http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
박남수(N. Park),허훈(H. Huh) 한국소성가공학회 2015 한국소성가공학회 학술대회 논문집 Vol.2015 No.10
This paper is concerned with modeling of a ductile fracture model considering the anisotropy of sheet metal to predict the sudden fracture of advanced high strength steel (AHSS) sheets in complicated forming processes. The Lou-Huh ductile fracture criterion is modified using the Hill`s 48 anisotropic plastic potential instead of the von Mises isotropic plastic potential to take account of the influence of anisotropy on the equivalent plastic strain at the onset of fracture. Two dimensional digital image correlation (2D-DIC) method is utilized to measure the strain histories on the surface of three different types of specimens during deformation. For the derivation of an anisotropic ductile fracture model, principal stresses (σ₁, σ₂, σ₃) are expressed in terms of the stress triaxiality, the Lode parameter, and the equivalent stress (ηH, L, σ ̅H) based on the Hill`s 48 anisotropic plastic potential. It is quantitatively verified that the anisotropic ductile fracture suggested can predict the onset of the fracture over a wide range of loading paths based on the confirmation of damage accumulation, such that it can be utilized for complicated sheet metal forming processes to evaluate the forming limit of advanced high strength steel (AHSS) sheets.
다양한 하중경로에서의 DP980 강판의 파단변형률 예측에 관한 연구
박남수(N. Park),허훈(H. Huh) 한국소성가공학회 2014 한국소성가공학회 학술대회 논문집 Vol.2014 No.10
This paper is concerned with prediction of fracture strains for DP980 steel sheets at a wide range of loading paths. The usage of DP980 steel is significantly increasing in automotive industries for enhanced safety and high fuel efficiency. The material behavior of advanced high-strength steels (AHSSs) sheets show unpredictable and sudden fracture in sheet metal forming processes. A modified Lou-Huh ductile fracture criterion is utilized to predict the formability of AHSSs because the conventional forming limit diagram (FLD) constructed based on necking is unable to evaluate the formability of AHSSs. Fracture loci were extracted from three dimensional fracture envelopes by assuming the plane stress condition to evaluate equivalent plastic strains at the onset of fracture at a wide range of loading paths. Three different types of specimens such as pure shear, dog-bone and plane strain grooved specimens were utilized for tensile tests to calibrate the fracture model of DP980 steel sheets. Fracture strains of each loading path were evaluated to show that there is little deviation between fracture strains predicted from the fracture model and experimentally acquired ones. Through the comparison, it is clearly shown that the three dimensional fracture envelopes can accurately predict the onset of the fracture of DP980 steel sheets in complicated loading conditions from compressive loading, and shear to equi-biaxial tension.
도재소부용(陶材燒付用) Ni-Cr 합금(合金)의 재주조(再鑄造)가 물리적(物理的) 성질(性質)에 미치는 영향(影響)에 관(關)한 연구(硏究)
김성일,김춘진,박남수,한무현,Kim, S.I.,Kim, C.C.,Park, N.S.,Han, M.H. 대한치과보철학회 1981 대한치과보철학회지 Vol.19 No.1
Some physical properties of Ni-Cr based alloy for porcelain veneering were compared after repeated casting without the addition of any new alloy. The specimen were cast in a centrifugal caster with an oxygen-propane torch at optimum temperature. The obtained results were as follows: 1. The yield strength and hardness of the second generation were no significant differences compared with first generation but the yield strength and hardness of the third generation slightly decrased. 2. The ultimate tensile strength and elongation appeared to decrease slightly in second, third generations. 3. The tensile fractured facets of the first generation specimen were normal in all specimen, but in the second generation there were six tensile specimen out of ten, in the third there were four tensile specimen out of ten.