• Title/Summary/Keyword: global-local numerical approach

Search Result 63, Processing Time 0.03 seconds

Numerical Simulation of Mechanical Behavior of Composite Structures by Supercomputing Technology

  • Kim, Seung-Jo;Ji, Kuk-Hyun;Paik, Seung-Hoon
    • Advanced Composite Materials
    • /
    • v.17 no.4
    • /
    • pp.373-407
    • /
    • 2008
  • This paper will examine the possibilities of the virtual tests of composite structures by simulating mechanical behaviors by using supercomputing technologies, which have now become easily available and powerful but relatively inexpensive. We will describe mainly the applications of large-scale finite element analysis using the direct numerical simulation (DNS), which describes composite material properties considering individual constituent properties. DNS approach is based on the full microscopic concepts, which can provide detailed information about the local interaction between the constituents and micro-failure mechanisms by separate modeling of each constituent. Various composite materials such as metal matrix composites (MMCs), active fiber composites (AFCs), boron/epoxy cross-ply laminates and 3-D orthogonal woven composites are selected as verification examples of DNS. The effective elastic moduli and impact structural characteristics of the composites are determined using the DNS models. These DNS models can also give the global and local information about deformations and influences of high local in-plane and interlaminar stresses induced by transverse impact loading at a microscopic level inside the materials. Furthermore, the multi-scale models based on DNS concepts considering microscopic and macroscopic structures simultaneously are also developed and a numerical low-velocity impact simulation is performed using these multi-scale DNS models. Through these various applications of DNS models, it can be shown that the DNS approach can provide insights of various structural behaviors of composite structures.

Estimation of the Fatigue Damage for an Ice-going Vessel under Broken Ice Condition Part II - Simplified Approach (유빙 하중을 받는 내빙 선박의 피로손상도 추정 Part II - 간이 해석법)

  • Kim, Jeong-Hwan;Kim, Yooil
    • Journal of the Society of Naval Architects of Korea
    • /
    • v.56 no.3
    • /
    • pp.231-241
    • /
    • 2019
  • In this study, a simplified analysis method was developed to evaluate the fatigue damage of an ice-going ship under broken ice condition. The global ice load, which is essentially calculated at the design stage of the Arctic vessel, and the hull form information were used to estimate the local ice load acting on the outer-shell of the ship. The local ice load was applied to the finite element analysis model, and the Weibull parameters for the target fatigue point were derived. Finally, fatigue damage was evaluated by applying the S-N curve and the Palmgren-Miner rule. For the verification of the proposed method, numerical analyses using direct approach were performed for the same conditions. A numerical model that implements the interaction between ice and structure was introduced to verify the local ice load and the stress calculated from the proposed method. Finally, the fatigue analyses of the Baltic Sea for actual ice conditions were performed, and the results of the proposed method, the method using numerical analysis, and the LR method were compared.

Numerical and Experimental Analysis of Spray Atomization Characteristics of a GDI Injector

  • Park, Sung-Wook;Kim, Hyung-Jun;Lee, Chang-Sik
    • Journal of Mechanical Science and Technology
    • /
    • v.17 no.3
    • /
    • pp.449-456
    • /
    • 2003
  • In this study, numerical and experimental analysis on the spray atomization characteristics of a GDI injector is performed. For numerical approach, four hybrid models that are composed of primary and secondary breakup model are considered. Concerning the primary breakup, a conical sheet disintegration model and LISA model are used. The secondary breakup models are made based on the DDB model and RT model. The global spray behavior is also visualized by the shadowgraph technique and local Sauter mean diameter and axial mean velocity are measured by using phase Doppler particle analyzer Based on the comparison of numerical and experimental results, it is shown that good agreement is obtained in terms of spray developing process and spray tip penetration at the all hybrid models. However, the hybrid breakup models show different prediction of accuracy in the cases of local SMD and the spatial distribution of breakup.

Numerical analysis on the behaviour of reinforced concrete frame structures in fire

  • Dzolev, Igor M.;Cvetkovska, Meri J.;Ladinovic, Dorde Z.;Radonjanin, Vlastimir S.
    • Computers and Concrete
    • /
    • v.21 no.6
    • /
    • pp.637-647
    • /
    • 2018
  • Numerical approach using finite element method has been used to evaluate the behaviour of reinforced concrete frame structure subjected to fire. The structure is previously designed in accordance with Eurocode standards for the design of structures for earthquake resistance, for the ductility class M. Thermal and structural response are obtained using a commercially available software ANSYS. Temperature-dependent nonlinear thermal and mechanical properties are adopted according to Eurocode standards, with the application of constitutive model for the triaxial behaviour of concrete with a smeared crack approach. Discrete modelling of concrete and reinforcement has enabled monitoring of the behaviour at a global, as well as at a local level, providing information on the level of damage occurring during fire. Critical regions in frame structures are identified and assessed, based on temperatures, displacements, variations of internal forces magnitudes and achieved plastic deformations of main reinforcement bars. Parametric analyses are conducted for different fire scenarios and different types of concrete aggregate to determine their effect on global deformations of frame structures. According to analyses results, the three-dimensional finite element model can be used to evaluate the insulation and mechanical resistance criteria of reinforced concrete frame structures subjected to nominal fire curves.

Modified Stiffness Matrix of Frame Reflecting the Effect of Local Cracks (국부적 균열의 영향을 고려한 수정된 프레임 강성행렬)

  • 이상호;송정훈;임경훈
    • Proceedings of the Computational Structural Engineering Institute Conference
    • /
    • 2002.04a
    • /
    • pp.353-360
    • /
    • 2002
  • The objective of this study is to develop a technique that analyzes the global behavior of frame structures with local cracks. The technique is based on frame analysis and uses the stiffness matrix of cracked frame element. An algorithm proposed here analyzes a frame structure with local transverseedge cracks, considering the effects of crack length and location. Stress intensity factors are employed to calculate additional local compliance due to the cracks based on linear elastic fracture mechanics theory, and then this local compliance is utilized to derive the stiffness matrix of the cracked frame element. In order to verify the accuracy and reliability of the proposed approach, numerical results are compared with those of Finite Element Method for the cracked frame element, and the effects of single crack on the behavior of truss structure are also examined.

  • PDF

Numerical Analysis of Ship Local Resistance (선체 국소 저항 수치 해석)

  • Park, Dong-Woo;Seo, Jang-Hoon;Yoon, Hyun-Sik;Chun, Ho-Hwan;Jung, Jae-Hwan;Kim, Mi-Jeong
    • Journal of Ocean Engineering and Technology
    • /
    • v.26 no.6
    • /
    • pp.74-79
    • /
    • 2012
  • The present study aims at suggesting the systematic approach to analyze the local drag components as the resistance performance characterized by the flow of the ship. In order to identify the local areas, the hull surface is decomposed into SVM (Station-Vertical Section Map) which consists of 20 stations along the longitudinal direction and 20 sections along the vertical direction (from the bottom to the waterline). Successively, on the SVM, the friction and pressure drag coefficients as the components of total drag coefficient have been analyzed for two different hull forms of Wigley and KVLCC by using CFD.

A Non-consecutive Cloth Draping Simulation Algorithm using Conjugate Harmonic Functions (켤레조화함수를 이용한 비순차적 의류 주름 모사 알고리즘)

  • Kang Moon Koo
    • Journal of KIISE:Software and Applications
    • /
    • v.32 no.3
    • /
    • pp.181-191
    • /
    • 2005
  • This article describes a simplified mathematical model and the relevant numerical algorithm to simulate the draped cloth on virtual human body. The proposed algorithm incorporates an elliptical, or non-consecutive, method to simulate the cloth wrinkles on moving bodies without resorting to the result of the past time-steps of drape simulation. A global-local analysis technique was employed to decompose the drape of cloths into the global deformation and the local wrinkles that will be superposed linearly The global deformation is determined directly by the rotation and the translation of body parts to generate a wrinkle-free yet globally deformed shape of cloth. The local wrinkles are calculated by solving simple elliptical equations based on the orthogonality between conjugate harmonic functions representing the wrinkle amplitude and the direction of wrinkles. The proposed method requires no interpolative time frames even for discontinuous body postures. Standing away from the incremental approach of time integration in conventional methods, the proposed method yields a remarkable reduction of CPU time and an enhanced stability. Also, the transient motion of cloth could be achieved by interpolating between the deformations corresponding to each static posture.

System identification of an in-service railroad bridge using wireless smart sensors

  • Kim, Robin E.;Moreu, Fernando;Spencer, Billie F.
    • Smart Structures and Systems
    • /
    • v.15 no.3
    • /
    • pp.683-698
    • /
    • 2015
  • Railroad bridges form an integral part of railway infrastructure throughout the world. To accommodate increased axel loads, train speeds, and greater volumes of freight traffic, in the presence of changing structural conditions, the load carrying capacity and serviceability of existing bridges must be assessed. One way is through system identification of in-service railroad bridges. To dates, numerous researchers have reported system identification studies with a large portion of their applications being highway bridges. Moreover, most of those models are calibrated at global level, while only a few studies applications have used globally and locally calibrated model. To reach the global and local calibration, both ambient vibration tests and controlled tests need to be performed. Thus, an approach for system identification of a railroad bridge that can be used to assess the bridge in global and local sense is needed. This study presents system identification of a railroad bridge using free vibration data. Wireless smart sensors are employed and provided a portable way to collect data that is then used to determine bridge frequencies and mode shapes. Subsequently, a calibrated finite element model of the bridge provides global and local information of the bridge. The ability of the model to simulate local responses is validated by comparing predicted and measured strain in one of the diagonal members of the truss. This research demonstrates the potential of using measured field data to perform model calibration in a simple and practical manner that will lead to better understanding the state of railroad bridges.

Improvement of Filling Characteristics of Micro-Bumps in the Stencil Printing Process (스텐실 프린팅 공정에서 미세범프의 성형성 향상을 위한 연구)

  • Seo, W.S.;Min, B.W.;Park, K.;Lee, H.J.;Kim, J.B.
    • Journal of the Korean Society of Manufacturing Technology Engineers
    • /
    • v.21 no.1
    • /
    • pp.26-32
    • /
    • 2012
  • In the present study, the stencil printing process using solder paste are numerically analyzed. The key design parameters in the stencil printing process are the printing conditions, stencil design, and solder paste properties. Among these parameters, the effects of printing conditions including the squeegee angle and squeegee pressure are investigated through finite element (FE) analysis. However, the FE analysis for the stencil printing process requires tremendous computational loads and time because this process carries micro-filling through thousands of micro-apertures in stencil. To overcome this difficulty in simulation, the present study proposes a two-step approach to sequentially perform the global domain analysis and the local domain analysis. That is, the pressure development under the squeegee are firstly calculated in the full analysis domain through the global analysis. The filling stage of the solder paste into a micro-aperture is then analyzed in the local analysis domain based on the results of the preceding global analysis.

Dynamic analysis of steel frames with semi-rigid connections

  • Zohra, Djouaher Fatma;Nacer, Ihaddoudene Touati Abd
    • Structural Engineering and Mechanics
    • /
    • v.65 no.3
    • /
    • pp.327-334
    • /
    • 2018
  • In the steel structures design, beam-to-column connections are usually considered either rigid or pinned, while their actual behavior lies between these two ideal cases. This consideration has a major influence on the results of the local and the global behavior of steel structures. This influence is noticed in the case of a static analysis, and has an important effect in the case of a dynamic analysis. In fact, pinned and rigid nodes can be considered as two specific cases of a semi-rigid behavior. To study the efficiency of the classification adopted in Eurocode 3, a numerical simulation of semi-rigid nodes has been carried out using the software ANSYS. In the aim to validate this simulation, the numerical results are compared to those of an analytical approach. After that, the validated numerical simulation has been used, to evaluate the efficiency of the classification adopted by the Eurocode 3, regarding semi-rigid connections. Finally, a new method is proposed to define a more accurate evaluation about semi-rigid connections.