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개선된 회귀착점 방법을 이용한 이방성 적층구조물의 소성해석
양승용,진두한,김정한 한국분말재료학회 2022 한국분말재료학회지 (KPMI) Vol.29 No.4
The plastic deformation behavior of additively manufactured anisotropic structures are analyzed using the finite element method (FEM). Hill’s quadratic anisotropic yield function is used, and a modified return-mapping method based on dual potential is presented. The plane stress biaxial loading condition is considered to investigate the number of iterations required for the convergence of the Newton-Raphson method during plastic deformation analysis. In this study, incompressible plastic deformation is considered, and the associated flow rule is assumed. The modified returnmapping method is implemented using the ABAQUS UMAT subroutine and effective in reducing the number of iterations in the Newton-Raphson method. The anisotropic tensile behavior is computed using the 3-dimensional FEM for two tensile specimens manufactured along orthogonal additive directions.
외연적 유한요소법을 이용한 적층제조 공정 중 응력 장 변화 계산
양승용,김정한,Yang, Seung-Yong,Kim, Jeoung Han 한국분말야금학회 2020 한국분말재료학회지 (KPMI) Vol.27 No.4
In the present work, an explicit finite element analysis technique is introduced to analyze the thermal stress fields present in the additive manufacturing process. To this purpose, a finite element matrix formulation is derived from the equations of motion and continuity. The developed code, NET3D, is then applied to various sample problems including thermal stress development. The application of heat to an inclusion from an external source establishes an initial temperature from which heat flows to the surrounding body in the sample problems. The development of thermal stress due to the mismatch between the thermal strains is analyzed. As mass scaling can be used to shorten the computation time of explicit analysis, a mass scaling of 108 is employed here, which yields almost identical results to the quasi-static results.
국내 골프장 이용객 수요예측에 따른 적정규모 수요 연구-시계열 모델과 인과모델의 비교분석-
양승용 한국관광연구학회 2006 관광연구저널 Vol.20 No.3
The aim of this study is to discuss the fact that the golf industry in Korea, especially for golf courses, has been highly developing and profiting as a result of less supply than demand. however current signs are beginning to show that an excess supply of golf courses is expected in next 5 years which might lead to a crisis of golf course industry. Evidently supporting this, the number of golf course users increased last year but this is only because of the new golf courses and, in fact, for the existing courses it has decreased since 2004 and last year the operating profits decreased as well. Therefore we would like to suggest a counter-action plan for a continuing growth of golf industry by creating an appropriate scale of demand and supply through demand forecast using monthly user data in accordance with seasonal pattern collected nationally from 224 golf courses in operation. The result of this research shows that the number of needed golf courses in 2010 would be 302. Applying the same tendency as an increase shown in 2005 from 78 courses to 224 courses, we can expect that, by 2010, 302 courses will be required which is 34.8% further establishments from 2005; based on 18 hole private courses, 205 courses by 2010 that is 52 more courses that 2005 and in basis of 11 hole public courses, we are talking 97 courses by 2010 that is 20 more than 2005. Therefore, for year 2010, the appropriate total number of golf courses is predicted as 344 which is a sum of 239 for private courses and 105 for public courses.
양승용,김정한 한국분말재료학회 2023 한국분말재료학회지 (KPMI) Vol.30 No.1
A fixed-point iteration is proposed to integrate the stress and state variables in the incremental analysis of plastic deformation. The Conventional Newton–Raphson method requires a second-order derivative of the yield function to generate a complicated code, and the convergence cannot be guaranteed beforehand. The proposed fixed-point iteration does not require a second-order derivative of the yield function, and convergence is ensured for a given strain increment. The fixed-point iteration is easier to implement, and the computational time is shortened compared with the Newton–Raphson method. The plane-stress condition is considered for the biaxial loading conditions to confirm the convergence of the fixed-point iteration. 3-dimensional tensile specimen is considered to compare the computational times in the ABAQUS/explicit finite element analysis.
도시하수 처리 혐기성 유동상 반응조의 후속공정으로서 화학응집의 가능성 평가
양승용,배재호 대한상하수도학회 2014 상하수도학회지 Vol.28 No.6
This study examined a feasibility of coagulation as post-treatment to remove sulfide and phosphorus for the effluent of anaerobic fluidized bed reactor (AFBR) treating domestic wastewater. Removal efficiencies of sulfide, phosphorus and COD by coagulation were not affected by pH in the range of 5.9 to 7.2. Alkalinity requirement could be estimated by the amount of Fe3+ to form Fe(OH)3(S) and to remove sulfide and phosphorus. At coagulant aid dosage of 2 mg/L, anionic polymer showed best results regarding size and settleability of flocs. Sulfide removal for the AFBR effluent at the Fe3+/S2- ratio of 0.64, close to the theoretical value of 0.67 found with a synthetic wastewater, was only 75.2%. One of the reasons for this low sulfide removal is that the AFBR effluent contains, phosphorus, hydroxide and bicarbonate which can react with Fe3+ competitively. Concentrations of sulfide and phosphorous reduced to below 0.1 and 0.5 mg/L, respectively, at the Fe3+/S2- ratio of 2.0. Average effluent COD of 80 mg/L, mostly soluble COD, was obtained at the dosage 50 mg Fe3+/L (Fe3+/S2- ratio of 2.0) with corresponding COD removal of 55%. For better removal of COD, soluble COD removal at the AFBR should be enhanced. Coagulation with Fe3+ removed sulfide, phosphorus and COD simultaneously in the AFBR effluent, and thus could be an alternative process for the conventional wastewater treatment processes where relatively high quality effluent is not required.