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곽승범(Seung-Bum Kwak),최낙삼(Nak-Sam Choi),신세문(Sei-Moon Shin),신외기(Wae-Gi Shin) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10
Rubber hoses for automobile radiators are apt to be degraded and thus failed due to the influence of contacting stresses of air and coolant liquid under thermal and mechanical loadings. The aging behaviors of the skin part of the hoses due to thermo-oxidative and electro-chemical stresses were experimentally analyzed. Through the thermo-oxidative aging test, it was shown that the surface hardness IRHD(International Rubber Hardness Degrees) of the rubber increased with a considerable reduction of failure strain as the aging time and temperature increased. On account of the penetration of coolant liquid into the skin part influenced by the electro-chemical degradation(ECD) test the weight of the rubber hose increased, whereas their failure strain and IRHD hardness decreased. The hardness of the hose in the side of the negative pole was the most deteriorated at the test site of the hose skin just below the coolant surface.
곽승범(Seung-Bum Kwak),최낙삼(Nak-Sam Choi) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
Rubber hose assembly for automotive hydraulic brake during operation is subject to combined stresses of cyclic pressure, cyclic bending and torsion as well as thermal load. The rubber hose in assembly is composed of ethylene-propylene diene monomer(EPDM) rubber layers reinforced by polyvinyl acetate(PVA) braided fabrics. A durability tester with loading rigs for applying the above cyclic stresses was used to investigate the failure durability of the rubber hose assembly. Interfacial delamination with a length of about 1㎜ between EPDM rubber and PVA fabrics appeared at the test cycles of 400,000. Such initial delamination grew to the rubber skin layer causing the final rupture of the hose.
자동차 냉각기 호스용 EPDM 고무의 복합 가속수명 평가
곽승범(Seung-Bum Kwak),최낙삼(Nak-Sam Choi),신세문(Sei-Moon Shin) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10
Coolant rubber hoses for automotive radiators can be degraded due to the influences of the locally formed electricity. In this study, we developed a test apparatus for rubber materials under combined electro-chemical stresses together with the simultaneous application of mechanical and thermal loads. Changing behaviors of the current and the resistance as a function of aging time were analyzed in consideration of tensile strains and aging temperature. The investigation on the sectioned specimens clarified failure mechanisms in the aged skin layer under the combined electro-chemical stresses. This study suggested some approximate predictions of accelerated life through an Arrhenius formula considering the aging temperature and mechanical strains.
자동차 냉각기 호스용 EPDM 고무의 전기화학적 복합노화시험 및 고장메커니즘
곽승범(Seung Bum Kwak),최낙삼(Nak Sam Choi),신세문(Sei Moon Shin) 대한기계학회 2013 大韓機械學會論文集A Vol.37 No.1
자동차용 냉각기 고무호스는 열과 기계적 하중을 받으면서 국부적으로 형성된 전기적 영향으로 인해 노화와 고장이 발생한다. 본 연구에서는 개선된 시험방법을 이용하여 고무호스의 파괴거동을 재현하였다. 냉각기 고무호스 재료인 카본블랙이 함유된 EPDM 고무를 사용하여 인장응력과 전기화학적 복합 스트레스를 가하여 노화거동을 분석하였다. 노화 시간에 따른 전류 및 저항의 변화거동을 관찰하였으며 인장 변형 스트레스와 전압 및 노화온도 조건에 따른 노화거동을 분석하였다. 고무 시험편을 수직면으로 정밀하게 절단하여 시험편 표면 및 내부의 변화거동을 분석하여 전기화학적 노화거동과 고장메커니즘을 규명하였다. Coolant rubber hoses for automotive radiators can degrade under thermal and mechanical loadings and thus fail owing to the influences of locally formed electricity. In this study, an advanced test method was developed to simulate the failure of a rubber hose. The aging behavior of carbon-black-filled ethylene-propylene diene monomer (EPDM) rubber used as a radiator hose material under a combination of electrochemical stresses and tensile strain was analyzed. The changing behaviors of the current and the resistance as a function of the aging time were analyzed in consideration of the tensile strain, voltage, and aging temperature. Sectioned specimens clarified the failure mechanisms of the aged skin layer under the combined electrochemical stresses.
냉각기 호스용 EPDM 고무의 인장변형중의 전기화학적 노화시험
곽승범(Seung-Bum Kwak),최낙삼(Nak-Sam Choi) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
Coolant rubber hoses for automotive radiators under thermal and mechanical loadings can be degraded and thus failed due to the influences of the locally formed electricity. In this study, an advanced test method was developed to simulate the failure problem of the rubber hose. For carbon black filled EPDM(ethylene-propylene dine monomer) rubber used as a radiator hose material the ageing behaviors by the electro-chemical stresses combined with a tensile strain were analyzed. As the tensile strain increased, the current of the rubber specimen reduced indicating an increase of the internal defects and electrical resistance of the rubber specimen. Elongation at break and IRHD hardness rapidly decreased with increasing the ageing time.