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RISS 인기검색어
- 검색키워드
- 저자 : M. Moslemi (검색결과 5 건)
- 무료
- 기관 내 무료
- 유료
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A Comparison between Three Numerical Criteria for Prediction the Forming Limit Diagram of St14 Steel
M. Moslemi,S.J. Hosseinipour,M.E. Hosseini,A.H. Gorji 한국소성가공학회 2011 기타자료 Vol.2011 No.8
In this paper, the forming limit diagram (FLD) of a low carbon steel St14 (DIN 1623) is investigated experimentally and numerically. The objective of this study is to find a numerical criterion which enables a simple and reliable determination of the FLD. For this purpose, Out-of-plane stretching test method with hemispherical punch was simulated by using commercial finite element software, ABAQUSE 6.9. One-quarter of the geometry was used due to symmetry. The material was modeled as elastoplastic and the anisotropic properties were described by the Hill quadratic yield criterion. The model was assumed to be rate independent. Coulomb friction law was defined for all contact surfaces. The simulation process was performed in two steps. In the first step the blank-holder moves down and deforms the blank into the draw-bead. Then the punch moves up at 20 increments and deforms the specimen to a specified displacement. Three numerical criteria including maximum second thickness strain derivative (CRIT1), equivalent plastic strain increment ratio (CRIT2), and total equivalent plastic strain ratio (CRIT3) were evaluated and the forming limit curve (FLC) were obtained. The predicted FLC were compared with experimental data. Unlike the CRIT2, the CRIT1 and CRIT3 were in good agreements with were experimental data. The CRIT1 criterion predicted the lower bound of the experimental results. While by using the CRIT3 criterion both the lower and upper bounds of the experimental results were predicted.
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S. M. H. Seyedkashi,H. Moslemi Naeini,G. H. Liaghat,M. Mosavi Mashadi,M. Mirzaali,K. Shojaee,문영훈 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.6
The precise control of internal pressure and axial force loading paths significantly affects the final product quality. In this study, the effect of tube dimensions on the pressure and force loading paths in tube hydroforming process is investigated by using simulated annealing optimization method linked to a commercial finite element code. The optimized loading paths, obtained for different tube geometries with a constant expansion ratio, are then compared. The effects of initial diameter and wall thickness on shape conformation, optimal internal pressure and axial force (or feed) are discussed on the basis of optimal loading paths. Several guidelines in prediction and determination of tube hydroforming parameters are obtained by optimization analysis.
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Polygonal finite element modeling of crack propagation via automatic adaptive mesh refinement
M. Shahrezaei,H. Moslemi 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.75 No.6
Polygonal finite element provides a great flexibility in mesh generation of crack propagation problems where the topology of the domain changes significantly. However, the control of the discretization error in such problems is a main concern. In this paper, a polygonal-FEM is presented in modeling of crack propagation problems via an automatic adaptive mesh refinement procedure. The adaptive mesh refinement is accomplished based on the Zienkiewicz–Zhu error estimator in conjunction with a weighted SPR technique. Adaptive mesh refinement is employed in some steps for reduction of the discretization error and not for tracking the crack. In the steps that no adaptive mesh refinement is required, local modifications are applied on the mesh to prevent poor polygonal element shapes. Finally, several numerical examples are analyzed to demonstrate the efficiency, accuracy and robustness of the proposed computational algorithm in crack propagation problems.
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Moslemi-Mehni Elaheh,Khoshahval Farrokh,Pour-Imani Reza,Amirkhani-Dehkordi M.A. 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.9
Due to neutron radiation, atomic displacement has a significant effect on material in nuclear reactors. A range of secondary displacement models, including the Kinchin-Pease (KeP), Lindhard, NorgettRobinson-Torrens (NRT), and athermal recombination-corrected displacement per atom (arc-dpa) have been suggested to calculate the number of displacement per atom (dpa). As neutron elastic interaction is the main cause of displacement damage, the focus of the current study is to calculate the atomic displacement caused by the neutron elastic interaction in order to estimate the exact amount of yield strength in a WWER-1000 reactor pressure vessel. To achieve this purpose, the reactor core is simulated by MCNPX code. In addition, a program is developed to calculate the elastic radiation damage induced by the incident neutron flux (RADIX) based on different models using Fortran programming language. Also, due to non-elastic interaction, the displacement damage is calculated by the HEATR module of the NJOY code. ASME E-693-01 standard, SPECTER, NJOY codes, and other pervious findings have been used to validate RADIX results. The results showed that the RADIX(arc-dpa)/HEATR outputs have appropriate accuracy. The relative error of the calculated dpa resulting from RADIX(arc-dpa)/HEATR is about 8% and 46% less than NJOY code, respectively in the ¼ and ¾ vessel wall.
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Feasibility study on optimized process conditions in warm tube hydroforming
S. M. H. Seyedkashi,H. Moslemi Naeini,문영훈 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.7
Feasibility study has been performed to estimate the optimized process conditions in warm tube hydroforming based on the simulatedannealing optimization method. Precise prediction and control of process parameters play an important role in forming at warm conditions. Optimal pressure and feed loading paths are obtained for aluminium AA6061 tubes through the simulated annealing algorithm in conjunctionwith finite element simulations. Numerous axisymmetric geometries are investigated and the effects of expansion ratio, corner fillet tothickness ratio, and initial diameter to thickness ratio are studied. For the feasibility estimation, warm hydroforming experiments have beenconducted on aluminum AA6061 under optimal designed conditions. The results show that the optimization procedure used in this researchis a reliable and feasible tool in determination of optimal process conditions for the sound warm hydroforming process.
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