• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.89-96
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• 2002

A two-degree of freedom model is suggested to understand the basic dynamical behaviors of the interaction between two masses of the friction induced vibration system. The two masses may be considered as the pad and the disk of the brake, The phase space analysis is performed to understand complicated dynamics of the non-linear model. Attractors in the phase space are examined for various conditions of the parameters of the model especially by emphasizing on the damping parameters. In certain conditions, the attractor becomes a limit cycle showing the stick-slip phenomena. In this paper, not only the existence of the limit cycle but also the size of the limit cycle is examined to demonstrate the non-linear dynamics that leads the unstable state. For the two different cases of the system frequency ((1)two masses with same natural frequencies, (2) with different natural frequencies), the propensity of limit cycle is discussed in detail. The results show an important fact that it may make the system worse when too much damping is present in the only one part of the masses.

• 한국소음진동공학회논문집
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• 제12권7호
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• pp.502-509
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• 2002

A two-degree of freedom model Is suggested to understand the basic dynamical behaviors of the interaction between two masses of the friction induced vibration system. The two masses may be considered as the pad and the dusk of the brake. The phase space analysis is performed to understand complicated dynamics of the non-linear model. Attractors in the phase space are examined for various conditions of the parameters of the model especially by emphasizing on the damping parameters. In certain conditions, the attractor becomes a limit cycle showing the stick-slip phenomena. In this Paper, not only titre existence of the limit cycle but also the sloe of the limit cycle is examined to demonstrate the non-linear dynamics that leads the unstable state. For the two different cases of the system frequency[(1) Two masses with same natural frequencies, (2) with different natural frequencies] . the propensity of limit cycle Is discussed In detail. The results show an important fact that it may make the system worse when too much damping Is present in the only one part of the masses.

• 한국소음진동공학회논문집
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• 제22권7호
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• pp.619-625
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• 2012

Since the fuel is always exposed to turbulent flow, the grid strap shows flow induced vibration characteristics that impact on the nuclear fuel soundness. The dynamic behavior of grids in nuclear fuels is quite complex, since two pairs of spring and dimple support are contacted with rods by friction in the limited space. This paper focuses on investigation of the grid strap(test fuel strap, TFS) vibration in one cell. TFS consists of a single spring and double dimples. To identify the grid strap vibration, modal analysis of the strap is performed using finite element method(FEM). Modal testing on a $5{\times}5$ grid structure without rods is performed. The modal testing results are compared to analytic results. In addition, random test considering rod effect is performed about a $5{\times}5$ grid with rods under real contact condition in the air. Finally, the strap vibration of a $5{\times}5$ fuel bundle in investigation of flow induced vibration(INFINIT) facility is measured in real fluid velocity condition without heating. It is shown that modal frequencies from the test are almost equal to those peak frequencies in the INFINIT test.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 춘계학술대회논문집
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• pp.236-240
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• 2005

This paper deals with friction-induced vibration of disc brake system under constact friction coefficient. A linear, finite element model to represent the floating caliper disc brake system is proposed. The complex eigenvalues are used to investigate the dynamic stability and in order to verify simulations which are based on the FEM model, The comparison of experimental and analytical results shows a good agreement and the analysis indicates that mode coupling due to friction force and geometric instability is responsible fur disc brake squeal. And the Front brake system reduced the squeal noise using design of experiment method(DOE). This helped to validate the FEM model and establish confidence in the simulation results. Also they may be useful during real disk brake model.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.820-825
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• 2004

This paper deals with friction-induced vibration of disc brake system under constant friction coefficient. A linear, finite element parameter model to represent the floating caliper disc brake system is proposed. The complex eigenvalues are used to investigate the dynamic stability and in order to verify simulations which are based on the FEM model, the experimental modal test and the dynamometer test are performed. The comparison of experimental and simulation results shows a good agreement and the analysis indicates that mode coupling due to friction force is responsible for disc brake squeal. And squeal type instability is investigated by using the parametric rotor simulation. This indicates parameters which have influence on the propensity of brake squeal. This helped to validate the FEM model and establish confidence in the simulation results. Also they may be useful during real disk brake model.

• Wind and Structures
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• 제26권4호
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• pp.215-229
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• 2018

The appearance of a rivulet at the upper surface of a stay cable is responsible for rain-wind-induced vibration (RWIV) of cables of cable-stayed bridges. However, the formation mechanism of the upper rivulet and its aerodynamic effects on the stay cable has not been fully understood. Large eddy simulation (LES) method is used to investigate flow around and aerodynamics of a circular cylinder with an upper rivulet at a Reynolds number of 140,000. Results show that the mean lift coefficients of the circular cylinder experience three distinct stages, zero-lift stage, positive-lift stage and negative-lift stage as the rivulet located at various positions. Both pressure-induced and friction-induced aerodynamic forces on the upper rivulet are helpful for its appearance on the upside of the stay cable. The friction-induced aerodynamic forces, which have not been considered in the previous theoretical models, may not be neglected in modeling the RWIV. In positive-lift stage, the shear layer separated from the upper rivulet can reattach on the surface of the cylinder and form separation bubbles, which result in a high non-zero mean lift of the cylinder and potentially induces the occurrence of RWIV. The separation bubbles are intrinsically unsteady flow phenomena. A serial of small eddies first appears in the laminar shear layer separated from the upper rivulet, which then coalesces and reattaches on the side surface of the cylinder and eventually sheds into the wake.

• 한국자동차공학회논문집
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• 제17권2호
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• pp.112-117
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• 2009

The new suspension, called ISU(In-arm suspension system) was developed for Infantry Fighting Vehicle. During vehicle field test, early failure of ISU's sealing system was occurred after driving the paved road. From the failure analysis, ISU's displacement data was obtained. In analysis of PSD data, track induced vibration which has high frequency and small amplitude characteristics, was dominant. Such track vibration would result in early seal failure because of friction increase and lack of lubrication. To simulate track vibration environment in laboratory, seals were tested under the condition of 20Hz, ${\pm}1$, ${\pm}2mm$ amplitude. The same type of seal failure occurred in vehicle test, was reproduced in the lab test under ${\pm}1mm$ amplitude. From the test results, the durability of improved seal was increased by 2.5 times compared with the previous one.

• 한국소음진동공학회논문집
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• 제18권10호
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• pp.1042-1048
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• 2008

Disc brake noise is an important customer satisfaction and warranty issue for many manufacturers as indicated by technical literature regarding the subject coming from Motor Company. This research describes results of a study to assess disk brake squeal propensity using finite element methods and optimal technique (Kriging). In this study, finite element analysis has been performed to determine likely modes of brake squeal. This paper deals with friction-induced vibration of disc brake system under contact friction coefficient. A linear, finite element model to represent the floating caliper disc brake system is proposed. The complex eigen-values are used to investigate the dynamic stability and in order to verify simulations which are based on the FEM model. In this paper, Kriging from among the meta-modeling techniques is proposed for an optimal design scheme to reduce the brake squeal noise.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.578-581
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• 2007

In this study, the seismic control performance of energy dissipation devices installed in a shear all-frame structure is investigated through nonlinear time history analysis of a 12-story building. Inelastic shear walls are modeled using the multiple vertical line element model (MVLEM) and inelastic columns and girders were modeled using fiber beam elements. For a seismic load increased by 38% compared to the design load, the seismic control performance was analyzed based on the results of a nonlinear time history analysis in terms of the inter-story drift, the story shear and the flexural strain. Friction type dampers was found to performs best if they are installed in the form of a brace adjacent to the shear wall with the friction force of 15 % of the maximum story shear force induced in the original building structure without dampers.

• International Journal of Naval Architecture and Ocean Engineering
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• 제10권3호
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• pp.361-366
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• 2018

Ice crushing occurs in many situations that involve a sliding frictional component such as sports involving ice-contact, ice interaction with ship hulls, and ice-on-ice sliding/crushing within glaciers and between interacting sea ice floes. Ice crushing-friction tests were conducted in the lab at $-10^{\circ}C$ using a set of acrylic ice-crushing platens that included a flat smooth surface and a variety of high-roughness surfaces with regular arrays of small prominences. The experiments were part of Phase II tests of the Blade Runners technology for reducing ice-induced vibration. Ice was crushed against the platens where the ice movement had both a vertical and a horizontal component. High-speed imaging through the platens was used to observe the ice contact zone as it evolved during the tests. Vertical crushing rates were in the range 10-30 mm/s and the horizontal sliding rates were in the range 4.14-30 mm/s. Three types of freshwater ice were used. Friction coefficients were extraordinarily low and were proportional to the ratio of the tangential sliding rate and the normal crushing rate. For the rough surfaces all of the friction coefficient variation was determined by the fluid dynamics of a slurry that flowed through channels that developed between leeward-facing facets of the prominences and the moving ice. The slurry originated from a highly-lubricating self-generating squeeze film of ice particles and melt located between the encroaching intact ice and the surfaces.