• Composites Research
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• v.29 no.4
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• pp.203-208
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• 2016

Metal and polymer sandwich composites, which are made of sheet metal sheath and polymer or fiber reinforced plastic core, have been reconsidered as an alternative to sheet metal due to their lightness and multifunctional properties such as damping and sound-proof properties. For the successful applications of these composites, the delamination prediction based on the adhesion strength is important element. In this study, the numerical simulation of the delamination behavior of polymeric adhesive tapes with metallic surfaces was performed using cohesive zone elements and finite element software. The traction-separation law of the cohesive zone element was defined using the fracture energy derived from peel mechanics and experimental results from peel test and implemented in finite element software. The peel test of the polymeric adhesive film against steel surface was simulated and compared with experiments, demonstrating reasonable agreement between simulation and experiment.

• The Journal of the Acoustical Society of Korea
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• v.29 no.7
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• pp.448-457
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• 2010

Vibrations and wave propagations in waveguide structures can be analysed efficiently by using waveguide finite element (WFE) method. The WFE method only models the 2-dimensional cross-section of the waveguide with finite elements so that the size of the model and computing time are much less than those of the 3-dimensional FE models. For cylindrical shells or pipes which have simple cross-sections, the external coupling with fluids can be treated theoretically. For waveguides of complex cross-sectional geometries, however, numerical methods are required to deal with external fluids. In this numerical approach, the external fluid is modelled by the boundary elements (BEs) and connected to WFEs. In order to validate this WFE/BE method, a pipe submerged in water is considered in this study. The dispersion diagrams and point mobilities of the pipe simulated are compared to those that theoretically obtained. Also the acoustic powers radiated from the pipe are predicted and compared in both cases of air and water as an external medium.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.8
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• pp.756-762
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• 2012

A method of the low-frequency noise reduction in an enclosure by using an array of Helmholtz resonator is presented. An integral form of equation, which represents the acoustical coupling between the internal sound field and the resonator array, is formulated so that the boundary element method can be applied to solve the coupling problem. It is shown that the resonator array on the surface of the enclosure can be regarded as impedance patches on the boundary element. Experiments on a simple enclosure acoustically coupled with an array of resonators are conducted to verify the method. The predicted noise reduction by the boundary element method shows good agreement with the measured one. The effects of the resistance of resonators as well as the number of resonators on the noise reduction are demonstrated. As a practical example, the presented method is applied to the payload fairing of a space launcher with resonator arrays. It is demonstrated that the resistance of resonators affects significantly the required number of resonators to achieve a desired noise reduction.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.772-777
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• 2006

An acoustic finite element model of a bridge is developed to evaluate the noise generated by the traffic-induced vibration of the bridge. The dynamic response of a multi-girder bridge, modeled by a 3-dimensional frame element model, is analyzed with a 3-axle(8DOF) truck model and a 5-axle(l3DOF) semi-trailer. The flat plate element is used to analyze the acoustic pressure due to the fluid-structure interactions between the vibrating surface and contiguous acoustic fluid medium. The radiation fields of noise with a specified distribution of vibrating velocity and pressure on the structural surface are also computed using the Kirchhoff-Helmholtz integral. In an attempt to illustrate the influence of the structural vibration noise of a bridge to total noise level around the bridge, the random function is used to generate the vehicle noise source including the engine noise and the rolling noise interacting between the road and tire. Among the diverse parameters affecting the dynamic response of bridge, the vehicle velocity, the vehicle weight, the spatial distribution of the road surface roughness, the stiffness degradation of the bridge and the variation of the air temperature changing the air density are found to be the main factors that increase the level of vibration noise. Consequently, The amplification rate of noise increases with the traveling speed and the vehicle weight.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.3
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• pp.226-233
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• 2013

Individual differences in head-related transfer functions(HRTFs) were calculated using boundary element(BE) models for three Korean adults. The BE models for the individuals were developed from the computerized tomography(CT) images of the individuals. The BE models were composed of the head, pinna, and ear canal. The frequency-dependent impedance boundary conditions were imposed on the skin, hair, and tympanic membrane. The HRTFs calculated from the individual BE models showed large difference above 2 kHz in magnitude and in the locations of peaks and valleys of the frequency spectrums, which should be considered in virtual auditory sound field. The identified individual differences in the HRTFs demonstrate that the developed BE models can be utilized successfully in order to obtain the HRTFs information of individuals.

• Transactions of Materials Processing
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• v.9 no.4
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• pp.348-355
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• 2000

The backward tracing scheme(BWT) of the finite element method has been extended lot the design of sheet blank in three-dimensional deformation. Originally the scheme was developed for preform design in bulk forming, and applied to several forming processes successfully. Its key concept is to trace backward from the final desirable configuration to an intermediate preform or initial blocker. A program for initial blank design in sheet forming which contains the capabilities of forward loading simulation by the finite element method and backward tracing simulation, has been developed and proved the effectiveness by applying to a square cup stamping process. In the blank design of square cup stamping, the backward tracing program can produce an optimum blank configuration which forms a sound net-shape cup product without machining after forming. For the confirmation of the analytic result derived from the backward tracing simulations as well as forward loading simulations, a series of experiment were carried out. The experiments include the first trial sheet forming process with a rectangular blank, an improved process with a modified blank preform and the final process with an optimum blank resulted from the backward tracing scheme. The experiments show that the backward tracing scheme has been implemented successfully in blank design of sheet metal forming.

• Transactions of Materials Processing
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• v.17 no.8
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• pp.600-606
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• 2008

In closed-die hot forging, a billet is formed in dies such that the flow of metal from the die cavity is restricted. Some parts can be forged in a single set of dies, whilst others, due to shape complexity and material flow limitations, must be shaped in multi sets of dies. The purpose of a performing operation is to distribute the volume of the parts such that material flow in the finisher dies will be sound. This study focused on the design of preforms, flash thickness and land width by theoretical calculation and finite element analysis, to manufacture the super hot forging product, 70MC type piston crown used in marine engine. The optimal design of preforms by the finite element analysis and the design experiment achieves adequate metal distribution without any defects and guarantees the minimum forming load and fully filling of the cavity of the die for producing the large piston crown. The maximum loads obtained by finite element analysis are compared with the results of experiments. The loads of the analysis have good agreements with those of the experiment. Results obtained using DEFORM-2D enable the designer and manufacturer of super hot forging dies to be more efficient in this field.

• Journal of the Korean Geotechnical Society
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• v.15 no.2
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• pp.139-152
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• 1999

These days we broadly apply drilled shafts for deep foundations to build infrastructures. The defects of the deep foundations cause the decrease of their support load capacity and the increase of settlement, and the subsequent damage of the super-structures. In consequence, non-destructive testings techniques of concrete piles are important for their integrity evaluation. To improve understanding and reliable application of the impact echo method for the integrity evaluation of the drilled concrete piles, numerical studies of the impact response of concrete piles by using axi-symmetric three-dimensional finite element method are peformed for (a) sound piles: (b) piles containing necks, voids and layers of low-quality concrete: and (c) piles in soil and/or above rock. The results of these studies show that the finite element method is effective for evaluating the impact response of drilled concrete piles.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.938-941
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• 2004

Sound generation and radiation from the duct-rotor system are calculated numerically. The wake geometries of a two-bladed rotor are calculated by using a time-marching fiee-wake method without a non-physical model of the far wake. Acoustic free field due to a rotating rotor is obtained by Lowson's equation. Using Kirchhoff source, rotating sources are modeled as stationary ones and can be inserted in the thin body boundary element method. The Kirchhoff source is validated through calculation of acoustic pressure due to a rotating point force. The thin body boundary element method (thin body BEM) is validated through calculation of acoustic radiation of ducted dipole. Using Kirchhoff source and thin body BEM, acoustic radiation of a ducted rotating source is calculated. Acoustic shielding is observed by inserting a duct and shows different phenomena at each major frequency. Acoustic radiation of a real duct-rotor system is also calculated using this method and the ducted acoustic field is significantly different from rotor only.

• Journal of The Korea Institute of Healthcare Architecture
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• v.26 no.2
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• pp.63-69
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• 2020

Purpose: The purpose of this study is to identify the neuro architecture items and detailed elements that can be considered for each detailed space in the future medical space design development through the development of a checklist of neuro architecture elements that can be utilized in medical space design. Methods:: This study first develops the neuro architecture element through theoretical research and prepares the basic plan for the checklist through consultation with the employees of the design company in which the researcher works. Finally, a checklist was developed through a survey of nine experts, including designers, hospital staff, and professors. Results: The result of this study 1) The neuro architecture component was developed in seven categories: light, color, sound, air, image, nature, ergonomic furniture and equipment. 2) Specifically, it consists of 49 elements including 7 light elements, 7 color elements, 5 sound elements, 4 air elements, 11 image elements, 6 elements in nature, 9 elements in ergonomic furniture and equipment. It was. 3) Although each of the detailed elements is more preferred according to the space, in general, all the elements should be considered in the context of the hospital space design. Implications: The checklist on the neuro architecture element will enable the development of the most faithful design as an efficient and useful tool for applying the neuro architecture philosophy that considers human beings in hospital design and pursues healing and happiness.