Estimation of penetration equation parameters by comparing numerical analysis and experimental results

조아현,박강,김건인 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.12

Penetration analyses are needed to improve the survivability of combat vehicles. The penetration analysis can be achieved by numerical analysis or experiments. Because excessive time is required to obtain results in both cases, it is needed to derive a penetration equation using numerical analysis. But, the constants for the penetration equation are hardly found in the literature. Therefore, in this paper, the penetration equation is derived using the following steps: (1) Setting up a numerical analysis model and proving it with experimental data, and (2) determining the constants of the penetration equations for various target materials and impact conditions using the numerical analysis model. This procedure can be used to predict penetration when there are no sufficient penetration experimental data for a given material and impact conditions. In this paper, ANSYS Explicit Dynamics was used for creating the simulated penetration data to estimate the parameters of the penetration equation. The penetration numerical analysis was performed for a high-velocity collision between a 7.62 mm AP (armor piercing) bullet and the targets, which include RHA (rolled homogeneous armor) steel and 7075 aluminum. As a result, the error rate between the results of the numerical analysis and penetration experiments is approximately 5 %, which verifies the accuracy of the numerical analysis. The constants of the penetration equation for RHA steel and 7075 aluminum were determined using the numerical analysis model. In vulnerability analyses, penetration equation with the constant that was identified using our methodology can replace the numerical penetration analysis, which requires excessive calculation time.

수치해석법을 활용한 압축부재 성능 해석의 가능성에 대한 연구

김광철 한국가구학회 2010 한국가구학회지 Vol.21 No.1

This is a leading study to replace the structural analysis methodology on the specific traditional joint by a numerical analysis. Tests were carried out to test the compressive methodologies with the numerical results. The Japanese larch was used as a sample. The Orthotropic property of wood was specifically considered for the finite element numerical analysis. Linear numerical analysis and non-linear numerical analysis for the BEAM element and the two SOLID elements of ANSYS were used to analyze the compressive performance. In addition, more finely divided elements were used to raise the accuracy of the numerical result. Finally, the statistically significant differences were tested between that of the analytical and numerical results. It could be concluded that the SOLID 64 element shows the most optimum result when the non-linear analysis with the more finely divided element was used. However, finely dividing of the element is a considerable time consuming process, and it is quite difficult to raise the accuracy of the non-linear numerical analysis. Therefore, if considering the vertical displacement to be of the only interest, the BEAM element is more efficient than the SOLID element because the BEAM element is reflected as a simple line, which is less time consuming and difficult in dividing the elements. But, the BEAM element cannot accurately model the knot as a strength defect factor which is an important property in the orthotropic property of wood. Therefore, the SOLID element should be used to model the strength defect factor, knot, as it can be efficiently applied on the structural size flexure member which could be more strongly effected by the knot. In addition, it is useful at times when the failure types of members are to be more closely investigated, as the SOLID element is able to examine the local stress distribution of the member. The conclusion drawn by this study is of the good concordance between analytical results and numerical results of compressive wood members, but how orthotropic properties should only be considered. The numerical analysis on the specific Korean traditional joints will be based on the current study results.

수리모형과 수치해석을 통한 만곡부 하천의 수리학적 특성 비교 고찰

서동일,최한규 강원대학교 산업기술연구소 2007 産業技術硏究 Vol.27 No.A

This study, regarding curved channel, was performed to compare and analyze hydraulic characteristics and the speed of water and water level for left bank and right bank through hydraulic model experiments and numerical analysis. Real channels that had characteristics of curved channel were selected as objectives. In order to easily operate one and two dimensional numerical analysis and comparison for total 2.4Km model channel, measuring point was set up as 200m. HEC-RAS model was applied as one dimensional numerical analysis program and SMS model was used as two dimensional numerical analysis program. In respect of speed of water, the average speed of water for right bank recorded 8.33m/s in a model experiment and 3.08m/s, 8.57m/s were average speed of water for right bank in one dimensional and two dimensional numerical analysis. The average speed of water of two dimensional numerical analysis was quite similar to that of model experiments. Also, as for water level, maximum observational errors between one and two dimensional numerical analysis for right and left bank of model experiments were 0.66m, 0.84m and 0.28m, 0.48m for each. It was found that two dimensional numerical analysis had a similar result to hydraulic model experiments. Accordingly, from the result of this study, two dimensional numerical analysis should be used rather than one dimensional numerical analysis, when numerical analysis for curved channel is conducted.

수치해석을 이용한 윤중제 흐름특성해석 적용성

최한규(Choi Han Kuy),김장욱(Kim Jang Uk),백효선(Baek Hyo Sun) 강원대학교 산업기술연구소 2008 産業技術硏究 Vol.28 No.1

When the existing polder levee was constructed, the river’s numerical analysis decided the bank raise by applying the planned flood stage or by using the result from the sectional 1st dimensional numerical analysis. But, it was presented that there is a limitation in the 1st dimensional value analysis when the structure like the polder levee obstructs the special shaped running water flow. Therefore, in order to verify the numerical value applicability when the polder levee is constructed, this report compared each other through the 1st and 2nd dimensional numerical analysis and the mathematical principle model laboratory. In case of the polder levee construction through the numerical analysis and the mathematical principle model laboratory, it was decided that there was no big problem in the 1st dimensional numerical analysis applied design, considering the uncertainty of mathematical principle analysis though the first dimensional numerical analysis was calculated a little bigger than the second. But, after construction, it was found that the water level deviation of the 1st, 2nd occurred biggest at the place where the flow was divided into two. Also, as a result of comparing the 1st, 2nd dimensional numerical analysis with the mathematical principle model laboratory, it was confirmed that the 1st numerical analysis applied design decreased the modal safety largely, as the left side water level was calculated smaller more than 0.5m in case of the 1st dimensional numerical analysis.

Verification of Accuracy and Calculation Efficiency of Global-Local Iterative Analysis Method for Large-scale Process-based TSPA

Hong Jang,Gil-Eon Jeong,Dong Hyuk Lee,Jung-Woo Kim 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.1

The most important thing in development of a process-based TSPA (Total System Performance Assessment) tool for large-scale disposal systems (like APro) is to use efficient numerical analysis methods for the large-scale problems. When analyzing the borehole in which the most diverse physical phenomena occur in connection with each other, the finest mesh in the system is applied to increase the analysis accuracy. Since thousands of such boreholes would be placed in the future disposal system, the numerical analysis for the system becomes significantly slower, or even impossible due to the memory problem in cases. In this study, we propose a tractable approach, so called global-local iterative analysis method, to solve the large-scale process-based TSPA problem numerically. The global-local iterative analysis method goes through the following process: 1) By applying a coarse mesh to the borehole area the size of the problem of global domain (entire disposal system) is reduced and the numerical analysis is performed for the global domain. 2) Solutions in previous step are used as a boundary condition of the problem of local domain (a unit space containing one borehole and little part of rock), the fine mesh is applied to the borehole area, and the numerical analysis is performed for each local domain. 3) Solutions in previous step are used as boundary conditions of boreholes in the problem of global domain and the numerical analysis is performed for the global domain. 4) steps 2) and 3) are repeated. The solution derived by the global-local iterative analysis method is expected to be closer to the solution derived by the numerical analysis of the global problem applying the fine mesh to boreholes. In addition, since local problems become independent problems the parallel computing can be introduced to increase calculation efficiency. This study analyzes the numerical error of the globallocal iterative analysis method and evaluates the number of iterations in which the solution satisfies the convergence criteria. And increasing computational efficiency from the parallel computing using HPC system is also analyzed.

Performance Analysis of Multiple Wave Energy Converters due to Rotor Spacing

Sunny Kumar Poguluri,Dongeun Kim,Haeng Sik Ko,Yoon Hyeok Bae 한국해양공학회 2021 韓國海洋工學會誌 Vol.35 No.3

A numerical hydrodynamic performance analysis of the pitch-type multibody wave energy converter (WEC) is carried out based on both linear potential flow theory and computational fluid dynamics (CFD) in the unidirectional wave condition. In the present study, Salter"s duck (rotor) is chosen for the analysis. The basic concept of the WEC rotor, which nods when the pressure-induced motions are in phase, is that it converts the kinetic and potential energies of the wave into rotational mechanical energy with the proper power-take-off system. This energy is converted to useful electric energy. The analysis is carried out using three WEC rotors. A multibody analysis using linear potential flow theory is performed using WAMIT (three-dimensional diffraction/radiation potential analysis program), and a CFD analysis is performed by placing three WEC rotors in a numerical wave tank. In particular, the spacing between the three rotors is set to 0.8, 1, and 1.2 times the rotor width, and the hydrodynamic interaction between adjacent rotors is checked. Finally, it is confirmed that the dynamic performance of the rotors slightly changes, but the difference due to the spacing is not noticeable. In addition, the CFD analysis shows a lateral flow phenomenon that cannot be confirmed by linear potential theory, and it is confirmed that the CFD analysis is necessary for the motion analysis of the rotor.

지반굴착 해석모델에 따른 변위거동에 관한 연구

정지승(Jeeseung Chung),신영완(Youngwan Shin),김만화(Manhwa Kim),국윤모(Yunmo Kook),정규경(Kyukyung Jeong),김필수(Pilsoo Kim),이상환(Sanghwan Lee) 한국지반환경공학회 2018 한국지반환경공학회논문집 Vol.19 No.4

제한된 토지의 효율적인 활용을 위해 과거로부터 지하공간 개발에 따라 수많은 지반굴착 공사가 이루어져 왔다. 지반굴착은 굴착면 주변지반의 응력변화와 변위를 수반함에 따라 굴착면의 안정성에 영향을 미치게 되어 지반거동에 대한 영향을 예측하는 것이 매우 중요한 문제이다. 이러한 영향 예측을 위한 방법으로 수치해석방법이 주로 이용되며, 최근 컴퓨터 성능 향상과 더불어 수치해석 프로그램의 발달로 매우 복잡한 문제도 적용이 가능해졌다. 그러나 일부 특수해석을 제외하고 대부분 해석모델을 산정 및 적용이 간편한 Mohr-Coulomb 해석모델을 적용함에 따라 굴착면 바닥부에서 실제보다 큰 변위가 발생하는 것으로 예측되어 필요 이상의 보강이 이루어지는 문제점이 발생한다. 본 연구에서는 지반굴착 과정을 모사하여 수치해석을 수행하였으며, 해석모델로 Mohr-Coulomb, Modified Mohr-Coulomb, Duncan-Chang, Hardening Soil 해석모델을 적용하여 그 결과를 비교분석하였다. 본 연구는 수치해석을 통한 지반굴착 문제해결 시 다양한 지반굴착 조건별로 적합한 해석모델 선정을 위한 기초자료로 활용될 것으로 기대된다. There were many ground excavation projects from past to present to make effective use of the limited land. And it is very important to predict the ground behavior depending on construction stage for ground excavation. Excavation of the ground involves changes in the stress and displacement of the ground around the excavated surface. Thus it affects the stability of the adjacent structure as well as the excavated surface. Therefore, it is very important to predict the ground behavior and stability of adjacent structure. And nowadays, numerical analysis methods are most often used to predict the effects of ground excavation. Recent, improvements of numerical analysis programs, along with improved computer performance, have helped solve complicated ground problems. However, except some specialized numerical analysis, most numerical analysis often predicts larger excavation floor displacement than field data due to adopt the Mohr-Coulomb analysis model. As a result, it raise the problem that increasing the amount of support on ground and structure. In this study, ground behavior analysis depending on analysis model (Mohr-Coulomb, Duncan-Chang, Modified Mohr-Coulomb and Hardening Soil model) has been carried out through the numerical analysis. When numerical analysis is carried out, this study is expected to be used as a basic data for adopting a suitable analysis model in various ground excavation project.

로마숫자를 통한 화성분석의 효용성을 위한 제언

송무경 한양대학교 음악연구소 2012 音樂論壇 Vol.28 No.-

The present research begins by examining the harmonic analysis by Roman numerals, which has been settled down as a most rudimentary way of music analysis in the undergraduate curriculum, and furthermore explores diverse ways of increasing its analytic validity by modifying and supplementing its concepts and notations. In spite of its crucial role, the Roman numeral analysis has been regarded merely as a labeling tool in its initial stage of analysis, not a systematized theory that has logical assumptions and hypotheses. The goal of this article is to propose a systematic and comprehensive method of tonal music analysis by taking useful concepts of the Schenkerian theory and applying them to the Roman numeral analysis. For this task, I will review undergraduate textbooks dealing with harmony and analysis and then explore what subsidiary symbols other than Roman numerals the authors of the textbooks devise and introduce in order to supplement the Roman numeral analysis. Second, I will first explore possible ways of carrying out the layered analysis using Roman numerals by referring to Neumeyer and Tepping’s didactic tutorial of the Schenkerian theory. Finally,I will assess validity of the methodology by contemplating an ultimate goal of harmonic analysis, in which prototypical structural harmonic progressions based on the cadential axiom and its elaboration and expansion are revealed in the analytic practice. 본 논문은 로마숫자를 통한 조성음악 분석의 효율적인 방법론을 제안을 목표로하는 실용적 성격의 글이다. 필자는 국내외에서 최근 10여년 이상 꾸준히 사용되어 왔던 화성법 및 분석 교재들을 비판적으로 검토하고 로마숫자가 단순한 명명방법이 아닌 보다 체계적인 분석 방법론으로 자리매김할 수 있는 방안을 모색하였다. 이를 위해 필자는 샤흐터(Carl Schachter)와 앨드웰(Edward Aldwell),Harmony and Voice Leading, 코스카(Stefan Kostka)와 페인(Dorothy Payne),Tonal Harmony with an Introduction to Twentieth-Century Music, 골딘(Robert Gauldin), Harmonic Practice in Tonal Music, 백병동 『화성학』, 김홍인 『화성』,허영한·한미숙 『조성음악의 화성진행』, 송무경 『연주자를 위한 조성음악분석』에서 전제하고 있는 기본화음(3화음, 7화음), 로마숫자 표기법, 그리고 통사론에대한 취급 방법 등에 대해 살펴보고 비교하였으며, 로마숫자를 보완하는 기호들을 검토하고 그 의미에 대해 고찰하였다. 또한 각 교재들이 제시하는 장점을 취하여 실제 분석에 적용함으로써 분석적 가능성을 탐구하였다.

고전계 응답 공간 전하 거동의 다중 물리 해석 및 수치 안정화 기법

이호영 국제차세대융합기술학회 2021 차세대융합기술학회논문지 Vol.5 No.4

본 연구에서는 단극성 전하 모델에서 전하 주입에 의한 공간 전하 전파 해석을 위해 전계-전하수송장으로 구성된 다중 물리계를 수학적으로 모델링하고, 수치 안정화 기법을 도입하여 양방향 다중물리 연성 수치해석법을 제안하였다. 수치해석은 2차원 평행 평판 전극 사이에 유전체가 존재하는 전기수력학적 모델을 선정하여 진행하였다. 고전계가 인가된 전극으로 전하가 주입되고, 유전체 내 단극성 공간 전하가 드리프트와 확산에 의해 거동하는 다물리 메커니즘을 수치해석으로 분석하였다. 인공 확산항을 도입하여 수치적 불안정성을 극복하였고, 기존 문헌에서 제안한 이론해와 비교하여 수치해석법의 타당성을 검증하였다. 유한요소법 기반의 양방향 다중물리 결합 해석은 기체, 유체, 고체 방전분야에서 적용할 수 있을 뿐만 아니라, 다양한 공학분야에서 다물리계 해석에서 활용할 수 있는 유용한 수치해석기법이다. In this study, for the analysis of space charge propagation by charge injection in a single charge model, a multi-physical system composed of an electric-charge transport field was mathematically modeled, and a bidirectional multi-physics coupled numerical analysis method was proposed by introducing a numerical stabilization technique. The model for numerical analysis was carried out by selecting an electro-hydrodynamic model in which a dielectric exists between two-dimensional parallel plate electrodes. The multi-physical mechanism in which electric charges are injected into the electrode to which a high electric field is applied and the unipolar space charge in the dielectric behaves by drift and diffusion was analyzed by numerical analysis. The numerical instability was overcome by introducing an artificial diffusion term, and the validity of the numerical analysis method was verified by comparing it with the theoretical solution proposed in the previous literature. The bidirectional multi-physics coupling analysis based on the finite element method is a useful numerical analysis technique that can be applied not only in gas discharge, fluid discharge, and solid discharge fields, but also in multi-physics analysis in various engineering fields.

Numerical analysis of under-designed reinforced concrete beam-column joints under cyclic loading

Saptarshi Sasmal,Balthasar Novák,K. Ramanjaneyulu 사단법인 한국계산역학회 2010 Computers and Concrete, An International Journal Vol.7 No.3

In the present study, exterior beam-column sub-assemblage from a regular reinforced concrete (RC) building has been considered. Two different types of beam-column sub-assemblages from existing RC building have been considered, i.e., gravity load designed (‘GLD’), and seismically designed but without any ductile detailing (‘NonDuctile’). Hence, both the cases represent the under-designed structure at different time frame span before the introduction of ductile detailing. For designing ‘NonDuctile’ structure, Eurocode and Indian Standard were considered. Non-linear finite element (FE) program has been employed for analysing the sub-assemblages under cyclic loading. FE models were developed using quadratic concrete brick elements with embedded truss elements to represent reinforcements. It has been found that the results obtained from the numerical analysis are well corroborated with that of experimental results. Using the validated numerical models, it was proposed to correlate the energy dissipation from numerical analysis to that from experimental analysis. Numerical models would be helpful in practice to evaluate the seismic performance of the critical sub-assemblages prior to design decisions. Further, using the numerical studies, performance of the sub-assemblages with variation of axial load ratios (ratio is defined by applied axial load divided by axial strength) has been studied since many researchers have brought out inconsistent observations on role of axial load in changing strength and energy dissipation under cyclic load.