다음과 같다. 1. 용융부 근처는 냉각개시 1초 이내에 950$^{\circ}C$/sec, 10초 이내는 40$^{\circ}C$/see 정도의 급격한 냉각속도가 형성되었다. 2. 열영향부(HAZ)는 용접 후 1초가 경과할 때 370$^{\circ}C$/sec의 가열속도로 온도가 증가한 후, 이 후 25$^{\circ}C$/sec 냉각속도로 온도가 감소한다. 용접종료 10초 후 모재 내부에는 1.64$^{\circ}C$/mm, 40초가 지났을 때는 0.26$^{\circ}C$/mm 정도의 온도구배가 형성되었다. 3. 용접부 근처는 길이 방향을 따라 격심한 온도편차를 보이고 있으나 두께방향으로는 거의 나타나지 않는다. 이 결과는 향후 캡스턴 드럼의 용접부 최적설계시, 탄소성 열응력 및 열변형 거동을 해석하는 연구의 기초자료로 활용될 수 있을 것이다.

• Journal of Welding and Joining
• /
• 제33권6호
• /
• pp.60-66
• /
• 2015

Molten zone shape of pulse laser welding is affected by welding conditions such as beam power, beam speed, irradiation time, pulse frequency, etc. and is divided into conduction type and keyhole type. It is necessary to design heat source model for irradiation of laser beam in the pulse laser welding. Shape variables and the maximum energy density value of the heat source model are different depending on the molten zone shape. In this paper, pulse laser welding simulation for joining of cylindrical part and circular cover was carried out. The heat source model for pulse laser beam with circular path was applied to the heat input boundary condition, radiative and conductive heat transfer were considered for the thermal boundary condition. For each phase, thermal and mechanical properties according to temperature were also applied to analysis. Analytical results were in good agreement with the molten zone size of specimen under the same welding conditions. So, the reliability of the welding simulation was verified. Finally, the improvements for reducing residual deformation after cover welding could be reviewed analytically.

• Journal of Welding and Joining
• /
• 제24권4호
• /
• pp.22-26
• /
• 2006

In lap welding of zinc-coated steel, porosity formation is one of most significant weld defects, which is caused by zinc vapor generated between the steel sheets. Various solutions have been proposed in the past years but development of more effective method is a worthwhile subject to be investigated. In this study, autogenous laser welding and laser-TIG hybrid welding was applied to the lap welding of zinc-coated steel without gap, and weld pool behaviors were observed by using high speed camera and the porosity generation mechanism was analyzed. The weld defects were successfully eliminated by laser-TIG hybrid welding. This is because the leading TIG arc partially melted the upper sheet and vaporized/oxidized the coated zinc on the lapped surfaces prior to the trailing laser illuminating the specimen.

• Journal of Welding and Joining
• /
• 제30권4호
• /
• pp.31-37
• /
• 2012

In recent years, a demand for precision-welding is increasing in wide industrial fields for getting a high quality welded structures. Although laser welding is commonly used for precision-welding, gas tungsten arc (GTA) welding is also attempted as a precision-welding due to the cost benefit. However, welding heat causes an uneven temperature distribution leading to welding deformation. Since it causes geometric errors and degrades product quality, welding distortion recently rises as an important issue in the field of automobile parts. To control welding deformation, it is needed to design in shapes that can maximize stiffness against deformation during welding; control the welding sequence; minimize heat input; and weld allowing reverse deformation; etc. Thus it is necessary to find the one, among such approaches, that can minimize the deformation range by mathematical analysis and understand how effective it would be when it is actually used in industrial fields. This study performs analyses by numerical calculations and experiments for the De-Tent Lever, one of transmission part that requires precision the most among automobile parts, as the subject of experiment. Decrease in welding deformation is required for this part, since there is currently a trouble in guaranteeing precision due to angular deformation by welding between boss and plate. Finally the ways to minimize welding deformation has been suggested in this study through analyses on it.

• International Journal of Korean Welding Society
• /
• 제1권2호
• /
• pp.51-60
• /
• 2001

A prediction method for determining the welding residual stress by artificial neural network is proposed. A three-dimensional transient thermo-mechanical analysis has been performed for the $CO_2$ arc welding using the finite element method. The first part of numerical analysis performs a three-dimensional transient heat transfer analysis, and the second part then uses the results of the first part and performs a three-dimensional transient thermo-elastic-plastic analysis to compute transient and residual stresses in the weld. Data from the finite element method are used to train a back propagation neural network to predict the residual stress. Architecturally, the fully interconnected network consists of an input layer for the voltage and current, a hidden layer to accommodate the failure mechanism mapping, and an output layer for the residual stress. The trained network is then applied to the prediction of residual stress in the four specimens. It is concluded that the accuracy of the neural network predicting method is fully comparable with the accuracy achieved by the traditional predicting method.

• Journal of Welding and Joining
• /
• 제27권3호
• /
• pp.85-91
• /
• 2009

A roll projection welding machine is introduced to fabricate metallic sandwich plate consisting of a structured inner sheet with projection-like shape and a pair of skin sheets. To fabricate the metallic sandwich plate of consistent and good quality, two process monitoring methods are introduced; dynamic resistance monitoring and skin sheet temperature monitoring. Dynamic resistance monitoring has no time delay but gives only averaged value over plate width. Skin sheet temperature monitoring has certain amount of time delay but is good for predicting weld quality of specified position. By the two complementary monitoring methods, the characteristics of the new welding process is successfully understood.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2003년도 추계학술대회
• /
• pp.1752-1756
• /
• 2003

Welding automation in shipbuilding process, especially in the assembly line is considered to be a difficult job because welding part is too huge , various and unstructured for a welding robot to weld the whole part automatically. We developed an automatic welding robot to improve those difficult process. This paper show how to systematically operate the integrated automation system which consists of several robots. We introduce our software and system integration method. Specially we focus that network communication and operating process. The developed system visualizes the operation environment using Open Inventor and communicates with the entire system via TCP/IP and FTP.

• Journal of Welding and Joining
• /
• 제11권1호
• /
• pp.2-8
• /
• 1993

A literature review was conducted to gather informations available on the welding metallurgy of aluminum alloys, emphasized on characteristics in the heat affected zone(HAZ). Nominal metallurgical reactions that occur in aluminum alloys provide a basis for understanding aluminum welding metallurgy. However, welding reactions differ to some extent because of the relatively short times involved, and the non-isothermal heating excursed. For non-heat treatable alloys, welding primarily affects these alloys by annealing (recrystallization and growth) and to a less extent, changes in low temperature precipitates. In the case of heat treatable alloys, the resulting HAZ properties depend upon alloy composition, starting temper, heat input and post weld heat treatments.

• Journal of Welding and Joining
• /
• 제20권6호
• /
• pp.796-801
• /
• 2002

Corrosion and tensile properties of zircaloy-4 cladding tube having a laser welding part in elevated temperature are studied to present the criterion of quality evaluation in nuclear reactor and find the scientific basis of SCC, with laser welding method using by coupling up cladding tube to end cap. In the result of tensile test($400^{\circ}C$), the fracture is not happened in the welding part but base metal and the result of corrosion test($400^{\circ}C$ 1500psi steam), corrosion rate of the molten zone and PMZ is a little higher than the other zone.