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박원웅(W. W. Park),김동규(D. K. Kim),임용택(Y. T. Im),권혁철(H. C. Kwon),최대곤(D. G. Choi),천명식(M. S. Chun) 한국소성가공학회 2012 한국소성가공학회 학술대회 논문집 Vol.2012 No.10
During strip coiling process, axial inhomogeneity of the stress distribution within a thin strip causes defects such as edge wave and center buckle which are the key concern of customer requirements. In the current study, an analytical model for determining the stress distribution and deformation was utilized to investigate the mechanism of flatness change of the strip and to prevent such defects. In the present model, the coil and the newly coiled strip was assumed to be a thick and thin hollow cylinder, respectively. The coiling process was modeled by consecutively coupling the thin cylinder, which is subject to the circumferential stress due to the coiling tension, onto the thick cylinder. Then, the thick cylinder is subject to the outer radial pressure resulting from the circumferential stress in the thin cylinder. In each coiling, the incremental stress field within the thick cylinder was solved by using Love’s stress function. The stress field within the coil during the coiling process was obtained via the principle of superposition of the additional stress field. In order to consider the axial inhomogeneity of the deformation, a thickness distribution of the strip due to the strip crown was taken into account in the analysis. According to the present analysis, it was found that the flatness improvement can be acquired by decreasing the strip crown and the coiling tension in terms of the circumferential stress distribution.
결정소성 유한요소해석을 통한 IF 강의 미세조직 및 집합조직 예측
김동규(D. K. Kim),김재민(J. M. Kim),박원웅(W. W. Park),임용택(Y. T. Im),이용신(Y. S. Lee) 한국소성가공학회 2013 한국소성가공학회 학술대회 논문집 Vol.2013 No.10
In the present investigation, a three dimensional crystal plasticity finite element method (CPFEM) was used to simulate microstructure and texture evolution of body-centered cubic (BCC) crystalline material during plastic deformation at room temperature. To account for crystallographic slip and rotation, a rate-dependent crystal constitutive law with hardening model was incorporated into an in-house program, CAMPform3D. Microstructural heterogeneity and anisotropy were taken into account by assigning a crystal orientation to each integration point of the element and determining the stiffness matrix of the individual crystal. Based on the experimental observation by electron backscatter diffraction (EBSD) measurement of the as-received IF steel sheet, a representative volume element (RVE) of the initial microstructure was generated by using the Voronoi tessellation scheme. The microstructure and texture evolution during plane strain deformation of IF steel was investigated by comparing numerical results with the experimentally measured microstructure by EBSD in terms of grain morphology and texture.