Failure with Strain Localization of Aluminum Alloy 7075 Sheets at Elevated Temperature and its Application to Two-Step Hybrid Forming

Jong‑Hwa Hong,Hyunki Kim,Wonjae Kim,Yong‑Nam Kwon,Daeyong Kim 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.4

In this work, the onset of failure induced by severe strain at elevated temperature was numerically estimated with crossformedempirical hardening law describing material softening. The hardening law can replicate the rate-sensitive behaviorof aluminum alloy 7075 sheets (thickness of 2.0 mm) with initial hardening and progressive material deterioration causedby dynamic recrystallization, dynamic recovery, and micro-void development. The characterized material was applied to thetwo-step hybrid forming process consisting of a drawing at 400 °C followed by a pneumatic forming at 470 °C to produce ashock absorber housing with an extremely complex shape. The user-defined subroutine codes, VUMAT (ABAQUS/Explicit)and UMAT (ABAQUS/Standard), were sequentially utilized for the drawing and the pneumatic forming, respectively. Theidentified hardening parameters based on uniaxial tensile tests were validated by simulating the two-step hybrid formingprocess and compared with the conventional Voce type law (converging function) and the combined Swift-Voce type law(ever-increasing function) since they play a key role in accurately predicting the onset of failure induced by severe strainlocalization. Finally, simulation results are reasonably well matched with experiments in terms of the moment of failureoccurrence, failure location, final blank shape, and thickness distribution.

I-環의 Radical에 關하여

洪慶和,朴鍾烈 弘益大學校 1983 弘大論叢 Vol.15 No.2

Recently J. Luh, W.E. Coppage and Shoji Kyuno studied the structure of Γ-ring and obtained various generalizations analogous corresponding parts in ring theory. The object of this paper is to study the radical properties of Γ-rings. The main result is the following theorem. If M is a Γ-ring with the operator domain øand R is a radical property then the R-radical of M considered as a Γ-ring with operator domain exists and this R-radical coincides with the R-radical of the ring considered without operator domain.

앉은 자세에 따른 등근육 근전도 해석

洪性燦,柳宗賢,白承殷,白承和 明知大學校 産業技術硏究所 2004 産業技術硏究所論文集 Vol.23 No.-

Today, many people stay lot of time sitting on chair in their life. If a sitting posture is not correct, there is some trouble with the waist. And if it goes on long time, sometimes it cause the hurts of waist or the deformded spinal column. A crouched posture is an obstacle to breath and it give rise to drowsiness because the lack of oxygen. Sitting posture is a habit so people can't feel it oneself and look over some kind of risks. It analyzes a condition of muscles by measuring EMG of spinal both side of spinal-bones. It can have a right sitting posture by the analyzing that increasing of muscles tention in one or the other side of muscles when the posture inclines on one side or ahead.

중성자에 조사된 원자로 압력용기 재료(SA508)의 Magneto-acoustic emission 효과

홍준화,박덕근,옥치일,김장환,이종규 韓國非破壞檢査學會 1999 한국비파괴검사학회지 Vol.19 No.6

원자로 압력용기 재료인 SA508 steel을 온도 70 ℃와 대기압하에서 최고 10 n/㎠까지 중성자를 조사시켜 조사량에 따른 미세경도 변화와 magneto-acoustic emission(MAE) 에너지를 측정하였다. 중성자 조사에 따른 경도의 변화는 조사량이 10 /㎠까지는 거의 일정하였으나, 조사량이 10 /㎠이상에서 급격히 증가하였다. MAE 에너지의 변화는 중성자 조사량에 따라 경도의 변화와 같은 형태로 변하였으나 그 변화량은 감소하여 그변화의 추이는 경도의 변화와는 역의 형태였고, 또한 MAE에너지의 상대적 변화와 경도 변화사이에는 아주 좋은 선형성을 보였다. 이러한 결과에서 SA508 강재는 10 /㎠이상의 중성자에 조사될 경우에 재료에 중성자 조사에 의한 미세 결함이 급격히 증가하여 전위(dislocation)이동에 대한 저항성을 나타내는 마찰경화의 증가가 경도의 증가를 유발하고, 또한 이러한 미세 결함은 자기장과의 반응에서는 90°자벽의 운동중에 자기탄성 변화를 유도하여 MAE 에너지의 감소를 유발함을 알 수 있었다. 그리고 경도의 변화량보다 MAE 에너지의 변화량이 더 크게 나타나, 중성자 조사에 의한 미세결함은 기계적 성질보다 자기적 성질에 더 민감하게 반응한다는 것을 알 수 있었다.따라서 MAE가 중성자 조사에 의한 재료의 미세 구조 결함을 비파괴적인 방법으로 평가하는 강력한 도구의 가능성이 있음을 알 수 있었다. Magneto-acoustic emission (MAE) energy and hardness were measured in the reactor pressure vessel steel (SA508 Steel) for the various neutron fluence, irradiated dose up to 10 n/㎠. The hardness was nearly a constant up to 10 n/㎠, but it was rapidly increased with an increase of the neutron irradiation above 10 n/㎠. It may be considered that the increase of hardness is due to the hindrance of dislocation motion induced defect clusters by irradiation. On the other hand, the MAE energy was slowly decreased as the neutron irradiation increased up to 10 n/㎠ and it was rapidly decreased with an increase of the neutron irradiation increased up to 10 n/㎠ and it was rapidly decreased with an increase of the neutron irradiation above 10 n/㎠. The decrease of the MAE energy may be considered as an increase of the defect clusters which is very sensitive to the 90°domain wall motion. Furthermore, the change of MAe energy and hardness had nearly a linear relationship, but the change of MAE energy was more significant than the change of the hardness. Therefore, MAe may be considered as a very useful technique for the nondestructive evaluation of irradiation damage.

대용어와 연결사, 조응 및 연계

홍종화 한국외국어대학교 외국어 종합연구센터 언어연구소 1993 언어와 언어학 Vol.19 No.-

林業稅制에 關한 考察 : 韓國, 日本, 美國의 制度에 대하여

金知洪,辛在萬,尹鐘和 江原大學校 森林科學硏究所 1985 Journal of Forest Science Vol.5 No.-

Introduced with a review of general taxation principles in Korea, the article provides details of the main type of tax related to forest resource management. The forest taxation of Japan and the United states is also examined to compare with the Korean legislation. The basic analysis is made upon provisions and interpretation of each tax, its history, and its influence on forest management. For Korean forest taxation, some points to be considered are as follows. 1) Since 500,000 won of special income tax deduction from total forest revenue is not likely to be remaining with its absolute value, it should be variable by socio-economic situation. 2) Income tax exemption from newly reforested land for 40 years may shorten rotation and induce heavy harvest cutting for long-term commercial timber species. 3) With a few exceptions, general forest managers are not offered favors in death tax and property tax for their forest land. Taxes have frequently been called the primary impediment factor for timber production because the effectiveness of incentives of programs has not been provided. Considered to the specific characteristics of forestry and resource conservation, Korean forest taxation should be revised and complemented to encourage forest management or maintenance.

전기절연유의 절연파괴에 미치는 전극간격 및 곡률반경의 영향

강성화,채홍인,이종필,임기조 한국안전학회 2004 한국안전학회지 Vol.19 No.1

In this paper, we investigated the influence of gap length and tip radius on breakdown of mineral based insulation oil. Applied voltages were DC and AC voltage. Electrode system was needle-plane structure. The tip radius of needle electrode was 5, 10, 20 and 25μm, respectively. We measured breakdown voltage for each of tip radius with increasing electrode gap, 2mm to 12mm. Electric breakdown strength at tip was calculated using Mason's equation contained geometric figure. As gap length increased, breakdown strength increased linearly. But, as tip radius of needle increased, breakdown strength decreased exponentially. It can be explained by the phenomenon that electron is easily injected, as tip radius increases, and effective work function decreases. When appling DC voltage, breakdown strength was higher when polarity of needle was negative than positive. It is because of the space charge effect in accordance with the influence of liquid motion.

4-Chloro-α-(4-chlorophenyl)-α-(trichloromethyl) Benzyl Alcohol(Dicofol)의 各種有機溶媒中에서의 安定性

申鉉和,洪鍾旭 한국응용생명화학회 1982 Applied Biological Chemistry (Appl Biol Chem) Vol.25 No.3

Dicofol의 各種 有機溶媒에 對한 安定性을 調査하기 위하여 -5℃에서 7日間 放置하여 그 沈搬生成有無를 調査하고, 50℃에서 56日間 處理한 다음 各種溶媒에 對해서 Dicofol의 分解形態를 T.L.C.로 確認하였으며, 그 主成分 分解率을 2週간격으로 ga5 chromatography로 測定하였다. 그 結果 Dicofol 水和劑와 N.N-dimethyiformamide 및 cyclohexanone 溶液에서는 Dicofol의 主成分 分解率이 各各 1.2%, 6.7%, 13.3%이었으나 xylene, touluene, M.I.B.K. 및 isophorone 溶液에서는 沈澱이 生成되어 Dicofol의 溶劑로서는 적합하지 못하였다. 이러한 事實로 미루어 볼 때 供試된 各種 有機溶媒中에서 Dicofol의 製濟上 가장 적합한 溶媒는 isophorone 임을 알았다. This experiment was carried out to investigate the stability of Dicofol solutions which were prepared with various organic solvents such as xylene, toluene, methylisobutyl ketone (H.I.B.K.), cyclohexanone, N.N.-dimetyl formamide (N.N.-D.M.F.) and isophorone under different temperature and storage period. The decomposition rate of Dicofol was increased in the order of cyclohexanone> N.N.-D.M.F.>W.P.>toluene, xylene, M.I.B.K. and isophorone. However, it was shown that precipitation was found in Dicofol solutions such as xylene, toluene and M.I..B.K. except isophorone. Therefore, isophrrone was recognized as the best of organic solvents tested for Dicofol in the case of emulsifiable concentrate formulation with it.

양성 및 음성 정신분열병 아형에서 사고의 정신병리적 특성에 관한 비교연구

김종숙,함웅,홍광화 대한신경정신의학회 1994 신경정신의학 Vol.33 No.3

The authors have studied the content and severity of thought disorder between the subjects of the positive and negative subtypes of schizophrenia. It's hypothetical ground is that the positive and negative subtypes of schizophrenics might bear highly significant differences in the pathogenesis, pathophysiology, psychopathology, also therapeutic and prognostic terms. In that regards, the author reported the neuropsychological significance in differentiating the two subtypes from each other, such that the negative subtype showed the worse function in the short-term recall against the auditory stimuli than the positive. To comparatively analyze the content and severity of thought disorder between the two subtypes, the authors utilized the Thought Discorder Index(TDI) scores and Holt's scale of the primary process thinking content. The results were as follows: 1) The total score of TDI as a whole, showed somewhat more thought disorder in the positive subtype subjects than the negative, though this failed to reach the statistical significance. In 0.75 level of TDI, the positive subtype subjects showed statistically significantly worse thought disorder than the negative. 2) In the comparative study of the primary process thinking content, the positive subtype subjects showed degree in the aggressive content but lower degree in the anxiety content than the negative subtype subjects with statistical significance. 3) In the correlation study, 0.5 level of TDI correlated with the libidinal content of the primary process with blunted affect and the aggressive content with lack of spontaneity and flow of conversation. The above result might suggest that the positive subtype of schizophrenia demonstrated more severe thought disorder, if we regard that responses scored at the 0.75 level of TDI represent clear thought disturbances. The negative subtype of schizophrenia tends to possess higher anxious and libidinal content of the primary process thinking.

주민등록제도 및 주민등록정보활용에 대한 연구 : 개인정보프라이버시 권리 확보를 중심으로

박홍윤,변종화,임동욱 忠州大學校 2003 한국교통대학교 논문집 Vol.38 No.1

To be progressed in information society, personal information protection is one of the most important things for desirable development of information society. This research investigates personal information infringements and effective protection means in resident registration system and use of resident registration information. First, this research is studied the history of Resident Registration Law(Korea ID law) and need of positive privacy by computer technology improvement, Second, this research evaluated the resident registration system on OECD's privacy protection principles: Collection Limitation, Data Quality, Purpose Specification, Use Limitation, Security Safeguards, Openness, Participation and Accountability. In conclusion, From the previous analysis and normative protection principles, the following alternatives are presented for the privacy protection a. use limitation of resident registration number and revision of the resident registration number system. b. establishment of personal information protective organization which can independently determine personal information protective action and policy. c. government faith restoration to the resident registration system