볼트결합부를 포함한 구조물의 정적 및 동적 해석을 위한 유한요소 모델링

권영두,구남서,김성윤,조민호,Gwon, Yeong-Du,Gu, Nam-Seo,Kim, Seong-Yun,Jo, Min-Ho 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.4

Many studies on the finite element modeling for bolted joints have proceeded, but the structures with bolted joints are complicated in shape and it is difficult to find out the characteristics according to joint condition. Usually, experimental methods have been used for bolted joint analysis. A reliable and practical finite element modeling technique for structure with bolted joints is very important for engineers in industry. In this study, three kinds of model are presented; a detailed model, a practical model and a simple model. The detailed model is modeled by using 3-D solid element and gap element, and the practical model is modeled by using shell element (a portion of bolt head) and beam element (a portion of bolt body), the simple model is modeled by simplifying practical model without using gap elements. Among these models, the simple model has the least degree of freedom and show the effect of memory reduction of 59%, when compared with the detailed model.

유한요소법을 이용한 박막이 있는 물체의 응력파해석

권영두,권혁춘,이상태,서병철 대한금속재료학회 2005 대한금속·재료학회지 Vol.43 No.2

Generally, as objects impact each other, coating layer is regarded as little affecting transmission and reflection of shock wave. However, we thought that material properties and thickness of coating layer would actually affect objects. So this paper was performed by finite element analysis (FEA) for transmission and reflection of stress wave propagation at two bars having different material properties. Also, as coating layer having different material properties was inserted between bars, we looked into the behavior of stress wave propagation and compared the result of FEA and theoretical result. As using them, FEA for actual piezo electric ceramic was performed. The damaged cause of piezo electric ceramic was confirmed by the effect of reflected wave. To decrease the effect of reflected wave, we analyzed it as changing thickness and material of coating layer and the shape of piezo electric ceramic. Afterwards, we inquired thickness and material of coating layer and the shape of piezo electric ceramic being able to minimize the effect of reflected wave. (Receivad September 30 2004)

운동 참여자의 운동 동기와 지속성, 지각된 건강 상태에 관한 집단 특성 조사

권영두,이재혁 대한스포츠물리치료학회 2023 정형스포츠물리치료학회지 Vol.19 No.1

Purpose: In this study, we investigated group characteristics such as purpose, motivation, and perceivedhealth status of adults who participated in exercise across various periods and also describe exercise guidancestrategies to improve exercise participation and adherence based on the results of the survey and findingsof previous studies. Methods: The study included 69 participants who underwent short- or long-term exercise. Participants wereprovided a mixed questionnaire containing optional questions regarding the purpose of exercise participationand descriptive questions regarding their motivation for exercise participation. Perceived health status wasmeasured using a General Health Questionnaire. Results: Participants indicated muscle training (37.5%) and physical strength improvement (30.15%) as themain purpose of exercise, and the instructor (26.74%), self-realization (24.42%), and educational environment(13.95%) as motivators for exercise. Perceived health status severity and exercise persistence showed anegative correlation (R=-0.27) in contrast to exercise time per day (R=0.14) and the number of exercisesessions per week (R=0.07). Conclusion: Similar to the findings of previous studies, our study highlights that in contrast to external factors,exercise motivation for adherence should focus on improved intrinsic factors such as encouragement duringexercise coaching and that gentle guidance methods including goal setting should be used to improve exercisepersistence.

5절점 상당요소에 의한 굽힘문제의 정적해석 및 자유진동해석

권영두,윤태혁,정승갑,박현철,Gwon, Young-Doo,Yun, Tae-Hyeok,Jeong, Seung-Kap,Park, Hyeon-Chul 대한기계학회 1996 大韓機械學會論文集A Vol.20 No.4

In the present study, we consider modified 5-node equivalent solid element which has smallest degree of freedom among 2-dimensional solid elements accounting bending deformation as well as extensional and shear deformations, We shall investigate static and dynamic characteristics of this element, which is very effective in thin beam, thick beam, large displacement problems, beam of variable thickness, and asymmetrically stepped beam, etc., as well as relatively simple problems of beam. The degree of freedom of this element is 10, which is smaller than 18 of 9-node element, 16 of 8-node elemtns, 12 of modified 6-node element and Q6 element. Therefore, this element is expected to broaden the effective range of application of the solid elements in the bending problems further.

Autofrettage 가공시 2중중공원주의 최적두께비

권영두 경북대학교 공과대학 1980 工大硏究誌 Vol.9 No.-

The optimal thickness ratios of doubly laminated hollow cylinder were investigated. The Tresca's yield criterion was applied. In autofrettage process without shrink fit, the outer cylinder need not be autofrettaged. One equation can represent the allowable pressure. In autofrettage process with shrink fit, there are three equations representing allowable pressure concerned with the available autofrettage pressure. The optimal thickness ratio was obtained and same in above two cases.

3차원 10절점-상당요소에 의한 굽힘문제의 정적.동적해석

권영두,윤태혁 한국전산구조공학회 1997 전산구조공학 Vol.10 No.4

In this paper, a modified 10-node equivalent solid element(MQM10 element), which has smallest degrees of freedom among 3-dimensional solid elements accounting bending deformation as well as extensional and shear deformations of isotropic plates, is proposed. The proposed MQM10 element exhibits stiffer bending stiffness due to the reduction of degrees of freedom from 20-node element or Q11 element. As an effective way to correct the relative stiffness stiffening phenomenon, the modification equation of Gauss sampling points is proposed. The quantity of modification is a function of Poisson's ratio. The effectiveness of MQM10 element is tested by applying it to several examples. It is noted that the results of static and free vibration analysis of isotropic plates using MQM10 elements show a good agreement with those using 20-node element. 본 논문에서는 등방성판의 인장이나 전단변형은 물론 굽힘문제에도 적용할 수 있는 3차원 고체요소들 중에서 최소의 자유도를 갖는 수정 10절점 상당요소를 제안하였다. 제안된 수정 10절점 상당요소는 Q11요소나 20절점요소로부터 자유도가 줄어듬에 기인한 과대한 굽힘강성을 나타낸다. 이러한 상대적 강성과잉 현상을 수정하기 위한 효과적인 방법으로 가우스 적분점 수정 방법을 제안하였다. 수정량은 포아송 비의 함수이다. 수정 10절점 상당요소의 효과를 여러 가지 예에 적용하여 검증하였다. 제안된 수정 10절점 상당요소에 의한 등방성판의 정적해석과 자유진동 해석의 결과들은 20절점요소를 사용한 결과들과 잘 일치하였다.

Al-Al_3Ni 複合材料의 비틀림特性에 관한 理論解析

權永斗,李永文,洪俊杓 慶北大學校 1980 論文集 Vol.30 No.-

The mechanical behavior of Al-Al_3Ni composites in torsion was analyzed. The Ludwik's equation S=Hγ^n was used as the shear stress and strain relation equation. The coefficients H and n were included in T-θ (torque-angle of twist) equation. The values of H and n were obtained by minimizing the errors between T-θ equation and the experimental data. The theoretical T-θ curves using computed values of H and n approach relatively well to the experimental data. Some discrepancy was observed in torque at a given twist angle with the solidification velocities. And so, an equation including the effect of solidification velocities was proposed without the experimental confirmation.

원추형봉 내의 응력분포

權永斗 경북대학교 공과대학 1977 工大硏究誌 Vol.6 No.-

The stresses in a truncated conical bar which is the standard viewports for submersibles, were obtained by differentiating the Airy stress function. The biharmonic Airy stress function with idealized boundary conditions was solved by Neou's polynomial method. In a particular problem of minor diameter=1˝, thickness=1˝, apical angle=90 deg, the maximum shear stress was appeared in highpressure face at vadius 0.75˝.

하중과 변위가 동시에 제어되는 문제의 좌굴후 현상 해석 ( Postbuckling Analysis of Load-Displacement Control Problem )

권영두,임범수,박철,최진민 대한기계학회 1996 대한기계학회 춘추학술대회 Vol.- No.-

Optimization of gap sizes for the high performance of annular nuclear fuels

권영두,권순범,김성수,조희정 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.4

Solid-type nuclear fuels have been used for nuclear reactors for a long time. Many countries are currently developing annular fuels toimprove the efficiency of nuclear fuels. The thermoelastic-plastic-creep analyses of solid- and annular-type rods were conducted underthe same conditions. The temperature and stress of the solid- and annular-type rods were compared on the basis of gap size. In this study,we examined the advantages and disadvantages of annular-type fuel regarding the temperature and stress of the pellet and cladding. Theinner and outer gaps between the pellet and cladding play important roles in the temperature and stress distributions of fuel systems. Therefore, the optimization of gaps in fuel systems was conducted for a low temperature under certain stress conditions. Thermoelasticplastic-creep analyses were conducted by using an in-house thermoelastic-plastic-creep finite element analysis program in VisualFORTRAN with the effective stress function algorithm. Nonlinear iterative stress analyses were conducted by nonlinear iterative temperatureanalyses; that is, a quasi-fully coupled algorithm was applied to this procedure. In this study, the thermoelastic-plastic-creepanalysis of pressurized water reactor annular fuels was conducted to determine the contacting tendency of the inner–outer gaps betweenthe annular fuel pellets and cladding, as well as to optimize the gap sizes by using the commercial package PIAnO for efficient heat transferat certain stress levels. Most analyses were conducted until the gaps disappeared. However, certain analyses lasted for 1582 days, afterwhich the fuels were replaced.