• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.10
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• pp.891-899
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• 2010

Since the working machine generates an excessive loud noise as much as its use-purpose and dimension, those damages are occurring to the exposed workers such as unpleasant sense, stress and occupational hearing-impaired. Accordingly, as one of the measures for prevention such loud noise, various soundproof protection tools were developed. However, such soundproof protection tools were presented the physical measured value only, it is real state that the psychological study result with regard to the soundproof effect which the workers are actually feeling, is not existing. On such point of view, with the object on the typical earplugs and earcaps among the soundproof protection tools, this study has ever tried a subjective evaluation about the degree of soundproof effect through Psycho-acoustics experiment. It is considering that such study result could be utilized as the useful material when establishing the soundproof measure for the workers in the future.

• The KSFM Journal of Fluid Machinery
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• v.12 no.4
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• pp.14-22
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• 2009

The head-capacity curves for pumps developed by the pump manufacturer are based on tests of a single pump operating in a semi-infinite basin with no close walls or floors and with no stray currents. Therefore, flow into the pump intake is with no vortices or swirling. However, pump station designers relying on these curves to define the operating conditions for the pump selected sometimes meet the reductions of capacity and efficiency, as well as the increase of vibration and additional noise, which were caused by air-entered flow in the pump station. From this background, the authors are carrying out a systematic study on the flow characteristics of intakes within a sump of pump station model. Multi-intake sump model with anti-submerged vortex device basin is designed and the characteristics of submerged vortex is investigated in the flow field by numerical simulation. In this study, a commercial CFD code is used to predict the vortex generation in the pump station accurately. The analysed results by CFD show that the vortex structure and effect of anti-submerged vortex device are different at each pump intake channel.

• Magazine of the Korea Concrete Institute
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• v.6 no.6
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• pp.143-150
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• 1994

Most widened bridges have been constructed by the joining-construction method that makes new and existmg bridges structurally a single structure. Since the joining-constructiori method has several problems in design and construction viewpoint, this study is conducted in order to investigate the flexural fatigue behavior of RC slabs, which are widened and influenced by traffic-induced vibration of existmg bridge during placing and curing of new concrete, with the prototype fatigue test. It was found that stress concentration at the jclmts anti slips between steel bar and concrete are occured. Hut, the general tx:havinrs are similar to the original state and joining-construction method using expansive concrete nut~gated the influence of the trafflc-induced vibration.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.4 s.97
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• pp.465-473
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• 2005

The impact sounds, generated by the walking of people, the dropping of an object or the moving of furniture, can be a source of great annoyance in residential buildings. The characteristics and level of this impact noise depends on the object striking the floor, on the basic structure of the floor, and on the finish materials of floor. The focus of this paper is to investigate the amount of improvement impact sound pressure level according to the change of the composition method of ceiling and wall. For this purpose, we tested impact sound pressure level of several cases which is the inserting of mineral wool, the increase of the thickness of air layer, the using of anti-vibration rubber in ceiling and attach the mineral wool on wall in the Floor Impact Sound Test Building of KICT. The results show that the composition method of ceiling and wall is more effective in the reduction of light weight impact sound specially in 125Hz and 250Hz.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.9 s.114
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• pp.904-911
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• 2006

A modified energy method for the fretting wear of the steam generator tube is proposed to calculate the wear-out depth between the nuclear steam generator tube and its support. Estimation of fretting-wear damage typically requires a non-linear dynamic analysis with the information of the gap velocity and the flow density around the tube. This analysis is very complex and time consuming. The basic concept of the energy method is that the volume wear rate due to the fretting-wear phenomena Is related to work rate which is time rate of the product of normal contact force and sliding distance. The wearing motion is due to dynamic interaction between vibrating tube and its support structure, such as tube support plate and anti-vibration bar. It can be assumed that the absorbed work rate would come from turbulent flow energy around the vibrating tube. This study also numerically obtains the wear-out depth with various wear topologies. A new dissection method is applied to the multi-span tubes to represent the vibrational mode. It turns out that both the secondary side density and the normal gap velocity are important parameters for the fretting-wear phenomena of the steam generator tube.

• KSTLE International Journal
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• v.10 no.1_2
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• pp.33-36
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• 2009

The nuclear steam generator is composed of a bundle of tubes. The length of these tubes is very long, but their diameter is small. Fluid exists inside of the steam generator and its flow causes vibration, therefore these tubes are supported by anti-vibration bars. The wear damage due to the vibration is known as fretting wear, which should be minimized to ensure the safety of the plants. Research needs to be done about decreasing the amount of fretting wear. Hard coatings have proven to be very effective in reducing the amount of wear. The commercial coatings of TiN and CrN have excellent wear resistance and are used to protect the Inconel tube from fretting wear. The tube-on-flat type tester was used for conducting the fretting wear tests. It was found that the wear amounts of the coated tubes decreased depending on the coating thickness. CrN was found to be very effective in reducing the wear, while the wear amounts were dependent on the coating thickness in the case of TiN and a thick coating of TiN was very effective on wear resistance.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.1
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• pp.84-91
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• 2013

Ultrasonic flip-chip bonding needs a precise bonding tool which delivers ultrasonic energy into chip bumps effectively to use the selected resonance mode and frequency of the horn structure. The bonding tool is excited at the resonance frequency and the input and output ports should locate at the anti-nodal points of the resonance mode. In this study, we propose new design method with topology optimization for ultrasonic bonding tools. The SIMP(solid isotropic material with penalization) method is used to formulate topology optimization and OC(optimal criteria) algorithm is adopted for the update scheme. MAC(modal assurance criterion) tracking is used for the target frequency and mode. We fabricate two prototypes of ultrasonic tools which are based on 3D optimization models after reviewing 2D and 3D topology optimization results. The prototypes are satisfied with the ultrasonic frequency and vibration amplitude as the ultrasonic bonding tools.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.6
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• pp.929-936
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• 1986

Free vibration characteristics of laminated orthotropic circular cylindrical shells with clamped free boundary condition are investigated. The solution is obtained through a direct solution procedure with axial mode displacements represented as simple Fourier series expressions. On the basis of the thin shell theories of Sanders, Love, Loo, Morley and Donnell, the 4*$ frequency determinant is derived and is expressed in a unified form. Various numerical examples determining the natural frequencies of circular cylindrical shells with isotropic material and also with layers of orthotropic elastic material arbitraily laminated either symmetrically or anti-symmetrically about the shell middle surface. The results obtained compared very well with some available experimental and numerical results.

• Structural Engineering and Mechanics
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• v.74 no.1
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• pp.33-54
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• 2020

The aim of this study is to calculate natural frequencies and harmonic responses of cracked frames with general boundary conditions by using transfer matrix method (TMM). The TMM is a straightforward technique to obtain harmonic responses and natural frequencies of frame structures as the method is based on constructing a relationship between state vectors of two ends of structure by a chain multiplication procedure. A single variable shear deformation theory (SVSDT) is applied, as well as, Timoshenko beam theory (TBT) and Euler-Bernoulli beam theory (EBT) for comparison purposes. Firstly, free vibration analysis of intact and cracked frames are performed for different crack ratios using TMM. The crack is modelled by means of a linear rotational spring that divides frame members into segments. The results are verified by experimental data and finite element method (FEM) solutions. The harmonic response curves that represent resonant and anti-resonant frequencies directly are plotted for various crack lengths. It is seen that the TMM can be used effectively for harmonic response analysis of cracked frames as well as natural frequencies calculation. The results imply that the SVSDT is an efficient alternative for investigation of cracked frame vibrations especially with thick frame members. Moreover, EBT results can easily be obtained by ignoring shear deformation related terms from governing equation of motion of SVSDT.

• Tribology and Lubricants
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• v.24 no.5
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• pp.250-254
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• 2008

The steam generator of nuclear power plant is composed with the bundles of long tubes. It is exposed fluid flow and weak in the vibration. The tubes are supported by anti-vibration bars. Due to vibration the wear damage is called as the fretting wear. It should be minimized for the safety of the plants. The hard coatings are very effective to reduce the amount of wear. The coatings of TiN and CrN are introduced in this study to protect the fretting surfaces. The tube-on-flat type tester was used for fretting wear tests. The results show that the wear amounts of the coated tubes were decreased depending on coating thickness. CrN was very effective to reduce the wear. In case of TiN the wear amounts were dependent on the coating thickness. Thick coating of TiN was very effective for wear resistance.