• Title/Summary/Keyword: Elasto-Plastic finite element analysis

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On the analysis of micro pattern forming on the thin sheet metal (마이크로 박판 미세 패턴 성형공정에 대한 해석적 연구)

  • Cha, S.H.;Shin, M.S.;Kim, J.H.;Kim, J.B.;Lee, H.J.;Song, J.H.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2009.10a
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    • pp.53-56
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    • 2009
  • Roll forming process is one of important metal processing technology because the process is simple and economical. These days, roll forming process is tried to be employed in manufacturing the circuit board, barrier ribs and solar cell plate for productivity. However, it is difficult to apply to the forming of micro scale or sub-micro scale pattern. In this study, the roll forming processing for the micro scale is designed and analyzed. In this study, the forming of micro pattern for solar cell plate by incremental roll forming process is analyzed. The solar cell plate may have thousands of patterns, and the analysis of forming considering all the patterns is impossible due to the computational costs. In this study, analyses are carried out for various numbers of patterns and the results are compared. It is shown that the analyses results with four row patterns and twelve row patterns are same. So, it is considered that the analysis can be carried out for only four rows of pattern for the design of incremental roll forming process. Also experiment is carried out process that is designed through simulation.

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Case study on stability performance of asymmetric steel arch bridge with inclined arch ribs

  • Hu, Xinke;Xie, Xu;Tang, Zhanzhan;Shen, Yonggang;Wu, Pu;Song, Lianfeng
    • Steel and Composite Structures
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    • v.18 no.1
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    • pp.273-288
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    • 2015
  • As one of the most common failure types of arch bridges, stability is one of the critical aspects for the design of arch bridges. Using 3D finite element model in ABAQUS, this paper has studied the stability performance of an arch bridge with inclined arch ribs and hangers, and the analysis also took the effects of geometrical and material nonlinearity into account. The impact of local buckling and residual stress of steel plates on global stability and the applicability of fiber model in stability analysis for steel arch bridges were also investigated. The results demonstrate an excellent stability of the arch bridge because of the transverse constraint provided by transversely-inclined hangers. The distortion of cross section, local buckling and residual stress of ribs has an insignificant effect on the stability of the structure, and the accurate ultimate strength may be obtained from a fiber model analysis. This study also shows that the yielding of the arch ribs has a significant impact on the ultimate capacity of the structure, and the bearing capacity may also be approximately estimated by the initial yield strength of the arch rib.

Fatigue Assessment of Reactor Vessel Outlet Nozzle Weld Considering the LBZ and Welding Residual Stress Effect (국부 취화부와 용접 잔류응력 효과를 고려한 원자로 출구노즐 용접부의 피로강도 평가)

  • Lee, Se-Hwan
    • Journal of Welding and Joining
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    • v.24 no.2
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    • pp.48-56
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    • 2006
  • The fatigue strength of the welds is affected by such factors as the weld geometry, microstructures, tensile properties and residual stresses caused by fabrication. It is very important to evaluate the structural integrity of the welds in nuclear power plant because the weldment undergoes the most of damage and failure mechanisms. In this study, the fatigue assessments for a reactor vessel outlet nozzle with the weldment to the piping system are performed considering the welding residual stresses as well as the effect of local brittle zone in the vicinity of the weld fusion line. The analytical approaches employed are the microstructure and mechanical properties prediction by semi-analytical method, the thermal and stress analysis including the welding residual stress analysis by finite element method, the fatigue life assessment by following the ASME Code rules. The calculated results of cumulative usage factors(CUF) are compared for cases of the elastic and elasto-plastic analysis, and with or without residual stress and local brittle zone effects, respectively. Finally, the fatigue life of reactor vessel outlet nozzle weld is slightly affected by the local brittle zone and welding residual stresses.

On the effective analysis method of micro pattern forming on the thin sheet metal (마이크로 박판 미세 패턴 성형공정에 대한 해석 효율성 연구)

  • Cha, S.H.;Shin, M.S.;Kim, J.H.;Kim, J.B.;Lee, H.J.;Song, J.H.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2009.05a
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    • pp.56-59
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    • 2009
  • Roll forming process is one of important metal processing technology because the process is simple and economical. These days, roll forming process is tried to be employed in manufacturing the circuit board, barrier ribs and solar cell plate for productivity. However, it is difficult to apply to the forming of micro scale or sub-micro scale pattern. In this study, the roll forming processing for the micro scale is designed and analyzed. In this study, the forming of micro pattern for solar cell plate by incremental roll forming process is analyzed. The solar cell plate may have thousands of patterns, and the analysis of forming considering all the patterns is impossible due to the computational costs. In this study, analyses are carried out for various numbers of patterns and the results are compared. It is shown that the analyses results with four row patterns and twelve row patterns are same. So, it is considered that the analysis can be carried out for only four rows of pattern for the design of incremental roll forming process.

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Searching for critical failure surface in slope stability analysis by using hybrid genetic algorithm

  • Li, Shouju;Shangguan, Zichang;Duan, Hongxia;Liu, Yingxi;Luan, Maotian
    • Geomechanics and Engineering
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    • v.1 no.1
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    • pp.85-96
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    • 2009
  • The radius and coordinate of sliding circle are taken as searching variables in slope stability analysis. Genetic algorithm is applied for searching for critical factor of safety. In order to search for critical factor of safety in slope stability analysis efficiently and in a robust manner, some improvements for simple genetic algorithm are proposed. Taking the advantages of efficiency of neighbor-search of the simulated annealing and the robustness of genetic algorithm, a hybrid optimization method is presented. The numerical computation shows that the procedure can determine the minimal factor of safety and be applied to slopes with any geometry, layering, pore pressure and external load distribution. The comparisons demonstrate that the genetic algorithm provides a same solution when compared with elasto-plastic finite element program.

Effects of Distributed Load on the Dynamic Response of the Reinforced Concrete Slabs (분포하중이 철근 콘크리트 슬래브의 동적 거동에 미치는 영향)

  • Oh, Kyung-Yoon;Cho, Jin-Goo;Choi, Soo-Myung;Hong, Chong-Hyun
    • Journal of The Korean Society of Agricultural Engineers
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    • v.50 no.2
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    • pp.19-26
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    • 2008
  • This study has been carried out to investigate the dynamic characteristics of RC slabs. For this purpose, the 20-node solid element has been used to discretize the RC slabs into two parts of concrete and rebar. The material non-linearity considering elasto-visco plastic model and the smeared crack model have been adopted in the finite element formulation. The applied load can handle step load, load intensity of harmonic load, area of distributed load and frequency. The frequency of harmonic load has an significant effect on dynamic behaviour in terms of displacement. As the frequency is increased, the effect of load amplitude is more serious. Especially, if the frequency of harmonic load exceeds 30 Hz, it is noted that the displacement by harmonic load is greater than that by step load. In case of harmonic load, the damping effect shows no certain tendency with respect to frequency of load. In details, the damping is effective when the frequency of harmonic load is 2 Hz, but there is no consistent tendency according to damping ratio. The dynamic response when the frequency of harmonic load is 3 Hz shows same result for undamped case as well as for damped case with 5% damping ratio. It is also noted that we can get the largest deflection for damped case with 1% damping ratio. However, there is not any damping effect when the frequency of harmonic load is greater than 4 Hz.

Stiffness of Bucket Foundation in Sand (사질토 지반에 설치된 버킷기초의 강성)

  • Park, Jeongseon;Park, Duhee;Yoon, Sewoong;Jang, Hwasup;Yoon, Jinam
    • Journal of the Korean GEO-environmental Society
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    • v.18 no.8
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    • pp.5-15
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    • 2017
  • To perform an integrated load analysis carried out to evaluate the stability evaluation of wind turbine generators, the six degree-of-freedom stiffness matrix of foundation, which describes relationships between loads and displacement, is needed. Since the foundation stiffness should accurately reflect the shape of foundation and the condition of soil, it is necessary to calculate the stiffness of the bucket foundation that considers the elasto-plastic behavior of the soil. In this study, finite element analyses were performed for a range of soils and shapes of bucket foundations to estimate the foundation stiffness. Normalized stiffness curves are developed from respective numerical simulations. Proposed results are considered to be useful because they can be directly applied in the design.

Distribution of Welding Residual Stresses in T-joint Weld with Root Gap (루트부 갭이 있는 양면 필릿용접 이음부의 용접잔류응력 분포)

  • H.S. Bang;S.H. Kim;Y.P. Kim;C.W. Lee
    • Journal of the Society of Naval Architects of Korea
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    • v.39 no.3
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    • pp.81-88
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    • 2002
  • The root joint in the welding structures are apt to failure by the stress concentration which is occurred by the external force. Therefore, in the safety and reliability of structure, the complete penetration joint welding which are obtained by the groove welding with edge preparation is generally required. Nevertheless, fillet T-joint welding without edge preparation is often carried out in the fields to reduce working time and consumption of welding electrode, however, this process is likely to produce inadequate joint penetration such as root gap. In this paper, the focus of research is to investigate distribution of welding residual stresses in the plate(or flange) and web of T-joint weld, and especially in the near of root gap notch that is due to incomplete joint penetration. For the analysis, we have chosen model of T-joint weld in the cases of single and multi-pass welding with submerged arc welding and analyzed model by using finite element programs considering the heat conduction and thermal elasto-plastic theory.

Stress Analysis of Arctic Thaw Settlement with Gas Pipeline using Finite Element Method (유한요소해석을 활용한 극한지 융해침하에 따른 천연가스배관의 응력해석)

  • Kim, Kyung Il;Yeom, Kyu Jung;Kim, Young-Pyo;Kim, Woo Sik;Oh, Kyu Hwan
    • Journal of the Korean Institute of Gas
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    • v.18 no.5
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    • pp.78-84
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    • 2014
  • It is important to secure the supply of gas in arctic region which is not developed recently due to depleting of fossil fuel. It is competing in order to secure the arctic region. The need for the occurring the pipeline design in arctic region is essential for development. In this study, we develop the model of thaw settlements for analysis the stress and displacement which applied with pipe in arctic region between $-40^{\circ}C$ to $20^{\circ}C$. The soil was applied with Mohr-coulomb theory and pipe was elasto-plastic method.

Nonlinear Analysis of Nuclear Reinforced Concrete Containment Structures under Accidental Thermal Load and Pressure (온도 및 내압을 받는 원자로 철근콘크리트 격납구조물의 비선형해석)

  • Oh, Byung Hwan;Lee, Myung Gue
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.14 no.3
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    • pp.403-414
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    • 1994
  • Nonlinear analysis of RC containment structure under thermal load and pressure is presented to trace the behaviour after an assumed LOCA. The temperature distribution varying with time through the wall thickness is determined by transient finite element analysis with the two time level scheme in time domain. The layered shell finite elements are used to represent the containment structures in nuclear power plants. Both geometric and material nonlinearities are taken into account in the finite element formulation. The constitutive relation of concrete is modeled according to Drucker-Prager yield criteria in compression. Tension stiffening model is used to represent the tensile behaviour of concrete including bond effect. The reinforcing bars are modeled by smeared layer at the location of reinforcements accounting elasto-plastic axial behaviors. The steel liner model under Von Mises yield criteria is adopted to represent elastic-perfect plastic behaviour. Geometric nonlinearity is formulated to consider the large displacement effect. Thermal stress components are determined by the initial strain concept during each time step. The temperature differential between any two consecutive time steps is considered as a load incremental. The numerical results from this study reveal that nonlinear temperature gradient based on transient thermal analysis will produces excessive large displacement. Nonlinear behavior of containment structures up to ultimate stage can be traced reallistically. The present study allows more realistic analysis of concrete containment structures in nuclear power plants.

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