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문형일(H. I. Moon),김헌영(Heon Young Kim),이명규(M. G Lee),김지훈(J. H. Kim),김대용(D. Kim) 한국소성가공학회 2011 한국소성가공학회 학술대회 논문집 Vol.2011 No.5
Recently, application of magnesium alloy sheets to automotive industry has been rapidly increasing. However, the application is still challenging due to the inferior formability, which should be overcome by proper design of forming process. Therefore, reliable experimental data to be used for the complex material models for the optimization of forming process with magnesium alloys are essential. In this paper, a new cyclic load tester, which can measure the stress-strain curves of thin sheet metals under non-monotonous condition such as tension/compression or compression/tension, was developed. Especially, the new cyclic loading tester has a direct heating system being heated up to 400℃, thus the stress-strain curves under various level of temperature can be measured. Preliminary test results are demonstrated for the commercially available magnesium alloy sheet. But more investigations are necessary to improve the current feature of the tester.
Numerical Analysis of Permanent Deformation of Rubber Door Seal
H. I. Moon(문형일),H. Y. Kim(김헌영),J. C. Park(박준철),B. K. Min(민병권) 한국소성가공학회 2010 한국소성가공학회 학술대회 논문집 Vol.2010 No.10
The automotive weather strip has functions of isolating water, dust, noise and vibration from outside. To achieve good sealing performance, weather strip should be designed to have high contact force and wide contact area. However, these design requirements cause excessive permanent deformation of weather strip. The permanent deformation is generally explained to be the chemical material deterioration and physical deformation under cyclic loading, etc. This paper suggested a numerical method to predict the permanent deformation using the time dependent viscoelastic model. Uniaxial tension and creep tests were conducted to obtain the hyperelastic and the viscoelastic material characteristics. The permanent deformation test was carried out under the lab. test conditions, which were accelerated during shorter time, 200 hours. The permanent deformation of weather strip was successfully predicted using the suggested numerical process.
온도 및 잔류응력을 고려한 플라스틱 부품의 점탄성 해석
문형일(H. I. Moon),김헌영(H. Y. Kim),최철우(C. W. Choi),정갑식(K. S. Jeong) 한국소성·가공학회 2008 소성가공 : 한국소성가공학회지 Vol.17 No.7
Plastics is commonly used in consumer electronics because of it is high strength per unit mass and good productivity. But plastic parts are usually distorted after injection molding due to the residual stress after filling, packing, cooling process, and etc. And plastic material is to be deteriorated according to various temperature conditions and operating time, which can be characterized by stress relaxation and creep. The viscoelastic behavior of plastic materials in time domain can be expressed by the Prony series of the commercial code, ABAQUS. In the paper, the process to predict the post deformation under cyclic thermal loadings was suggested. The process was applied to the real panel, and the deformation predicted by the analysis was compared with that of real test, which showed the possibility of applying the suggested process to predict the post deformation of plastic product under thermal loadings.
강유석(Y.S. Kang),서오석(O. S. Seo),문형일(H. I. Moon),김헌영(Heon Young Kim),이명규(M. G. Lee),김지훈(J. H. Kim),김대용(D. Kim) 한국소성가공학회 2011 한국소성가공학회 학술대회 논문집 Vol.2011 No.10
Recently, Mg alloy sheet has been used widely in the field of automotive and electronic industries because of its lightweight. e.q. However, some difficulties exists in characterizing the material, poor formability and abnormal stress-strain behavior. In this pater, a new cyclic tension-compression tester is developed for characterization of constitutive equation and failure behaviors of Mg alloy sheet. The horizontal type tester range of temperature(R.T.~400℃). It using the laser extensometer was installed and operated in an indirect way. The apparatus was used to evaluate the stress-strain relation under tension-compression loading. Temperature distribution in the specimen is also investigated Mg alloy sheets for stress-strain and temperature distribution of specimen.