• 한국산학기술학회논문지
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• 제20권11호
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• pp.144-150
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• 2019

본 연구는 고 장력 강판 SGAFC 780소재를 이용하여 저항 점 용접을 실시 하였으며, 조건에 따른 너깃 지름 측정, 유한 요소 해석 비교를 하였다. 너깃 지름 측정 결과 용접 전류 7kVA의 용접시간 18cycle 이상의 용접조건에서는 용접 최소 직경인 4.3mm 이상을 만족하는 것으로 나타났다. 9kVA과 10kVA이상에서 최소 너깃 직경인 4.3mm 이상으로 만족 하였으나, 높은 전류와 시간으로 인해 날림 현상이 발생하였고, 그로 인한 깊은 압흔이 잔류하였다. 용접성 평가 결과 최소 너깃 지름에서는 만족하지만 날림 현상이 발생하여 용접 불량으로 평가되는 구간이 존재함을 확인하였다. 하지만 날림 현상이 일어났음에도 충분한 하중 부담 능력을 가지는 영역도 확인했다. 유한 요소 해석 비교 결과 적정용접 구간에서의 유한 요소 해석과 실험 결과에서의 너깃 지름을 비교 했을 시 4.2% 미만의 오차율을 확인 했으며, 유한 요소 해석의 신뢰성을 확인 할 수 있었다.

• Journal of Welding and Joining
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• 제12권3호
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• pp.109-117
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• 1994

Spot welding has wide used with a high work efficiency in the automotive and aerospace industries. Up to the present, the technique mainly used to test spot welds on production lines has been entirely depended upon destructive chisel or peel testing. Therefore, it's being very important assignment to secure the NDE technique which can be evaluate spot weld quality with more efficiency and high reliability. This paper discusses the feasibility of UNDE techniques to evaluate spot weld quality. For the sake of the approach to the quantitative measurement of nugget diameter and the discrimination of a the corona bond from nugget, ultrasonic c-scan image and distribution of reflective echo amplitude was measured by immersion method with the mechanical and the electronic scanning of point-focussed ultrasonic beam(25 MHz). As the results of this study, corona bond which is the most dangerous types of interface defects can be successfully detected, as well as expulsion and voids. Ultrasonic testing results were confirmed and compared by optical microscope and SAM(Scanning Acoustic Microscope) observation of the spot-weld cross section. The results show that the nugget diameter can be successfully measured with the accuracy of 0.8 mm.

• 동력기계공학회지
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• 제17권4호
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• pp.115-119
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• 2013

The resistance spot welding of high strength steel degrades the weldability because of its high strength with rich chemical composition and coating layer to protect from corrosion. And the weld Expulsion is prone to occur and severely affect the nugget guality when the initial gap between automatic borrowing galvanied steel sheets(SGARC35) and Zn-coateel trip steels(GA580TRIP and GA980 TRIP) exist in resistance spot welding(RSW). RSW is one of the most popular welding processes used to join sheet metals. but weld guality sometimes do creases due to welding condition. in this paper to verity tue weldability using spot welding with the hemispherically concaved electrode, tensile shear strength and cross-tensile strength were measured by a universal test machine. in addition, the nugget size on cross-sectional area of the weld was observed by optical and electron microscopy. As a result, the nugget size of this specimen is increased with increasing welding current and Max load of tensile-shear strength is increased with welding current is increasing.

• 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.

• 한국가금학회지
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• 제43권2호
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• pp.105-109
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• 2016

본 연구는 닭고기 스킨의 첨가가 닭고기 너겟의 품질 특성에 미치는 영향을 조사하였다. 처리구별로 닭고기 스킨을 0%(control), 5%, 10%, 15%를 첨가하여 제조하였다. 수분함량은 닭고기 스킨의 첨가량이 증가할수록 유의적으로 감소하였으나(P<0.05), 지방함량은 닭고기 스킨의 첨가량이 증가할수록 유의적으로 증가하였다(P<0.05). 단백질함량은 닭고기 스킨의 첨가량이 증가할수록 감소하는 경향을 보였다. 회분함량은 닭고기 스킨의 첨가량이 증가할수록 증가하였으나, 대조구와 처리구 간에 유의적 차이는 발견하지 못하였다. 명도는 닭고기 스킨을 첨가함에 따라 유의적으로 증가하는 경향을 보였으나(P<0.05), 적색도와 황색도는 닭고기 스킨의 첨가량이 증가할수록 감소하는 경향을 보였다. 튀김수율은 닭고기 스킨의 첨가량이 증가할수록 감소하는 경향을 보이며, 경도(hardness), 검성(gumminess)과 씹힘성(chewiness)은 닭고기 스킨의 첨가량이 증가함에 따라 감소하는 경향을 보였다. 관능평가에서 다즙성(juiciness)과 전체적인 맛(overall acceptability)은 닭고기 스킨의 첨가량이 증가할수록 증가하는 추세를 보였다. 이러한 결과로 보아 닭고기 너겟에 닭고기 스킨을 첨가 시 품질 특성을 증진시키는 것으로 나타났으며, 관능평가를 기초로 하여 물성 및 튀김수율을 고려하였을 때 약 10%의 닭고기 스킨 첨가가 닭고기 너겟의 적정 첨가비율이라고 판단된다.

• 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.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1988년도 한국자동제어학술회의논문집(국내학술편); 한국전력공사연수원, 서울; 21-22 Oct. 1988
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• pp.370-373
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• 1988

Althouah there have been many attempts to control weld quality in resistance spot welding processes, design method for an on-line feedback controller based upon process dynamics has not been suggested. This is due to the fact that the resistance spot welding is a highly complicated process, whice involves the interaction of electrical, thermal, mechanical and metallurgical phenomena. In this paper, an optimal control method based on FDM model with shunt effect is presented, which can regulate the nugget size, at the same time minimizing the control heat input. Optimal PI gain of the controller were determined by numerical optimization. Simulation results show that, as a result of the proposed optimal control, the weld nugget can be made to approach a desired nugget size with less control heat input than that required for the conventional spot welding process in the face of the shunt effect.

• Journal of Welding and Joining
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• 제12권4호
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• pp.127-140
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• 1994

Resistance spot welding has been widely used in the sheet metal joining processes because of its high productivity and convenience. In the resistance spot welding processes the size of molten nugget is a criterion to assess weld quality. Many research have founded on measuring weld nugget size at the same time monitoring welding process parameters such as dynamic resistance and electrode movement. With increasing demand of energy saving, many efforts were made to employ aluminum alloys that are lighter than steel and have relatively equivalent strength to steel in the automobile industry. In this paper, spot weldability of aluminum alloys for various welding conditions were examined by series of experiments. One of the 6000 series (Mg-Si) aluminum alloy, 6383-T4 was chosen, which is currently considered as a substitute for the galvanized steel. Dynamic resistance, electrode movement and corresponding nugget size were observed and compared to the case of steel. Finally, resistance spot welding of dissimilar material (galvanized steel-aluminum alloy) was attempted.

• 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.

• 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.