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박길현,양승현,황선하,정경덕 朝鮮大學校 建設技術硏究所 2003 建設技術硏究 Vol.23 No.1
Through the exterior features on reinforced concrete slab, crack density and crack originate deflections ratio crack density, decrease percentage of load carrying capacity, crack originate deflections ration and decrease percentage of load carrying capacity were statistically analyzed. Crack density, crack originate deflections ratio and decrease percentage of load carrying capacity are very closely related each other with 0.724, 0.821 and 0.317 of correlation coefficient within 95% of mind level. However, the correlation between crack originate deflections ratio and decrease percentage of load carrying capacity was low. Through the regression equation curve method in which crack density selected as independent variable, crack originate deflections ratio and decrease percentage of load carrying capacity as dependent variable, regression equations were presumed. Equations exist in mind level range of F(0.05, S-curve showed the highest, conformance with 79.5%, 72.2%. The regression equation between CRD or LCCD and CD was also shown. The overall judgement of load carrying capacity of bridges can be possible through the moreover investigation of crack density, the time needed precision could be valuable data for lower maintenance cost, the degree of deterioration of bridges and safety judgement.
Aerobic Biodegradability of Polyester/Polylactic Acid Composites for Automotive NVH Parts
Jeoung, Sun Kyoung,Ha, Jin Uk,Ko, Youn Ki,Kim, Bo-Ram,Yoo, Seung Eul,Lee, Ki Dong,Lee, Su Nam,Lee, Pyoung-Chan Korean Society for Precision Engineering 2014 International Journal of Precision Engineering and Vol.15 No.8
The biodegradability of the environmental dash isolation pad was determined under aerobic conditions (ISO-14855-1). The environmental dash isolation pad was fabricated with polyester fiber and low-melting PLA fiber (LM-PLA), instead of low-melting polyester fiber. The results showed a biodegradation of 27% under aerobic conditions within a period of 45 days of composting. The commercial dash isolation pad using LM-PET (polyethylene terephthalate) fiber did not biodegrade under aerobic condition. The decrement of tensile strength and weight loss of PET/30% LM-PLA composite after 40 days were 50% and 24%, respectively, since the LM-PLA was degraded due to the progression of biodegradation. The change of molecular weight of LM-PLA fiber was examined by Gel Permeation Chromatography (GPC). The degradation of the polymer chains was caused by aerobic bacteria and its molecular weight was gradually reduced. The environmental dash isolation pads were left with 18 months under atmospheres, however, the change of tensile strength were lowing 19.8%, while the commercial dash isolation pad resulted in 19.6%. It showed a reduction of 50% in its tensile strength under aerobic conditions, no deformation or cracks were observed after the durability test.
자동차 내장부품용 나노복합재료의 난연성 및 내구내열성 향상 연구
정선경(Sun Kyoung Jeoung),유승을(Seung Eul Yoo),이평찬(Pyoung-Chan Lee),곽성복(Sung Bok Kwak),남재도(Jae-Do Nam),이기윤(Kee Yoon Lee) 한국자동차공학회 2009 한국자동차공학회 학술대회 및 전시회 Vol.2009 No.11
Polypropylene(PP) is one of the most widely used polyolefins, not only because of its balance of physical and mechanical properties but also because of its recycling ability and low cost. However, the ability for PP to be used ad an engineering thermoplastic is still limited by its poor mechanical properties and thermal resistance, in particular impact resistance, modulus and flame retardment. Therefore, it is expected that the simultaneous incorporation of an elastomeric phase and a rigid phase(organoclay) could lead to an attractive material with simultaneous enhancements in impact resistance and modulus relative to the neat PP. The purpose of this study is to examine the mechanical properties and flame retardment of PP reinforced with an organoclay and toughened with an elastomer made by melt processing. To promote exfoliation of clay platelets in PP, a polypropylene-grafted-maleic anhydride(MPP) material is premixed with the organoclay prior to melt processing. The mechanical properties and flame retardment of PP/clay nanocomposites depend stronglretn the change in the ratio of PP/clay, PP/elastomer, and PP/flame retardant. The PP/clay nanocomposites provided a 52%, 13%, and 48% reduction of the Max-heat release rates, total heat release, and effective heat of combustion, in spite of 33% increment of time to ignition compared with the pristine PP.
친환경 소재를 이용한 조수석 에어백 충격 안전장치의 내구성 향상 연구
정선경(Sun Kyoung Jeoung),이평찬(Pyoung-Chan Lee),유승을(Seung Eul Yoo),곽성복(Sung Bok Kwak),윤성현(Sunghyun Yun),임원규(Won Kyu Lim) 한국자동차공학회 2010 한국자동차공학회 부문종합 학술대회 Vol.2010 No.5
The demand for automotive passenger safety has recently expanded, the rate of airbag installation increase. Passenger airbag(PAB) is consist of Door, Chute and Module. In this study, PAB Chute is developed using the same materials with Instrument Panel in order to recycle the interior parts. PAB Chute is used local reinforcement system(LRS) because of highly the required properties. PAB Chutes of three type are fabricated according to woven shapes(square, diagonal and dense type). Mechanical properties of PAB Chute is measured by UTM and Izod impact tester. In order to predict crack expansion, high speed impact tests are in progress. PAB Chute of the dense type provided a 75% increase of the max energy.
단일 공정을 통한 자동차 내장부품(Door trim)의 신뢰성 향상 연구
정선경(Sun Kyoung Jeoung),이평찬(Pyoung-Chan Lee),유승을(Seung Eul Yoo),김보람(Bo Ram Kim),한인수(In Soo Han),조지현(Ji Hyun Cho) 한국자동차공학회 2011 한국자동차공학회 학술대회 및 전시회 Vol.2011 No.11
최근 자동차 산업에서는 경량화, 친환경, 고감성을 중심으로 자동차용 소재를 연구·개발하고 있다. 자동차의 내장재인 Door trim은 실내장식, 차음, 흡음, 추돌시 탑승자 보호의 기능을 갖는 중요한 자동차 내장부품 중 하나이다. 본 연구에서의 Door trim 제조공정인 단일공정 표피 일체화 기술은 동시 압출-사출 기술(ILC; In-Line Compounding)과 표피 일체화 기술(ISF; Intergral Skin Foam)이 복합된 새로운 개념의 기술이다. 이 기술을 통해 기존 3공정을 단일 공정(ILC+ISF)으로 단순화됨으로서 생산성이 향상될 것으로 기대된다. 또한, Door trim의 개발 소재는 다층의 소재를 단일화하여 재활용이 용이하고 친환경 소재 적용을 통해 환경유해물질(VOCs)이 저감되었다. 단일 공정 표피 일체화 기술을 이용한 Door trim의 내구성을 평가하기 위하여 기계적인 물성과 내환경성을 측정하였다. 소재와 부품에서 요구 물성을 만족하였고 내환경성 평가 결과 자동차 내장부품으로 적용 가능함을 확인하였다.
정선경(Sun Kyoung Jeoung),이평찬(Pyoung-Chan Lee),유승을(Seung Eul Yoo),김보람(Bo-Ram Kim),임명혁(Myung Hyuk Im),강원구(Won-Gu Kang) 한국자동차공학회 2011 한국자동차공학회 부문종합 학술대회 Vol.2011 No.5
최근 자동차 R&D 동향은 친환경, 고기능성, 그리고 경량화이다. 자동차 외장재용 polupropylene은 물질 성능과 가격 등의 이점으로 사용량이 증가하고 있으나 도장이 어렵다는 문제점을 가지고 있다. PP를 도장하기 위해 염소화 수지와 수지의 용해를 위한 용매를 사용하고 있으나 이는 환경규제 의 대상이 되고 있다. 따라서, 본 연구에서는 비염소화 수지를 개발하였다. 비염소화 도료 시스템의 내구성을 평가하기 위하여 기계적인물성과 내환경성을 측정하였다. 비염소화 도료 시스템은 염소화 도료와 동등 수준의 결과를 보이고 있어 자동차 범퍼용 도료에 적용 가능함을 확인하였다.