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신석우(Seok-Woo Shin),이종훈(Jong-Hun Lee),박상흡(Sang-Heup Park) 한국산학기술학회 2017 한국산학기술학회논문지 Vol.18 No.10
자동차 부품 업체에서는 납기 준수, 생산 원가 절감, 품질 관리 향상 등의 고객의 필수적인 요구 사항을 만족하기 위하여 자동화를 추진하고 있다. 현재의 수작업을 통한 육안 검사 공정에서는 이러한 필수 요구 사항을 만족하기에는 불가능하다. 따라서 본 연구에서는 품질 관리 개선을 위하여 도어 힌지 브라켓 부품에 대한 현재의 수작업 육안 검사 공정을 대체할 수 있는 자동 선별 시스템을 제안하고자 한다. 본 제안은 도어 힌지 브라켓 부품의 용접너트 누락 불량 발생을 방지하여 고객사의 검사 요구사항 등을 만족할 수 있도록 설계하였다. 검사 공정 알고리즘 및 유사 척도 매칭 알고리즘 프로그램을 자동 선별 시스템에 적용하여 정상 제품과 불량 제품을 구별할 수 있도록 하였다. 검사 공정 알고리즘 및 유사 척도 매칭 알고리즘의 검증 시험을 통하여 검출정확도 98%의 성공적인 검사 결과를 나타내었고 이를 생산 현장에 적용하여 불량 제품 감소에 따른 생산성 향상에 기여하였다. Meeting the growing demand deadlines, reducing the production cost and upgrading the quality control measurements are the reasons why automotive part manufacturers are venturing into automation. Attaining these objectives is impossible with human inspection for many reasons. Accordingly, the introduction of inspection system purposely for door hinge bracket inspection is presented in this study as an alternative for human inspection. This proposal is designed to meet the demands, features and specifications of door hinge bracket manufacturing companies in striving for increased throughput of better quality. To improve demerits of manual operation, inspection system is introduced. As the inspection algorithm, template matching algorithm is applied to distinguish the articles of good quality and the poorly made articles. Through the verification test of the inspection process algorithm and the similarity metric matching algorithm, the detection accuracy was 98%, and it was applied to the production site to contribute to the improvement of the productivity due to the decrease of the defective product.
차체용 1.2GPa급 초고장력 TRIP강판의 저항 점 용접부 너겟 지름 예측에 관한 연구
신석우(Seok-Woo Shin),이종훈(Jong-Hun Lee),박상흡(Sang-Heup Park) 한국산학기술학회 2018 한국산학기술학회논문지 Vol.19 No.3
최근 자동차 산업에서는 연비향상 및 안전규제 강화에 따라 차량 경량화가 필수적으로 요구됨에 따라 DP강(Dual Phase steel), CP강(Complex Phase steel), MS강(Martensitic Steel), TRIP강(Transformation Induced Plasticity steel), TWIP강(Twinning Induced Plasticity steel) 등과 같은 인장강도 700MPa 이상인 초고장력강(Ultra High Strength Steel)의 적용이 증가하고 있다. 초고장력강을 차체에 적용하기 위해서는 용접공정이 필수적이며, 원가 측면에서 유리한 전기저항점용접(Resistance Spot Welding, RSW)이 차체 용접에서 80%이상으로 가장 많이 적용되고 있다. 초고장력강은 강도향상을 위해 합금원소 함량을 늘이기 때문에 일반적으로 용접성이 열악한 것으로 알려져 있다. 이러한 초고장력강의 저항점용접의 경우 적정 용접조건 영역이 축소되고 용접부에서 계면파단 및 부분계면파단이 발생하는 것으로 보고되어 있어 결함 및 품질을 실시간으로 예측할 수 있는 용접품질 판정 연구가 활발히 진행되고 있다. 이에 따라 본 연구에서는 저항 점 용접을 수행할 때 검출되는 2차 회로 공정 변수를 이용하여 용접부의 동저항을 모니터링하고, 이 동저항 패턴에서 용접 품질 판단에 필요한 인자들을 추출하였다. 추출한 인자들을 상관분석하여 용접 품질과의 상관성을 파악하였으며, 상관성이 높은 인자들을 이용하여 회귀분석을 실시하였다. 이를 근거로 현장 적용이 가능한 회귀 모델을 제시하였다. In the automobile industry, in order to increase the fuel efficiency and conform to the safety regulations, it is necessary to make the vehicles as light as possible. Therefore, it is crucial to manufacture dual phase steels, complex phases steels, MS steels, TRIP steels, and TWIP from high strength steels with a tensile strength of 700Mpa or more. In order to apply ultra-high tensile strength steel to the body, the welding process is essential. Resistance spot welding, which is advantageous in terms of its cost, is used in more than 80% of cases in body welding. It is generally accepted that ultra-high tensile strength steel has poor weldability, because its alloy element content is increased to improve its strength. In the case of the resistance spot welding of ultra-high tensile steel, it has been reported that the proper welding condition area is reduced and interfacial fracture and partial interfacial fracture occur in the weld zone. Therefore, research into the welding quality judgment that can predict the defect and quality in real time is being actively conducted. In this study, the dynamic resistance of the weld was monitored using the secondary circuit process variables detected during resistance spot welding, and the factors necessary for the determination of the welding quality were extracted from the dynamic resistance pattern. The correlations between the extracted factors and the weld quality were analyzed and a regression analysis was carried out using highly correlated pendulums. Based on this research, a regression model that can be applied to the field was proposed.
차체용 1.2㎬급 초고장력 TRIP강판의 저항 점 용접 강도 예측에 관한 연구
신석우(Seok-Woo Shin),이종훈(Jong-Hun Lee),박상흡(Sang-Heup Park) 대한용접·접합학회 2018 대한용접·접합학회지 Vol.36 No.1
Recently, in the automobile industry, it has become necessary to increase the fuel efficiency and the safety regulations to make the vehicle lightweight. Therefore, it is necessary to manufacture the dual phase steel, the complex phase steel, the MS steel, the TRIP steel, and TWIP have been increasingly applied to high strength steel with a tensile strength of 700MPa or more. In order to apply ultra high tensile steel to the body, welding process is essential. Resistance spot welding, which is advantageous in terms of cost, is applied more than 80% in body welding. It is generally known that ultra high tensile strength steel has poor weldability because it increases the alloy element content to improve strength. In the case of resistance spot welding of ultra high tensile steel, it has been reported that the proper welding condition area is reduced and interfacial fracture and partial interfacial fracture occur in the weld zone. In order to overcome such problems, researches on welding quality judgment that can predict the defect and quality in real time are actively conducted. In this study, the dynamic resistance of the weld is monitored using the secondary circuit process variables detected during resistance spot welding, and the factors necessary for welding quality determination are extracted from the dynamic resistance pattern. Using the analyzed factors, a regression model that could estimate weld strength was developed. Two regression equations of model were suggested depending on the factors, and it was showed that the model developed by backward elimination method was effective one for weld quality estimation. Based on this, a regression model that can be applied to the field was suggested.
신석우(Seok-Woo Shin),이종훈(Jong-Hun Lee),김대환(Dae-Hwan Kim),박상흡(Sang-Heup Park) 한국산학기술학회 2017 한국산학기술학회논문지 Vol.18 No.12
자동차 산업에서는 환경 문제와 국제 유가 상승 등으로 인한 차량 경량화에 대한 요구가 증대되고 있다. 이에 따라 알루미늄 합금과 특수 소재 등이 차량 중량을 줄이는데 활용되고 있지만 비용과 강도 측면에서 철강소재를 극복하기에는 여전히 많은 어려움이 있다. 따라서 강도와 성형성이 좋은 AHSS(Advanced High Strength Steel) 소재의 적용이 증가하고 있다. 특히 운전자 보호를 위한 안전 규제가 강화되면서 센터필러 (Center Pillar), 루프레일 (Roof Rail) 부분에 1.2GPa급 초고강도 강재의 적용이 점차 늘어나고 있으며 이종강재에 대한 자동차 차체 적용 또한 점차 증가하고 있다. 본 연구에서는 SGAFC1180 1.2t 강재의 저항 점용접성 및 용접부의 특성을 파악하였다. 시뮬레이션을 이용하여 너깃의 생성 및 성장 거동을 관찰하였으며 예측 성능은 오차율 10% 이내에서 유사한 경향을 나타내었다. 또한 이러한 거동이 공정변수인 동저항에 미치는 영향을 파악하였고 전단인장강도 및 너깃 직경과의 상관관계를 고찰하였다. 본 연구를 통하여 동저항의 패턴을 인식하여 패턴의 형태에 따라 용접 상태를 분류하고 용접 품질을 판단하는 시스템도 제안할 수 있을 것으로 사료된다. In the automobile industry, there is growing demand for lightweight vehicles due to environmental problems and rising oil prices. Therefore, aluminum alloys and special materials are being used to reduce the weight of vehicles, but there are still many difficulties to overcome in terms of cost and strength. Therefore, the application of advanced high strength steel (AHSS)is increasing. AHSS has good strength and formability.Safety regulations are becoming stricter, and 1.2-GPa super-high-strength steels are gradually being applied for the center pillar and roof rails. Thus, the application of different kinds of steels in automobile bodiesis also increasing gradually. This study evaluates the resistance point weldability and the characteristics of a welded part of SGAFC1180 1.2t steel. A simulation was used to observe the nugget formation and its growth behavior. The prediction performance showed a similar tendency within an error rate of 10%. Also, the effect of this behavior on the process resistance and dynamic resistance was investigated,along with the correlation between the shear tensile strength and nugget diameter.
김홍태 ( Hong Tae Kim ),박창광 ( Chang Kwang Park ),신석우 ( Seok Woo Shin ) 한국물환경학회 2002 한국물환경학회지 Vol.18 No.6
It is very important to determine the reaction time in the process which is used to intermittent aeration system. This study was performed to evaluate the applicability of ORP(Oxidation Reduction Potential) for determining the optimum reaction time in SBR. During the aerobic phase, ammonia valley^(5) was shown remarkably in ORP curve, and nitrate valley was also conspicuous in anoxic phase. But during anaerobic phase, there is no special valley in ORP curve. Therefore we have used ORP slope curve, which made it possible to find the end point of P-release. It has been concluded that ORP is a useful and reliable parameter to determine reaction time and that it is possible to optimize reaction time using ORP curve and ORP slope curve in SBR.