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예비변형률 효과를 고려한 고변형률 속도에서의 차체용 강판의 물성 특성
김석봉(Seokbong Kim),임지호(Jiho Lim),허훈(Hoon Huh),임종대(Jongdae Lim) 한국자동차공학회 2004 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Most auto-body members fabricated by the sheet metal forming process. During this process the thickness and material properties of the sheet metal are changed with the residual stress and plastic strain. This paper deals with the material properties of the sheet metal at the high strain rate considering the pre-strain effect. Specimens are selected from sheet metals for outer panels and inner members, such as SPCEN, SPRC45E, SPRC35R and EZNCD. The specimens are prepared with the prestrain of 2, 5 and 10 % by tensile elongation in Instron 5583, which could be equivalent to the plastic strain in sheet metal forming, High speed tensile tests are then carried out with the pre-stained specimens at the strain rate of 1 to 100 /sec. The experimental result informs that the material properties are noticeably influenced by the pre-strain when the yield stress of the specimens is moderate as SPCEN, SPRC35R and EZNCD. The result also demonstrates that the ultimate tensile strength as well as the yield stress is increased as the amount of the pre-strain is increased.
배기계용 고내식 알루미늄 도금강판의 부식특성에 관한 연구
최재웅(Jaewoong Choi),정범구(Bumgoo Chung),임종대(Jongdae Lim) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Effect of Cu₂S for improvement in corrosion resistance of highly corrosion-resistant aluminized steel sheet was investigated by means of corrosion test and heat-corrosion resistance test. For the test similar to actual driving conditions, test was carried out by the following methods which are chipping test at room temperature and salt spray test for 1300 hours after heating the specimen for 24 hours at 400, 500, and 600℃. And also, after cycle corrosion test, maximum pit depth measurement was executed for testing of heat-corrosion resistance for highly corrosion-resistant aluminized steel sheet. The contents variation of between coating surface and substrate was measured by GDS. Effect of Cu₂S for improvement in corrosion resistance was verified by the test above.
김의준(Eui-Jun Kim),정범구(Bumgoo Chung),임종대(Jongdae Lim) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
The perforation corrosion frequently occurs in the hemming joint and inside of closed structures because water and corrosive stuff are easy to stagnate and hard to get dry. So there is a need to develop the method which can be possible to predict the expected life of those parts. This paper describes a corrosion characteristic of hemming joints according to the application of anticorrosion subsidiary materials and the anticorrosion life of those parts based on the accelerated corrosion test which allows corrosion evaluation to be completed in a shorter period of time.
이창구(Changku Lee),고영상(Yongsang Ko),김성환(Sunghwan Kim),박현수(Hyounsoo Park),임종대(Jongdae Lim) 한국자동차공학회 2007 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
A new high strength microalloyed steel has been developed for fracture split connecting rods for heavy duty diesel engines that provides advantages in cost saving and weight reduction. This new splittable steel has higher fatigue strength than conventional steel with improved machinability. The key issue with this development is how to increase the mechanical strength without sacrificing both splittability and machinability. This goal was achieved by substituting the conventional high carbon microalloyed steel with a new type of alloy design that combined an optimized splitting capability and can rod geometry. This research focused on optimizing two major technical considerations for this application - new medium carbon chemical composition with a high silicon range to maximize the splittability without any plastic deformation. Secondly, process parameters for both the hot forging and fracture splitting process were developed to ensure a consistent microstructure and fracture surface. Systematic studies have been conducted to verify several characteristics including material properties during controlled cooling and machining. The con rod with the new type of steel is expected to have a 30% increase in fatigue and yield strength with, at least, a 10% weight reduction.
윤광민(Gwangmin Yoon),강동하(Dongha Kang),고영진(Youngjin Ko),임종대(Jongdae Lim) 한국자동차공학회 2009 한국자동차공학회 학술대회 및 전시회 Vol.2009 No.11
High level vacuum die casting (HLVD) allows the casting products heat treatable with aid of minimized gas contents (e.g. max 3cc/100gAl), therefore it shows improved mechanical properties. In order to decrease the gas content of castings, vacuum level in cavity should be maintained under 5kPa during mold filling process. For the quality control of mass production, the practical inspection system should be required in the production process. In this study, we have focused on finding the relationship between process parameters and gas porosity, one of the main casting defects. We developed thin walled bracket with HLVD process to achieve weight reduction as well as cost saving. In addition, improved mechanical properties and productivity were acquired.
정재규(Jaegyu Jung),오승택(Seungtaik Oh),이두환(Doohwan Lee),임종대(Jongdae Lim) 한국자동차공학회 2011 한국자동차공학회 부문종합 학술대회 Vol.2011 No.5
This paper deals with cyclic stress and strain responses during thermo-mechanical fatigue (TMF) on ferritic stainless steels, which is used for an exhaust manifold in automobiles. With the new developed life prediction model parameters, the plastic material response and the lifetime in TMF test can be accurately described. HD parameter was applied to predict the number of cycles to failure of τ-ENG exhaust manifold using finite element simulations. Good agreement between the predicted and the tested number of cycles to failure in real components is acquired. A further optimization of the design of the manifold is now possible based on computer experiments, thus saving development time & cost and leading to more reliable prototypes.
윤광민(Gwangmin Yoon),김민수(Minsoo Kim),고영진(Youngjin Ko),임종대(Jongdae Lim) 한국자동차공학회 2007 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Aluminum alloys play and important role in the weight reduction of the automobiles because of excellent combination of strength, cost and specific weight. So, the major car maker increase the aluminum chassis components. In this study, Cast-foring process applied to achieve very good productivity, high strength and lower cost than aluminum hot forging. As a result of this study, 45% weight reduced(compare to the steel product) and had good mechanical properties and productivity aluminum rear carrier is achieved.