• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.6
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• pp.527-532
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• 2009

In this paper simulations for the impact into ceramics and/or metal materials have been discussed. To model discrete nature for fracture and damage of brittle materials, we implemented cohesive-law fracture model with a node separation algorithm for the tensile failure and Mohr-Coulomb model for the compressive loading. The drawback of this scheme is that it requires a heavy computational time. This is because new nodes are generated continuously whenever a new crack surface is created. In order to reduce the amount of calculation, parallelization with MPI library has been implemented. For the high-speed impact problems, the mesh configuration and contact calculation changes continuously as time step advances and it causes unbalance of computational load of each processor. Dynamic load balancing technique which re-allocates the loading dynamically is used to achieve good parallel performance. Some impact problems have been simulated and the parallel performance and accuracy of the solutions are discussed.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.1
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• pp.35-44
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• 2009

This paper describes an application of domain decomposition method for parallel finite element analysis which is required to large scale 3D structural analysis. A parallel finite element method system which adopts a domain decomposition method is developed. Node is generated if its distance from existing node points is similar to the node spacing function at the point. The node spacing function is well controlled by the fuzzy knowledge processing. The Delaunay triangulation method is introduced as a basic tool for element generation. Domain decomposition method using automatic mesh generation system holds great benefits for 3D analyses. Aa parallel numerical algorithm for the finite element analyses, domain decomposition method was combined with an iterative solver, i.e. the conjugate gradient(CG) method where a whole analysis domain is fictitiously divided into a number of subdomains without overlapping. Practical performance of the present system are demonstrated through several examples.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.14 no.3
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• pp.381-390
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• 2001

In this paper, a new improved crack analysis technique by Element-Free Galerkin(EFG) method is proposed, in which the singularity and the discontinuity of the crack successfully described by adding enrichment terms containing a singular basis function to the standard EFG approximation and a discontinuity function implemented in constructing the shape function across the crack surface. The standard EFG method requires considerable addition of nodes or modification of the model. In addition, the proposed method significantly decreases the size of system of equation compared to the previous enriched EFG method by using localized enrichment region near the crack tip. Numerical example show the improvement and th effectiveness of the previous method.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.157-157
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• 2015

최근 들어, 송 배수 시스템의 펌프운영을 최적화하여 운영비용을 절감하기 위한 연구가 활발히 진행되고 있다. 펌프운영을 모의하기 위해서는 수 일간의 시간모의가 필수적이며, 최적화 알고리즘 등과의 연계를 통한 시뮬레이션이 필요한 경우가 많다. 하지만, 대규모 네트워크의 경우 관로 및 절점의 수가 수천, 혹은 수 만개에 달해 수리해석 및 최적화에 소요되는 시간이 길어지는 문제가 발생한다. 이에 본 연구에서는 효율적인 수리해석을 위해 상수관망 네트워크를 골격화(skeletonization)하는 방법을 제안한다. 상수관망시스템의 골격화는 본래의 상수관망 수리 거동을 변화시키지 않는 범위에서 관로와 절점의 삭제, 통합을 통해 복잡한 상수관망을 단순화하는 과정이다. 이러한 골격화 방법은 단순골격화 방법과 등가길이관 방법(Equivalent Length Pipe Method)으로 구분할 수 있다. 단순 골격화 방법은 해당 상수관망 수리해석에 큰 영향을 미치지 않는 소구경관을 삭제하거나, 특정 구역의 여러 수요절점을 하나의 수요절점으로 통합하는 방법이다. 등가길이관 방법은 관경과 연장이 상이한 복수의 관에 동일한 유량이 흐르는 경우, 관경, 연장, 조도계수 등을 조절하여 동일한 수두 손실이 발생하는 하나의 관으로 통합하는 방법이다. 국내에 실제 운영되고 있는 지방상수도를 대상으로 골격화를 진행하였으며, 수리해석 프로그램은 미국 환경청에서 개발한 EPANET을 사용하였다. 본 연구에서 개발한 골격화 기법을 통해 대규모 상수관망의 해석에 소요되는 시간을 단축할 수 있으며, 실제 상수관망의 운영에 도움이 될 것으로 기대한다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.12
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• pp.1021-1030
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• 2017

This paper describes the algorithm of computing thermal contact conductance between unmatched grid interfaces for finite element thermal analysis. Because grid interfaces should be coincident with adjacent meshes for finite element method, large amount of man hours and huge computations are required to match interfaces between many numbers of complex subdomains. A novel method that distributes feasibly the conductances to interface nodes is proposed. The aims of the method are described, and details of the nodal conductance distribution algorithm with less dependency on meshes are represented. The algorithm can be applied both the flat and curved interfaces in 3 dimensional space, and proposed method can combined with many finite element application including thermal analysis.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.271-271
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• 2017

상수관망 수리해석 기법은 절점의 사용량 및 누수량을 기지의 값으로 고려하여 총 수요량이 모두 공급될 수 있다고 가정하여 해석하는 수요기반해석(Demand Driven Analysis, DDA)과 사용량과 누수량은 절점 압력수두에 의해 달라질 수 있어, 공급가능량 및 누수량과 절점의 압력수두 모두를 미지수로 고려하여 해석하는 수압기반해석(Pressure Driven Analysis, PDA)으로 구분될 수 있다. 본 연구에서는 수압기반사용량 모의(Pressure Dependent Demand, PDD)와 수압기반누수량 모의(Pressure Dependent Leakage, PDL)기능이 모두 구현되고, 다양한 시나리오 분석이 가능한 소프트웨어(SW)인 K-NRisk를 개발하였다. K-NRisk는 2016년 7월에 공개된 상수관망 해석범용모형인 EPANET3 소스코드 기반으로 개량 개발되었으며, 기존 EPANET2와 비교하였을 경우 사용자 편의성 증대를 위한 입출력 기능 및 SW 활용도 제고를 위한 대표업무분석 기능이 신규 개발, 강화되었다. 개발된 SW를 관망정비 및 공급안정성 확보 목적을 위한 수리해석 시 적용하여 그 결과를 분석하였다. 적용결과 기존 수요기반해석이 가지고 있는 한계점을 보완하고, 실제업무 시 활용가능함을 확인하였다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.13 no.4
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• pp.485-500
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• 2000

In this paper the adaptive crack propagation analysis based on the estimated local and global error in the element-free Galerkin (EFG) method is presented. It is possible to keep consistency and accuracy of analysis in each propagation step by adaptive analysis. The adaptivity analysis in crack propagation is achieved by adding and removing the node along the background integration cell that are refined or recovered as estimated error. These errors are obtained by calculating the difference between the values of the projected stresses and original EFG stresses. To evaluate the performance of proposed adaptive procedure, the convergence behavior is investigated lot several examples. The results of these examples show the efficiency of proposed scheme in crack propagation analysis.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.9
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• pp.2091-2096
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• 2013

This paper present a method of efficiency circuit design based on directed graph which was represented by tree structure relationship between input and output of nodes. In this paper, we introduce the concept of mathematical analysis based on tree structure which was designed by optimal localized computable circuit. Using the proposed circuit design algorithms in this paper, it is possible to design circuit which directed tree graph have any node number. The proposed method is more effective, regularity and extensibility than former method.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.4
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• pp.257-263
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• 2019

Multilayered structures include lamination by relatively thick plies and thin interlayers. For efficient peridynamic analysis of dynamic fracturing multilayered structures, the interlayer is modeled using ghost peridynamic particles while the ply is formulated via real peridynamics. With the nonlocal ghost interlayer, one may keep the discretization resolution low for the ply. In this study, the characteristics of dynamic wave propagation through the nonlocal ghost interlayer in peridynamic analysis are investigated. It is observed that the interlayer not only binds adjacent plies, but also significantly influences energy transfer between plies, and thereby their deformation and motion. In addition, near a surface or boundary, peridynamic particles do not have a full nonlocal neighborhoods. This causes the effective material properties near the surface to be different from those in the bulk. Surface correction based on neighborhood volumes is employed. The impact of surface correction on wave propagation in multilayered structures is investigated.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.398-402
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• 2005

Structureborne noise induced by shipboard equipment is one of the most significant noise source of ships and can be effectively reduced by resiliently mounting them. In this paper, the pole parameter method is investigated for estimating the structureborne noise reduction of resiliently mounted equipment. In addition, we suggest how to evaluate pole parameters from dimensional and material information of each component consisting of resiliently mounted equipment. To validate and discuss the proposed method numerical analysis for single and double resiliently mounted equipment systems using both pole parameter method and FEM have been done.