• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2000년도 특별강연 및 추계학술발표대회 개요집
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• pp.43-45
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• 2000

Resistance Spot Welding has been one of the important process in the sheet metal fabrication of auto-body industry It is well known that the nugget formation of RSW is the major factor for the strength of the body. A high speed camera was used to consider initial melting and growth of the weld nugget in order to find out the nugget formation mechanism. It was observed that such mechanism had an effect on the dynamic resistance, which was a process parameter of resistance spot welding. Also, the relationship between the mechanism and process parameter was considered for the industrial application.

• Journal of Welding and Joining
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• 제12권2호
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• pp.76-86
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• 1994

Spot welding behavior of galvanized steel has been studied using both numerical and experimental techniques. The model that used to calculate temperature distribution within weldment is two-dimensional axis-symmetric finite difference method, and nugget sizes of specimen welded in condition of welding current and time has been estimated by experiment Results have shown that nugget sizes are increased in proportion to welding current and time, but the growth rate of nugget is decreased. Shear-tensile strength tests have shown interface fracture when welding current is 7, 9KA, welding time is 8-14cycle and 11KA, 8-10cycle respectively, but above 7, 9KA fracture shows button type. In button fracture, shear-tensile strengths have been proportional to nugget sizes.

• 한국산학기술학회논문지
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• 제11권9호
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• pp.3155-3160
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• 2010

최근 자동차 산업은 고효율 자동차의 개발에 박차를 가하고 있으며 이에 따라 차체 경량화 및 내식성 방지를 위한 고강도강 및 도금강의 사용이 증가하고 있다. 이에 따라 본 연구에서는 자동차 차체에 쓰이는 3종의 다른 강판에 대하여, 겹침 순서에 따른 용접 특성을 시뮬레이션 기법을 이용하여 분석하였다. 자동차 차체에 많이 사용되는 EDDQ 급의 도금강판 0.7t와 인장강도 440 MPa급의 440R 1.2t, 그리고 AHSS (Advanced High Strength Steel)인 DP 590 0.2t 판재에 대하여 겹치기 순서에 따른 용접 특성을 시뮬레이션 하였고, 너겟 성장 곡선 및 전류에 따른 너겟의 크기로 그 용접성을 분석하였다. 또한 용접 시 발생되는 각 접촉부의 접촉저항을 이용하여 겹침순서에 따른 너겟의 크기를 분석하였으며, 이를 통해 최적의 겹치기 순서를 제안할 수 있었다.

• 대한기계학회논문집
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• 제10권5호
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• pp.661-669
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• 1986

In this study, the resistance spot welding process of an aluminum alloy was analyzed through the numerical simulation including the electric contact resistance and the heat generation in the electrode. The finite element model was used to solve the electro-thermal responses in weld cycles. The resistance of the contact area was represented as the contact element modeling, but the thermal resistance between the contact surfaces was neglected. Welding tests of Alclad 2024-T3 aluminum alloy were made not only to get the input data for the numerical simulation, but also to compare the numerical results. The contact resistance was determined initially by the contact resistance tests and assumed to decay exponentially up to the solidus temperature. The temperature distributions and dynamic resistance obtained numerically were in good agreement with the experimental results. Numerical results revealed that nugget growth depends mainly on the heat generated in the workpiece and its contact area. The heat generated in the electrode has, however, only a little effect on the nugget growth, and the heat generation in the electrode-workpiece interface is initially high but decrease repidly.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1997년도 추계학술대회 논문집
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• pp.140-145
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• 1997

In case of spot-welded joints, the fatigue cracks generally originate from the weld interfaces of the neighborhood nugget tips, and propagate toward the outer surfaces of the sheets. Generally, because fatigue crack was observed in nugget around, strain gage was attached at nugget zone. Accordingly, it was very difficult to detect the generation time of fatigue crack in spot-welded joints and to measure the propagation speed of fatigue crack. We developed the non-destructive method, according to which th fatigue crack propagation rate can be quantitatively estimated by utilizing information obtained from strain gages bonded on the electrode indentations of spot welds. The results measured by real crack were compared with the data which was measured by strain gauge method in fatigue testing. And so fatigue strength was evaluated by stress intensity factor. In this study behavior of fatigue crack propagation under repeated load were considered.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1997년도 추계학술대회 논문집
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• pp.127-131
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• 1997

In systematic and orderly estimation of fatigue strength of the spot welded lap joints, because the influence of residual stress of fatigue crach initiation and growth is not negligible, there need to estimate fatigue strength considered residual stress at near spot weld part of the lap joints. Therefore, in this thesis, peformed stress distribution and residual stress analysis at near the spot weld part by F.E.M and X-ray diffraction method, and obtained the maximum principal stress considered residual stress at nugget edge by superposing residual stress at nugget edge by superposing their results. From the results obtained above, we could find that fatigue strength of the IB-type spot welded lap joints was rearranged by the maximum principal stress considered residual stress at nugget edge and was entirely low about 13 percents compare with that neglected residual stress.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1999년도 특별강연 및 춘계학술발표대회 개요집
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• pp.233-236
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• 1999

The welding residual stress should be considered in fatigue stress analysis because it develope during the process of the electric resistance spot welding and it causes bad affect on the fatigue crack initiation and growth at nugget edge of spot welded points. Therefore the accurate estimation of residual stress is crucial. In this study, nonlinear finite element analysis on welding residual stress generated during the process of the spot welding was conducted, and their results were compared with the experimental data measured by X-ray diffraction method. From the results, it was found that welding residual stress existed as tension in the nugget center and as compression around the nugget edge.

• Journal of Welding and Joining
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• 제19권6호
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• pp.622-629
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• 2001

The aim of this experiment is to establish the method that obtains symmetrically two nuggets in microresistance series spot welding. The sheets of austenite stainless steel STS304 applied to various electronic parts were experimented by the inverter welding power source of polarity controllable type and by the twin head for left and right electrode force to be controlled separately. The experimental results were obtained as follows : 1) When series spot welding was carried out by DC 1 pulse as welding current with same electrode force at left and right, the asymmetry of nuggets was resulted from the larger nugget of the (-) pole because of the Peltier effect. The dynamic resistance of weld spot at left and right was appeared differently according to the growth of nuggets. 2) When AC 1 cycle by welding power source of polarity controllable type was applied, the nuggets were almost symmetrically formed. 3) In a twin head, if the electrode force of (-) pole was larger than that of (+) pole, the diameters of two nuggets became to same. It was confirmed that the dynamic resistance of (-) pole was decreased to the same level as it of (+) pole. 4) Although the forces of left and right electrode were same, and only DC 1 pulse was applied, symmetric nuggets were obtained if the conductivity of (+) pole was lower than it of (-) pole.

• 한국식품과학회지
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• 제22권2호
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• pp.155-161
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• 1990

가열조리 냉동된 닭 가슴살 patty와 nugget을 계육가공공장으로부터 얻어서 진공과 비진공으로 포장한 뒤 $2-4^{\circ}C$로 냉장저장하였다. 이 제품의 품질을 28일간 4일 간격으로 측정하였다. 진공포장방법으로는 냉장저장된 제품의 미생물 총균수는 줄이지 못하였으며 비진공 포장된 제품의 총곰팡이 수는 실험기간 동안 증가한 반면 진공포장된 제품은 log값 3.5부터 정체기에 들어갔다. 진공포장은 TBA값의 증가를 막지 못했으며 유지방산 값은 실험기간 동안 낮은 일정한 값을 보였다. 진공 및 비진공포장 방법 그 어느 경우에도 제품색깔은 현저하게 변했다.

• International Journal of Korean Welding Society
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• 제5권1호
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• pp.53-59
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• 2005

Auto industry has employed resistance spot welding(RSW) to join steel sheets for structural rigidity of automobile body. Driven by the need to reduce weight and fuel consumption, car companies have been evaluating aluminum intensive vehicles(AIVs) as a way to reduce vehicle weight without downsizing. During the transition from all steel-construction vehicle body to aluminum intensive body, joining aluminum to steel sheets emerges as a serious contender in automobile body. This paper deals with application of transition material to RSW aluminum to steel. Placing transition material insert between the aluminum/steel interface was found very effective to overcome physical incompatibility between aluminum and steel. Use of transition insert allows for two separate weld nuggets to be formed in their respective aluminum/aluminum and steel/steel interfaces. This RSW processes was monitored with the aid of dynamic resistance sampling. Typical patterns in sampled dynamic resistance curves indicated formation of sound nugget. The growth of two separate nuggets was examined by micro-cross section test.