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.

W및 Cu-粉末 成形體의 收縮比에 관하여

權永珣,李鍾和,문인형 울산대학교 1979 연구논문집 Vol.10 No.2

기계적 성질을 달리하는 Cu및 W 분말성형체에서 소결시 收縮異方性에 미치는 粉末粒度, 成形壓, 燒結 시간의 영향을 조사하고 燒結進行에 따르는 收縮比의 거동을 알아 보았다. W분말 성형체에서는 收縮比는 微細한 粉末粒度에서 보다 安定한 값을 나타내었으며 粗大한 粒度에서는 燒結初期에 成形壓의 영향이 현저하게 나타났고 그 이후의 燒結進行에 따른 成形壓의 영향은 보이지 않았다. Cu-분말 성형체에서는 粗大한 분말 성형체에서 소결이 진형됨에 따른 R/A에 미치는 성형壓의 영향은 현저하며 적은 성형壓에서 보다 큰 收縮比値를 보여 주었다. 소결시 소결단계에 따른 조밀화, 재배열 과정에서 소결체 內의 氣孔의 형상학적 거동이 收縮比에 미치는 영향을 논의하였다. The anisotropic shrinkage during sintering in compacts made of tungsten and copper powder with irregular shape has been investigated as function of powder particle size, compacting pressure and sintering time. The behavior of radial/axial(R/A) shrinkage ratio throughout the sintering process has been studied. Tungsten powder compacts showed more stable value of R/A ratio for smaller particle size. The influence of compacting pressure on R/A ratio for coarse powder compacts was pronounced in the early stage of sintering but became negligible in the later stage. In the case of coarser powder compacts of copper, the R/A ratio was found to be strongly affected by the sintering process and the compacting pressure; e.g., the lower the compacting pressure was, the higher the R/A ratio was observed. The possible morphological changes of residual pores in the early and later stages of sintering, such as anisotropy and densification due to rearrangement of particles, was discussed together with other factors to explain the phenomena.

통신망 통합시뮬레이터의 구축방안에 관한 연구

권호열,김화종 강원대학교 산업기술연구소 1992 産業技術硏究 Vol.12 No.-

We proposed an integrated simulator scheme for communication networks. The network modeling and Analysis methologies are firstly discussed along the design procedure of a network simulator, and then, the structure, kernel, and user interfaces are defined for the simulator. Finally, for the verification of our approach, simulations are performed for a simple queueing network and a pure ALOHA system using Ptolemy, a multi-paradigm simulation enviroment

大豆未熟子葉祖織의 營養培地條件에 따른 器官分化

元鍾樂,權貞淑,鄭圭和,張權烈 慶尙大學校 1987 論文集 Vol.26 No.1

大豆의 末熟子葉組織을 사용하여 여러가니 營養培地에서 칼루스와 胚狀體로부터 器官을 分化시키고자 하였던 바 얻어진 결과를 要約하면 다음과 같다. 1. 칼루스誘起는 MS 基本培地에 1.0mg/12,4-D,와 2.0mg/1kinetin을 첨가하거나 (M5培地) 하였을 때 가장 효과적이었다. 2. M4培地에 培養한 칼루스로부터 生長點모양의 완전한 구조를 갖춘 細胞群을 組織學的으로 관찰할 수 있었다. 3.칼루스를 器官分化를 위한 培地에 ?代培養하였을때 根分化, 칼루스로부터胚狀體의 形成, 胚狀體로부터 싹이나 잎의 分化는 供試한 大豆系統이나 使用한 營養培地에 따라 약간의 差異는 있으나 비교적 용이할 것으로 여겨졌다. 4. 供試한大豆系統인 뱀콩의 末熟子葉組織을 M4培地에서 칼루스를 誘起시킨 후 MS基本培地에 0.005mg/1 picloram 과 2.0 mg/1 BAP를 첨가한 培地(OM2培地)에 ?代培養하였을 때 칼루스로부터 胚狀體의 形成이 잘 되었고 胚狀體들로 부터 잎이 分化되었다. The experiments were conducted to investigate organ differentatin rom calls and embryoid under various media using immature ctyledon of soybeam. The results obtained were as followings: 1. 1. Omg 2,4-D plus 0.2mg kinetin or 0.2 mg BAP perr litre on MS basal mediu were efective growth regulators for callus induction. 2. Meristematic structure was observed from the callus induced by 1.0mg 2,4-D plus 0.2mg kinetin per litre in MS basal medium in which callus growth showed best response. 3. Root and embryoid from callus and shoot or leaflet from embryoid were differentiated on the medium subcultured for organ different on the soybean lines and media applied. 4. Embryoid from callus and leaflet from the embryoid were differentiated on the nutritional condition subscultured with 0.005mg picloram plus 2.0mg kinetin per litre on MS in immature cotyledon of spybean line Baemkong.

6-Dimethylaminopurine 및 Cycloheximide의 처리가 돼지난포란의 단위발생에 미치는 영향

김종화,박병권,한만희,이규승 충남대학교 농업과학연구소 2007 농업과학연구 Vol.34 No.1

This study is aimed at finding an optimum density for 6-Dimethylaminopurine (6-DMAP) and cycloheximide which have an effect on the revitalization of porcine oocytes. The results were summarized as follows: 1. When 6-DMAP was treated with 2 mM for 2 hours. It showed a significantly (P<0.05) different high result in activation rate, cleavage rate and blastocyst growth rate of 51.2%, 52.7% and 25.2% respectively. 2. When Cycloheximide was treated with 5 ug/ml for 6 hours, It showed a significantly (P <0.05) different high result in activation rate, cleavage rate and blastocyst growth rate of 47.7%, 46.8%, and 27.3% respectively. 3. When it was cultured in the culture medium, NCSU, for 7 days after inducing activation with 6-DMAP and cycloheximide, it showed no differences in the number of inner cell mass (ICM) and total cell of blastocysts. To conclude, it has been examined for porcine oocytes to be suitable when 6-DMAP was treated with 2 mM for 2 hours, Cycloheximide with 5 ug/ml for 6 hours.

사군자탕이 항암제를 투여한 마우스의 면역세포에 미치는 영향

殷載淳,金大根,柳東和,權鎭,洪鍾星,蘇俊魯,全焄,吳贊鎬 우석대학교 의약품개발연구소 1997 藥學硏究誌 Vol.2 No.-

The purpose of this research was to investigate effects of Sa-Kunja-Tang(SKT) on immune cells of antitumor drugs administered mice. The apoptosis and T lymphocytes subpopulation were tested using a flow cytometry, and the proliferation was tested using a MTT assay. The administration of etoposide. vincristine or doxorubicin increased the apoptosis of T-lymphocytes, but the action of doxorubicin was decreased by the administration of SKT. The administration of etoposide or vincristine decreased helper T and cytotoxic T cells population of T lymphocytes, but the action of vincristine was recovered by the administration of SCT. The administration of etoposide, vincristine or doxorubicin decreased the proliferation of T-lymphocytes, but the action of doxorubicin was increased by the administration of SKT. These results suggest that SKT has a regulative function of T-lymphocytes in anti-tumor drugs administered mice.

Novel Electromagnetic Bandgap with Triangular Unit Cells for Ultra-Broadband Suppression of Simultaneous Switching Noise

KWON, Jong Hwa,SIM, Dong Uk,KWAK, Sang Il,YOOK, Jong Gwan The Institute of Electronics, Information and Comm 2009 IEICE TRANSACTIONS ON COMMUNICATIONS - Vol.92 No.6

<P>To build a stable power distribution network for high-speed digital systems, simultaneous switching noise (SSN) should be sufficiently suppressed in multi-layer PCBs and packages. In this paper, a novel hybrid uni-planar compact electromagnetic bandgap (UC-EBG) with two triangular-type unit cells designed on power/ground planes is proposed for the ultra-broadband suppression of SSN. The SSN suppression performance of the proposed structure is validated both numerically and experimentally. A -35dB suppression bandwidth for SSN is achieved, starting at 800MHz and extending to 15GHz and beyond, thereby covering almost the entire noise band.</P>

Analysis of electromagnetic interference under different types of near-field environments

Kwon, Jong-Hwa,Park, Seungkeun,Jeon, Sangbong,Kim, Dongho Institution of Electrical Engineers 2014 Electronics letters Vol.50 No.9

The effect of different interferences on a victim wireless device in electric and magnetic near-field (NF) environments is investigated. Using a four-port transverse electromagnetic (TEM) cell, those NF environments are generated by varying wave impedance in the cell, which can be done by applying an external interference signal. As a measure of interference, the bit error rate performance of the victim device is chosen, which shows both NF environments have significant but distinctive interference effects on the victim device.

Partial EBG Structure with DeCap for Ultra-wideband Suppression of Simultaneous Switching Noise in a High-Speed System

Jong Hwa Kwon,Sang Il Kwak,Dong-Uk Sim,육종관 한국전자통신연구원 2010 ETRI Journal Vol.32 No.2

To supply a power distribution network with stable power in a high-speed mixed mode system, simultaneous switching noise caused at the multilayer PCB and package structures needs to be sufficiently suppressed. The uni-planar compact electromagnetic bandgap (UC-EBG) structure is well known as a promising solution to suppress the power noise and isolate noise-sensitive analog/RF circuits from a noisy digital circuit. However, a typical UC-EBG structure has several severe problems, such as a limitation in the stop band’s lower cutoff frequency and signal quality degradation. To make up for the defects of a conventional EBG structure, a partially located EBG structure with decoupling capacitors is proposed in this paper as a means of both suppressing the power noise propagation and minimizing the effects of the perforated reference plane on the signal quality. The proposed structure is validated and investigated through simulation and measurement in both frequency and time domains.

Novel Electromagnetic Bandgap Array Structure on Power Distribution Network for Suppressing Simultaneous Switching Noise and Minimizing Effects on High-Speed Signals

Jong Hwa Kwon,Dong Uk Sim,Sang Il Kwak,Jong Gwan Yook IEEE 2010 IEEE transactions on electromagnetic compatibility Vol.52 No.2

<P>To supply high-speed digital circuits with stable power, power/ground noise, such as simultaneous switching noise (SSN) and ground bounce noise caused in multilayer printed circuit boards (PCBs) and packages need to be sufficiently suppressed. The electromagnetic bandgap (EBG) is widely recognized as a good solution for suppressing the propagation of SSN in the gigahertz range. However, a typical coplanar EBG structure etched onto the power and ground planes may degrade the quality of high-speed signals passing over the perforated reference plane. In this paper, a novel method of arranging EBG unit cells on both the power/ground planes in multilayer PCBs and packages is proposed, not only as a means of sufficiently suppressing the propagation of power noise, but also as a means of minimizing the effect of EBG-patterned reference planes on a high-speed signal. On the assumption that noise sources and noise-sensitive devices exist only in specific areas, the proposed method partially positions EBG unit cells only near these critical areas. The SSN suppression performance of the proposed structure is verified by conducting simulations and measurements in the time and frequency domains. Furthermore, signal quality is investigated to verify whether the proposed EBG-patterned reference planes are superior to conventional EBG-patterned planes in terms of signal integrity.</P>