• 한국정밀공학회지
• /
• 제26권12호
• /
• pp.94-101
• /
• 2009

In diesel engines, it is inevitable that the torsional vibration is produced by the fluctuation of engine torque. Therefore, it is necessary to establish preventive measures to diminish the torsional vibration. The sleeve spring type damper is one of the preventive measures for reducing the torsional vibration. In this study, 2-roll bending process was proposed to manufacture sleeve spring; The program to calculate the initial radius including springback effect was developed and the FEA method to analyze elasto-plastic problem was verified through analysis of 90 degree bending process. The elasto-plastic analysis of 2-roll bending process was carried out by the FEA method verified to set a new criterion, and the new process design parameter(contact angle) in the 2-roll bending process was proposed.

• 소성∙가공
• /
• 제20권4호
• /
• pp.273-278
• /
• 2011

Employing the TRIZ problem solving technique, a hybrid-type center plate for the molten carbonate fuel cell(MCFC) was developed for the purpose of improving gas sealing and maintenance. The manufacturing method of the hybrid-type center plate was divided into a trimming operation and a two-step bending process. In the latter, a modified punch shape was used to reduce springback. Using finite element(FE) simulations, bending stresses in the thickness and the in-plane directions were computed and the bending conditions were optimized. The optimized results of the two-step bending process were used as a basis for the design of the trimming process of the hybrid-type center plate. Finally, the external manifold-type center plate and the hybrid-type center plate were fabricated using a die set that accounts for the optimized conditions. It was found that the numerical simulation results were in good agreement with the experiments.

• Structural Engineering and Mechanics
• /
• 제17권1호
• /
• pp.1-14
• /
• 2004

Numerical solution to linear bending analysis of circular plates is obtained by the method of harmonic differential quadrature (HDQ). In the method of differential quadrature (DQ), partial space derivatives of a function appearing in a differential equation are approximated by means of a polynomial expressed as the weighted linear sum of the function values at a preselected grid of discrete points. The method of HDQ that was used in the paper proposes a very simple algebraic formula to determine the weighting coefficients required by differential quadrature approximation without restricting the choice of mesh grids. Applying this concept to the governing differential equation of circular plate gives a set of linear simultaneous equations. Bending moments, stresses values in radial and tangential directions and vertical deflections are found for two different types of load. In the present study, the axisymmetric bending behavior is considered. Both the clamped and the simply supported edges are considered as boundary conditions. The obtained results are compared with existing solutions available from analytical and other numerical results such as finite elements and finite differences methods. A comparison between the HDQ results and the finite difference solutions for one example plate problem is also made. The method presented gives accurate results and is computationally efficient.

• Structural Engineering and Mechanics
• /
• 제2권1호
• /
• pp.17-34
• /
• 1994

This paper proposes a new four node degenerated shell element. In the formulation of the new element, the assumed covariant shear strains are used to avoid the shear locking problem, and the assumed covariant membrane strains are applied to alleviate the membrane locking problem and also to improve the membrane bending performance. The assumed covariant strains are obtained from the covariant strain field defined with respect to the element natural coordinate system. This formulation enables us to obtain a shell element, which does not produce spurious singular modes, avoids locking phenomena, and excels in calculation efficiency. Several examples in this paper indicate that, despite its simplicity, the achieved accuracy and convergence are satisfactory.

• Structural Engineering and Mechanics
• /
• 제26권1호
• /
• pp.69-86
• /
• 2007

A four-noded plate bending quadrilateral (PBQ4) and an eight-noded plate bending quadrilateral (PBQ8) element based on Mindlin plate theory have been adopted for modeling the thick plates on elastic foundations using Winkler model. Transverse shear deformations have been included, and the stiffness matrices of the plate elements and the Winkler foundation stiffness matrices are developed using Finite Element Method based on thick plate theory. A computer program is coded for this purpose. Various loading and boundary conditions are considered, and examples from the literature are solved for comparison. Shear locking problem in the PBQ4 element is observed for small value of subgrade reaction and plate thickness. It is noted that prevention of shear locking problem in the analysis of the thin plate is generally possible by using element PBQ8. It can be concluded that, the element PBQ8 is more effective and reliable than element PBQ4 for solving problems of thin and thick plates on elastic foundations.

• 대한조선학회논문집
• /
• 제41권4호
• /
• pp.45-52
• /
• 2004

Exact solution on the anti-symmetric response of ships having uniform sectional properties in waves is derived. Boundary value problem consisted of Timoshenko beam equation and free-free end condition is solved analytically. The responses are assumed as linear and wave loads are calculated by using strip method. Horizontal bending moment, shear force and torsional moment are calculated. The developed analysis model is used for the benchmark test of the numerical codes in this problem. Also the application on the preliminary design of barge-like ships and VLFS (Very Large Floating Structure) is expected

• Computers and Concrete
• /
• 제23권3호
• /
• pp.171-188
• /
• 2019

This study proposed a new and efficient 2D damage-plasticity model within the framework of Isogeometric analysis (IGA) for the geometrically nonlinear damage analysis of concrete. Since concrete exhibits complicated material properties, two internal variables are introduced to measure the hardening/softening behavior of concrete in tension and compression, and an implicit gradient-enhanced formulation is adopted to restore the well-posedness of the boundary value problem. The numerical results calculated by the model is compared with the experimental data of three benchmark problems of plain concrete (three-point and four-point bending single-notched beams and four-point bending double-notched beam) to illustrate the geometrical flexibility, accuracy, and robustness of the proposed approach. In addition, the influence of the characteristic length on the numerical results of each problem is investigated.

• Structural Engineering and Mechanics
• /
• 제70권3호
• /
• pp.367-380
• /
• 2019

The paper concerns topology and geometry optimization of statically determinate beams with arbitrary number of supports. The optimization problem is treated as a bi-criteria one, with the objectives of minimizing the absolute maximum bending moment and the maximum deflection for a uniform gravity load. The problem is formulated and solved using the Pareto optimality concept and the lexicographic ordering of the objectives. The non-dominated sorting genetic algorithm NSGA-II and the local search method are used for the optimization in the Pareto sense, whereas the genetic algorithm and the exhaustive search method for the lexicographic optimization. Trade-offs between objectives are examined and sets of Pareto-optimal solutions are provided for different topologies. Lexicographically optimal beams are found assuming that the maximum moment is a more important criterion. Exact formulas for locations and values of the maximum deflection are given for all lexicographically optimal beams of any topology and any number of supports. Topologies with lexicographically optimal geometries are classified into equivalence classes, and specific features of these classes are discussed. A qualitative principle of the division of topologies equivalent in terms of the maximum moment into topologies better and worse in terms of the maximum deflection is found.

• 한국융합학회논문지
• /
• 제6권4호
• /
• pp.9-14
• /
• 2015

본 논문은 기타의 목 부분의 형상에 따라 가해지는 힘에 의한 휘어짐의 문제를 해결하기 위한 것으로, 기존의 기타를 보강하여 실제 사용 시, 하중에 취약한 부분을 파악하는 방법을 연구하였다. 본 연구에서는 실제 기타에 적용되는 목재의 물성치를 연구모델에 적용하고 모델링 한 후, 유한요소해석을 수행하였다. 본 논문의 연구를 통해 나온 결과를 사용하여 기존의 기타의 문제로 지적되어온 휨과 파손에 대한 기반자료를 얻을 수 있을 것으로 사료되며 이를 보강 할 수 있는 디자인을 연구하여 그 기타를 개선하고자 한다. 개선된 연구모델에 대한 결과를 토대로 실제 설계에 응용한다면 휨과 파손을 방지하여 내구성을 향상시킬 수 있으며 디자인 면에서의 융합기술로의 접목도 가능하며 미적인 감각을 나타낼 수 있다.

• 대한가정학회지
• /
• 제41권5호
• /
• pp.89-97
• /
• 2003

Fitness of clothes becomes a major concern in apparel industry. But high-school boys had difficulties to buy ready-made clothes of good fit. To solve this problem, it is necessary to classify boys' upper body into several kinds of somatotypes. The purpose of this study was to classify upper body types of high school boys based on the analysis of their upper body types. The subjects for anthropometric measurement were 99 high school boys of 16 to 18 year-old. The result of factor analysis indicated that 5 factors were extracted from anthropometric measurements through analysis and those factors comprise 68.44% of total variance. 3 clusters were categorized using 5 factor scores by cluster analysis. Type 1 was taller than other types and was bending somatotype. Type 2 was straight somatotype and had average size. Type 3 was characterized by short and small figure and had bending somatotype.