• Structural Engineering and Mechanics
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• 제33권5호
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• pp.543-560
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• 2009

The rotating Rayleigh-Timoshenko beam element based on B-spline wavelet on the interval (BSWI) is constructed to discrete short shaft and stiffness disc. The crack is represented by non-dimensional linear spring using linear fracture mechanics theory. The wavelet-based finite element model of rotor system is constructed to solve the first three natural frequencies functions of normalized crack location and depth. The normalized crack location, normalized crack depth and the first three natural frequencies are then employed as the training samples to achieve the neural networks for crack diagnosis. Measured natural frequencies are served as inputs of the trained neural networks and the normalized crack location and depth can be identified. The experimental results of fatigue crack in short shaft is also given.

• Structural Engineering and Mechanics
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• 제74권5호
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• pp.577-588
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• 2020

A unified solution is presented for the buckling analysis of rectangular laminated composite plates with elastically restrained edges. The plate is subjected to biaxial in-plane compression, and the boundary conditions are simulated by employing uniform distribution of linear and rotational springs at all edges. The critical values of buckling loads and corresponding modes are calculated based on classical lamination theory and using the Ritz method. The deflection function is defined based on simple polynomials without any auxiliary function. The verifications of the current study are carried out with available combinations of classic boundary conditions in the literature. Through parametric study with a wide range of spring factors with some classical as well as some not classical boundary conditions, competency of the present model of boundary conditions is proved.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.645-650
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• 2004

There have been lots of efforts to analyze the dynamic characteristics of mechanical systems. However, it is difficult to know the dynamic characteristics of mechanical systems composed of many parts with joints. Specially, in case of a bolted joint structure, no effective modeling method has been defined to acquire dynamic characteristics of the structure, using the finite element (FE) analysis. In this research, a linear dynamic model is developed for bolted joints and large interfaces using con frusta method and linear spring elements, respectively. The developed modeling method for bolted joints is verified based on the experimental result.

• 한국음향학회지
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• 제15권2호
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• pp.33-39
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• 1996

비선형 건마찰 감쇠를 가진 외팔보의 강제진동 응답을 건마찰 감쇠기와 가진력의 위치변화에 대하여 미끄러진 변위와 힘레벨을 수치해석하였다. 구성모드의 분석은 비선형 감쇠를 가진 계를 해석하기 위해 구속조건과 Lagrange 승수에 기초를 두고 분석하였다. 외팔보의 진동분석 결과 건마찰 감쇠기가 부착된 단순 지지된 보(beam)에서 보여진 응답특성과 유사한 특성이 나타났다.

• 한국소음진동공학회논문집
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• 제14권10호
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• pp.990-998
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• 2004

There have been lots of efforts to analyze the dynamic characteristics of mechanical systems. However, it is difficult the know the dynamic characteristics of mechanical systems composed of many parts with joints. Specially, in case of a bolted Joint structure, no effective modeling method has been defined to acquire dynamic characteristics of the structure using the finite element (FE) analysis. In this research, a linear dynamic model is developed for bolted feints and large interfaces using con frusta method and linear spring elements, respectively. The developed modeling method for bolted joints is verified based on the experimental result.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.1004-1006
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• 2014

This study was conducted to improve the understanding of factors affecting an automobile seat cushion in dynamic conditions. When there are two dummies on the seat to measure each places respectively at once, the shape of the transfer function changes because the dummies affect each other as if they are linked with some kind of a spring when under excitation. A simple two-degree-of-freedom linear model is used to define a translational stiffness of dynamic coupling phenomenon. The cushion deflection model was created to find the relation between dynamic coupling and distance. Experimental set-up was made to compare with the two-degree-of-freedom linear model. The dynamic coupling factor could be utilized to improve the dynamic comfort of automobile seats.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 D
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• pp.2683-2686
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• 2002

In this paper, it has been investigated that the design and simulation of linear motor for medical appliances. Vacuum pump consists of unified plunger and piston part, coils, inlet valve and outlet valve. Operating principal of vacuum pump show that air is to flow to go inside through the inlet valve, when the magnetic force (16N) is exerted, whereas, air is to flow to go outside through outlet valve, when spring force (14.8N) is exerted. The results of simulation, it was turned out that magnetic force was loaded with 16 Newton, displacement of actuator was about 8mm.

• 한국기계가공학회지
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• 제17권1호
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• pp.42-47
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• 2018

This paper describes the dynamical behavior of the bicycle and its nonlinear effect when magnetic repulsive forces are applied to the bicycle cushion system. A finite-element method was used to obtain its reliabilities by comparing the experimental and numerical values and select the proper magnet sizes. The Equivalent spring stiffness values were evaluated in terms of both linear and nonlinear approximations, where the nonlinear effect was specifically investigated for the ride comfort. The corresponding equations of linear and nonlinear motion were derived for the numerical model with three degrees of freedom. Dynamic behaviors were observed when the bicycle ran over a curvilinear road in the form of a sinusoidal curve. The analysis in this paper for the observed nonlinearity of magnetic repulsive forces will be a useful guide to more accurately predict the cushion design for any vehicle system.

• 연구논문집
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• 통권30호
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• pp.25-32
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• 2000

A free piston and free displacer(FPFD) Stirling cryocooler for cooling infrared and cryo-sensors is currently under development at KIMM(Korea Institute of Machinery & Materials). A Stirling cryocooler is relatively compact, reliable, commercially available, and uses helium as a working fluid. The FPFD stirling cryocooler consists of two compressor pistons driven by linear motors which makes pressure waves and a pneumatically driven displacer piston with regenerator. The FPFD Stirling cryocooler employs 1) the Stirling cycle for refrigeration, 2) linear for driving the cryocooler, 3) spring and gas support systems, and 4) fine gap for clearance seals. It is the most suitable design for a mechanical cryocooler utilized in night vision environment. In order to get optimum operating frequency, natural frequency of piston and displacer, optimum phase angle between piston and displacer, cooling capacity, performance tests of the Stirling cryocooler by the frequency characteristics were performed.

• 한국철도학회:학술대회논문집
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• 한국철도학회 1998년도 창립기념 춘계학술대회 논문집
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• pp.580-587
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• 1998

For many decades, the railway was constructed using tracks with jointed rails of relatively short lengths in accordance with rolling and handling technology. The joints cause many drawbacks in the track and lead to significant maintenance cost. So, railroad engineers became interested in eliminating joints to increase service loads and speeds by improving rolling, welding, and fastening technology, Continuous welded rail(CWR) track has many advantages over the conventional jointed-rail track. But in the case of the elimination of rail joints, it may cause the track to be suddenly buckled laterally by thermal and vehicle loads. Thermal loads are caused by an increase in the temperature of railway track. In this paper, CWR track model and CWRB program are developed for linear buckling analysis using finite element method(FEM). The finite element discretization is used with a total of 14 degrees of freedom for each rail element. The stiffness of the fastener, tie, and ballast bed are included by a set of spring elements. The investigation on the buckling modes and temperature of CWR track is presented in the paper.