가변 극성 아크의 알루미늄 용접성 향상에 관한 연구

조정호,Cho, Jungho 대한용접접합학회 2014 대한용접·접합학회지 Vol.32 No.1

Low arc weldability of aluminum alloy is enhanced by applying variable polarity TIG and the result is theoretically investigated to figure out the mechanism. Conventionally, it is well known fact that DCEP (reverse polarity) arc is effective on aluminum welding. The reason is due to oxide layer removal by plasma ion bombardment and therefore it is named as cleaning effect. Another fact of polarity characteristic is that DCEN shows higher heat input efficiency therefore conventional variable polarity arc used to apply DCEP portion as small as possible. However, higher DCEP portion shows bigger weldment in this research and it is explained by adopting a theory of arc concentration on oxide layer with tunneling effect which was not clearly mentioned before in several variable polarity TIG welding research. Disagreement between variable polarity TIG welding result and conventional arc polarity theory is rationally explained for the first time with help of electron emission theory.

한국 국방 연구개발 프로젝트 일정 관리 및 예측을 위한 Earned Schedule 기법의 적용 효과와 한계 분석

조정호,임재성,Cho, Jungho,Lim, Jaesung 한국군사과학기술학회 2018 한국군사과학기술학회지 Vol.21 No.3

Earned Value Management(EVM) has been used to manage and forecast defense project schedule and cost over the last two decades in the world. However to support the lacking ability of schedule analysis in traditional EVM, earned schedule(ES) has been introduced as a tool to more accurately estimate schedule performance. This paper compares which method EVM or ES, provides more accurate schedule predictors in 32 Korean defense research and development projects. As a result of comparison, the ES method can predict the future schedule more reliably than the EVM method. We also analyze early warning function of schedule performance index considering project duration extension point. Through the analysis results, we confirm that both the EVM and the ES method lack the ability of the early warning in terms of the current schedule management criterion.

신경망 알고리즘을 이용한 아크 용접부 품질 예측

조정호,Cho, Jungho 대한용접접합학회 2013 대한용접·접합학회지 Vol.31 No.3

Artificial neural network (ANN) model is applied to predict arc welding process window for automotive steel plate. Target weldment was various automotive steel plate combination with lap fillet joint. The accuracy of prediction was evaluated through comparison experimental result to ANN simulation. The effect of ANN variables on the accuracy is investigated such as number of hidden layers, perceptrons and transfer function type. A static back propagation model is established and tested. The result shows comparatively accurate predictability of the suggested ANN model. However, it restricts to use nonlinear transfer function instead of linear type and suggests only one single hidden layer rather than multiple ones to get better accuracy. In addition to this, obvious fact is affirmed again that the more perceptrons guarantee the better accuracy under the precondition that there are enough experimental database to train the neural network.

차체 이음 유발 용접 불량에 대한 분석과 해결 방안

조정호,이중재,배승환,이용기,박경배,김용준,문세민,Cho, Jungho,Lee, Jungjae,Bae, Seunghwan,Lee, Yongki,Park, Kyungbae,Kim, Yongjun,Moon, Semin 대한용접접합학회 2015 대한용접·접합학회지 Vol.33 No.2

The importance of emotional quality of car is getting higher in these days. Noise takes great portion in emotional quality because it is detectable problem with just a few rides. The sources of car noise during operation are various and the related technical issues are vast. Sometimes weldments of auto body are referred as the source of noise and the suspicious weldment shows unsatisfactory welding quality in most cases. In this research, cases of noise making weldments are investigated to figure out the solution for welding quality improvement. They are categorized into several groups in according to the inferred types of the error source then appropriate solutions are suggested. Auto body has weldments of resistance spot welding and gas metal arc welding in general. Therefore the solutions are suggested as adjustment of welding process variables and related machineries. Inevitable error source is also referred which is originated from thermal expansion rate difference between ultra high strength steel and mild steel. This new approach is validated through simple calculation then more concrete investigation with numerical analysis is remained as further works to be done.

신경망 알고리즘을 이용한 차체용 강판 아크 용접 조건 도출

조정호,Cho, Jungho 대한용접접합학회 2014 대한용접·접합학회지 Vol.32 No.2

Famous artificial neural network (ANN) is applied to predict proper process window of arc welding. Target weldment is variously combined lap joint fillet welding of automotive steel plates. ANN's system variable such as number of hidden layers, perceptrons and transfer function are carefully selected through case by case test. Input variables are welding condition and steel plate combination, for example, welding machine type, shield gas composition, current, speed and strength, thickness of base material. The number of each input variable referred in welding experiment is counted and provided to make it possible to presume the qualitative precision and limit of prediction. One of experimental process windows is excluded for predictability estimation and the rest are applied for neural network training. As expected from basic ANN theory, experimental condition composed of frequently referred input variables showed relatively more precise prediction while rarely referred set showed poorer result. As conclusion, application of ANN to arc welding process window derivation showed comparatively practical feasibility while it still needs more training for higher precision.

가변 극성 알루미늄 아크 용접의 이론적 배경 고찰

조정호,이중재,배승환,이용기,박경배,김용준,이준경,Cho, Jungho,Lee, Jungjae,Bae, Seunghwan,Lee, Yongki,Park, Kyungbae,Kim, Yongjun,Lee, Junkyung 대한용접접합학회 2015 대한용접·접합학회지 Vol.33 No.2

Cleaning effect is well known mechanism of oxide layer removal in DCEP polarity. It is also known that DCEN has higher heat input efficiency than DCEP in GTAW process. Based on these two renowned arc theories, conventional variable polarity arc for aluminum welding was set up to have minimum DCEP and maximum DCEN duty ratio to achieve the highest heat input efficiency and weldability increase. However, recent several variable polarity GTA research papers reported unexpected result of proportional relationship between DCEP duty ratio and heat input. The authors also observed the same result then suggested combination of tunneling effect and random walk of cathode spot to fill up the gap between experiment and conventional arc theory. In this research, suggested combinational work of tunneling effect and rapid cathode spot changing is applied to another unexpected phenomena of variable polarity aluminum arc welding. From previous research, it is reported that wider oxide removal range, narrower bead width and shallower penetration depth are observed in thin oxide layered aluminum compared to the case of thick oxide. This result was reported for the first time and it was hard to explain the reason at that time therefore the inference by the authors was hardly acceptable. However, the suggested combinational theory successfully explains the result of the previous report in logical way.

이음 유발 차체 용접부 원인 분석 및 해결 방안

조정호(Jungho Cho),이용기(Yongki Lee),박경배(Kyungbae Park),김용준(Yongjun Kim),문세민(Semin Moon) 대한용접·접합학회 2015 대한용접학회 특별강연 및 학술발표대회 개요집 Vol.2015 No.05

차체용 알루미늄 아크 용접부의 피로성능에 관한 연구 Part 1. 맞대기 이음

조정호(Jungho Cho),김한솔(Hansol Kim),신승철(Seungcheol Shin),유호진(Hojin Yoo),이건호(Gunho Lee),전종호(Jongho Jeon),김민수(Minsoo Kim),조영래(Youngrae Jo) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.6

알루미늄 맞대기 아크 용접부 형상이 피로강도에 미치는 영향

조정호(Jungho Cho),백성진(Sungjin Baek),신승철(Seungchul Shin),이건호(Gunho Lee),강문구(Mun-Gu Kang),조영래(Young-Rae Jo) 대한용접·접합학회 2021 대한용접·접합학회지 Vol.39 No.1

The use of aluminum in auto odies is increasing due to the requirement of mass reduction for gas mileage enhancement. However, few open studies have been conducted on the fatigue strength of arc welded aluminum butt joints. In this study, the fatigue strength of arc welded butt joints of aluminum sheets was investigated. The material was 6061-T6 with a thickness of 4 mm. Welding specimens were prepared to determine the effects of the top bead toe angle, penetration depth, top surface misalignment, and alternative double-butt joint formation. Results showed that the top surface misalignment and partial penetration were more critical than the top bead toe angle on fatigue strength. Partial and full penetration revealed the lowest and highest fatigue strength, respectively. Because of the low viscosity and surface tension, achieving full penetration in butt joint aluminum arc welding without a backing component while also controlling penetration depth are impossible. An alternative solution to this problem is to apply a double-butt joint design, with experimental results showing for the first time the validity of this solution in terms of fatigue strength.

에스겔 18:5-9과 레위기 19장의 본문상호성과 그 신학적 함의

조정호(Jungho Cho) 한국신학정보연구원 2021 Canon&Culture Vol.15 No.1

이 연구의 목적은 레위기 19장의 거룩함이 에스겔 18장에서는 공의로 변주된다는 것을 밝히는 것이다. 이를 위하여 에스겔 18:5-9절을 주석하여 레위기 19장과의 본문상호성을 규명하였다. 주석은 본문상호적해석, 수사비평, 어휘연구의 방법으로 진행하였다. 에스겔 18:5-9은 구약성경의 다양한 본문을 참고하거나 인용한다. 그럼에도 불구하고 에스겔 18:5-9에 대한 주석은 본문의 어휘, 주제, 구조의 측면에서 다른 어떤 본문들보다 레위기 19장과 가장 일관적인 관련성을 가진다는 것을 보여주었다. 에스겔 18:5-9은 (정의와) 공의를 행하거나 법도와 규례를 지키는 사람을 의롭다고 함으로써 (정의와) 공의를 행함과 법도와 규례 준수를 동일시한다. 그들이 지켜야 하는 규례는 우상숭배 금지, 정결한 성생활, 가난하고 연약한자들을 학대하거나 착취하지 않으며 그들의 필요에 대한 적극적인 공급, 진실한 재판으로 불의를 행하지 않는 것이다. 여기에는 하나님과의 관계에서 지켜야 하는 순수 종교 영역, 내밀한 사생활, 사회도덕적 영역 등 삶의 모든 영역이 포함된다. 이스라엘 백성이 행해야 하는 정의와 공의가 삶의 모든 영역에 미쳐야 한다는 것이다. (정의와) 공의에 대한 에스겔 18장의 관점은 구약성경의 다른 책들이 사회윤리의 측면에 국한하여 이해하던 정의와 공의의 개념을 광범위하게 확대한 것이다. 특히 레위기 19장에서 공의는 거룩함을 구성하던 하나의 요소였다. 그러나 에스겔 18장이 공의의 개념을 인간 삶의 모든 영역에 적용되는 것으로 확대함으로써 에스겔 18장에서 공의는 레위기 19장의 거룩함과 동일한 수준의 개념으로 격상되었다. 레위기 19장의 거룩함은 에스겔 18장에서 변주된다. The purpose of this study is to reveal that the holiness of Leviticus 19 is transformed into righteousness in Ezekiel 18. To this end, first, I commented on Ezekiel 18:5–9 and found the intertextuality between Ezekiel 18:5–9 and Leviticus 19. The methods of exegesis are intertextuality, rhetoric criticism, and vocabulary research. Ezekiel 18:5–9 cites or refers to various texts from the Old Testament. Nevertheless, an exegesis of Ezekiel 18:5–9 showed that there is more consistent relevance to Leviticus 19 than to any other text in terms of vocabulary, subject, and structure. Ezekiel 18:5–9 equates the practice of (justice and) righteousness with the observance of the laws and ordinances by claiming that those who practice (justice and) righteousness or keep the laws and ordinances are righteous. The ordinances they must keep are the prohibition of idolatry, having a pure sex life, not abusing or exploiting the poor and the weak, actively supplying their needs, and excluding injustice in judgment. These cover all areas of life, such as the realm of pure religion, private life, and social ethics, and means that Israel’s righteousness must extend to every area of their lives. The view of Ezekiel 18 regarding (justice and) righteousness is a broad extension of the concept of justice and righteousness, which other Old Testament texts understood only in terms of socialethics. Moreover, righteousness was an element of holiness in Leviticus 19. Therefore, when Ezekiel 18 expanded the concept of righteousness to apply to all areas of human life, righteousness in Ezekiel 18 was elevated to the same level as the holiness of Leviticus 19. Thus, the holiness of Leviticus 19 is transformed into righteousness in Ezekiel 18.