• Title/Summary/Keyword: finite element numerical simulations

Search Result 435, Processing Time 0.024 seconds

A combined experimental and numerical study on the plastic damage in microalloyed Q345 steels

  • Li, Bin;Mi, Changwen
    • Structural Engineering and Mechanics
    • /
    • v.72 no.3
    • /
    • pp.313-327
    • /
    • 2019
  • Damage evolution in the form of void nucleation, propagation and coalescence is the primary cause that is responsible for the ductile failure of microalloyed steels. The Gurson-Tvergaard-Needleman (GTN) damage model has proven to be extremely robust for characterizing the microscopic damage behavior of ductile metals. Nonetheless, successful applications of the model on a given metal type are limited by the correct identification of damage parameters as well as the validation of the calculated void growth rate. The purpose of this study is two-fold. First, we aim to identify the damage parameters of the GTN model for Q345 steel (Chinese code), due to its extensive application in mechanical and civil industries in China. The identification of damage parameters is facilitated by the well-suited response surface methodology, followed by a complete analysis of variance for evaluating the statistical significance of the identified model. Second, taking notched Q345 cylinders as an example, finite element simulations implemented with the identified GTN model are performed in order to analyze their microscopic damage behavior. In particular, the void growth rate predicted from the simulations is successfully correlated with experimentally measured acoustic emissions. The quantitative correlation suggests that during the yielding stage the void growth rate increases linearly with the acoustic emissions, while in the strain-hardening and softening period the dependence becomes an exponential function. The combined experimental and finite element approach provides a means for validating simulated void growth rate against experimental measurements of acoustic emissions in microalloyed steels.

Optimization of the Integrated Seat for Crashworthiness Improvement (일체형 시트의 충돌특성 개선을 위한 최적설계)

  • 이광기;이광순;박현민;최동훈
    • Journal of the Computational Structural Engineering Institute of Korea
    • /
    • v.16 no.4
    • /
    • pp.345-351
    • /
    • 2003
  • Due to increasing legal and market demands for safety in the automotive design process, the design of integrated seat is important more and mote because it should satisfy the conflict between stronger and lower weight for safety and environmental demands. In this study for crash simulations, the numerical simulations have been carried out using the explicit finite element program LS-Dyna according to the FMVSS 210 standard for safety test of seat. Since crash simulations are very time-consuming and a series of simulations that does not lead to a better result is very costly, the optimization method must be both efficient and reliable. As a result of that, statistical approaches such as design of experiments and response surface model have been successfully implemented to reduce time-consuming LS-Dyna simulations and optimize the safety and environmental demands together with nonlinear optimization algorithm. Design of experiments is used lot exploring the design space of maximum displacement and total weight and for building response surface models in order to minimize the maximum displacement and total weight of integrated seat.

Deep-beams with indirect supports: numerical modelling and experimental assessment

  • Pimentel, Mario;Cachim, Paulo;Figueiras, Joaquim
    • Computers and Concrete
    • /
    • v.5 no.2
    • /
    • pp.117-134
    • /
    • 2008
  • An experimental and numerical research was conducted to gain a deeper insight on the structural behaviour of deep-beams with indirect supports and to assess the size effects in the ultimate state behaviour. The experimental campaign focused on the influence of the reinforcement tie distribution height on the compression check of the support region and on the benefits of using unbonded prestressing steel. Three reduced scale specimens were tested and used to validate the results obtained with a nonlinear finite element model. As a good agreement could be found between the numerical and the experimental results, the numerical model was then further used to perform simulations in large scale deep-beams, with dimensions similar to the ones to be adopted in a practical case. Two sources of size effects were identified from the simulation results. Both sources are related to the concrete quasi-brittle behaviour and are responsible for increasing failure brittleness with increasing structural size. While in the laboratory models failure occurred both in the experimental tests as well as in the numerical simulations after reinforcement yielding, the numerically analysed large scale models exhibited shear failures with reinforcement still operating in the elastic range.

Usefulness Verification for Flexible Stretch Forming Process using finite Element Method (유한요소법을 이용한 가변 스트레치 성형공정의 적합성 검증)

  • Seo, Y.H.;Heo, S.C.;Park, J.W.;Song, W.J.;Ku, T.W;Kim, J.;Kang, B.S.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
    • /
    • 2009.10a
    • /
    • pp.241-244
    • /
    • 2009
  • This paper deals with a usefulness verification of stretch forming process using flexible die. The stretch forming method is widely used in aircraft and high-speed train industries for manufacturing of skin structure, which is made of sheet metal. A great number of solid dies are originally used and developed for specific shapes with respect to different curvature radii of the skin structures. Accordingly, flexible stretch forming process is proposed in this study. It replaces the conventional solid dies with a set of height adjustable discrete punches. A usefulness of the flexible die is verified through extensive numerical simulations of the stretch forming process for simply curved sheet plate. The elastic recovery is considered and formability evaluations are conducted through a comparison of symmetry plane configurations.

  • PDF

BAYQUAL Model for the Water Quality Simulation of a Bay Using Finite Element Method (유한요소법에 의한 하구의 수질모델 BAYQUAL)

  • 류병로;한양수
    • Journal of Environmental Science International
    • /
    • v.8 no.3
    • /
    • pp.355-361
    • /
    • 1999
  • The aim of this study is to develop the water quality simulation model (BAYQUAL) that deal with the physical, chemical and biological aspects of fate/behavior of pollutants in the bay. BAYQUAL is a two dimensional, time-variable finite element water quality model based on the flow simulation model in bay(BAYFLOW). The algorithm is composed of a hydrodynamic module which solves the equations of motion and continuity, a pollutnat dispersion module which solves the dispersion-advection equation. The applicability and feasibility of the model are discussed by applications of the model to the Kwangyang bay of south coastal waters of Korea. Based on the field data, the BAYQUAL model was calibrated and verified. The results were in good agreement with measured value within relative error of 14% for COD, T-N, T-P. Numerical simulations of velocity components and tide amplitude(M2) were agreed closely with the actual data.

  • PDF

Finite Element Analysis on the Shaft Fitting to Inner Raceway of Radial Ball Bearing (레이디얼 볼베어링의 내륜 끼워맞춤에 관한 유한요소해석)

  • Ko, Byung-Du;Lee, Ha-Sung
    • Design & Manufacturing
    • /
    • v.6 no.1
    • /
    • pp.45-51
    • /
    • 2012
  • The main goal of this paper is to establish an interference tolerance for determining optimal amount of clearance in the shaft-bearing system supported by radial ball bearings. The 2-D frictional contact model was employed for the FE analysis between the shaft and the inner raceway. Several examples were simulated using different material properties for the solid shaft. Efforts were focused on the deformation applied in the radial direction to select suitable bearings. The analysis results showed that the initial axial preload applied on the bearings plays a significant role to reduce bearing fatigue life. The proposed design parameters obtained by numerical simulations can approximately predict a rate of bearing life reduction as a function of shaft diameter ratio. This analysis can also be used to calculate the optimal initial radial clearance in order to obtain a shaft-bearing system design for high accuracy and long life.

  • PDF

Establishment of Fracture Criteria on Human Femur (넙다리뼈에 대한 파괴기준의 설정)

  • Chung, Nam-Yong
    • Transactions of the Korean Society of Automotive Engineers
    • /
    • v.15 no.6
    • /
    • pp.62-72
    • /
    • 2007
  • Fracture analysis of human bone is necessary to predict the failure of musculoskeletal structures and to heal them by several possible mechanisms under different loading conditions. But human bone is a complex material, with a multiphase, heterogeneous and anisotropic microstructure. Due to the difficulty of obtaining experimental and clinical results, the importance of numerical analysis and computational simulations in biomechanics are increasing gradually. In this study, stress analysis for human femur model is performed by using the 2-dimensional finite element method(FEM) and its stress distribution is determined. From these results, the fracture mechanic parameters are calculated and the fracture criteria on human femur are investigated and discussed.

Dynamic Modeling and Analysis of General Rotor Systems with Open Cracks (열린 균열이 있는 일반 회전체계의 동적 모델링 및 해석)

  • 홍성욱;최성환;이종원
    • Transactions of the Korean Society for Noise and Vibration Engineering
    • /
    • v.13 no.4
    • /
    • pp.290-299
    • /
    • 2003
  • This paper presents an efficient modeling and dynamic analysis method for open cracked rotor bearing systems. An equivalent bending spring model is introduced to represent the structural weakening effect in the presence of cracks. The proposed modeling method is validated through a series of simulations and experiments. First, the proposed method Is rigorously compared with a commercial finite element code. Then, an experiment is performed to validate the proposed modeling method. Finally, a numerical example is introduced to demonstrate the possible application of the proposed method in the crack diagnosis for rotor systems.

Mode Truncation Method in Frequency Response Analysis (주파수 응답해석의 모드 축약법)

  • 조태민;이은경;임경화
    • Proceedings of the Korean Institute of Intelligent Systems Conference
    • /
    • 2001.12a
    • /
    • pp.91-94
    • /
    • 2001
  • In the frequency response analysis using a modal method, it is very important to determine the number of modes involved with the formulation of a frequency response function. Most engineers are inclined to determine mode truncation with their experience. But it is difficult for non-experts to decide the mode truncation reasonably in many problems of dynamic analyses. In this study, fuzzy theory is used to standardize the empirical determination of mode truncation so that not only the experts but also non-experts can decide a proper mode truncation easily. Fuzzy rule base is based on the simulation results using finite element method. Numerical simulations show that the developed mode truncation method is a very effective method to choose the number of the considered modes.

  • PDF

Analytical and experimental fatigue analysis of wind turbine tower connection bolts

  • Ajaei, Behrouz Badrkhani;Soyoz, Serdar
    • Wind and Structures
    • /
    • v.31 no.1
    • /
    • pp.1-14
    • /
    • 2020
  • This paper presents a method of estimation of fatigue demands on connection bolts of tubular steel wind turbine towers. The presented method relies on numerical simulation of aerodynamic loads and structural behavior of bolted connections modeled using finite element method. Variability of wind parameters is represented by a set of values derived from their probability densities, which are adjusted based on field measurements. Numerically generated stress time-series show agreement with the measurements from strain gauges inside bolts, in terms of power spectra and the resulting damage. Position of each bolt has a determining effect on its fatigue damage. The proposed framework for fatigue life estimation represents the complexities in loading and local behavior of the structure. On the other hand, the developed procedure is computationally efficient since it requires a limited number of simulations for statistically representing the wind variations.