• 한국소음진동공학회논문집
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• 제13권12호
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• pp.923-929
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• 2003

As for the marine propulsion shafting system using 4 stroke diesel engine, it is common to apply a reduction gear box between diesel engine and shafting to increase propulsion efficiency, which requires inevitably a certain elastic coupling to avoid chattering and hammering inside of gear box. In this study, the optimum method of rectifying propulsion shafting system in case of 750 ton fishing vessel is theoretically studied in a view of dynamic characteristics of torsion. After the replacement of diesel engine and gear box, the torsional vibration get worse and so some countermeasures are needed. The elastic coupling is modified from a present rubber coupling of block type having relatively high torsional stiffness to a rubber coupling haying two serially connected elements. Torsional vibration damper was installed at crankshaft free end additionally and moment of inertia of flywheel was adjusted. The dynamic characteristics of shafting system was improved by these modification. The theoretical analysis of torsional vibration are compared to measurement results using two laser torsion meters during the sea trial.

• 한국전기전자재료학회논문지
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• 제29권2호
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• pp.84-89
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• 2016

We present the results of a study of a piezoelectric generator that generates electricity by the application of tension to an element. A device is named "EYE-type generator". The EYE-type generator consists of a rectangular ceramic and two elastic body plates that are attached to upper and lower surfaces of a ceramic. If tension is applied to both ends of the elastic body, that tension is transformed to pressure on the ceramic through a change in the form of the elastic body, causing a piezoelectric effect whereby electricity is generated by the ceramic. This generator is relatively durable because a forces are not applied directly to the ceramic. We examined dependencies of the generator's output characteristics on the size of the ceramic and elastic body. A resonance and output characteristics were analyzed by using a finite element method. The generator was fabricated based on results of the analysis, and this was attached to a frequency-controllable vibrator to measure the output characteristics. The measured results were compared with results of the simulation, and the results pointed to the practicality of the design.

• Steel and Composite Structures
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• 제48권1호
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• pp.27-41
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• 2023

Under the long-term effect of corrosive environment, many cold-formed steel (CFS) structures have serious corrosion problems. Corrosion leads to the change of surface morphology and the loss of section thickness, which results in the change of instability mode and failure mechanism of CFS structure. This paper mainly investigates the elastic local buckling behavior of corroded CFS columns. The surface morphology scanning test was carried out for eight CFS columns accelerated corrosion by the outdoor periodic spray test. The thin shell finite element (FE) eigen-buckling analysis was also carried out to reveal the influence of corrosion surface characteristics, corrosion depth, corrosion location and corrosion area on the elastic local buckling behaviour of the plates with four simply supported edges. The accuracy of the proposed formulas for calculating the elastic local buckling stress of the corroded plates and columns was assessed through extensive parameter studies. The results indicated that for the plates considering corrosion surface characteristics, the maximum deformation area of local buckling was located at the plates with the minimum average section area. For the plates with localized corrosion, the main buckling shape of the plates changed from one half-wave to two half-wave with the increase in corrosion area length. The elastic local buckling stress decreased gradually with the increase in corrosion area width and length. In addition, the elastic local buckling stress decreased slowly when corrosion area thickness was relatively large, and then tends to accelerate with the reduction in corrosion area thickness. The distance from the corrosion area to the transverse and longitudinal centerline of the plate had little effect on the elastic local buckling stress. Finally, the calculation formula of the elastic local buckling stress of the corroded plates and CFS columns was proposed.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1998년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Spring 1998
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• pp.188-195
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• 1998

The main objective of this study is to observe the effect of visco-elastic damper on seismic behavior of structure. A small shaking table was designed and manufactured using the materials and machinery available in the market by the authors. Also, two small-scale models with and without visco-elastic dampers were made. Dynamic characteristics, such as natural periods and damping ratios, were measured with free vibration tests. Finally, the earthquake simulations tests by using this shaking table were performed to these models. Based on the test results, the effect of visco-elastic damper on the seismic response of models is evaluated.

• 터널과지하공간
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• 제33권3호
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• pp.150-168
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• 2023

암석의 이방성 거동은 조암광물들의 방향성 배열과 미세균열의 분포 특성이 주된 원인이다. 특히, 퇴적암과 변성암은 횡등방성 강도 및 변형 특성을 또렷이 나타내는 경우가 많다. 그러므로 암석역학적 설계과정에서는 횡등방성 암석의 변형 및 파괴 특성을 정확하게 이해하는 것이 중요하다. 횡등방성 암석의 변형은 실내시험을 통해 측정할 수 있는 5개의 독립된 탄성정수를 이용하여 기술된다. 이 연구에서는 문헌에 보고된 실험자료를 이용하여 횡등방성 암석의 겉보기 탄성정수의 방향성 변화 특성을 분석하였다. 임의 방향으로 회전된 직각좌표계에서 겉보기 탄성정수 값을 효율적이고 체계적으로 계산하기 위해 Mehrabadi & Cowin의 구성방정식을 도입하였다. 문헌에 보고된 4개 횡등방성 암석을 선택하여 연약면의 방향 변화가 겉보기 탄성계수, 겉보기 전단 탄성계수, 겉보기 포아송비의 변화에 미치는 영향을 분석하였다. 이러한 분석 결과를 바탕으로 새로운 탄성정수 제약 조건식을 제안하였다. 제안한 제약 조건식을 만족하면 횡등방성 암석에서 겉보기 탄성정수의 방향성 변화는 직관적으로 예측되는 경향과 일치하게 된다.

• 대한기계학회논문집
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• 제15권2호
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• pp.523-536
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• 1991

This dissertation analyzes the running mechanism of flexible and thin tape above rotating head through the numerical simulation and the experiment. The scope of analysis is confined to the phenomena of two dimensional elasto hydrodynamic lubrication between the protruded bump on a rotating cylinder and the running tape. This model is based on the elastic deformation equation of plate and shell and Reynolds equation. Finite difference method is employed as a numerical technique to calculate (1) the distribution of pressure between the running tape and rotating bump and (2) the vertical deformation of elastic thin tape over he rotating bump under hydrodynamic pressure. In numerical analyses, the effects of bump size on flying characteristics of the tape were evaluated and examined considering the influence of tension and stiffness of tape.

• 한국정밀공학회지
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• 제22권3호
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• pp.154-161
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• 2005

In this study, the leaflet motion of a mechanical heart valve and the characteristics of two-dimensional transient blood flow in an elastic blood vessel have been numerically investigated by using fluid-structure interaction method. Here, blood has been assumed as a Newtonian, incompressible fluid. Pressure profiles have been used as boundary conditions at the ventricle and the aorta. As a result, closing motion of the leaflet is faster than opening one. While opening angles of leaflet grow up, vortex is detected at the sinus and backward of the leaflets. When the leaflet is fully closed, vortex is detected at the ventricle and at that moment maximum displacement of the elastic blood vessel is observed in the vicinity of the sinus region. Maximum displacement is caused in association with the blood flow that is oriented toward the elastic blood vessel.

• Journal of Advanced Marine Engineering and Technology
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• 제22권3호
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• pp.328-336
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• 1998

Marine reduction gears are usually used to increase the propulsion efficiency of propellers for ships powered by medium and small sized high speed diesel engines. Most of shaft systems adopt flexible couplings to absorb the transmitted vibratory torque from the engines to the reduction gears and to prevent the chattering phenomenon of reduction gears. However some elastic couplings show non-linear characteristics due to the variable torque transmitted from the main engines and the change of ambient temperature. In this study dynamic characteristics of flexible couplings sare investigated and their effects upon various vibratory conditions of propulsion systems are clarified. A calculation program of torsional vibration for the propulsion systems are clarified. A calculation program of Results of the program developed are compared with ones of the existing linear method and propulsion systems with the elastic couplings the transfer matrix method is adopted which is found to give satisfied results.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 춘계학술대회논문집
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• pp.90-95
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• 2008

Medium and high speed marine diesel engines have been widely used as prime mover in small car ferries and fishing vessels with reduction gear. These propulsion shafting system should be installed and matched the elastic coupling between engine and reduction gear to isolate the vibratory torque. In this paper, the elastic dynamic characteristics of coupling with rubber type circular segments is confirmed by the theoretical analysis using the FEM and the hydraulic exciting test at shop. And its adaptation is investigated in the torsional vibration test in factory shop.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1996년도 추계학술대회 논문
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• pp.34-39
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• 1996

In many industrial applicatiosns such as machine tools and automation equipments the control performance of the feed-drive systems as positioning devices of the tools and workpieces have great influences on the quality of related machines. For many electrically driven mechanical feed systems resilient couplings between motors and mechanical elements which mostly consist of elasttic shafts and gears often are unavoidable. Commonly these systems can be regarded as an elastic multi-mass systems can be regarded as an elastic multi-mass system which is dealt with this contribution. S high performance speed or position control can only be achieved with the considering of the mechanical elastic characteristics of the system. n this paper some practic characteristics of the system In this paper some practical information is given about experience in modeling design simulation and experiments for linear elastic multi-mass system,